introduction to quality for structural engineers

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INTRODUCTION TO QUALITY FOR STRUCTURAL ENGINEERS

Introduction

Every individual, group, company or organization must act and that action must be in

accordance with some expectation. The art and science of achieving that expectation interms of a defined Standard for the final product is called Quality Management . Quality Engineering is that part of Quality Management that deals with the development andapplication of quality systems for building and sustaining quality into the product, and isassociated with the comprehensive use of statistical and allied methods.

1.0 What is Quality

1.1 Defining Quality

The word “quality” is such a commonly used word that it can mean many things.Therefore, in order to clarify the technical meaning of the term “quality” it is perhapsmost useful to begin by stating what quality is not.

One typical source of confusion is mistaking grade for quality. For example, between aMercedes Benz and a Nissan Sentra, which is the higher quality car? Most people wouldsay the Benz, but this would be wrong – the Benz is a higher grade car in that it has morefeatures. The same holds for any product – the product is available in a range of gradesfrom the basic to the premium. This also applies to services, so in quality terminology,we include services when we speak of products. What then is the definition of Quality?

In the classical quality literature there are the 3 Quality Philosophies of Deming, Juranand Crosby:

W. Edwards Deming (1900-1993) - Deming defines Quality (indirectly) as low statisticalvariation of the product’s characteristics. Regarded as the father of quality technology,and a major source of Japan’s economic success, Deming’s quality philosophy ischaracterized by the use of long-term holistic approaches, and statistics to achieve andcontrol quality. He is also well known for his “14 Points for Management”, and “The 7Deadly Diseases of Management”. Deming emphasizes the process.

Joseph M. Juran (1904 - pres) – Juran defines Quality as fitness for use by the customer.

Juran, who also visited Japan in the 1950s, advocates a philosophy of a universal way ofaddressing quality called the Quality Trilogy: quality planning, quality control, andquality improvement. Juran emphasizes the customer.

Philip B. Crosby (1928 - pres) – Crosby defines Quality as conformance to requirementsor specifications. His quality philosophy is characterised by the drive for zero defects,the development of his 14-Step Cost-of-Quality Method, and the focus on qualityassurance over quality control.

In its most rigorous form, quality is defined mathematically using Statistics and has beena central theme of the earlier era of quality management where emphasis was on quality

control. In general, Statistics is applied to:

• The definition of the product Specifications

• The control of the process by which the product is produced

• The Acceptance Sampling procedure of the product Inspection and Testing

Operations Research, Optimization, Experiment Design, and other mathematical tools arealso used to improve understanding of the process, and in problem-solving to removecauses of variation.

It is noteworthy that since quality is conformance, the terms “good quality” or, “bad

quality” are meaningless. That is, the product either conforms or does not conform,though the product can exceed or fall short of whatever defines conformance.


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Though the attainment of desired quality requires the commitment and participation of allmembers of the organization, the responsibility for quality management belongs to topmanagement, who, it is acknowledged, contributes to 85% of the quality problems (alsocalled the common causes). Quality is a science of problem-solving.

1.2 The Primary Objective of Quality – Minimizing the Cost of Quality

It may be said that the primary goal of Quality Technology is to minimize the cost ofquality by reducing failure costs. The Cost of Quality (COQ) is the sum of thePrevention Cost, the Appraisal Cost, the Internal Failure Cost, and the External FailureCost.

Prevention Cost

Prevention costs are those expenses associated with steps taken to make sure the productwill be made to the required condition.

Examples of prevention cost items are: Project Quality Plan; Quality Planning; QualityControl Plan; Quality Auditing; Assuring Vendor and Sub-Contractor quality; Reviewingand Verifying Designs; Insurance, etc.

Appraisal Cost

Appraisal costs relate to expenses incurred while checking and inspecting the work toconfirm that it has achieved the required condition.

Examples of appraisal costs are: Receiving Inspection; Inspection and Non-DestructiveTesting; Procuring Inspection and Test Equipment; Materials consumed duringinspection and testing; Analysis and Reporting of Test and Inspection Results; FieldPerformance Testing, etc.

Internal Failure Costs

These costs relate to expenses incurred within the company due to product failure andinefficiencies.

Examples of internal failure costs are: Replacement, Rework or Repair; Scrap and Waste

Metal; Re-Inspection and Re-Testing; Defect Diagnosis; Down Time, etc.

External Failure Costs

These costs relate to expenses incurred outside the company, usually motivated by yourClient.

Examples of external failure costs are: Receiving and Actioning Complaints; WarrantyClaims; Products rejected and returned; Concessions; Loss of Future Sales; IncreasedMarketing to replace lost clients; Recall costs, etc.

The criterion for success is that the increase in prevention costs over time due to theadoption of quality technology, should be less than the reduction in failure costs.

The COQ has become a major measurement of quality and requires the development of aQuality Information System (QIS) for tracking and reporting the changes in the qualitycosts, among other related concerns.


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External Failure Costs

External Failure CostsInternal Failure Costs

Internal Failure Costs

Appraisal Costs Appraisal Costs

Prevention CostsPrevention Costs

S A V I N G S

TIME

TOTAL QUALITYCOST ($)


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The Quality Model shown above (Juran and Gryna, 1980) illustrates that as preventionand appraisal costs increase, the failure costs will decrease until an optimum point isreached. After this point, increases in appraisal and prevention costs will not be offset bythe decreased failure costs.

1.3 Quality Technology Definitions

SpecificationA set of conditions and requirements, of specific and limited application, that provide adetailed description of the procedure, process, material, product, or service for use primarily in procurement and manufacturing. Standards may be referenced or included ina Specification.

StandardA prescribed set of conditions and requirements, of general and broad application,established by authority or agreement, to be satisfied by a material, product, process, procedure, convention, test method; and/or the physical, functional, performance, orconformance characteristic thereof. A physical embodiment of a unit of measurement(for example, an object such as the standard kilogram or an apparatus such as the cesium beam clock). (U.S. Bureau of Standards, 1983)

Quality SystemThe organizational structure, collective plans, activities, and events that are provided toensure that a product, process, or service, will satisfy given needs. (ANSI/ASQC, 1987).The ISO 9000 Series are standards for quality systems.

Quality AssuranceAll those planned and systematic actions necessary to provide confidence that a productor service will satisfy given needs. (ANSI/ASQC, 1987).

100%Good

100%Bad

COST PERGOOD UNIT

FAILURE

COSTS

PREVENTION PLUSAPPRAISAL COSTS

TOTALQUALITY

COST

OptimumPoint

MODEL OF OPTIMUM QUALITY


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Quality ControlThe operational techniques and activities used to fulfill requirements for quality by bothmonitoring a process (primarily by inspection and testing) and eliminating causes ofunsatisfactory performance at relevant stages.

Quality PlanAfter analysis of the quality requirements, detailed documentation, called the QualityPlan, is produced explaining how the company will assure that the product will meet theclient’s requirement. A major part of the Quality Plan is the Quality Manual.

Quality ManualThe quality manual is a major component of the Quality Plan. It documents in detail allthe procedures, processes, checklists, etc. used to assure that quality is built into the product. It is updated as quality improvements are made via the PDCA cycle.

ISO 9000-9004 (ANSI/ASQC 9000-9004)Standards for a quality system. Provides a consistent reference framework for the globaleconomy thereby facilitating trade. Details what general factors shall be considered andthe structure of the documentation, without reference to a specific industry.

ISO 9000. Guidelines for selection and use of the standards.

ISO 9001. Quality systems model for quality assurance in design, development, production, installation and servicing.

ISO 9002. Quality systems model for quality assurance in production, installation andservicing.

ISO 9003. Quality systems model for quality assurance in inspection and testing.

ISO 9004. Guidelines for quality management and quality system elements. That is, forinternal quality assurance, whereas 9001 to 9003 are for external quality assurance.


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1.4 The Quality Cycle

THE DEMING (OR SHEWHART) CYCLE OF QUALITY IMPROVEMENT

PLAN – Analyze the customer requirements and devise a quality systemDO - Implement the quality systemCHECK - Observe the quality changes via a Quality Information System; use at least

COQ as the quality measurementACT - Analyze the observed quality changes

Re-do in an infinite loop for continuous quality improvement.

QUALITY SYSTEM

QUALITY PLAN

• Quality Manual

•

Checklists, etc

ORGANISATIONALSTRUCTURE

MANAGEMENT

PROCESSES

PRODUCTPROCESSES

INTERNALPROCESSES

EXTERNAL(SUPPLIER/VENDOR)PROCESSES

QUALITY CONTROL PLAN

• Inspection

• Testing

QUALITYANALYSIS ANDPLANNING

PLAN

DO

CHECK

ACT


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1.5 Summary of Quality

MAXIMISED WHENAPPLIED TO

RATHERTHAN TO

BASICS:

QUALITY IS CONFORMANCE TO CUSTOMER REQUIREMENTS (HENCE THERE IS NO SUCH THING AS GOOD OR BAD QUALITY)

THE CUSTOMER IS WHOEVER YOU GIVE A PRODUCT TO AFTER YOU HAVEPROCESSED SOME OTHER PRODUCT FROM A SUPPLIER

THE SUPPLIER IS WHOEVER GIVES A PRODUCT TO YOU THAT YOU WILLPROCESS TO FORM ANOTHER PRODUCT

HENCE EVERYONE IS A CUSTOMER AND A SUPPLIER, INTERNAL OR EXTERNALTO AN ORGANISATION

A PRODUCT IS TANGIBLE OR INTANGIBLE; A SERVICE IS ALSO A PRODUCT

QUALITY IS A MOVING TARGET BECAUSE NEEDS AND CONDITIONS CHANGECONSTANTLY

TO PRODUCE “PERFECT” PRODUCTS REQUIRES AN INFINITE INVESTMENTCOST

QUALITY MANAGEMENT AND ENGINEERING INCREASES PROFITS

MINIMISATION OF FAILURE COSTS

THRU

THE STATISTICS OF FAILURE (AND HENCEACCPETANCE

THRU

REDUCING VARIATION (IN THE PRODUCTCHARACTERISTICS

THRU

UNDERSTANDING THE CAUSES OF VARIATION

THRU

APPLICATION OF THE PROBLEM SOLVINGTECHNIQUES SUCH AS:

BRAIN STORMING; THE 7 Q/TOOLS; THE 7MANAGEMENT TOOLS; EXPERIMENT DESIGN;

BOOTSTRAP; OPERATIONS RESEARCH; ETC.

THRU

CYCLICALLY – (PDCA-PLAN/DO/CHECK/ACT)IN A FEEDBACK LOOP THAT LEADS TO

CORRECTIVE ACTION BASED ONUNDERSTANDING THE PROBLEM

(HENCE IMPROVEMENT IS CONTINUOUS AND

INFINITE (CHANGING REQUIREMENTS))

HOW?

HENCE INFORMING THEQUALITY MANUAL WHICH

CONTINUALLY EVOLVES

HENCE REQUIRING A QISFOR TRACKING PROGRESSAND THE ASSOCIATED

COSTS

THE ENTIRE ORGANISATION –THIS IS TOTAL QUALITY

MANAGEMENT

IT RESTS ON 5 PILLARS:ORGANISATION; PRODUCT;

PROCESS; LEADERSHIP;COMMITTMENT

THE BLUE COLLAR LEVEL ONLY

AND WHEN

THE FOCUS ISON

QUALITY ASSURRANCE:GETTING IT RIGHT THE FIRST

TIME, EVERY TIME(MINIMUM TESTING)

RATHERTHAN ON

QUALITY CONTROL:CHARACTERISED BY MUCH

TESTING AFTER PRODUCTION,AND HENCE REPRESENTATIVE

OF A POOR QUALITY PLAN


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2.0 Product Quality

Product Standards/Specifications

Almost any product has an associated standard published by an international organization

and frequently several organizations offer standards for the same product. At the locallevel, there is typically a central body responsible for developing standards for the particular local conditions. For example in Trinidad and Tobago, there is the Trinidadand Tobago Bureau of Standards (TTBS).

Standards define the acceptable characteristics or properties of the product (e.g. physicaland chemical properties), and depending on the product, the process under which it is to be manufactured. The word “standard” can be an umbrella term that includes otherrelated documents. Associated with standards are Codes of Practice, Guidelines, and Regulations. A Code of Practice is a statement of criteria for properly performing anaction. Guidelines are less comprehensive that standards but may evolve to become a

standard. Regulations are legal requirements of municipalities or states.

The development of a standard takes place along a rigorous and well-defined process inwhich the proposed document is exposed to much review and adjustment before launch.Even then, Standards evolve over time so it is important that the particular version of thestandard be referenced. Standards can also be withdrawn or renamed.

The following are just a few of the main international sources of Standards, Guidelinesand Codes of Practice:

• ISO – International Standards Organization

• ASTM – American Society for Testing and Materials

• BSI – British Standards Institute

• EN – Euro Norm

Professional bodies, Trade Groups, and other interest groups also offer publications thatthough not standards, can be used to build Specifications or Contract Documents. Giventhe length of time before a standard is revised, theses sources often reflect the state-of-the-art and influence the revision of standards.

Quality Systems for The Product Production Process

Given the international impact of Quality many organizations have published QualitySystems or Quality Assurance/Control Plans for products and services. For example, theASQ has published the Quality Handbook for the Architectural, Engineering, andConstruction Community by Roger D. Hart.

3.0 Special Inspections and Tests Required for Seismic Construction

Chapter 17 of the IBC requires that at the time of applying for approval, the owner’srepresentative must submit a statement of Special Inspections to be undertaken. SuchSpecial Inspections are required irrespective of seismic conditions.

For seismic conditions, the following is noteworthy, but the reader must refer to the IBCfor details and the complete information.

1. For structural steel in SDC C, D, E, or F, continuous special inspection isrequired for structural welding in accordance with AISC 341, except for filletwelds less than 7.9mm, and except for floor and roof deck welding.

2. For engineered masonry in SDC C, D, E or F and Occupancy Category I, II, orIII, certificates of compliance must be submitted, as well as verification of f m

’, prior to construction. If the O.C is IV, than in addition, the proportions ofmaterials used in mortar and grout must be verified.

3.

For structures in SDC C, D, E, or F, for reinforcing and prestressing steel,certified mill test reports shall be provided for each shipment of reinforcing steel


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used to resist flexural, shear, and axial forces in reinforced intermediate frames,special moment frames, and boundary elements in of special reinforced concreteor reinforced masonry shear walls. Where ASTM A 615 reinforcing steel isused to resist earthquake-induced flexural and axial forces in special momentresisting frames and in boundary wall elements of shear walls in structures

assigned to SDC D, E, or F, the testing requirements of ACI 318 shall be met.Where ASTM A 615 reinforcing steel is to be welded, chemical tests shall be performed to determine weldability in accordance with Section 3.5.2 of ACI318.

4. For structures in SDC C, D, E, or F, the testing contained in the qualityassurance plan shall be as required by AISC 341and the additional requirements below. The acceptance criteria for NDT shall be as required in AWS D1.1.Base metal thicker than 38 mm, where subjected to through-thickness weldshrinkage strains, shall be ultrasonically tested for discontinuities behind andadjacent to such welds after joint completion. Any material discontinuities shall be accepted or rejected at least on the basis of ASTM A 435 or ASTM A 898

(Level 1 criteria).5. Structural Observation is the visual observation of the structural system by aregistered design professional for general conformance to the approvedconstruction documents at significant construction stages and at completion ofthe structural system. Structural Observation shall be provided for thosestructures included in SDC D, E, or F, where one or more of the followingconditions exist:

a. The structure is classified as O.C III or IV. b. The height of the structure is greater than 22.86 m above the base.c. The structure is assigned to SDC E, is classified as O.C II or III, and is

greater than two stories in height.