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SECTION 9

MISCELLENEOUS

ASME District F - ECTC 2013 Proceedings - Vol. 12 287

ASME District F - Early Career Technical Conference Proceedings ASME District F - Early Career Technical Conference, ASME District F – ECTC 2013

November 2 – 3, 2013 - Birmingham, Alabama USA

EXPERIMENTAL STUDY ON ANALYZING HUMAN FACTOR IN THE PROCESS OF PLANNING OF VERTICAL TRANSPORTATION

Magdalena Krstanoski

Ss. Cyril and Methodius University Faculty of Mechanical Engineering

Skopje, Macedonia

Kristina Jakimovska Ss. Cyril and Methodius University Faculty of Mechanical Engineering

Skopje, Macedonia

ABSTRACT The objective of this paper is to explore some of the areas

related to the human factor when planning vertical transportation, to explore the benefits of analyzing the parameters that describe the relationship between the human element and planning, and give a general overview of some important elements to be considered during the planning of the vertical transportation process, that may serve as bases for valuable assumptions to understand the relationship between human factor and planning of the vertical transportation in the concept phase. It is beneficial to research how human factors interact with the passenger elevators in a country where vertical transportation is planned. The idea of this paper was to explore, and help understand how human factors are integrated in the process of planning, by conducting a pilot survey targeting elevator end users, via reaching to the community. The survey-based information is gently touching a few human factors patterns applicable for Macedonia. The analysis of the survey, taking local knowledge and user input, may further assist in understanding the importance of observing human patterns in the geographical region where elevators are going to be employed, and at the same time to utilize a survey to learn about possible areas of improvement. By introducing and utilizing survey questionnaire and analysis, once the completed facility is placed in service, during the Facility Management phase, the input from the users/occupants may serve as a valuable base for analysis of the assumptions made during concept design, and planning for future similar projects.

INTRODUCTION In today’s world as the population is increasing, it is

observed that, people tend to concentrate more in the cities, in search of opportunities, and life perspectives. Building up instead of out, has become more evident in the past years, as a result of the population growth, and sustainability orientation. The development, and advancement of drafting technology, opens the concept of how the project, once envisioned, may look in more visual terms, and defines the limits of the building height. Humans living and interacting in the tall structures move in horizontal and vertical directions. Human movement in the buildings generates need for the transportation means. Office buildings are associated with the space rentals that

indirectly are related to the best vertical transportation solution, and to the quality of the service. The importance of conveying systems has become even more crucial in large buildings.

While early in the project phase some limited data may be known, or not defined yet, which is typical for the project at the concept design phase, same may be subject to change in the early phase of the project development. Many factors directly or indirectly connected to planning, may influence the planning of conveying systems, and the same needs to be further explored. In some respects, passenger elevator space in buildings has been viewed through the lens of a non-money-making area, space that cannot be leased, but at the same time is required. The areas most often discussed in the early phase are mostly related to the area planned for vertical transportation (dimension closely related to the capacity and inside car dimensions), travel speed, travel height, conveyance type. In addition, waiting times and round trip times, are becoming important parts of the planning as project information becomes available, or if the project information as pertinent to the vertical transportation changes. Depending on the project, ride comfort, and acoustics, and in recent years sustainability have been added to the list of topics potentially to create more attention in the near future.

To better approach the planning of the conveying systems, and to understand some of the factors that influence the planning, it is important to employ a process of analyzing human factors as related to the project location, in addition to the building purpose. Some of the areas are related to understanding of personal space, of passengers’ responses and acts, the perception of comfort from the elevator passengers’ perspective related to the personal space. When humans are confined in a closed space such as an elevator car, personal space represents the positions the passengers are taking once in the elevator car, and the factors that passengers pay attention to the most, once in the car. This is important because all this information, is going to serve to better understand the car’s loading, depending on the project location.

Human responses and actions when utilizing passenger elevators depend on the culture observed, and they are unlikely to be the same in different cultures; therefore the perception of personal space varies, as well. In this paper, a survey is employed as method to research some of the human factors from the elevator user point of view. This paper experiments


with the survey results on some elements of human factors, to compare the same with some data known in the industry, and technical literature. The survey was an independent and enthusiastic effort of the authors of this paper, as part of the research, where the survey was randomly submitted to various age groups, and feedback collected from Skopje, Macedonia, with the general assumption that the same may be applicable for those regions with similar population backgrounds in Southeast Europe.

CITY THROUGH THE AGES Skopje is the capital of Macedonia with 506,926

inhabitants [1], as per the 2002 Census. At present, during the daily working hours, the city’s population may easily reach a million, which makes it nearly half of the country’s population of over two million, as per the 2002 Census. It is an old city, as per some records[2], mentioned in II century BC as an antique settlement Scupi, and around I century AD[2] as part of the Roman Empire; it was the birthplace of the Byzantine Emperor Justinianus I (483-565), born in the fortification Taoresium (today’s village of Taor, in the close vicinity of Skopje) [3].

Three catastrophic earthquakes destroyed the city in the years 518, 1555 and 1963[2].

On July 26th 1963, a catastrophic earthquake hit the city, claiming the lives of more than 1070 people[2], injuring more than 2900 people[2], and causing severe material damage; it destroyed buildings (4/5 of the residential buildings[2]), hospitals, academic buildings, factories, schools, theaters, the railway station, and the infrastructure. Soon after, the city was rebuilt, and rose as a modern academic, industrial, and cultural center, with famous architects living their mark, such as Japanese architect Kenzo Tange, selected in 1965 as a winner of the International competition to help redesign, and rebuild the city.

The first elevator installed in the City was German “STIGLER” by Augusto Stigler, installed in year 1929 in the palace called “Risticeva Palata” (eng. Ristic’s Palace) built in 1926th, and named for its owner, the pharmacist Vladislav Ristic. The Palace was one of a few large buildings that survived the 1963 earthquake, today being a Cultural Heritage Landmark, and serving as a complex of offices. This elevator was the oldest in Macedonia, and was among the first in the region. However, due to deficiencies in parts, in February 2011, the present building owners decided to donate the “STIGLER” elevator to the Museum of the City of Skopje, where it is displayed today.

At present, Skopje is a modern metropolis that continuously keeps growing. Urban sprawl is been taking an active part in the past decade, and migration to the City has increased the population. Like the majority of the cities in Europe, the growth of population in the capital has been an evident process. The new portion of Skopje is predominantly with buildings above four stories. For comparison reason only, as per the 2002 Census[4], Macedonia had a total of 446,235 buildings; 1954 buildings between 6 and 11 floors (G+5 – G+10), where 842 were located in Skopje; and 158 buildings

between 11 and 21 floors (G+11-G+20), where 124 were located in Skopje[4].

In the past decade, and mostly in the past four years, the construction industry in the building sector significantly increased, ranging from residential, to office and hotel types.

METHODOLOGY AND KEY FINDINGS To assess how humans interact with elevators, and to

identify the challenges that currently an elevator planning engineer targeting Macedonian, and the area of Southeast European market may be facing, in June-July 2012 an online survey was conducted, containing 10 questions with multiple choice answers. This was randomly sent to 80 individuals predominantly in the capital Skopje. 56 individuals started the survey, and 46 completed the survey; that makes 82.14% completed responses (see Figure 1). Students at the University Ss. Cyril and Methodius, Faculty of Mechanical Engineering also participated in the survey.

Age/Gender

Female Male Not

completed Started /

Completed

26 20 10 56 /46 Below 30 9 6 / / 15 30-50 15 11 / / 26 Above 50 2 3 / / 5

Figure 1. Participants in the survey by age and gender

A separate survey question addressed the numbers of

elevators in the residential buildings where respondents reside, and a separate question addressed both, the office or academic buildings where survey takers work or study. The number of elevators in the office, vs. number of elevators in the academic buildings was not a question in the survey. The majority of answers i.e. 28.6%, or 16 individuals, responded that they live in a building with up to 15 floors. 23.2% responded that they live in buildings with up to 8 floors. Most answers, or 28.6%, responded that they live in a residential building with their apartment located between the 0-4th floors (answers in the survey were divided in floor segments without specifying floor numbers), whereas 17.9%, or 10, responded that their apartments were located between the 4th-8th floors, and 7.1% responded their apartments were located above the 8th floor. Only 3.6% responded that they reside in building with 15 floors or more.

The majority of respondents, 37.5% or 21, stated that their residential building does not have an elevator, vs. 32.1% ,or 18, that responded there is one elevator. 19.6%, or 11, responded that there are 2 elevators, 7.1%, or 4, responded there are 3 elevators, and only 1.8% equally responded that there are 4, and more than 4 elevators in the building, respectively.

These results are not conclusive, as other information needs to be obtained, such as year these buildings were built, and the applicable Standards under which these buildings were given the permit to be built. However these responses suggest


that the number of elevators in the existing buildings is related to the practice of planning in the past, and this further opens the question of the quality of service under current standards, to be further investigated. Based on observation, as well as the survey outcome, in the city of Skopje at present, there are buildings with 4 floors, even 6 or 7 floors that do not have elevators planned or incorporated in the buildings. This fact addresses another subject, very important in planning, which is accessibility, and accessibility of people with disabilities. This appears not to have been considered in the past, and is now clearly a deficiency.

To the multiple choice question “In what time of a day do you most often use the elevators?” 32.1%, i.e. 18 individuals, responded that they use the passenger elevators in their residential building daily, without particular pattern. 21.4%, or 12 people, responded that they use elevators in the early morning, whereas 17.9%, or 10, responded in the afternoon hours, versus 14.3%, or 8, that responded in the evening. Another 17.9%, or 10 individuals, selected that they do not use elevators because they prefer to use the stairs/walk to their destination. See Figure 2.

The survey does not address line of work, and working hours, which may would have influenced the responses. Based on the survey results, the use of elevators without particular pattern varies, covering all groups, from below 30 to above 50 years of age. Most of the females in the age group below 30, and between ages 30-50, prefer to walk instead of using elevators in their residential buildings. In general, it is observed that walking in lieu of riding an elevator is a common choice of the younger population in the region. This is not unusual; different age groups can be seen to use stairs in lieu of elevators, in their residential buildings for various reasons.

Based on the responses from the survey, 37.5%, or 21, work or study in the building up to 4 floors, 21.4%, or 12, work or study in a building up to 8 floors, 8.9%, or 5, selected work or study in a building up to 15 floors, and only 1, or 1.8 %, work/study in a building with 15 and more floors.

Figure 2. Frequency of use, Residential Building

Respectively 28.6%, or 16 individuals, responded that

there is one elevator in the building, 26.8%, or 16, responded that there are no elevators in the building where they do their

daily business, 19.6%, or 11, responded that there are only 2 elevators, 12.5%, or 7, responded that there are 3 elevators and only 7.1%, or 4, responded that there are 4 and more elevators in their building.

The majority of individuals, 34%, or 16, responded that they ride the elevators in the office building, without a particular pattern throughout the day. Equal number of individuals 21.3%, or 10, responded they mostly use the elevators in the morning, and same number of individuals responded that they prefer to walk to their destination instead using the elevators. 14.9%, or 7, selected in the afternoon, whereas 12.8%, or 6 individuals, responded that they use elevators during lunch hour. 13 persons responded (herein including both answer selections), that their building does not have an elevator and answer is not listed. See Figure 3.

The survey does not address the building type (single office building, multi office building), location of the building (center of the city, proximity to malls or restaurants), location of possible cafeteria in the building that occupants may be using during the lunch hour. The survey does not address whether the office building has a designated smoking area, and its location (designated smoking area which would more reflect Central/South/Southeast European, rather than other regions in Europe), the type of work, or parking location (if located in the building’s grade level, and under grade level that, affect the use of the elevators, and number of stops, mostly reflecting traditional mall design in the city, and some larger office buildings). All the above will affect the vertical communication in the building, and the frequency of the use of the elevators.

Figure 3. Frequency of use, Office or Academic building

What happens if more than one person waits for an elevator in the lobby? About half of the survey takers, or 51.1% (24 individuals) selected depending on the number of people waiting for an elevator, they sometimes let other passengers

Early Mornin

g

Lunch Hour

Afternoon

Evening

Without

particular

pattern

Prefer to walk instead using the

elevator

Building does

not have an elevato

r

Don't work

or study

Answer is not listed

(please clarify)

Series2 10 6 7 2 16 10 5 0 8

Series1 21.30% 12.80% 14.90% 4.30% 34.00% 21.30% 10.60% 0.00% 17.00%

10

6 7

2

16

10

5

0

8


enter the car, and they continue to wait for the next car available. About a quarter, 25.5%, or 12 individuals, prefer to walk to their destination if there are other passengers that are waiting in the lobby, whereas only 9 enter the elevator car regardless of the number of people waiting for the elevator. 8.5%, or 4, selected that they prefer walking the stairs instead using an elevator.

The survey does not ask the respondents on which floor is their destination. However, based on cultural observation, it is not uncommon for people to choose to walk to their destination to be more than 2 floors up and/or down. Walking down the stairs is more often observed among the general population (predominantly younger, but also, healthier, older population, as well), even in buildings up to six floors. The reason may be familiarity with some of the exiting low-rise residential buildings built before, and soon after the 1963 earthquake. These do not have elevators, and users may be familiar with using the stairs as part of their daily routine, since no elevators may have been originally in the building; another factor may be the fitness awareness that is part of the culture that has been embraced, and carried over from the past. One individual selected that, even in a case of one elevator in the building, he or she would let other passengers that waited for an elevator to fill the car, and would wait for an empty car. In cases when a building has more than one elevator, 2 individuals selected they would let other passengers to enter the car, regardless of the space in the car, and would wait for an empty car to arrive.

All of the above suggests that an individual preferred personal space distance. For the majority of the survey takers this is an important factor, and the space may be considered invaded when other passengers, are entering in a space such as an elevator car. Herein based on the observation and familiarity with the Macedonian culture, it is assumed other passengers that wait for an elevator are unknown to the survey taker. The survey does not ask whether the survey taker would have the same response, should other passengers waiting for the elevators in the lobby know, or be familiar with each other, not knowing or not being familiar to the survey taker, and how that would affect the response to the same question.

Personal space distance as a subjective category reflects the distance that individuals consider their own comfort area, and is part of the Proxemics, (1963)[5] (the word Proximal[5]

comes from the Latin word Proximus (1727) one meaning is “situated close to: proximate”) [5]. Proxemics is defined as “the study of the nature, degree, and effects of the spatial separation individuals naturally maintain (as in various social and interpersonal situations) and of how this separation relates to environmental and cultural factor”. [5]

Once in the car, 34%, or 16 survey takers, find a radius of around 0.5 m as a comfortable distance, as opposed to an equal percentage 34%, or 16, selecting distance to others not being significant for the individual taking the survey. An equal number of individuals, 8.5%, or 4, selected that a radius of less than 0.5m is their comfort distance, as opposed to the same percentage 8.5% that selected radius more than 0.5m. Only 4.3%, or 2, responded that they did not know. See Figure 4.

It appears that, men in the age group 30-50, perceive distance differently than women that belong to the same age group. Based on the responses, the majority of the 34% that selected distance from others not being significant, are male within the age group of 30-50, whereas the majority of the other 34% that responded distance of approximately 0.5 m radius as comfortable, are women within the age group 30-50, and women in the age group less than 30. This suggests that women’s perception of personal space is more structured towards creating a neutral zone, as opposed to men, where distance appeared to be of a less significant dimension.

What happens when two passengers are in the car and a third person enters car? Again it depends. How many people already wait in the lobby, and how many will enter the car? Once in the car, a passenger’s position is again related to the personal distance radius. See Figure 5.

Figure 4. Distance Radius

46.7% of the respondents choose the free side of the car, regardless of the handrail being on that car side wall or not. These 46.7% respondents are in equal numbers male and female within the age group 30-50, males above 50, and females below the age of 30.

Figure 6 shows selected responses based on the perception of what is important to an individual, or what an individual pays attention to, once in the car. The time that the respondent waits and/or is willing to wait for the car to arrive, based on the passenger observations, is not included as an option response in the survey, but rather the list to select from, was comprised of other in-car related elements, and the option to include other non listed item was given. See Figure 6.

8.5%

34%

8.5%

34%

4.3% 10.6%

8.5%

34%

8.5%

34%

4.3%

10.6% Less than 0.5 metar radius

Around 0.5 metar radius

More than 0.5 metar radius

Distance from others does not bother me

I don't know

The answer is not listed


Figure 5. Preferred positions in the car The majority of the individuals, 53.3% of the answers or

24 individuals, selected ride quality, followed by temperature and light, air flow, and all the above. Respondents input safety under answers not listed above, and this subject is closely related to the standards and regulations, inspection and maintenance. Figure 7 shows the preferred elements of importance for the age group above 50, as ride quality and air flow, whereas Figure 8 shows the selection of the age group 30-50, suggesting all of the above, ride quality, air flow, light and temperature.

Figure 6. Importance as per passenger’s perception Figure 9 shows the selection of the age group below 30.

Male in all age groups mostly selected ride quality as the most important factor they pay attention at once in the car, followed by the light. In addition to the listed items, women selected smooth ride, air flow, and temperature.

Figure7. Preferred importance elements for age group above 50

DISCUSSION AND CONCLUSIONS This paper reviews questions with the most selected

responses only, and some need to be viewed in light of certain limitations, and for information only.

The survey did not include questions regarding the maturity of the vertical transportation, the year the buildings were built, building type, survey takers’ work or study (office, bank, mixed use, dormitory, academic building, mall etc.). It did not address the possible location of points of interest such as cafeterias, restaurants, viewing decks, designated smoking areas, parking location, main lobby location, gym. It also did not consider the line of work the survey taker is engaged with, that may affect the frequency an individual is using the vertical transportation throughout the day (is it more sedentary, or is it more related to communication with different floors, or out of the building type of job, that may require frequent use of the elevators).

Figure 8. Preferred importance elements for age group 30-50

11.1% 46.7% 0.0% 20.0% 8.9% 0.0% 0.0% 13.3%

5

21

0

9

4 0 0

6

On the free side next to

the handrail;

On the free side of the

car, no difference if there is a handrail or

not;

On the center of the car;

Right in front of the car doors, having the rest of the passengers behind you;

On the back of the car, having the rest of the passengers in front of

you;

I will not enter, but stay and wait for

another car;

I will exit on the next landing & continue

using stairs to my

destination;

Answer is not listed

above (Explain)

33.30%

33.30%

26.70%

2.20%

11.10%

53.30%

24.40%

2.20%

15.60%

15

15

12

1

5

24

11

1

7

Light (type, intensity, color)

Temperature

Air Flow

Humidity

Acoustics, sound

Ride Quality

All the above

None is important

Answer is not listed above (clarify)

Male >50 yrs

Female >50 yrs

5 4

3

0 2

6

1 1 1

3 3 5

1 2 5

7

0 0

Male 30-50 yrs Female 30-50 yrs


Figure 9. Preferred importance elements for age group <

30 The survey shows some critical times of elevator traffic,

particularly in the case of the office/academic buildings, and in general, critical times need to be addressed when making initial planning, such as morning hours and lunch hour, as related to the building type, building location, occupancy type, type of working hours (fixed or flexible), and lunch hour.

Downtown location of the office building, and close proximity to the public transportation system may also affect the elevator traffic in the building during morning hours.

As many of the questions were not addressed in this particular survey, the idea was that learning about the actual project location, will address many factors in order to make a valuable assumption. The results are more close to accurate, if the assumptions are more accurate. The strength and benefits of this type of study is incorporating observations of the culture, cultural awareness knowledge, anthropological factors, in addition to the industry standards, in order to create a utilized concept that will bring a valuable input into the further traffic analysis.

Although in the case of an office building, critical times are often assumed to be early in the morning, lunch hour and at the end of the working hours, careful consideration needs to be taken of additional information that may further narrow the analysis. In case of the survey results from Macedonia, the majority of the survey takers responded that they use the elevators without particular pattern, followed by use of elevators in the early morning, for both cases office and residential. This suggests that the same may be a result of the flexible working hours that a majority of the companies in the country are practicing now-a-days, as opposed to the structured fixed working hours that used to be a practiced several years back, and which were likely to create peak elevator traffic hours at almost the same time. Use of elevators early in the morning, in both cases for office and residential, suggests times most likely the elevators to experience peak traffic. Equal numbers of individuals selected, ‘use of elevators in the early morning,’ and ‘prefer to walk instead of using the elevators,’ when they are in their office or academic building; this suggests that younger individuals prefer to use the stairs in lieu of waiting for an elevator.

A particular location of the building in the city and designated lunch hour may result in an entire building having a lunch hour at almost the same time, which can create a critical traffic time. Therefore, it is critical to determine what are the peak traffic times, considering building type, occupancy type and project location, as related to the social aspects and local culture. If the local custom is to visit local restaurants and cafeterias, or to take a walk during the fixed lunch hour, that will create a critical peak time of elevator and will be more critical than flexible morning hours.

Human weight is directly related to the elevator car size, and is also related to the personal space humans consider as a comfort dimension. In most countries, the weight is noted in the country applicable standards. It is assumed 75 kg to be an average weight[6] for the Europeans, also referenced in EN81 standard[14], which is applicable for Macedonia as well. The same weight of 75 kg is assumed in the calculation for North America, and the ASME A17[11] stipulates maximum inside net platform areas for the various rated loads. For South America, weight is assumed to be within the range of 70 kg. For some Asian countries the average weight is assumed to be around 68 kg, again varies between 65-70 kg depending on the country and the country industry standards. In some Middle East countries average weight assumptions as used in the calculations are related to EN 81 average weight value, although again depends of the country. For Australia, the assumed average weight is 68 kg[10].

Witnessing that more people are becoming overweight, it is more likely that the perception of the average weight is changing for certain countries, herein including North America and some European countries, and may be a subject to reconsideration in the future. For example another reference[7] suggests that North America has the highest average body mass of 80.7 kg, as compared to Asia, which has the lowest average body mass of 57.7 kg, and Europe with average body mass of 70.8 kg [7].

In general, The loading car factor as used in the traffic study calculations is considered 80% of the car nominal load, with a rationale that cars in most cases will be filled up to 80% of the nominal load, and again with the practical reasons of considering personal space. In respect to the survey results, the loading factor for office buildings in Macedonia may be less than 80%, depending on the office building, and line of work.

Human comfort space or personal space, has been discussed in the past by anthropologist Edward Hall[9] and Barney[8]. Hall’s work is mostly associated with the Proxemics[9], the study of human perception of space as related to the culture. In that regard, the conducted survey has resulted in an interesting conflicting outcome. Equally 34% percent of individuals (female) selected that once in the car, they are comfortable with a personal radius space of around 0.5 m (20 in) and yet, an equal number of 34% of the individuals (male) selected that the distance is not of significance.

For this survey, a distance of 0.5 m has been selected as a reference point distance, having an example of the women’s umbrella with the approx radius of 0.5 m found in the European

Male <30 yrs

Female <30 yrs


market. This value has been assumed as an example of possible personal space for an individual. In the U.S. market however, other umbrellas with the radius about and over 0.5 m can be found (for example a radius of 0.5 m (20 in) refers to Medium coverage, a radius of 21in-24in refers to Large coverage, a radius of 28in-34in refers to Extra Large coverage). For the purpose of comparison, in this study, a radius of 0.5 m was assumed as a starting point.

Barney[8] observes that in non crowded situations, women are comfortable with a neutral zone of 0.5 m2 or 0.8 m diameter circle (0.4 m radius), compared to a woman’s umbrella area of approx 0.5 m2, whereas in the same conditions, he observes male being comfortable with personal buffer zone of 0.8 m2 or 1.0 m diameter circle (0.5 m radius).[6]

To compare the survey findings with the above, the results from this survey where female passengers find comfortable a radius of around 0.5m is in line with above observations. However, survey results in the case of male passengers who find neutral personal space not to be significant suggest that women in general value their buffer comfort zone and need more personal neutral space than men. At the same time cultural and geographical differences, are a factor to consider in these assumptions when planning how congested and crowded the area may be (for example in the lobby, in the car, circulation areas, escalators, waiting areas).

Architects Julius Panero[12] and Martin Zelnik[12] discuss Anthropometrics[12], and explore human dimension and interior space. Radius of 53.3 cm (21 in), or area of 0.95cm2 (10 ft2), have been referred to as a Personal Zone, where radius of 45.7 cm (18 in) have been referred to as a No-Touch zone. Both Panero and Zelnik, as well as Barney[8] refer to the body ellipse dimensions. Panero and Zelnik as a body unit envisioned template of 655 mm (25.8 in) wide by 368 mm (14.5 in) width. Barney[8] envisions a body ellipse template of 600 mm length by 450 mm width.

Geographical locations, cultural background, gender, purpose of the building and building class, significantly influence the planning parameters and personal space radius, and all need to be carefully considered. Although in most cases, elevators are intended for large mixed use populations, at the same time they need to accommodate specific groups such as elderly persons, college students, even a specific gender only, in some geographical areas. Such accommodations require that additional considerations in respect to the human factors must be considered during the planning, in order to respect the elevator passengers/users needs.

The next question is very closely related to the previous one, and the results are confirming the same, i.e. 46.7% of the individuals will position themselves on the free side of the car regardless of whether there is a handrail or not. That would be a result of the individual personal space that everyone is experiencing once in the close, tight space such as an elevator car. Again, there are limitations to be drawn, for example, if two or more people know each other, the assumption is that the personal space may be smaller. Also, the gender of the persons entering the car, and the cultural background, will make a

difference in addition to the personal space. Observing in general, depending on the car capacity, when four people enter the car, all four corners appear to be taken, and the fifth usually positions in the center; based on the survey results this appears not to be preferred, and in a way it is not a comfortable position in respect to the personal space, considering the proximity of space in the car.

Many passenger elevator cars in Europe, in the existing buildings built in the past, have a small capacity. The cultural background will make a difference as to how the car loading will be perceived, in respect to the personal comfort area. In the case of older residential buildings, built before, around or soon after 1963 earthquake in Macedonia and with passenger elevators still in service that have rated loads of 320 kg, to accommodate 4 persons, and maximum car area of 0.9 m2, (900 mm x 1000 mm), these elevators not only that are not wheelchair accessible, but the ergonomic factors, and personal space appears to be neglected in the internal dimensions of the car, and the personal space[13].

Another example of how persons react, in regard to the perception of the personal space in the lobby, is the person’s choice to enter the car depending on the number of people waiting for the car. 51.1%, or 24 individuals, responded that depending on the number of people that are waiting for the elevator, they sometimes let other passengers to enter the car and they wait for the next car. 25.5%, or 12 individuals, prefer to walk to their destination. This brings other questions, such as the building and occupancy type, building class, number of cars, knowing other passengers that waits in the lobby or not, time of the day the waiting occurs, as well as the direction of travel (traveling up or down). Again, a significant percent (25.5%) chooses to walk to the destination (herein brings the question, which floor is the destination that passengers are willing to walk, if up or if in down direction).

In general one size does not fit all. Elevator planning analysis is a complex process where many factors during planning of the traffic need to be considered, in order to begin. This study provides a basic understanding of the importance of cultural awareness, the current standing, and areas to look for improvements. To the best of our knowledge, this type of analysis has been the first for Macedonia that explores the elevator user’s perception, and hopefully this will help to better understand the concept of community awareness, by going out into the community or by researching the human factors that eventually will influence the design when planning. At the same time, conducting a survey of similar nature may help to identify areas of further improvement during occupancy. For example the survey question that refers to the preferred importance elements for various age groups, not only that identifies the areas for improvements and users satisfaction, but also opens a field to research the elements that are important to the humans. A limited outcome data from this survey, in case of using the stairs in lieu of elevators, are not to be used for reducing the number of elevators when traffic study is performed, but for information purpose only, when analyzing


building type, and human behavior, if occupancies are known to belong to a certain age group.

Early involvement of industry experts with the collaborative discussions with other project drivers concerning vertical transportation at the project conception may give a new direction to the vertical transportation concept, with careful study of the human factors that may influence the planning of the conveying systems. This study may also help further in the way of understanding the planning of vertical transportation in the region, encourage designers to employ the process of survey during facility management to identify possible areas of improvement, occupant satisfaction and care, once the construction is completed.

Future work will investigate and compare the difference in the human factors depending of other geographical locations, comparison study, and vertical transportation evaluation process considering these differences.

REFERENCES [1] Makedonski: Republika Makedonija, Dr`aven Zavod za Statistika, Popis na naselenieto, doma}instvata i stanovite vo Republika Makedonija, 2002, str.20/52. Eng. Republic of Macedonia State Statistical Office, Census of Population, Households and Dwellings in Republic of Macedonia, 2002, pp.20/52, available online at: http://www.stat.gov.mk/Publikacii/knigaXIII.pdf; [2] Vojna Enciklopedija, Drugo izdanje 8, Beograd 1974, Stampa, Knjigotisak, Bakrotisak, Ofset i Povez, Graficki Zavod Hrvatske, Zagreb, pp.652-654; [3] Official Portal of City of Skopje, History, available online at: www.skopje.gov.mk; [4] Makedonski: Republika Makedonija, Dr`aven Zavod za Statistika, Popis na naselenieto, doma}instvata i stanovite vo Republika Makedonija, 2002, Kniga III: Stanovi, Zgradi i Domakinstva, str.174/230, str.164/230 Eng. Republic of Macedonia State Statistical Office, Census of Population, Households and Dwellings in Republic of Macedonia, 2002, Book III: Dwellings, Buildings and Households. pp.174/230, pp.164/230 available online at: http://www.stat.gov.mk/publikacii/knigaIII.pdf; [5] Merriam-Webster’s Collegiate Dictionary Eleventh Edition: 2003;An Encyclopedia Britannica Company, Merriam-Webster, Incorporated Springfield, Massachusetts, U.S.A. pp.1002; [6] Transportation systems in buildings; CIBSE Guide D: 2010, September 2010 (4th Edition) The authors /The Chartered Institution of Building Services Engineers London; pp.2-1-2-4. [7] Sarah C. Walpole, David Prieto-Merino, Phil Edwards, John Cleland, Gretchen Stevens, and Ian Roberts, Research article “The weight of nations: an estimation of adult human biomass” BMC Public Health 2012, 12:439; Published: 18-June-2012; available online at: http://www.biomedcentral.com/1471-2458/12/439; [8] Barney G., 2003, “Elevator Traffic handbook Theory and practice”, Spon Press Taylor & Francis Group, London and

NewYork,pp.3-7; [9] Nina Brown, “ Edward T. Hall: Proxemic Theory, 1966”, Center for Spatially Integrated Social Science, available online at:http://www.csiss.org/classics/content/13; [10] Robert Yeoh: 17-December-2004; Article Australian Standards Lift Code AS1735 Part 2(2001), available online at: http://users.tpg.com.au/robyeoh/AS1735p2.htm; [11] The American Society of Mechanical Engineers ASME A17.1 2007/CSA B44-07 Safety Code for Elevators and Escalators; pp.64; pp.243; [12] Julius Panero, AIA, ASID and Martin Zelnik, AIA, ASID: “Human Dimension & Interior Space A Source Book of Design Reference Standar ds”: First published 1979 in the United States and Canada by Whitney Library of Design an imprint of Watson-Guptill Publications, Inc. /New York;pp.37-45, pp.266; [13] Krstanoski Magdalena, 2004, “Harmonization between Macedonian standards and American Code regarding designing and calculation of passenger elevators” Master degree thesis, pp.49; [14] CEN European Committee for Standardization European Standard EN81-1:1998, Safety rules for the construction and installation of lifts-Part 1: Electric lifts; August 1998, pp.21;


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A MULTIPLICATION TOY FOR CHILDREN: THE COLOR CROSS CUBE

Michael D. Walker Department of Graphic Design

Virginia Commonwealth University Richmond, VA, USA

Ramana M. Pidaparti Department of Mechanical and Nuclear Engineering

Virginia Commonwealth University Richmond, VA, USA

ABSTRACT For very young children, learning multiplication might be a

challenge that could discourage them from pursuing STEM fields later in school. Introducing complex concepts in multiplication through a toy might facilitate understanding and perk interest in STEM fields. This study examined the possibility of teaching multiplication to children seven and younger through the creation of a toy that explains the multiplication process kinesthetically.

Existing educational toys were examined based on ability to merge pedagogical and entertaining elements. Research was carried out on devices used to teach multiplication, including flashcards and number charts. Diagrams were made of a three-dimensional device that would convey the same concepts as traditional two-dimensional models. A design concept was developed and refined following a systematic process. Scaled drawings were produced and a preliminary model was constructed. A digital rendering of the toy was created and a final model was made of cut Plexiglas.

The result, called the Color Cross Cube, is composed of a hollow tower and twenty colored pegs representing the numbers one through ten. Pegs are inserted into slots on two sides of the tower and are viewed from above. A light illuminates the translucent pegs and allows users to count the product of numbers being multiplied. When light passes through the pegs, it emphasizes areas where they overlap and change color. These color changes are also projected above the toy by the base light. The toy may be used in the classroom, as an aid for homework completion, or for entertainment purposes.

INRODUCTION Primary school teachers explain multiplication using a

plethora of written techniques. These are widely catalogued and include processes such as lattice, western-standard, crisscross, and equidistant multiplication [1, 2]. Memorization of number triads is built through student interaction with tools such as flash cards, multiplication tables, and even multiplication websites. Concepts taught through two-dimensional models are used in conjunction with learned

patterns to build multiplication fluency. For example, students may be instructed to count on their fingers when solving multiplication problems. They may use rhythmic finger counting to identify patterns or special finger positioning to completely solve problems, as is the case with the nines rule [3]. To utilize pattern-based techniques such as finger counting and eventually progress to a state of learned product recognition, students must first understand the mechanics of multiplication. This may be difficult for some students as explanations of multiplication mechanics are often visual in format. To help children who learn primarily through non-visual styles of teaching, an alternative approach to explaining multiplication is needed.

Caron [4] claims that teaching rote memorization of multiplication facts is “questionable” because the process emphasizes recitation, not understanding. It may make mathematics unpleasant, especially for frustrated students [4]. While many prefer a tabular approach to multiplication [5] both parties suggest that “translations within and among various modes of representation make concepts meaningful for students [6].”

Sherin and Fuson [3] write that even kindergarteners are capable of solving basic multiplication problems. Yet multiplication is often taught later, in the early stages of grade school. To introduce the multiplication process to children under the age of seven and to help kinesthetic learners better understand multiplication, we decided to create a toy that teaches multiplication mechanics using an engaging visual format.

DESIGN METHODS The toy design process took place over an eight week

period and began as part of an interdisciplinary research study at Virginia Commonwealth University.

A survey of toys was made to assess the need for an educationally entertaining kinesthetic device. Of particular focus were toys that used design to relay pedagogical concepts. Of the designs reviewed, fifteen were chosen for further study. Two toys identified are described below in order to clarify design goals.


Figure 1. Preliminary Drawings of the Color Cross Cube

Figure 2. AutoCAD model of the Color Cross Cube

Maria Montessori’s 1911 teaching materials [7] were studied due to their educational intent. The collection includes seven lacing, hooking, and buttoning frames, a geometric cabinet, counting sticks, a pink tower, and a cylinder block among other things [8]. One of these, the pink tower or Montessori tower, is made of ten cubes that are designed to be vertically stacked in order of decreasing volume [9]. The toy is intended to help students understand the limits of physical space but it only functions as an educational device when the stacking task is assigned. The tower exemplifies the complication of the Montessori toy collection. Without being asked to complete a task, a child may have no incentive to interact with a given toy.

The modular building set ZOOB invites child interaction.

Purportedly inspired by the structure of nucleotides, the name is an acronym for zoology, ontology, ontogeny, and botany [10]. The extent to which the toy addresses these studies is unclear. It may be arranged in structures such as a double-helix, but the end product of playtime is child-determined. ZOOB allows for self-directed discovery but does not impart learned knowledge that is essential for gaining fluency in subjects such as multiplication.

Toys considered to be more successful addressed educational topics through play. This collection includes sound-producing animals designed by Libuše Niklová, a peg maze termed Zebra designed by Barbara Brand, the Be-B created by Danielle Pecora, and letter puzzles made by Charlotte Hitz. These toys address the needs of young kinesthetic learners and established a format we used to create our multiplication toy. They all integrate play and discovery in

a single action that is initiated through simple, easy to understand design.

After the toy survey was complete, drawings were made of several three-dimensional models for multiplication instruction. One of these is shown in Fig. 1. A final design was selected, refined, and scaled proportionately. A preliminary three-dimensional model was developed based on ascertained measurements. From this model, a rendering was produced in AutoCAD. This digital blueprint was then used to cut a final model out of Plexiglas. CUBE DESIGN CONCEPT

A diagram of the most recent model of the toy, called the Color Cross Cube, is shown in Fig. 2. The design was inspired by the use of number lines in basic arithmetic instruction. To solve an addition problem such as seven plus three, a student may be given a number line and asked to first locate the number seven with their finger. The student is then instructed to move their finger to the right three units and point to the number ten, the answer. This procedure is a process-based explanation of arithmetic that utilizes the count-on method in conjunction with physical movement and diagram manipulation. The Color Cross Cube teaches multiplication using these same teaching styles and the count-all technique. This allows students the chance to solve and understand multiplication problems as soon as they are able to count.

The Cube relies on a grid-based explanation of

multiplication founded on the Cartesian product. This is illustrated in Fig. 3. To solve the problem two times three using this method, a student is first instructed to draw two parallel lines representing the number two. They are then asked to draw three perpendicular lines that intersect the original two. The


Figure 3. Grid-based explanation of the equation two times three

Figure 4. Drawing of the Color Cross Cube showing vertical row spacing on adjacent faces

Figure 5. Prototyped model of the Color Cross Cube from above

student then counts the number of line intersections to find the product of the two numbers.

The Cube allows for the creation of multiplication grids using twenty multi-colored transparent pegs instead of hand-drawn parallel lines. Each peg is split into one or more rods, which correspond to color-differentiated numerical units. These pegs are inserted into the side of a hollow central tower shaped like an inverted trapezoid. Each face of the tower is perforated with an array of rectangular holes. These holes hold inserted rods and organize pegs into vertical layers. For example, a peg with one rod is inserted on the bottom layer, a peg with two rods on the next highest layer, and a peg with three rods above that.

To allow rods to visually cross, just as lines do in the grid method, the faces of the central tower are organized into two pairs. Each pair consists of two parallel faces containing

corresponding layers of holes. The holes in pair two form the same triangular arrangement as the holes in pair one. However, the arrangement of holes in pair two is shifted upwards, making it so that rods inserted in adjacent sides of the cube do not collide. This relationship is illustrated in Fig. 4. Horizontal lines spanning the length of the figure show the relative position of rows on adjacent faces.

To solve a problem such as two times three, a student locates the peg with two rods and inserts it into one side of the tower. The student then locates the peg with three rods and inserts it into an adjacent side of the tower. The two pegs, both placed inside the tower, are then viewed from above. The transparent rods will appear to overlap because they are physically above or below one another. The student counts the instances of overlap to find the product of factors, in this case six. Instances of overlap are emphasized due to the coloration of pegs. For example, if the peg with two rods is blue in color and the peg with three rods is yellow in color, the instances of overlap will appear to be green. This color change is facilitated by an upwards shining light housed in the base of the tower.

RESULTS AND DISCUSSION The current model of the Color Cross Cube is a tabletop

device measuring six cubic inches and containing ten peg rows per face as shown in Fig. 5. It may be used to solve any multiplication problem involving factors up to ten. It is unlikely that students will use the cube to solve problems with factors greater than six, due to the time it takes to count product


units. Rows seven through ten were incorporated to illustrate how the multiplication process operates with larger digits and to allow for student experimentation. For example, students may place varying numbers of pegs in the tower at once to view color combinations and changes. Resulting colors are projected above the toy by the base light; this allows students to use the Color Cross Cube as a vibrant night-light or bedroom lamp. The cube may also be customized using a dry-erase marker. Rows may be labeled one through ten numerically or pictorially and images may be drawn on pegs to aid in product visualization. This allows for the incorporation of traditional written techniques. Students may also use markers to implement original ways of using the cube. One possibility is to label rows with units of tens, hundreds, or thousands instead of single digits.

Because the Cube functions as a toy and teaching aid, students will have greater incentive to use it. We predict that children will willingly use the toy in order to visualize color change and, as a result of manipulating this optical phenomenon, will intuitively discover how the cube physically operates. This reduces the level of initial instruction required for students to use the device in class. A teacher, parent, or instructional booklet will need to explain only mathematical concepts as they apply to the cube.

Overall prototyping expense for the cube was minimal; a marketable version of the Cube could be made of Plexiglas at a price of approximately $3 per unit. The current Cube model could be improved in regards to ease of use, ease of storage, and modularity. It is difficult to slide pegs with more than four rods through both faces of the toy. Future iterations of the device could include larger holes or wide horizontal slots. These slots could be used to calculate virtually any number, no matter how large, through a process called line multiplication [11]. Faces could also be made to snap into the base of the cube. This would allow the entire model to come apart and fold flat, optimizing storage of multiple units in settings such as a classroom. To pique the interest of children outside the target age range, alternative faces with varying numbers of holes could be created. Special play models could be developed that glow in the dark or reflect colored light with built-in mirrors.

To determine what improvements need to be made to the Cube and whether or not it is effective as a teaching aid it will need to be tested in a classroom environment. A hypothetical experiment would expose children to the toy when they are first introduced to multiplication. First, four groups of primary school students would be given a brief written assessment of multiplication skills. After the initial test, one group of students would use the Color Cross Cube as an instructional aid, another would be given cubes only for home use, and a third group would be taught multiplication exclusively with the Cube. After a set number of lessons student knowledge would be reassessed by means of a second written examination. Test results would be compared to a control group (group four) that did not use the Cube to learn multiplication.

A second study would examine the mechanics of Cube usage. Students with various levels of multiplicative understanding would be asked to complete a written multiplication test with the option of using the cube as an aid. The time each student spends using the cube would be measured. Observers would also record how students manipulate the Cube in order to suggest design modifications.

A third hypothetical study would allow children to use Cubes at home for a given amount of time. A parent survey would be used to assess how much time each child played with the Cube and what activities they completed. This test would gauge how much incentive a child needs to interact with the toy outside the classroom. CONCLUSIONS

Methods for teaching multiplication were studied and a toy called the Color Cross Cube was designed to teach multiplication mechanics to kinesthetic learners under the age of seven. The Cube incorporates pedagogical and entertaining features in order to teach through play. After existing educational toys were assessed, digital and physical models of the Cube were made and refined. The current Plexiglas model of the Cube is a fully-functioning, customizable device that may be improved in regards to ease of use, ease of storage, and modularity. The toy needs to be tested in order to assess its educational impact. ACKNOWLEDGEMENTS

The authors thank the VCU Honors College (Dr. Smith-Mason) for their support. Thanks also to Mr. Robert Honeycutt for help with the design prototype.

REFERENCES [1] Dabell J., 2002, “Raising Mathematical Achievement in the Teaching and Learning of Multiplication,” Mathematics in School, 31(1), pp. 22-27. [2] Vest, F. R., 1971, “A Catalog of Models for Multiplication and Division of Whole Numbers,” Educational Studies in Mathematics, 3(2), pp. 220-228. [3] Sherin, B., and Fuson, K., 2005, “Multiplication Strategies and the Appropriation of Computational Resources,” Journal for Research in Mathematics Education, 36(4), pp. 347-395. [4] Caron, T. A., 2007, “Learning Multiplication: The Easy Way,” Clearing House, 80(6), pp. 278-282. [5] Gierden, F., 2009, “More than multiplication in a 12x12 multiplication table,” International Journal Of Mathematical Education In Science & Technology, 40(5), pp. 662-669. [6] Suh, J. M., 2007, “Tying It All Together: Classroom Practices That Promote Mathematical Proficiency for All Students,” Teaching Children Mathematics, 14(3), pp. 163-169. [7] The Museum of Modern Art, 2012, “Century of the Child: Growing by Design 1900-2000,” from http://www.moma.org/interactives/exhibitions/2012/centuryofthechild/


[8] National-Louis University Archives and Special Collections, “Montessori Toys, 1914-1920,” from archon.ni.edu/archon.index.php?p=collections/controlcard&id=95 [9] Consortium of Academic and Research Libraries in Illinois, “Montessori Tower,” from http://collections.carli.illinois.edu/u?/nlu_kinder,527 [10] Infinitoy, “What is Zoob?,” from http://www.infinitoy.com/zoob/whatiszoob.shtml [11] Su, F. E., 2010, “Mudd Math Fun Facts: Visual Multiplication with Lines,” from http://www.math.hmc.edu/funfacts/ffiles/10006.1.shtml




MONITORING THE HEALTH OF A BEAM REMOTELY BY USING SCANNING LASER VIBROMETER

Hadi Fekrmandi Florida International University

Miami, Florida, USA

Javier Rojas Florida International University

Miami, Florida, USA

Michael Wolff Florida International University

Miami, Florida, USA Turkey

Ibrahim Nur Tansel Florida International University

Miami, Florida, USA

Sergio Gonzalez Florida International University

Miami, Florida, USA

Balemir URAGUN Unmanned Aircraft Design and

Development Space Technologies Research

Institute Ankara, Turkey

ABSTRACT The loading location estimation capability of the surface

response to excitation (SuRE) method was studied for a beam. Load was applied to different locations of a beam. The surface was excited with a piezoelectric element. A scanning laser vibrometer was used to monitor the surface response characteristics of the entire surface. These characteristics were presented with 2-D pseudo-colored plots. The study indicated that the surface response characteristics change with application of a significant load to a beam, and the sensitivity of the scanning laser vibrometer is satisfactory to monitor surface waves. These changes may be detected almost at the entire beam. The maximum change of the surface response characteristics is around the load application point. Various sensors may be used to detect load and to estimate its location.

INTRODUCTION The propagation of elastic surface guided waves on

structures has been studied extensively, and structural health monitoring (SHM) systems have been developed [1]. The majority of the studies used either the Lamb wave or impedance methods.

Surface guided waves (Lamb waves) are introduced to the structure through a piezoelectric actuator in the Lamb wave approach and their propagation is monitored at the same and/or additional point(s) via sensor(s). Structural problems are detected from the change of the characteristics of the monitored signals. Generally, development of additional wave patterns and their delay indicated defects and their locations. A comprehensive review of these methods is presented at reference [2]. This approach can be used for many structures, including very large ones, since the generated Lamb waves are

able to travel along the plates of many materials with very little attenuation [3-5]. However, the difficulty of sampling such a high speed wave action, of following multiple wave modes, and the complexity of wave propagation and reflections from boundaries create significant challenges for researchers [6].

The second major SHM approach is the impedance method [7]. This approach evaluates the impedance of a piezoelectric element attached to the surface of the structure. Experimental studies have shown that the impedance characteristics, within a carefully selected frequency range, change when various defects are created at the structure or when loading changes. Most of the researchers used an impedance analyzer, which automatically generates the signal and analyzes the collected data. Tansel et al. [8] developed the surface response to excitation method (SuRE) to evaluate the same characteristics by using a simpler experimental setup. The SuRE method uses a piezoelectric element to excite the surface, and the surface response is evaluated with a sensor. This sensor is generally a similar piezoelectric element. The impedance and SuRE methods calculate the sum of the squares of the differences of the real part of the impedance and magnitude of the transfer function respectively. The impedance method is more sensitive to the loading conditions compared to the Lamb wave and single piezoelectric element is used. Detection of a point load on the structure could be used for remote sensing of load imposed on the structure by bolts in the joints. Therefore the integrity of structural bolted joints could be examined using this method, and any possible loose components could be identified.

The SuRE method requires a separate sensor in addition to the piezoelectric actuator. Piezoelectric elements are cheap and their sensitivities are very high. However, it is not practical to attach tens of piezoelectric elements to a surface to evaluate the


surface response characteristics of many points. In this study, a scanning laser vibrometer was used to evaluate the surface response characteristics at a grid. Most researchers have used laser vibrometers for health monitoring by evaluating the modal parameters like mode shapes, natural frequencies and damping ratios [9-10]. Sharma [11] used the scanning laser vibrometer to get information to calculate the strain energy distribution for defect detection. Staszewski et al. [12-14] have used the laser vibrometer to capture the lamb waves to evaluate the integrity of an aluminum plate. Marterelli [15] also made important contribution to laser based scanning.

Time Reversal Acoustics (TRA) analysis is a new trend in SHM, which uses a set of sending and receiving acoustic transducers to detect defects. Fink [16] and Wu et al. [17] have discussed the TRA process. Sohn et al. [18] have implemented it for damage detection in composite plates.

THEORETICAL BACKGROUND The SuRE method [8] was developed for SHM

applications that do not use impedance analyzers by considering a similar trend by the major researchers [19-22]. One piezoelectric element excited the surface and another one monitored the vibration. The magnitude of the transfer function between the input and the output or the spectrum of the monitored signal was calculated. The magnitude and spectrum both captured the same characteristics of the structure. Depending on the condition of the structure and loading, some frequencies were transmitted better compare to the others. The sum of the squares of the differences of the magnitudes of the transfer functions were calculated to evaluate the structural integrity or changes at the loading conditions by using the following equation: 𝐸 = ∑ �𝑀𝑗,𝑖 − 𝑀𝑟,𝑖�

2𝑛𝑖=1 (1)

where Mj,I is the magnitude of the transfer function or spectrum of the jth data. It is compared with the magnitude of the reference signal represented by Mr,i. The magnitude of the transfer function was calculated at n different points on the surface of beam. In this equation the i is the index from 1 to n. The reference signal was taken at the beginning without any loading. In this study, only the loading was changed without introducing any defects to the beam. Theoretically, when there is no loading, the magnitude or the spectrum should be identical and the sum of the difference between the test cases and the reference (E) is zero. The magnitude of E is supposed to increase when load is applied.

EXPERIMENTAL SET UP The experimental set up is shown in figure 1. The

experimental setup was prepared to study the surface response of an aluminum plate when loads were applied to the different points of it while a piezoelectric element excited the surface.

An APC piezoelectric element with 0.75 inch diameter was

attached to an aluminum beam with 2” width, 1/32” thickness and 36” length (figure 2). LOCTITE Hysol Product E-30CL epoxy adhesive was used to attach the piezoelectric element to the aluminum beam. Two additional beams were prepared similarly by using aluminum beams with 1/16” and 1/8” thicknesses.

The aluminum beams were installed into the experimental setup presented in figure 3. The aluminum beam was hold in the frame. There were 10 bolts in the frame to apply load to the beam at the desired point(s).

A Polytec PSV-400 junction box generated the excitation signal. The sweep sine wave was generated in a 20-40 kHz frequency interval to keep the signal to noise ratio at a maximum. The signal was magnified by using a TEGAM power amplifier model 2348 to the 30 Vpp amplitude. The piezoelectric element was excited with the magnified signal.

The PSV-400 Polytec scanning laser vibrometer directed

the laser beam to the programmed grid points and measured the surface vibrations.

Figure 2. The aluminum beam with the attached piezoelectric element

Figure 1. Experimental set up including: laser head, junction box and control center, amplifier,

beam frame.


RESULTS The fundamental assumptions of the SuRE method and the

impedance method are similar. The impedance method assumes that real part of the impedance of any point on the structure within a carefully selected frequency range is like a finger print. For the SuRE method this is the magnitude of the transfer function or the spectrum of the monitored signal. This representative curve should be the same as long as the structural integrity or loading is not changed. The spectrum of the monitored signal without any change at the loading condition is presented in figure 4. The spectrum changed drastically when the load was applied in figure 5.

The effect of loading on the surface response of different

points distributed to the beam was studied by using the scanning laser vibrometer. The vibrations of 72 points located on a 3X24 grid were monitored automatically (Figure 6). As is shown in figure 6, the points on the piezo are deactivated, which means that laser vibrometer is not going to scan them. The reason is that the target structure to be scanned is the beam surface, and points on the piezo do not reflect the surface vibration of beam. For scanning any target it should always considered to eliminate scan points on the piezo element because, due to high noise existing on the piezo, including these spectrum in the post processing, these could lead to problematic results.

Figure 7 shows the results at three different loading

conditions. In each case the hot spot was just around the bolt which applied a force to the beam. The color map diagram shows the distribution of the normalized value of the sum of square of differences between the no load and loaded spectruma. Since the values are normalized, they don’t have any physical meaning. A force was applied to the left side, center and right side of the beam.

Figure 6. Scanning grid; blue is scan points, white is already scanned and brown is

deactivated points

Figure 5. Spectrums of a point on the grid before and after the load was applied

2 2.5 3 3.5 4x 104

0

2

4

6

8x 10-3

Frequency (Hz)

Mag

nitu

de (V

)

NoLoad vs Load

NoLoadLoad

Figure 4. The spectruma of a point on the grid for two successive no load scans

2 2.5 3 3.5 4x 104

0

2

4

6

8x 10-3

Frequency (Hz)

Mag

nitu

de (V

)

NoLoad vs NoLoad

NoLoad 1NoLoad 2

Figure 3. (a) Frame (b) Bolts to apply load to the beam


Similar results were obtained when the tests were repeated with three beams which have different thicknesses (1/8”, 1/16” and 1/32”). The thinner plate was affected the most, since the torque applied to the bolts was the same in all experiments. The hot spot most accurately identified the loading location for the thinnest plate.

CONCLUSION In this study, the loading location estimation accuracy of

the surface response to excitation (SuRE) method was studied. To evaluate the oscillations of the entire surface, a scanning laser vibrometer was used. The sum of the squares of the differences was calculated respect to references of 72 points on a 3X24 grid. The study indicated that the scanning laser vibrometer may be used for implementation of the SuRE method and that the location of the applied force on a plate may be detected.

Based on these results, the SuRE method may be used for remote sensing of structural problems and loose components. Based on the results of this paper about using multi sensing points to locate the structural defect, in cases where the location is not accessible or where it is not economically possible to implement the laser scanning vibrometer, the defect or loading location may be estimated by using the SuRE method if multiple piezoelectric elements are used for sensing.

REFERENCES [1] Raghavan, A., & Cesnik, C. E. (2007). Review of

guided-wave structural health monitoring. Shock and Vibration Digest, 39(2), 91-116.

[2] Su, Z., Ye, L., & Lu, Y. (2006). Guided Lamb waves for identification of damage in composite structures: A review. Journal of sound and vibration, 295(3), 753-780.

[3] Lee, B. C., & Staszewski, W. J. (2003). Modelling of Lamb waves for damage detection in metallic structures: Part I. Wave propagation. Smart Materials and Structures, 12(5), 804.

[4] Lee, B. C., & Staszewski, W. J. (2003). Modelling of Lamb waves for damage detection in metallic structures: Part II. Wave interactions with damage. Smart Materials and Structures, 12(5), 815.

[5] Staszewski, W., Boller, C., & Tomlinson, G. R. (Eds.). (2004). Health monitoring of aerospace structures: smart sensor technologies and signal processing. Wiley. com..

[6] Giurgiutiu, V., Bao, J., & Zhao, W. (2003). Piezoelectric wafer active sensor embedded ultrasonics in beams and plates. Experimental Mechanics, 43(4), 428-449.

[7] Park, G., Sohn, H., Farrar, C. R., & Inman, D. J. (2003). Overview of piezoelectric impedance-based health monitoring and path forward. Shock and Vibration Digest, 35(6), 451-464.

[8] Tansel, I. N., Singh, G., Korla, S., Grisso, B. L., Salvino, L. W., & Uragun, B. (2011, June). Monitoring the integrity of machine assemblies by using surface response to excitation (SuRE) approach. In Recent Advances in Space Technologies (RAST), 2011 5th International Conference on (pp. 64-67). IEEE.

Figure 7. Location of application of force on the plate and the variation of normalized sum of the

squares of the differences


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COBB COUNTY-MARIETTA WATER AUTHORITY PUMP STATION MAINTENANCE OPTIMIZATION PLAN

William Cline, Pranita Saraswatula, Kambui John, Adeel Khalid, Kamran Moghaddam Southern Polytechnic State University

Marietta, GA, USA

ABSTRACT In this project, a spreadsheet based decision support system

has been developed to estimate the operational costs, failure distribution parameters, and reliability requirements of equipment. The goal is to determine the optimal preventive maintenance and replacement schedule for a multi-component system over a long planning horizon. Maintenance, replacement, failure, and downtime costs are the necessary cost parameters that need to be input by the user. The system employs a mathematical programming software to minimize the total cost function while satisfying a threshold for system reliability resulting to the optimal decisions (do nothing, maintain, or replace) for each component in each period. To verify the accuracy of the model, a sample problem, with proven correct results, is solved and checked for validity. We use the developed decision support system to solve a real world application involving a pump assembly at Cobb County-Marietta Water Authority. The results serve as a recommended guideline for long-term pump maintenance and replacement actions. Sensitivity analyses are also performed on all types of cost parameters to capture the robustness of the method.

INTRODUCTION Cobb County-Marietta Water Authority (CCMWA)

provides clean water to customers in and around the Cobb County area. It was established in 1951 and became a political subdivision to the state of Georgia. Today, the water authority has two main water treatment plants located on either side of Cobb County. The James E. Quarles Water Treatment plant is located in East Cobb and serves much of that area as well as parts of North Fulton County. It was also the first water treatment plant built under the CCMWA. Quarles pulls its water from the Chattahoochee River and produces close to 86 million gallons of water a day. The Hugh A. Wyckoff Water Treatment Plant was built to serve West Cobb and most of Paulding County. Built in the 1960s, Wyckoff produces close to 72 million gallons of water per day and gets its water from Lake Allatoona. For this study, the water treatment process at the Quarles plant is taken into consideration.

Many of the high service water pumps in both the Quarles and Wyckoff Water Treatment Plant have been there since the late 1950s. Water pumps have high life expectancy, especially

many of the older models. These days most water pumps last for about 20 years before they start to break down. The Quarles Water Treatment Plant has five high service water pumps that pump water out to holding tanks. From the holding tanks, the water is released to customers on a need basis. Over the years, the manufacturers of the pumps have changed, so there is no uniformity amongst them to conduct proper efficiency studies. In 2005, Quarles placed two new high service pumps manufactured by Patterson to serve lines 1 and 5. Line 5 has a variable frequency drive (VFD), which controls the rate at which the water is pumped. Several parameters are continually used at both plants to test for defects in the pumps. Maintenance crews provide vibration testing, oil analyses, electrical work, using resistance temperature devices (RTDs) to confirm that the pumps are in good shape. There is daily maintenance on all the pumps and every six months the pumps go through vibration testing, which is conducted by an outside source. There are no more than 2-3 pumps running at the same time, and this allows the other pumps to be shut down and gone under maintenance. This project was defined to develop a maintenance and replacement schedule for the system as well as performing a cost analysis on their newly installed VFD.

The main objective of this project is to develop a mathematical model that optimizes a repair versus replace schedules for pump station equipment. The maintenance and replacement schedule provides a basis for when and what type of preventive maintenance actions should be performed. In addition to obtaining an optimal schedule, a MS-Excel based decision support system is developed that allows users to change cost and failure parameters to solve for similar systems. The justification for the study lies in management’s need for concrete replacement schedule guides for expensive equipment. CCMWA has spent countless dollars on repairing 60 plus year old equipment, adding up to much more than it would cost to replace with new. The study also provides a sensitivity analysis on the optimization model used to create a maintenance and replacement schedule for the CCMWA. The following system-level requirements are used to communicate what the system is expected to do at the end of the study. • The system shall output an optimal maintenance and

replacement schedule that minimizes total costs and achieves required reliability.


• The system shall output an expected cost for optimal solution over a long-term planning horizon.

• The system shall output sensitivity analysis results.

LITERATURE REVIEW In this section, we will briefly look at existing literature to

point out important factors and draw backs in each study. They will present a basis for this study and show patterns that have been in the industry regarding cost benefits. Cheng et al. [1] considered the cost and benefit of the VFDs placed on a pumping system in China’s Eastern Route Project. They divided the study up into several sections first starting with the optimal operation of the pumps. The objective function was to minimize the cost of daily electricity consumption to determine how much water was being pumped daily by minimizing total electric cost. The results from a non VFD pump and a VFD pump were compared and a dynamic programming model was also used to solve the optimal daily model. The authors also studied the different electricity costs based on the area to which the water was being pumped. The costs during different times of day were included in the study based on when the VFD was running the most. Overall, they found that there was almost a 14.01%-26.69% savings by using a VFD compared to a generic regular motor with no VFD.

Lingireddy and Wood [2] explored the economic and hydraulic benefits of using variable speed pumps to determine required or optimum pump speeds associated with energy savings. To carry out a cost analysis the authors used an electricity rate of 8 cents/kWh with pump efficiencies at 75%. This calculation was without the VFD and the total daily cost for the company would be $1,403. The analysis with the VFD produced results of $1,196, which means an energy savings of 15%. The paper further explains the benefit of having a VFD for leaks that occur. The authors also provide an optimized tank operation using the VFD pumps. They use genetic algorithms to compute optimal pump operating speeds that minimize the pump costs.

Shalaby et al. [3] developed an optimization model for preventive maintenance scheduling of multi-component and multi-state systems. They defined sequence of preventive maintenance activities as decision variables and the summation of preventive maintenance, minimal repair, and downtime costs as the objective function. In addition, they considered system reliability, minimum intervals between maintenance actions, and crew availability as the constraints into the model. Finally, a combination of genetic algorithm and simulation was utilized to optimize the model.

Another excellent study in this area is by Tam et al. [4] who developed three nonlinear optimization models: one that minimizes total cost subject to satisfying a required reliability, one that maximizes reliability at a given budget, and one that minimizes the expected total cost including expected breakdown outages cost and maintenance cost. They utilized MS-Excel Solver as the optimization software that uses a generalized reduced gradient algorithm to solve the nonlinear optimization models. Using these models, they could determine

optimal maintenance intervals for a multi-component system but their models consider only maintenance actions for components and do not consider replacement actions.

Moghaddam and Usher [5] presented a method for predicting the optimal preventive maintenance policy for a repairable and maintainable series system of components with an increasing rate of occurrence of failure (ROCOF). The authors developed mathematical models to minimize the total cost subject to achieving some minimal reliability and to maximize the total reliability of the system subject to a budgetary constraint. They utilized dynamic programming as the solution approach and showed the effectiveness of the approach through the use of a numerical example.

In another study Moghaddam and Usher [6] developed a new multi-objective optimization model to determine Pareto optimal solutions (trade-off curves) between the total cost and overall reliability in multi-component systems. Because of the complexity and highly nonlinear structure of the model, as well as the consideration of multiple objectives, they employed and analyzed the effectiveness of two heuristic solution methods, generational genetic algorithm and a simulated annealing with three different fitness functions.

DEVELOPMENT OF MATHEMATICAL MODEL The Excel-based decision support system developed in this

project uses mathematical programming model to optimize the scheduling plan for the water authority, while minimizing the total cost. This model may also be used for any multi-component system that needs a scheduling plan over a long planning horizon. A user can maintain, replace, or do nothing to the components based on the schedule output from the Excel application. Maintaining a component would require small fixes to the component whereas replacing would mean installing a completely new part. The age of the component drastically changes once it has been maintained or replaced, going back to either a percentage its original age or starting back at zero, respectively. The overall model will consider these factors to optimize the cost of the either maintaining or replacing a multi-component system. • Notation Parameters:

𝑁 = Number of components 𝑃 = Length of planning horizon

𝑇 = �1 if annual interval

2 if semi − annual interval4 if quarterly interval

�

𝜆𝑖 = scale parameter of component 𝑖 𝛽𝑖 = shape parameter of component 𝑖 𝛼𝑖 = improvement factor of component 𝑖 𝐹𝑖 = expected failure cost of component 𝑖 𝑀𝑖 = maintenance cost of component 𝑖 𝑅𝑖 = replacement cost of component 𝑖 𝑆𝐴𝑖 = starting age of component 𝑖 𝑍 = �ixed cost of system shutdown 𝑅𝑅 = required reliability of the system


Decision Variables: 𝑋𝑖,𝑗 = effective age of component 𝑖 at the start of period 𝑗 𝑌𝑖,𝑗 = effective age of component 𝑖 at the end of period 𝑗

mi,j = �1 if component i is maintained at period j0 if otherwise

�

𝑟𝑖,𝑗 = �1 if component 𝑖 is replaced at period 𝑗0 if otherwise

�

The above parameters and decision variables define the different parts of the objective function and constraints. The parameters are used for the inputs, while the decision variables are the outputs. The objective function builds off of the effective ages of the components based on whether they are maintained or replaced. Both the maintenance and replacement decision variables are binary, so they are represented with a 1 if true and a 0 if false.

For a general repairable multi-component system there are three different system results: maintain, replace, and do nothing. These results are based on the system configuration: series, parallel or k-out-of-n. For this particular problem, a series system is chosen, but the model can be changed at any time to reflect any system configuration changes. The reliability function and the objective function would change based on whether the user wants a parallel or k-out-of-n instead of a series system. Another important factor to consider before maintaining, replacing, or do nothing is the effective age of the component. All components start out with an age of zero when first placed in the system. As the years go by the components age as well, but the age of a component can be reset to zero or a smaller value by either maintenance or replacement. • Maintenance

There are several factors that go into calculating the maintenance aspect of the system. The reliability of the component, the maintenance cost, and the effective age of the component all affect how the maintenance is calculated. In the case of maintenance, the effective age of the component returns to a certain percentage of the original age. This action reduces the age of component i before the start of the next period j. Equation 1, demonstrates how the new effective age is changed by the improvement factor αi and the ending effective age of the current period.

𝑋𝑖,𝑗+1 = 𝛼𝑖 ∗ 𝑌𝑖,𝑗 (1)

The cost to maintain a system is simply the maintenance taken multiplied by the cost of maintenance. Mi, refers to the maintenance cost of a component i and it is enforced at the end of period j. • Replacement

The replacement action simply brings the effective age of a component back to zero. This option causes the system to act like new and failure rate of the system goes back to zero as well.

𝑋𝑖,𝑗+1 = 0 (2)

The replacement cost of a system is similar to the maintenance cost. Ri, denotes the replacement cost in the objective function and like the maintenance cost it is multiplied by the replacement action. This cost is also incurred at the end of period j and the cost of replacement is equal to the initial price of component i. • Do Nothing

This option makes no changes to the system of components. There is no effect on the system and therefore the system continues to age at certain rate. The effective age and failure rate of component i will continue to increase and by the end of a given period j the system will completely fail. The following equations reflect the effect that the do-nothing option has on the system:

𝑌𝑖,𝑗 = 𝑋𝑖,𝑗 + 1𝑇 (3)

𝑋𝑖,𝑗+1 = 𝑌𝑖,𝑗 (4) • Failure Cost

The components in the given system will always continually fail. The maintenance and replacement actions only delay the failure rate of the component or they set the failure rate back to zero. Regardless of when the system fails there is a cost associated with it failing. Even though the components may be maintained or replaced, there is no guarantee that they will not sporadically fail. The failure cost that is defined in the objective function by Fi, takes into the account that the system can fail at any given time. This unexpected failure cost may be a predetermined average of previous failure costs. • Fixed Shutdown Cost

Any system that is working in series that needs either maintenance or replacement requires that the whole system be shut down. For parallel or k-out-of-n configurations this may not be the case. In a parallel system even if there is one component shut down so that it can be maintained or replaced, the other components in the system can continue to work. In a k-out-of-n system depending on the configuration of the system the same case holds true. In both those scenarios there is no cost incurred from shutting down the system. For a system in a series configuration there will be a fixed shutdown cost. If one component fails, the entire system has to be shut down to maintain or replace that particular component. The cost for shutting down that system because of lost revenue or any other factor associated has to be included in the overall objective function. • Mathematical Model

Minimize Cost = ∑ ∑ �𝐹𝑖 ∗ 𝜆𝑖 ��𝑌𝑖,𝑗�𝛽𝑖 − �𝑋𝑖,𝑗�

𝛽𝑖� +𝑃∗𝑇𝑗=1

𝑁𝑖=1

𝑀𝑖 ∗ 𝑚𝑖,𝑗 + 𝑅𝑖 ∗ 𝑟𝑖,𝑗� + ∑ �𝑍�1 −∏ (1− (𝑚𝑖,𝑗 + 𝑟𝑖,𝑗))𝑁𝑖=1 ��𝑃∗𝑇

𝑗=1 (5)

Subject to: 𝑋𝑖,1 = 𝑆𝐴𝑖 ∀𝑖 (6)

𝑋𝑖,𝑗 = �1 −𝑚𝑖,𝑗−1��1 − 𝑟𝑖,𝑗−1� ∗ 𝑌𝑖,(𝑗−1) + 𝑚𝑖,𝑗−1�𝛼𝑖 ∗ 𝑌𝑖,𝑗−1) ∀𝑖,∀𝑗 (7)


𝑌𝑖,𝑗 = 𝑋𝑖,𝑗 + �1𝑇� ∀𝑖,∀𝑗 (8)

𝑚𝑖,𝑗 + 𝑟𝑖,𝑗 ≤ 1 ∀𝑖,∀𝑗 (9)

∏ ∏ 𝑒−�𝜆𝑖��𝑌𝑖,𝑗�𝛽𝑖−�𝑋𝑖,𝑗�

𝛽𝑖��𝑃∗𝑇𝑗=1

𝑁𝑖=1 ≥ 𝑅𝑅 (10)

𝐵𝐼𝑁𝐴𝑅𝑌�𝑚𝑖,𝑗 , 𝑟𝑖,𝑗� (11) 𝑋𝑖,𝑗,𝑌𝑖,𝑗 ≥ 0 (12)

Equation 5 is the objective function to minimize the total

cost of failure, maintenance, replacement, and shutdown of the system. It is subject to several constraints including effective age constraints and system reliability requirement. Equation 6 sets the decision variable Xi,j to the parameter of the starting age of the component i. Equation 7 calculates the effective age of components depending on which action was taken in the previous period. If a component was replaced in the previous period then 𝑟𝑖,𝑗−1 = 1,𝑚𝑖,𝑗−1 = 0, so that its next effective age drops down to 𝑋𝑖,𝑗 = 0, if a component is minimally repaired then 𝑟𝑖,𝑗−1 = 0,𝑚𝑖,𝑗−1 = 1 and its effective age becomes 𝑋𝑖,𝑗 = 𝛼𝑖 ∗ 𝑌𝑖,𝑗−1. Finally if no action was taken 𝑟𝑖,𝑗−1 =0,𝑚𝑖,𝑗−1 = 0, the component continues its normal aging as 𝑋𝑖,𝑗 = 𝑌𝑖,𝑗−1.

Equation 8 states that the ending effective age of the component is equal to the beginning effective age plus the period length. This resets the new effective age to equal Yi,j, which was the previous ending effective age. Equation 9 forces the mathematical model that either maintenance or replacement action should be carried out for each component in each period. Equation 10 insures that the optimal schedule provides a specified reliability requirement. It is over the components 1 to N and starts from period 1 and goes to periods P*T. P*T defines the number of periods for the system as well as the number of intervals (annually, semi-annually, and quarterly). The maintenance and replacement decision variables are binary variables presented in equation 11. The last constraint, equation 12 ensures that all effective age decision variables are positive by limiting the beginning effective age and ending effective age to be greater than or equal to zero.

EXCEL BASED DECISION SUPPORT SYSTEM The Excel-based decision support system for this study

was built through several stages. It required extensive knowledge of VBA, LINGO, and Excel and how the three pieces interact with each other. To create the decision support system, first the project was started with a basic excel sheet and added UserForms and ActiveX controls to navigate the program. Behind the user interface is layers of VBA code embedded in each worksheet and UserForm. The Excel application is required to communicate with LINGO, where the mathematical computation takes place. To do so, a native Microsoft function called Object Linking and Embedding (OLE) is used in the LINGO code. This OLE function gives LINGO the ability to receive data (inputs) from the Excel file and also output the optimal solution to Excel. Within LINGO, a coding language is used to convert the algebraic mathematical

model into executable code. To automate the decision support system, the authors embedded the LINGO code into a range in Excel named “Model”.

Figures 1 and 2 represent the back end processes for the Excel-based decision support system. Figure 1 shows the overall structure and flow of these processes from the user to how it is performed by the Excel application. The user can view the application on the monitor and from there the CPU (Central Processing Unit) takes over. The CPU “talks” to both Microsoft Excel and LINGO software and then displays the results on the monitor, which the user can view.

Figure 1. Structure of the decision support system

Excel has several components that cause the application to run. Using a programming language called Visual Basic for Applications (VBA), a code is developed to work with LINGO to solve the optimization problem. The Excel application has several screens that the user has to go through. The first screen to come up when the user opens the program is the Welcome Screen; on that page the user has the option to learn more about the mathematical model used to optimize the schedule. From the Welcome Screen the user is taken to an input form where he/she inputs information on the number of components, planning horizon, etc. From there the user is directed to the Failure Parameter Screen where he/she is given the option to input any failure parameters he/she may have. That screen feeds into the Cost Input Screen where any costs relating to the system are entered. From there Excel works with LINGO to solve the problem and an Output Screen is displayed with a Report Options page. There are four different report options: View Schedule, Reliability vs. Time, Cost vs. Time, and the Total Cost. During this entire process, LINGO is working in the background gathering information and outputting information all the way from the Input Form to the Output Screen.

Figure 2 shows how the Excel application follows the processes from the start page to the ending screens. It also starts with the Welcome Screen which then flows into two options of the Model Info Screen or the Input Form. The Model Info


Screen has the option to go back to the Welcome Screen whereas the Input Form does not. The Input Form feeds directly into the Failure Parameter Calculator page, and from there it navigates to the Cost Input Screen. At this point the user selects the option to solve the model and LINGO is put to work in the background. Finally LINGO reports the results onto the Output Screen that has several report options. At this point, the user can View Schedule, view the Reliability vs. Time graph, view the Cost vs. Time graph, and see a display of the Total Cost.

Figure 2. Layout of the decision support system

APPLYING THE MODEL To solve a real world application with the previously

explained mathematical model, we look at the situation of Cobb County Marietta Water Authority’s large equipment replacement policy. Currently, the organization chooses to replace equipment only after an irreparable failure. This policy will always seem to be the most cost effective in the short run, but it does not take into account the costs incurred over a long planning horizon. To find this optimal “long term” policy, we applied the optimization model using the developed Excel-based decision support system. To test the robustness of the system, and to show the importance of the data gathering phase, a sensitivity analysis is performed on several associated costs of the equipment and other variables.

The problem is introduced as the Water Authority Management’s need of concrete support for major equipment replacement. The current strategy consists of waiting until the component fails and then replacing it. The consequence of following this plan is spending hundreds of thousands of dollars maintaining a piece of equipment that is deteriorating exponentially. The focus of this study is on three separate components, a motor, pump, and ball valve, in series configuration and located in the High Service Pump Station of the Quarles Water Treatment Plant. The three components listed previously are referred to as a Pump Unit for the remainder of this report to avoid repetition. These pieces of equipment play a small, but essential role in the overall system. It is important to note here that there are five separate sets of Pump Units, within the High Service Pump Station, working in parallel for redundancy. In addition, a planning horizon of 60 years is selected based on the fact that it is long enough to include the typical replacement period of all components and it is not too long that accuracy is compromised.

• Maintenance and replacement costs Maintenance and replacement costs for the pump of

interest are the first costs the team identifies. The focus of this report is on Pump Unit 1 out of 5, but the model can be scaled out to solve for any other components given that the required data is available. Pump 1 is built by Patterson Pumps ® and is capable of pumping 25 million gallons per day. According to records, a complete refurbishment is performed on the pump about every 15 years. The refurbishment consists of a dynamic balance and replacing shaft sleeves, bearings, and wear rings. Table 1 shows the costs associated with each of these tasks.

Table 1. Pump refurbishment costs Task Cost

Dynamic Balance $300.00 Shaft Sleeves $4,000.00 Bearings $2,000.00 Wear Rings $7,500.00 Total $13,800.00

In addition to the motor refurbishments, the pump also has

mechanical seals that are typically replaced every 10 years at a cost of $10,000. To be consistent, it is necessary to normalize all maintenance costs to the same maintenance interval. For this problem, we choose the refurbishment period of the motor, which is 9 years. To find the 9-year cost of the pump maintenance, the total refurbishment cost is multiplied by (9/15). Similarly, the cost of mechanical seal is multiplied by (9/10). Dynamic balancing tests and priming chamber seal replacements are performed every 5 years at a cost of $700. The total of all these costs equates to the maintenance cost of the pump to be used in the mathematical model and is shown in equation 13.

𝑀𝑎𝑖𝑛𝑡𝑒𝑛𝑎𝑛𝑐𝑒 𝐶𝑜𝑠𝑡𝑃𝑢𝑚𝑝 = $13,800 ∗ (9/15) + $10,000 ∗ (9/10) + $700 ∗ (9/5) = $18,540 (13)

The cost to replace the pump with a similar capacity pump made by Patterson® is about $180,000. Next, similar data for the motor of interest is found. Pump Unit 1’s motor is a 2,250 horsepower electric horizontal motor manufactured by General Electric®. The maintenance costs are all normalized to the motor’s 9 year refurbishment period; therefore the costs associated with its refurbishment are not changed. During this period, all bearings and oil seals are replaced, and windings are cleaned, re-dipped, and baked for a total cost of about $18,000. Similar to the Patterson® pump, the motor has mechanical seals that are replaced about every 10 years for roughly $5,000. Also, an independent third party company performs vibration testing on the motor every year at a cost of $750 each. Equation 14 demonstrates the total maintenance cost of the motor. The 2,250 horsepower GE motor can be replaced at a cost of roughly $100,000.

𝑀𝑎𝑖𝑛𝑡𝑒𝑛𝑎𝑛𝑐𝑒 𝐶𝑜𝑠𝑡𝑀𝑜𝑡𝑜𝑟 = $18,000 ∗ �99�+ $5,000(9/

10) + $750(9/1) = $29,250 (14)


Due to technical reasons, the maintenance schedule for the 16 inch Golden Anderson® Ball Valve was found to be quite different from the other two components. Unlike the pump and motor, the ball valves do not undergo refurbishments. Historical data shows the individual parts that make up the valve have a useful life about the same as the valve as a whole. To replace the ball valve, the Authority expects to pay about $28,000 for a 16 inch Golden Anderson®. • Failure Cost

Determining failure costs requires an understanding of the system of interest and the role it plays in the overall system. In many systems, a manufacturing system for instance, a failing piece of equipment incurs expenses other than the cost to simply replace the failed equipment. These incurred expenses can include production loss, damaged products, cleanup costs, and many other unforeseen costs. Failure cost is often difficult to estimate because it is frequently unclear what side effects come with a failed component. In the Water Authority case, the failure cost is equal to the cost of replacement for reasons introduced previously. Because CCMWA provides a necessity for the public, it is vital the water is available at all times. This is the reason for the redundancy built into the Quarles Water Treatment Plant. If one of the Pump Units fails, the operators simply switch the demand on any of the backup Pump Units resulting in zero productivity loss. Also, the ability of the operators to immediately shut off any Pump Unit line from a remote control room means the failure will not incur any other expenses, such as clean up or other damages costs. This leaves us with the assumption that the failure cost of any of the three components in Pump Unit 1 is equal to the replacement cost. • Failure Data

In practice, it is common to associate equipment failure data with the Weibull Distribution. Previous studies suggest almost all equipment failures follow this particular distribution. Using the Weibull curve to represent the equipment’s likelihood of failure requires the estimation of two parameters: the characteristic life (scale) and the shape parameters. To estimate these parameters, the team first determines the Mean Time to Failure (MTTF) and Standard Deviation of that failure for each component. Searching manufacturer O&M Manuals for useful life estimations and considering expert advice from CCMWA’s employees provides acceptable values for these two parameters. Table 2 shows the initial values for each of the components’ MTTF and standard deviation.

Table 2. Component MTTF and standard deviation Component MTTF

(years) Standard Deviation

(years) Motor 40 8 Pump 30 5

Ball Valve 30 6

After obtaining these values, the scale and shape parameters of each is calculated for the Weibull Distribution using the following equations 15 and 16.

𝑀𝑇𝑇𝐹 = 𝜃 ∗ Γ�1 + �1𝛽�� (15)

𝜎2 = 𝜃2 ∗ �Γ �1 + �2𝛽�� − �Γ �1 + �1

𝛽��

2

� (16)

Table 3 depicts the values for scale and shape, θ and β respectively, after solving using the above relationships.

Table 3. Component scale and shape parameters of Weibull distribution

Component Scale (θ) Shape (β) Motor 43.19 5.79 Pump 32.06 7.06

Ball Valve 32.40 5.79

The Weibull Distribution is a good representation of non-repairable systems; however, it does not accurately depict the distribution of repairable equipment. Therefore, this distribution is sufficient for the period between preventive maintenance events (refurbishments or replacements), but requires another distribution to account for the event period. The Non-Homogeneous Poisson Process (NHPP) is a transformation of the Weibull Distribution used for repairable systems. To convert the Weibull scale and shape parameters to NHPP parameters, the following equations, 17 and 18, are used.

𝜆𝑁𝐻𝑃𝑃 = ( 𝛽𝑤𝑒𝑖𝑏𝑢𝑙𝑙𝜃𝑤𝑒𝑖𝑏𝑢𝑙𝑙

𝛽𝑤𝑒𝑖𝑏𝑢𝑙𝑙) (17)

𝛽𝑁𝐻𝑃𝑃 = 𝛽𝑤𝑒𝑖𝑏𝑢𝑙𝑙 − 1 (18) Table 4 gives the parameters converted to NHPP. These are the scale and shape values used to solve the model.

Table 4. Component scale and shape parameters of NHPP

Component Scale (λ) Shape (β) Motor 1.91E-09 4.79 Pump 1.64E-10 6.06

Ball Valve 1.01E-08 4.79

When determining an acceptable reliability, the length of the planning horizon and the application and configuration of the components in question must be taken into account. As mentioned in the Failure Cost section, the service provided by CCMWA is a basic need for the citizens of Cobb and surrounding counties; therefore, a high reliability of the High Service Pump Station is vital. The built-in redundancy takes some of the high level reliability requirement off each individual Pump Unit and distributes it over the others. To achieve 99% reliability, over the 60-year planning horizon, we must achieve a reliability of 0.999833 for each year. Required Reliability (RR) in the equation 19 is the reliability constraint used in the CCMWA application of the model.

0.999833 = 1 − (1 − 𝑅𝑅)5 → 𝑅𝑅 = 0.824392 (19)


This requirement indicates that the Pump Unit 1, as a whole, must maintain reliability above 0.83 for the length of the planning horizon. The configuration of each Pump Unit is series, thus,

𝑅𝑀𝑜𝑡𝑜𝑟 ∗ 𝑅𝑃𝑢𝑚𝑝 ∗ 𝑅𝑉𝑎𝑙𝑣𝑒 ≥ 𝑅𝑅 (20)

• Other Assumptions To input all necessary parameters, we were forced to make

a few assumptions based on the characteristics of the system. The first assumption is to input a high maintenance cost for the ball valve component. Since a complete refurbishment is impractical on this particular component, a cost is selected that ensures the mathematical model will not select to perform this type of preventive maintenance. The maintenance cost of the ball valve is set to $999,999.

The shutdown cost of the system is incurred each time the Pump Unit 1 line is forced to be shut down, whether it be for maintenance or replacement. To find an appropriate shut down cost, the team looks at the process of performing preventive maintenance on any of the three components. Since the components are in series, to shut down one, the remaining two must also be shut down. In most cases, and in this case, it is beneficial to perform preventive maintenance on all three while the system is already shut down instead of shutting down the line three different times. To ensure the preventive maintenance of each component lines up within the same period as the other two, a relatively high shutdown cost of $500,000 is assumed.

The final assumption is that of the effect each maintenance activity has on the effective age of the component. To avoid making an uneducated guess, the cost of the maintenance relative to the cost of replacement is used as an indicator of the effect the maintenance activity has on the component and can be seen in the equation 21.

𝛼 = �𝐶𝑅𝑒𝑝.−𝐶𝑀𝑎𝑖𝑛𝑡.𝐶𝑅𝑒𝑝.

� (21)

With this equation, the higher the cost of the maintenance performed, the more it affects the age of the component. Table 5 shows the calculated alpha values for each component.

Table 5. Component improvemnet factor values Component Improvement factor (α)

Motor 0.29 Pump 0.10

Ball Valve 35.71

• Optimal Maintenance and Schedule For the Water Authority application, the model

recommends a replacement of the motor and ball valve and a refurbishment of the pump in year 24. While the system calls for actions to be taken in period (year) 24, we know it does not take the entire year to perform these actions. To refurbish the pump and replace the motor and ball valve it takes the CCMWA maintenance staff, working with outside crews, a month at longest. The actual month the Water Authority chooses to perform this preventive maintenance may depend on their fiscal budget or other management concerns. Figure 3 shows the optimal preventive maintenance schedule for Pump Unit 1 with

a total expected cost of $1,239,088.12 for following this preventive maintenance schedule. This number is the expected cost of maintaining all three components for the 60 year planning horizon.

Figure 3. CCMWA Optimal Maintenance Schedule

Besides the schedule, the decision support system allows users to view other useful information regarding the three components. By clicking the “Reliability vs. Time” button, a table displaying the reliability of each component in each period is formed. Figure 4 shows the reliability of the system, as a whole over the 60 years.

Figure 4. CCMWA overall reliability per year

The overall reliability of the system never drops below the 83% reliability requirement over the entire run. Where the first round of preventive maintenance was performed is distinct, at 24 years, and, slightly less distinct, is the second round at 39 years. The first round is much more visible because both the motor and the ball valve are replaced in this period, whereas only the ball valve is replaced in year 39. At the end of the 60 years, the reliability is hovering just above the 83% mark. Selecting the “Cost vs. Time” button on the main schedule page takes users to a page displaying the cumulative cost and the cost per period of the three components over the 60 year period. Figures 5 and 6 show the CCMWA cost analysis outputs.

As shown in figures 5 and 6, the Water Authority can expect two large expenditures in years 24 and 39 following the recommended schedule. Management can use this graph to show the Budget Committee when larger fiscal budgets are necessary. These three outputs (the schedule, reliability graph, and cost graphs) are performed by the Excel application. It is important to note that these outputs are meant to be strictly decision support material. The system reliability and cost


values are used and, when plotted on a scatter plot, show the cost of a less reliable system as plotted in Figure 7. It is inferred that as the reliability of the system decreases, the cost will increase. The sharp decline in cost falls between 90% and 93% reliability. This indicates that as the system approaches the reliability range below 90%, a major preventive maintenance overhaul is recommended.

Figure 5. CCMWA total cost per year

Figure 6. CCMWA Ccumulative cost per year

Figure 7. CCMWA Cost vs. Reliability

CONCLUSION AND FUTURE EXTENSIONS The purpose of applying this optimization model to Cobb

County-Marietta Water Authority’s Quarles High Service Pump Unit 1 is to determine a mathematically optimal preventive maintenance schedule. It is recommended to replace the motor and ball valve after 24 years of service, and the ball valve once again during the 39th year. It is not cost effective to replace the pump in the 60 year run because it has such a low failure rate. Also playing into the decision not to replace the pump is the effect a refurbishment has on the component. As mentioned

earlier, performing a refurbishment returns the pump back to an effective age equal to just 10% of the actual age. This means the overhaul greatly affects the condition of the pump.

A complete understanding of the system is vital when interpreting the results and using the output for decision making. For instance, Water Authority employees indicated there is not actually a cost associated with shutting down Pump Unit 1, but the team selected to set the shutdown cost to $500,000. As explained earlier, this was simply done because there is, in fact, value in performing all preventive maintenance tasks at the same time. The output of the Excel application does not take this into account when displaying the System Cost vs. Time information. Therefore, the authors used the raw output data and modified it slightly by subtracting $500,000 incurred shutdown cost. As a result CCMWA Management can expect to spend over $140,000 in year 24 and almost $80,000 in year 39, as opposed to the original output values of over $600,000 and $500,000 respectively. With this in mind, the total cumulative cost over the 60 year planning horizon is equal to the output of Excel minus the two shutdowns’ costs.

It is essential that the optimal mathematical solution is treated as decision support only. CCMWA Managers are also recommended to use their own experience, in conjunction with the output schedule, when selecting actual refurbishment and replacement periods of the components. It is mathematically cost effective to select the preventive maintenance periods shown in Figure 3, but other factors may play a role in determining the actual optimal schedule. Such factors include new technology, abnormal wear, or any other unforeseen circumstances.

REFERENCES [1] Cheng, J., Zhang, L., Zhang, R., Gong, Y., Zhu, H., Deng, D., Feng, X., Qiu, X., 2009, “Optimal Operation of Variable Speed Pumping System in China’s Eastern Route Project of S-to-N Water Diversion Project”, American Institute of Physics Conference Proceedings 1225, pp. 169-175. [2] Lingireddy, S., Wood, D.J., 1998, “Improved Operation of Water Distribution Systems Using Variable-Speed Pumps”, Journal of Energy Engineering, Vol. 124, No. 3, pp. 90-103. [3] Shalaby, M.A., Gomaa, A.H., Mohib, A.M., 2004, “A Genetic Algorithm for Preventive Maintenance Scheduling in a Multiunit Multistate System”, Journal of Engineering and Applied Science, Vol. 51, No. 4, pp. 795-811. [4] Tam, A.S.B., Chan, W.M., Price, J.W.H., 2006, “Optimal Maintenance Intervals for Multi-Component System”, Production Planning and Control, Vol. 17, No. 8, pp 769-779. [5] Moghaddam, K.S., Usher, J.S., 2011a, “Preventive Maintenance and Replacement Scheduling for Repairable and Maintainable Systems using Dynamic Programming”, Computers and Industrial Engineering, Vol. 60, No. 4, pp. 654-665. [6] Moghaddam, K.S., Usher, J.S., 2011b. “A New Multi-Objective Optimization Model for Preventive Maintenance and Replacement Scheduling of Multi-Component Systems”, Engineering Optimization, Vol. 43, No. 7, pp. 701-719.




CONCEPT REVIEW OF THE PARAMETERS AS RELATED TO THE GREEN ASPECTS OF ELEVATORS IN DECISION-MAKING PROCESS

Magdalena Krstanoski Ss. Cyril and Methodius University Faculty of Mechanical Engineering

Skopje, Macedonia

ABSTRACT In recent years it is observed that the growing interest in

sustainability is more evident and becoming an important part of the building industry. Recognizing the importance of sustainability, demands for green products are expected to increase, and so exploring for possibilities that may contribute to a product or project to become green. Buildings generate demand for vertical transportation solutions. The idea of this paper is to provide a basic overview about some current green movements as related to the sustainability and vertical transportation. These will serve as background information, for future research work towards efforts to implement green strategies. In addition we make a parallel observe the current challenges in Macedonia in identifying green aspects, some of the initiatives, and we underline opportunities and challenges to explore the paths to increase the attention, and to generate future action on the subject. This study gives an overview of the attributes that may be beneficial decision-making factors when studing an elevator for possible sustainable, green features. With an overview of the current sustainability benefits, and possible steps to identify opportunities for the future, this paper explores what may be potential impacts of the green requirements, and potential performance metrics, by utilizing Strengths, Weaknesses, Opportunities and Threats analysis.

INTRODUCTION The motivation to conduct this on-going research is the

increased sustainability interest, energy preservation subject, and green orientation, not only when discussing products, manufacturing processes, but also in construction and building systems, which elevators are part of. As the elevators in Macedonia are still hardly getting any attention in respect to the green aspects and energy efficiency, the idea was to search for a comprehensive database of elevators that are installed and operating in the country. Using that, the idea was to investigate what may be possible challenges to introduce the sustainability concept, as related to some of the current green building

movement initiatives. As that information was not obtained at the time of preparing this paper, this work may further serve as a baseline for further research into means and methods to formulate the best available approach to implement green orientation, and to implement strategies in the conveying systems field in the countries that experience similar situation in the region, and beyond. This is a work in-progress study. Data have been observed over a period of time, and some of the data need to be revisited again in the future.

With the development of carbon footprint awareness, renewable energy initiatives, and rise of the electrical energy cost, sustainability and energy efficiency is another subject that requires further attention. Having that in mind, sustainability, and energy efficiency will continue to be important areas in the planning processes, seeking for more questions about the products to be observed, and seeking overall to address the green aspects of vertical transportation.

As the technology is changing fast, green is becoming more than a trend. Demand for sustainability is growing in many areas. Buildings generate demand for transportation. Buildings in general, and particularly high rise buildings, cannot be viewed separately without including efficient solutions for vertical transportation. While green building focuses on aspects of the building construction and building services, it is not going to be complete if the vertical transportation communication is not part of it. Building up, considers not only the cost of the material, installation and labor costs, but the energy cost, as well. Selection of the conveying system equipment is an important decision from many perspectives, including planning considerations, and decisions on factors, such as good elevator service – the two major performance requirements (quality and quantity of service) and sustainability aspects. Conveying systems take approximately 10% of all building construction cost [9], and depending on the number of floors in the office building, the cost of the elevator work for a 20 story office building may take


from 10.9%, and reach up to 12.2% for a 60 story office building [9].

In this study Strengths, Weaknesses, Opportunities & Threats are analyzed when considering sustainability and green vertical transportation solution. This concept study is looking from a general perspective and attempts to address some major challenges via initiating some related questions. Analyzing green aspects of the elevators can be viewed as an integrated process in all phases of the facility life cycle, not only as an individual phase.

The CSI Project Delivery Practice Guide [1], describes

facility life cycle organized in the following phases: Project conception, Project delivery, Design (Schematic Design, Design Development), Construction Documents, Procurement (Bidding/Negotiating/Purchasing), Construction, and Facility Management [1]. In general, project phases often are described in these areas: Project conception, Schematic design, Design development, Construction documents development, Procurement, Construction, Close-out and Occupancy. Sustainability discussions have been related to the project concept idea, design, construction, and post occupancy (operation) period, where all relevant players involved in the project, aiming for sustainability, put their skills into the project.

CONCEPT OF SUSTAINABILITY AND BASIC OVERVIEW

Observing an increased demand for sustainability and green product orientation in almost every aspect of the industry, together with green and an efficient solution aspects, the sustainability concept develops as an integrative process involving communication among all involved in the project together, throughout the entire building life cycle. Sustainability is not only related to the materials and resources, water conservation, waste reduction, indoor environmental quality, energy efficiency, renewable energy, sustainable sites, but also, expands into productivity in the work place or study, introduction of incentives, and social impacts such as job creation, market competition, and the economy.

Founded in 1993[2] USGBC (Abbrev. U.S. Green Building

Council) had a mission to promote sustainability in the building and construction industry. Seven years later in 2000 it developed the LEED (Abbrev. Leadership in Energy and Environmental Design) Green Building Rating System[2], with the “triple bottom line” approach (defined by John Elkington (1994))[11]. It addressed equally the three dimensions: social aspects (people), economic prosperity (profit), and the environment (planet). Introduced in 2007, GBCI (Abbrev. The Green Building Certification Institute) administers the LEED accreditation program, administers third-party LEED project certification, and professional credentials [11].

Energy and identifying energy efficient solutions have become the major priority in the recent years. Several areas have been drivers in that respect: reducing the energy demand by different measures, such as monitoring and verification of the energy consumption, developing and defining performance indicators and strategies to identify opportunities for energy savings, ongoing energy performance by tracking the energy consumption, measuring and verification of the same after construction is completed, ensuring that a building meets or exceeds the design intent, and exploring renewable energy solutions such as: solar, wind, wave, biomass, hydro, geothermal.

LEED recognizes two types of energy: regulated (ex.

lighting, HVAC, and service water heating) and processed (ex. office equipment, computers, kitchen equipment – cooking and refrigeration, washing and drying, water features)[11]. In addition, elevators and escalators are considered to be processed energy, and are not subject to the minimum LEED performance requirements [11].

As the most widespread in United States, LEED and Green

Globes rating systems are most present in North America. In Europe, founded in 1990[5] the preeminent place goes to the UK’s BREEAM (Abbrev. Building Research Establishment Environmental Assessment Method) rating system. However, both LEED and BREEAM are worldwide presences and expanding, and LEED is gaining popularity in Europe, depending on the client’s preferences.

On the other side of the Atlantic, The European

Commission’s The Europe 2020 Strategy [3] launched in 2010 as a strategy for the next ten years for economic prosperity, addresses two major objectives in Europe by 2020. It stresses important indicators for climate and energy, and their relationship with the climate change, sustainability, low carbon, energy efficiency, renewable energy, economy and job creation. The Europe 2020 Strategy, or 20-20-20, sets an objective to increase energy efficiency by 20% by 2020, to reduce greenhouse gas (GHG) emissions by 20%, and to produce 20% of energy consumption from renewable energy sources (RES)[3]. In compliance with the European strategy and methodology, Macedonia sets a target on national renewable sources (RES) share in 2020 at 20.5% (rounded at 21%) [26].

In general, buildings are responsible for 40% of the total

energy consumption and are primary contributors to greenhouse gas emissions with 36% of total CO2 gas emissions in the EU[4]. The Directive 2002/91/EC of the European Parliament and of the Council of 16 December 2002 on the energy performance of buildings[22], discusses energy performance in building systems, setting energy performance requirements, introducing energy performance certificates, and enhancing of overall energy performance in new, and existing buildings as related to the air conditioning, water heating equipment


(boilers). Article 7 of the Directive addresses energy performance certificates for buildings and related items, among other includes: validity, recommendations, including references such as applicable standards and benchmarks, and placement of the same. However, this Directive does not address conveying systems in the overall energy consideration.

The Energy Performance of Buildings Directive - Directive

2010/31/EU of the European Parliament and of the Council of 19 May 2010 [6], supersedes the Directive 2002/91/EC, and, although it discusses the need for measures to further improve the energy efficiency in buildings, minimum program requirements for energy performance of buildings and bases to be calculated, energy performance certification of buildings, etc., it again does not address conveying systems in the energy consideration.

Later, ISO/TC178 working group experts developed ISO

25745-1:2012 Energy performance of elevators, escalators and moving walks, addressing measuring of the energy consumption and verification of the energy performance.

On the other hand, in 2009 The Association of German

Engineers VDI on its VDI 4707 guidelines, addresses energy consumption and introduced the first elevator classification method, energy assessment and labeling, as related to their energy performance; it introduced seven classifications from A through G, and measures referring to elevator installation cases. The guideline analyzes two types of energy consumption (stand-by and running)[13] to serve as a voluntary tool for construction industry, elevator market, consultants and building owners.

ELEVATORS AND LEED

Conveying systems, herein including elevators, escalators and moving walks represent from 3% to 8% of total energy building consumption [7], about 5% of building electricity use [10] in North America office buildings. Depending on the building type, number of elevators, and type of conveying system, may represent up to 10% of the total building energy consumption.

Commercial and industrial buildings in the U.S. are

responsible for nearly half of the U.S. energy use, and 40 % of carbon emissions. [8]

With increasing numbers of green buildings in the world,

LEED and green are gaining popularity across the globe. Although the U.S. leads the world in the number of certified buildings, (44,998 registered and certified LEED projects in North America)[12], only 1,706 green buildings are in Europe, and this shows the tremendous potential growth of the green building movement beyond North America[12].

Being considered processed energy, although not subject to the minimum LEED performance requirements, over the period of time, it is observed that elevators may possibly contribute in a few LEED areas, again depending on the project requirements, project location, installation methods, equipment, and the intent of the prerequisites and credits, per project bases, as following:

a. Materials and Resources (MR) – credit MRc7: Certified Wood (use of wood-based materials and products that are certified according to the Forest Stewardship Council’s (FSC) principles and criteria);

b. Indoor Environmental Quality (EQ) – credit EQc4.1:Low-Emitting Materials, Adhesives and Sealants (VOC content not to exceed the limits listed in the South Coast Air Quality Management District (SCAQMD) applicable rules and limits), credit review depends upon whether, during the installation process, these applications are applied on-site. In most cases no adhesive and sealants are applied-on site);

c. Indoor Environmental Quality (EQ)- credit EQc4.2:Low Emitting Materials – Paintings and Coatings (low-VOC, limits as per applicable established SCAQMD and Green Seal Standards rules–credit review depends upon whether, during the installation process, paint and coatings are applied on-site, during construction);

d. Indoor Environmental Quality (EQ) – credit EQc4.4:Low-Emitting Materials-Composite Wood (no added urea-formaldehyde resins);

e. Energy and Atmosphere (EA) – credit EAc1: Optimize Energy performance (for ex. as a part of whole building energy simulation analysis, and energy cost);

f. Energy and Atmosphere (EA) - credit EAc5: Measurement and Verification (covering a period no less than one year of occupancy, after construction is completed)

g. Innovation in Design (ID) – credit IDc1: Innovation in Design (ex. exemplary performance); -credit IDc2: LEED Accredited Professional (ex. one principal participant in the project is LEED AP);

In addition to complying with the Construction Waste Management Plan during construction, there is a possibility to explore opportunities to aid in the following areas:

h. Energy and Atmosphere (EA) - Prerequisite 1: Fundamental Commissioning of the Building Energy Systems - to support the total building commission process in the part of energy efficiency, and verification that the systems meet design intent, and project requirements;

i. Energy and Atmosphere (EA) - Prerequisite 2: Minimum Energy Performance, as related to the technologies to maximize the energy performance, as part of the whole building energy system. (minimum energy efficiency requirements).

With the fast development of the technology, possibilities of potential exploration of opportunities to contribute in the near future exist in these areas:

k. Energy and Atmosphere (EA) – credit EAc6: Green Power (as a part of the total building electricity from the renewable source to come from off-site) and/or


l. Energy and Atmosphere (EA) - credit EAc2: On-Site Renewable Energy (if the renewable sources come from on-site, for ex. solar panels independently from the grid).

METHODOLOGY AND DISCUSSION The importance of determining and setting the objectives

have been emphasized by Drucker(1974) [14], identifying the basics for objectives, communication, measurement of performance, motivation, innovation and achievement, human and social aspects, who also establishes and defines the basics of “management by objectives” [14].

SWOT analysis, which is abbreviated from Strengths-Weaknesses-Opportunities-Threats has been suggested to be one of management’s trustiest tools by Heller (2006)[15]. As a part of the Project Risk Management [23], the method researches four areas of the task, analyzing strengths, weaknesses, opportunities and threats of the given objectives. It also investigates ways to identify opportunities that may come from the areas where strengths are visible, and researching threats from external factors, that may also be a result from internal unobserved weaknesses. This tool is also looking into weaknesses that may possible be a future opportunity [23].

Once the objectives of achieving the green orientation in the segment of the conveying systems industry are understood from all involved in the task, this tool can be applied to search for knowledgeable answers on factors that, if performed well, will aid the decision-making process and/or improve the same. If identifying Strengths and Opportunities are factors on one side of the scale, as factors that stimulate objective progress, identifying Weaknesses and Threats on the other side, are factors that if not observed timely and objectively, may affect the process of achieving the objectives. While on Strengths and Weaknesses are referred as internal elements, mostly because they are related to the search of the internal components that identify the factors who can contribute to reach the desired objectives, Opportunities and Threats are considered external elements, as they depend on identifying the external factors, and influences that may affect the process of reaching the objectives, and need to be carefully researched by analyzing the parameters that may influence each category. (Figure1).

While Strength and Opportunity are driving factors in achieving the goal, Weaknesses and Threats are factors that are in a way questioning the objectives from achieving the goal. Like a chair with four legs, SWOT analysis requires equally addressing all four sides, meaning all four legs need to be analyzed equally objectively in order to address all possible objectives’ pros and cons.

The idea behind this approach is, by targeting questions, to provide a background for understanding of the potential of the sustainability aspects of the conveying systems, researching the benefits to include conveying systems green potentials in

consideration when discussing green buildings and building systems, and identifying possible obstacles in the process.

Analyzing each of the four categories means addressing questions that are related to the objectives to be achieved. As a concept idea, with analyzing green aspects, by addressing some areas and related phases where green products are interacting with, some possibilities that may influence the decision-making process are listed in all four categories of the analysis. Targeted questions are listed below in each category: Strengths, Weaknesses, Opportunity and Threats, that may apply to different concerned parties involved in the process, assisting in better understanding the targeted objectives.

S - Strengths W- Weaknesses

O- Opportunities T - Threats

SWOT

InternalFactors

External Factors

Figure 1

Strengths

- Why green orientation and how long has that practice been adopted? What is achieved by green?

- Who benefits from the green objective? - What aspects of green does the product address? - What certification path is the building project

intended to pursue? - What differentiates a particular product from the

rest on the market? - What is currently a green key selling point? - How can product green features contribute

towards applicable credits? - How much can energy efficiency be quantified to

support green aspects? - How much cost savings annually are contributed

to the green orientation? - What are the best practices that would be

beneficial to address? - What are the main manufacturing strong aspects

that contribute in the green orientation? - What renewable energy sources are utilized?


- How does the local utility company recognize clean energy solutions?

- Are any innovation, research or proprietary aspects employed?

Weaknesses - What may be the impact, if there was no previous

experience with the green product direction? - How beneficial is introducing a new strategy in

the current big/small market? - Are all parties involved in the process supporting

the initiative to achieve the objective? - Are there enough already skilled members on the

team to contribute to the project, ready to grasp the objective, or additional education is need?

- What would be the impact if objective result is not achieved? What would be the consequence if the product is not accepted by the current market?

- What may be the (ex. manufacturing) obstacles if the process is not sustainably driven, but needs changes?

- How will the process affect the supply chain? - Are developing new packaging concepts to reduce

waste material and optimize installation time needed?

- What other products/concepts exist on the market that may affect the objective?

- How will the cost structure be influenced, if manufacturing and the supply chain cross borders (trade with different currencies)?

- How may the labor cost and installation cost affect the objective?

- What are additional certifications required, and applicability with the regulations in effect?

Opportunities - What are the benefits for introducing the objective

to new markets, or being first in the market? - What applicable regulations are in effect that the

objective complies with, or others benefit from? - What may be further change in regulations? - Are any tax incentives available, and how

beneficial are for the objective? - In what areas / credits may the product

contribute? - What are the possibilities to identify alternatives

that will offer substitute for similar cost? - What differentiates the particular objective from

the rest on the market? - What is the effect of a population concentrating in

the big cities, making the cities to grow taller and denser? A result of the increase of urban population and urbanization in the world [16] ;

- How will the increase of the elderly population 65 and over affect the objective? (for ex. in the U.S. is projected to more than double, and reach 92.0 million in 2060, as comparison to 2012) [17] ;

- What is the calendar of industry trade shows, seminars and events on this topic that will create opportunities to introduce the objective?

- What are the opportunities if renewable energy solutions are introduced? What current strategies are in place that will develop an opportunity for research and innovation?

- What resources are available for education towards achieving the objective?

Threats - What are the effects of the global economy slow-

down and slow recovery on the volatile construction industry market?

- What is the initial vs. return on investment cost of green for the building owner, tenants?

- What if the cost allocated for potentially achieving the objective, results in no return on investment?

- What are the legal aspects of the decision to go for the green objective?

- What if the strong competitors’ market needs further differentiator strategies?

- What may be the currency exchange rate and its impact, if the objective needs resources from abroad?

- What may be the inflation rate projection for anticipated time?

- How does the cost on raw materials and the related factors - energy, oil and copper - affect the objective?

- What is the impact of a proprietary product and product cost on the objective?

- Are more stringent regulations, policies, and permitting processes affecting the objective?

- How may the rise of the labor cost and demands affect the objective?

- What does the analysis of product quality, and quality control measures show (if product in part or in whole, is coming from different geographical regions)?

- How is the objective affected by the cross-cultural communications, if influenced by the economy and political events?

- How does uncoordinated policy and implementation from the major energy stakeholders affect the objective?

- How are the regulations in effect and approval processes affecting the objective?

The volatile construction industry in the field of new

construction creates an opportunity for upgrades on the existing elevator equipment, although the slow recovery may also result in a slow new feature introduction initiative due to the market uncertainty. There are estimated to be around 5 million elevators in operation in Europe (although the number cannot


be verified easily depending of the countries statistics), whereas the EU counts for more than 4 million elevators[18]. Considering that elevators have a long life cycle that may go from 15 to 25 years before some major upgrades take place, and eventually creates some time frame when these elevators will reach the point to be considered for upgrades.

On the other hand, increased electricity consumption per

year in the EU countries, in areas such as: office buildings, institutional buildings, hotels, shopping malls, as well as residential buildings, is expected to increase of more than 2% in the next years[18], opening an opportunity for research and innovation in the elevator sector, and at the same time to explore the possibility if any, and under what conditions, local utility company may recognize the energy savings upgrades.

It appears that exploring innovation in the elevator sector is

at the same time an opportunity, and in a way threat to invest in, due to new buildings construction market uncertainty, and global economic slow-down.

Cross-cultural communication and globalization increase

the opportunity for exchange of information, better understanding of different best practices and objectives, to further explore objectives when applied in different geographical areas. However, cross–cultural communication can be affected by the economic aspects. A proprietary product may be a strength for the supplier, but on the other hand a threat for the building owner that may need to be locked in a maintenance agreement with that supplier, unless otherwise other options are possible, depending on the regulations in place for certain types of buildings, and any change if not observed timely during planning may create a financial threat further in the process.

When analyzing elevators as a part of the building systems,

many factors need to be taken into initial consideration, some are shown on Figure 2. Although steps are already made forward since the first sustainability initiative took place, the benefits of the green aspects of elevators further expand in the energy efficiency field. They may contribute to market competitiveness, energy savings, job creation, and sharing of best practices, that contribute to shape the objectives in the effort to make buildings more sustainable for building owners, facility managers, renters and occupancy.

Upgrades of older equipment components, such as drives,

controllers, with the new technology, brings the subject of measuring the energy for each elevator or elevator bank or submetering, as well as the verification process, analysis and evaluation of the results. These will help distinguish the differences between the elevator original equipment and the performed upgrades, over period of time, an energy cost-savings analysis for various solutions before, and after the upgrades for various building types, depending on the number

of floors, and frequency of use may serve as a starting benchmark regarding the value of the energy savings, and monitor the energy efficiency and cost savings over defined period of time.

Machine room temperature and humidity are required to be

maintained within certain temperature range as per the manufacturer’s recommendation, that depending of the regulations in effect, may require HVAC equipment. Older elevator equipment in the machine room may dissipate more heat than the newer equipment, in addition to the unique local weather condition typical for the area, and it may increase the use of means to maintain the temperature in the recommended values, that in return may affect the electrical cost that the building owner, or that occupants pay. This area is certainly worth analyzing in the current existing building situation in Macedonia.

Figure 2

Basic SWOT analysis of the potential to increase the

attention on the elevator market in Macedonia is shown on Figure 3. Several factors such as type and selection of car lights and car ventilation, may also affect the energy consumption. In addition, solutions might be pursued to allow lights and fans to be turned off when elevators are not in service for period of time, as per applicable regulations in effect. Herein, careful consideration needs to be made; in cases when passengers are trapped in the elevator, lights and fans need to remain in running mode, and certainly in conditions when the elevator that is approaching the landing, stops in close proximity of the landing but it is not leveled with the landing). Another look at how energy efficiency is perceived might be

• Occupancy Type

• Frequency of use

• Traffic study (original equipment vs.modernized )

• Green Building certification (rating, version)

• Green policies and coordinated approach;

• Tracking annual energy consumption per elevator /bank;

• Measuring and verification of the elevator systems;

• Developing a best practices portfolio;

• Traction • Hydraulic • MRL • Year of original

installation • Year of retrofit • Year of

modernization

• Office • Residential • Institutional • Educational • Shopping Mall • New

construction • Existing

building Building Type

Elevator

Type

Occupancy Energy &

Green Orientation


STRENGTHS WEAKNESSES 1.Developed strategy on Renewable Energy Sources (RES) in Macedonia by 2020 [24] that encourage innovations in renewable energy, and available resources; 2.Increased public interest in solar power and photovoltaic systems; 3.Increased new buildings construction in the past few years (residential, offices, malls) in the country, that opens the possibility for new sustainable direction; 4.Reforms and adoption of the EU Norms that eventually will extent to the conveying systems field;

1.Maturity of some of the existing dwellings in the country (in Skopje alone(427 built before 1918; 2754 built (1919-1945); 13,507 dwellings built (1946-1960))[25] (info not available if these dwellings are in the building with an elevator); 2.Maturity of the existing elevators in the country, and need of detailed analysis of current standings, here in including safety, and if contain asbestos in the old brake linings; 3.Absence of legal measures to stay or put the elevators out of service depending of the mandatory inspection outcome; 4.Deficiency of parts for older elevator models that may require costly retrofit that building owners will be mandated to pay; 5.Absence of incentives, financial mechanisms and measures to encourage and stimulate building owners and investors to build or retrofit towards green solution, to include measurement of energy and verification process with the building systems and elevators;

OPPORTUNITIES THREATS 1.Although small percentage in RES share target for 2020[24] goes to solar energy, possibility to research on implementation of solar power in conveying systems, due to the increased interest in energy efficiency field; 2.Recent Building Management and/or Owner’s association concept in effect for residential buildings, is expected to increase attention on the elevators and energy efficiency; 3.Participation on international conferences to exchange and gain knowledge on the subject; 4.USGBC LEED Earth initiative to accelerate sustainable movement and free LEED certification for the first projects to certify in new groundbreaking markets[26];

1.Anticipated increase of the electricity cost in the region, and developing methods to overcome the challenge (taxpayers or end-consumers); 2.Absence of developed National strategy to regulate conveying systems (elevators, escalators and moving walks), via central registered database, with info available on line on annual inspections and deficiencies noted for every elevator in the country; 3.Absence of developed and adopted coordinated strategy and sets of measures for implementation among energy company, energy influencers, and institutions; 4.Cost of the technology to use solar power for electricity generation;

Figure 3.

obtained from application of destination control and utilization of the traffic study to analyze, evaluate, and compare different solutions to transport passengers to their destination in effective way, and how the same is related to the number of starts and stops as compared to the conventional solutions, particularly in the multi-purpose buildings with mixed occupancy.

In general, in both existing and new installations, traffic study and energy efficiency analysis of the elevator banks during peak hours (hours that elevators are likely to be used the most), and frequency of the use of the elevators based on the occupancy and building type; in addition to the major energy consumption of the elevators during running period, and energy consumptions during period of waiting or stand-by, need to be observed. Whereas, estimated daily energy use of the elevator consists of the energy consumption during period elevator is running and energy consumption during waiting stand-by period, yearly consumption will be related to the frequency of use (Fig.4).

An additional challenge is faced with the old elevators

that haven’t been retrofitted, as they may have brake linings

installed more than 20 years ago made of asbestos [19]. As the asbestos lining is not used anymore, additional measures of

Figure 4 identifying and tracking older elevators with over 20 years older brake lining solutions that may contain asbestos need to be addressed. The issues of possible asbestos in the old elevators shafts that used to be coated with fire retardant that may contain asbestos, were addressed back in 1987 [20].

Although the use of asbestos is not allowed in EU countries and most of Europe, for example Scandinavian countries between 1970 and 1980, Germany in 1993 and EU issued directive in 2005 [21], based on the date the individual country had set up the regulations, the same may be still present in the older existing buildings. For existing buildings built years before the date of adoption of the regulation, if original elevators are still in-service, it may still be present in the friction materials for elevator brakes pads[21], therefore risk assessment, special training, best practices and applicable licenses and regulations need to be addressed. In case of Macedonia, considering that the first elevator installed in the country, in 1929, was in operation until 2011, when it was gifted and displayed to the Museum of the City of Skopje; at the time of the preparing this paper, it was not explored if the information of possible asbestos was present on the original installation. See Figure 3 weaknesses. Today in Macedonia, there are elevators in service that were originally installed before and around 1962, further research needs to focus on identifying the total number of elevators prior to the 1960s and after, and addressing the above mentioned asbestos related challenges, if present.

CONCLUSIONS AND FUTURE DIRECTIONS The benefits of the SWOT analysis can be applied in many

areas. The major benefit of the analysis review is to give an overview for future planning, and possibilities to identify critical areas and area of improvements, based on analysis of each of the four segments.

Sustainability is not an individual attribute that is

happening in one area only, but needs to be observed as a

Energy Considerations

Energy consumption during running

period

Energy consumption during stand-by waiting period

Frequency of use

Building type

Occupancy type

Building class


process that is an integral part of the whole building, building system and community. Analysis of the whole building, herein including elevators, creates an understanding of long term effects, not only on energy and occupancy, but also how these interact with the cost of operating the elevator in the long run, and opens the possibility for improvements, cost savings and sustainable living.

Potential in the exploring the solar and wind energy

sources that can contribute to the total building energy systems are present in Macedonia and the countries of Southeast Europe. In line with the European efforts, as per the Strategy on use of Renewable Energy Sources (RES) in Macedonia by 2020[24], it is planned that renewable sources will count for 21% in total energy consumption in Macedonia by 2020. At the time of the preparation of this paper, it was observed that there was no record of a building certified, or being under consideration on any of the green building rating systems (LEED, Green Globes, or BREEAM) in Macedonia. As the popularity of the green buildings is increasing, eventually the process to be considered may become a reality. What may appear to be further challenges in Macedonia, in addition to all previously mentioned in the effort to consider green building certification, and include elevators in consideration, aside from exploring the financial mechanisms to encourage building owners, occupants, and investors to build or retrofit toward green solution, it is also developing and adopting an effective and coordinated policy among major energy influencers, and institutions, herein energy companies, government agencies, standards body and policy creators on local levels (specifically tailored for each city and town), and developing sets of measures for implementation, principles on monitoring, optimizations, sharing experiences, measuring and verification of the energy.

In the future research needs to focus on finding effective

ways to address all the previously mentioned challenges. Further areas of research include developing a list of strategies based on the indicators, identifying the obstacles, and further implementing the strategies to overcome the challenges, developing methods of increasing public awareness, training aspects and education, enhancing motivation to achieve better solutions towards energy efficient buildings with efficient conveying systems, defining best practices for residential, office, educational and institutional buildings, benchmarking by comparing and evaluating the existing solutions, with potentially proposed changes, tailored to the country’s economic and social aspects.

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