report of post-earthquake field investigation bohol ... · report of post-earthquake field...

Report of Post-Earthquake Field Investigation Bohol, Philippines

February 2015

UNESCO Paris

International Platform for Reducing of Earthquake Disaster

Cover photo: Fault lines appeared after the earthquake at Inabanga

Back Cover photo: Uplifted coastal terrace at Maribojoc

1

Foreword

Post-Earthquake Field Investigation Team of International Platform for Reducing

Earthquake Disaster (IPRED)

UNESCO is promoting a conceptual change in the reflection of post-disaster reaction to

pre-disaster action and enhancing the resilience of communities to cope with natural

hazards in a true multidisciplinary fashion, through education, using innovating

scientific decision support tools, in an inclusive manner and via cultural sensitive

approach.

As discussed in United Nations World Conference on Disaster Reduction in 2005, it is

important to improve the safety of buildings and housing as a basic and vital priority for

the world’s disaster reduction efforts and thus it was proposed that a “building disaster

reduction network” should be established.

Following this recommendation, an IPRED meeting was held in UNESCO Paris in 2008.

Representatives of major earthquake prone countries attended this meeting. IPRED’s

mission is to identify gaps and priorities through the sharing of scientific knowledge

and experience in the field of seismology and earthquake engineering, and to support

the development of political will and public awareness, for the purpose of ensuring the

better preparation against earthquakes and building a culture of safety for the people in

the world.

IPRED members meet annually for sharing latest activities and knowledge of each

member. Additional to the annual meeting, IPERD is establishing post-earthquake field

investigation, where IPRED members go to earthquake stricken countries for scientific

investigation, after acceptance of the mission by the government. The two main

objectives of this system are: to share scientific findings and lessons from earthquake

disasters with other earthquake-prone countries for future disaster risk reduction, and

to provide technical information, such as reports of the investigations to countries

affected by earthquake disasters, which could be further be utilized in the

implementation of preventions measures and policies.

2

M7.1 earthquake happened on 08:12 local time, 15th October in Bohol, Philippines and

the epicentre was near the city of Catigbian on Bohol. There have been reported that

there were continuous after shock after the big shake on 15th October and the number

of victims and number of destroyed buildings were rising. On 21st October, UNESCO

Disaster Risk Reduction Unit asked the IPRED members the willingness to join the

field investigation, after UNESCO received the willingness from Institute of Seismology

in Kazakhstan, UNESCO contacted National Commission for UNESCO through

Permanent Delegation to UNESCO if they would accept UNESCO IPRED team and

UNESCO. Through meetings with UNESCO National Commission of Philippines on

November in Paris and December in Manila, and emails, we finalized the detail of

UNESCO post-field investigation mission from 24th to 28th February 2014.

The report consists of two parts, one is for analysing Reinforced Concrete buildings and

the other is for analysing Historical Churches. Mr. Ruslanzhan Sadyrov and Mr.

Kanatbay Ryskulov from Institute of Seismology, Ministry of Education and Science,

Kazakhstan, Dr Tomoya Matsui from Toyohashi Institute of Technology, Japan, Dr

Koichi Kusunoki from Yokohama National University (now Tokyo University), Japan,

Mr Soichiro Yasukawa from UNESCO Paris are responsible for Reinforcement Building.

Mr Stephen Kelley Wiss, Janney, Elstener Associate, Inc from U.S.A (now a Historic

Preservation Specialist) is responsible for Historical Churches.

3

Acknowledgements

In addition to the experts from Kazakhstan, Japan and U.S., the UNESCO would like to

express our sincere thanks to the many following organizations and individuals for their

support prior, during and following this mission, without whom we would not have been

able to carry out the field investigation and research so effectively. UNESCO especially

would like to thank:

・ Permanent Delegation to UNESCO for facilitating obtaining visas,

・ Dr. Virginia A. Miralao, Dr. Reynaldo B. Vea and Mr. Freddie A. Blanco, Natcom

for UNESCO for organizing the mission including inviting national and local

experts and coordinating the itinerary,

・ Engr. Bienvenido Cervantes and Engr. Eduardo Villamor, Mapua Institute of

Technology from Manila for supporting the field investigation and conducting

the testing of materials that we got from Bohol

・ Dr. Mario Aurelio, National Institute of Geological Science for supporting the

field investigation including the proposals of sites for investigation and also

facilitating acquiring data for our analysis

・ PHIVOLCS for providing us with the ground motion data of the earthquake.

・ Fr. Ted Torralba, Permanent Committee on Church Heritage for coordinating in

selecting churches for investigation,

・ Arch. Anthony Manding, Tagbilaran's Commission for the Cultural Heritage for

supporting the field investigation and producing documents following the

mission,

・ Mr. Joselito “JJ” Corpus, Heritage Conservator for supporting the field

investigation and producing documents following the mission,

・ Ms. Socorro T. Rigor, Diocese of Tagbilaran for supporting the field investigation

and producing documents following the mission, and

・ Mr. Lemuel Barol, Local coordinator for coordinating the itinerary effectively

based on the traffic situation in Bohol.

UNESCO would also thank the Edgardo M Chatto, Governor of Bohol, who invited the

mission members to his residence and coordinated our visiting with mayors of

municipalities. Also we thank Bishop Leonardo Medroso, who shares with us his

concerns.

4

Contents

Foreword .............................................................................................................................. 1

Acknowledgements .............................................................................................................. 3

1. Purpose of the investigation ........................................................................................... 6

2. Overview of the earthquake ............................................................................................ 7

3. Seismic Evaluation Tools .............................................................................................. 12

3.1 Outline of Post-earthquake Damage Evaluation in Japan ................................. 12

3.2 Standard for seismic evaluation of the existing reinforced concrete buildings .. 14

3.3 Computer analysis tools ........................................................................................ 17

4. Result of Field Investigations ....................................................................................... 23

4.1 Building A: Sagbayan city hall (at Sagbayan) ..................................................... 25

4.2 Building B: House (at Sagbayan) ......................................................................... 29

4.3 Building C: Hospital No. 1 (at Loon) ................................................................. 33

4.4 Building D: Hospital No. 2 (at Loon) ................................................................. 38

4.5 Building E: Hospital No. 3 (at Loon) ................................................................. 42

4.6 Building F: Governmental Building (at Tobigron) ............................................... 48

5. Conclusion for RC buildings ......................................................................................... 59

6. Condition Assessment of Four Heritage Churches on the Island of Bohol ................. 62

6.1 Church of Our Lady of the Immaculate Conception in Baclayon .......................... 62

6.2 The Church of Santa Monica in Alburquerque ....................................................... 67

6.3 The Church of Our Lady of the Village in Corella .................................................. 72

6.4 The Church of Saint Anthony of Padua in Sikatuna ............................................. 77

6.5 Drawings .................................................................................................................. 83

6.6 Tensile Testing of Steel Reinforcing ...................................................................... 106

7. Conclusions for the churches ...................................................................................... 109

Church of Our Lady of the Village in Corella ............................................................. 110

References ........................................................................................................................ 112

Annex ............................................................................................................................... 113

5

Mission member ........................................................................................................... 113

Itinerary ....................................................................................................................... 115

6

1. Purpose of the investigation

The Post-Earthquake field investigation was conducted by the support of UNESCO

-International Platform for Reducing Earthquake Disaster (IPRED) programme. The

two main objectives of the UNESCO-IPRED programmes are: to share scientific findings

and lessons from earthquake disasters with other earthquake-prone countries for future

disaster risk reduction, and to provide technical information, such as reports of the

investigations to countries affected by earthquake disasters, which could be further be

utilized in the implementation of preventions measures and policies.

In this investigation, the team focused on reinforced concrete buildings and historical

churches. For reinforced concrete buildings from sight evaluation, detailed damage

evaluation as well as computer analysis in order to determine the building seismic

resistance and to draw lessons for securing safer buildings in the future. For historical

churches, we collected oral histories, drew the CAD plan of damaged churches and

conducted material tests for future measures.

Team members and itinerary are attached in the annex.

Field investigation was conducted in mainly three locations, which were Sagbayan,

Tubigon, and Loon as shown in Figure 2.1.

Totally 11 buildings were surveyed from outside and 4 buildings were investigated in

detail. The investigated buildings were listed in Table 4.1.

7

2. Overview of the earthquake

M7.1 earthquake happened on 08:12 local time, 15th October in Bohol, Philippines and

the epicenter was The epicenter coordinates are in latitude 9.78°N and in longitude

124.00°E near the city of Catigbian on Bohol. There have been reported that there were

continuous after shock.

The state of Philippines is located on the Philippines Islands forming a part of Malay

Archipelago in the west of the Pacific Ocean including over 7100 islands located between

4°23' and 21°25' N and 116°55' 126°36' E. The archipelago length from north to south is

about 1800 km, and from west to east 1100 km. In the east and north-east the

Philippines’ coasts are swept by the Philippine Sea, in the west and north-west by the

South China Sea, and in the south by the Sulawesi Sea. The land area makes up 298 170

sq. km., the coastline length is 36 289 km.

The islands of the Philippines are formed by the ridges areas of underwater elevations

and are distinguished by the mountain relief. All these mountain structures are an

element of the active volcano belt spreading over the marginal zone of the Pacific Ocean

and called the “Pacific Ring of Fire.” In this region the plates forming the floor of the

Indian Ocean and western part of the Pacific Ocean go under the Asian plate.

Lateritic red and yellow soils are mostly represented in the Philippines, in the

mountains there are mountain chestnut and mountain podzolic soils. In the plains,

especially in the valleys of the biggest rivers, the soils are alluvial as a rule. In the

coastal plains the soils were formed as a result of weathering of coral limestones. In the

water-logged deltaic bottomlands the moor-type soils are developed.

The island and province of Bohol is located in the centre of the Visaya group of islands. It

is the tenth largest island in the country. The administrative centre of the province is

Tagbilaran. Bohol is a neighbour of Cebu Island in the west, Leyte Island in the

north-east, and Mindanao Island in the south, from which it is separated by the

Mindanao Sea.

The 2013 Bohol earthquake occurred on 15 October 2013, at 8:12 am (PST) in Bohol in

Central Visayas. The earthquake measured 7.0-7.2 on the Moment Magnitude Scale

(Mw), and the epicenter was near the city of Catigbian, latitude 9.78°N and in longitude

124.00°E. It affected the whole Central Visayas region, particularly Bohol and Cebu

8

(Figure 2.1). The quake was felt in the whole Visayas area and as far north as Masbate

Island and in southern Mindanao.

Figure 2.1 Moment Magnitude Inertia Scale map of Bohol and Cebu. (US Geological

Survey)

Figure 2.2 Ground shaking map of Bohol that reveals the location of the North Bohol

Fault. (website of Provincial Planning & Development Office of Bohol)

Previously, Bohol was hit by an earthquake on 8 February 1990 that damaged several

buildings and caused a tsunami.

According to the Philippine Institute of Volcanology and Seismology (PHIVOLCS), the

earthquake may have been caused by a previously undiscovered fault line transecting

Bohol running ENE-WSW parallel to the island's northwest coast (Figure 2.2). This was

apparent in the pattern of epicentres of the subsequent aftershocks. It was also noted

that Bohol gained around 500 metres more of shoreline due to the quake and shifted 55

centimetres west towards Cebu Island. PHIVOLCS reported that the North Bohol Fault

(NBF) is a northeast-southwest trending reverse fault along the western sector of Bohol

9

Island. Surface ruptures ranging from 0.10 to 5 metres in vertical displacements were

exposed in Barangay Anonang and Barangay Inabanga.1

The Philippines has a total of 65 seismic stations as of 2008 [1]. The central operating

station is located at PHIVOLCS Main Office, Diliman, Quezon City. Figure 2.3 shows

acceleration time histories recorded in Tagbilaran City. Seismic station was located near

Tagbilaran airport and about 40 km southwest of the epicenter. PGA was 214 cm/s, the

duration of principal motion record was about 30 second. Response spectra are shown in

Figure 2.4. Acceleration response spectra shows peak at period of 1.6 second and 2.7

second, respectively.

1 "Phivolcs: New fault line may have been source of Bohol earthquake".GMA News. October 16, 2013.

Retrieved October 17, 2013.

10

Figure 2.3 Acceleration time history

-3

-2

-1

0

1

2

3

Acc

ele

ratio

n (m

/s2)

150100500

Time (sec)

NS

MAX: 1.92T: 46.4

-3

-2

-1

0

1

2

3

Acc

ele

ratio

n (m

/s2)

150100500

Time (sec)

EW

MAX: 2.14T: 38.4

-3

-2

-1

0

1

2

3

Acc

ele

ratio

n (

m/s

2)

150100500

Time (sec)

UD

MAX: 1.23T: 42.5

11

Figure 2.4 Response Spectra (h=0.05)

1000

800

600

400

200

0Acc

eler

atio

n re

spon

se s

pect

ra (

cm/s

2 )

1086420Period (sec)

NS EW

h=0.05

500

400

300

200

100

0V

elci

ty r

esp

onse

spe

ctra

(cm

/s)

1086420Period (sec)

NS EW

h=0.05

250

200

150

100

50

0

Dis

plac

emen

t res

pons

e sp

ectr

a (c

m)

1086420Period (sec)

NS EW

h=0.05

12

3. Seismic Evaluation Tools

In this section, Post-earthquake Damage Evaluation of reinforced concrete structures,

which is used for the existing buildings after an earthquake, Standard for seismic

evaluation of the existing reinforced concrete buildings, which is also for the existing

buildings but before an earthquake, and numerical analysis tools, which is used for new

buildings, are introduced.

3.1 Outline of Post-earthquake Damage Evaluation in Japan

The Post-earthquake Damage Evaluation method in "Guideline for Post-earthquake

Damage Evaluation and Rehabilitation" [1] is introduced in this section.

Damage level of building is classified according to Residual Seismic Performance ratio,

R, which is calculated according to the damage class of columns as shown in Table 3.1.1

If the damage level of beam or beam-column joint is severer than that of column,

damage class of the beam or beam-column joint is applied instead of the damage class of

the column.

Table 3.1.1 Criteria of damage classification of RC column and wall

Damage

class

Description of damage

I Less-visible crack on concrete surface (Crack width is less than 0.2

mm)

II Clearly visible crack on concrete surface (Crack width is about 0.2 - 1.0

mm)

III Remarkable crack occur (Crack width is about 1.0 - 2.0 mm)

Slight crash or spalling of cover concrete

IV Remarkable and many crack occur (Crack width is more than 2.0 mm)

Remarkable crash of cover concrete with exposed reinforcing bars

V

Buckling of reinforcing bars

Crash of core concrete

Visible vertical or lateral deformation to columns or walls

There are two types of calculation method of Residual Seismic Performance ratio in

reference [2]. These are a calculation by using the seismic capacity index on basis of the

"Standard for Seismic Evaluation of Existing Reinforced Concrete Buildings" [3] and a

13

simplified calculation. The simplified calculation method of Residual Seismic

Performance ratio of R is drawn below.

(%)100 org

j

A

AR

where

000000 62 CWCCWWMSA

111111 7.59.195.095.095.0 CWCCWWMSA

222222 6.32.16.075.06.0 CWCCWWMSA

333333 8.16.03.05.03.0 CWCCWWMSA

44 1.0 MA

05 A

sumsumsumsumsumorg CWCCWWMSA 62

:,,,,,, 543210 sumSSSSSSS

Number of each shear column judged as damage class of 0 - V and total of them

:,,,,,, 543210 sumMMMMMMM

Number of each flexural column judged as damage class of 0 - V and total of them

:,,,,,, 543210 sumWWWWWWW

Number of each wall without boundary column judged as damage class of 0 - V and total

of them

:,,,,,, 543210 sumCWCWCWCWCWCWCW

Number of each wall with column on one side judged as damage class of 0 - V and total

of them

:,,,,,, 543210 sumCWCCWCCWCCWCCWCCWCCWC

Number of each wall with columns on both side judged as damage class of 0 - V and total

of them

The Guideline defines the damage class as shown in Table 3.1.2.

14

Table 3.1.2 Damage class of building according to

The Residual Seismic Performance ratio: R

Damage class

Slight 95 % ≦ R

Minor 80 % ≦ R < 95 %

Moderate 60 % ≦ R < 80 %

severe ≦ R < 60 %

Collapse Regard as R ≒ 0 due to overall or partial collapse

3.2 Standard for seismic evaluation of the existing reinforced concrete

buildings

Seismic capacity of the building is calculated based on the constant energy theory as

shown in Figure 3.2.1 according to the standard. The seismic performances of the

buildings of which strain energies are the same as shown in Figure 3.2.1 are evaluated

as same.

Deformation

Restoring force

Cracking

Yielding

High strengthshear wall

High ductilityopen frame

=

Figure 3.2.1 Constant Energy Concept

15

The evaluation is simple as shown in Equation 3.2.1.

soSi II Equation 3.2.1

Where, Si I is the calculated seismic performance index for i-th story, and soI is the

required seismic capacity index.

The seismic performance index Si I , is calculated as equation 3.2.2.

TSEI DiSi 0 Equation 3.2.2

Where 0Ei is seismic capacity index for i-th story, DS is unbalance index, and T is

aging index.

0E is the fundamental index and calculated based on the constant energy theory as

Equation 3.2.3.

FCA

Ei

1

0 Equation 3.2.3

Where Ai is the story shear force distribution factor, C is the strength of each story, and

F is the ductility of each story.

Since the vertical load carried by lower story is heavier, lower story needs higher

strength then upper story as shown in Figure 3.2.2.Therefore, the story strength needs

to be normalized according to the story shear force distribution factor, Ai, which is

defined in Building Standard Low of Japan.

Figure 3.2.2 Story shear force distribution factor

Ductility index, F is calculated according to the shear failure margin to the flexural

yielding strength. Strength index, C is the sum of the strength index of each member.

16

When the strengths are summed up, the difference of the ductility indexes are taken

into account as shown in Figure 3.2.3.

Figure 3.2.3 Relationship between strength index C and ductility index F

Unbalance index, DS , is a reduction factor to take the effect of lateral and vertical

unbalances as shown in Figure 3.2.4 into account. DS varies from 0.4 to 1.0.

Eccentricity Vertical irregularity

Aging index, T, is also a reduction factor to consider the effect of the building age. The

index is calculated from the site investigation results on ground deformation, cracks,

finishing deterioration, and history of fire accidents.

There are three levels of evaluation. First level evaluation needs just area of columns

and walls. F is assumed as 1.0, which means no ductility. First level is useful for the

17

buildings of which drawings are missing and bar arrangements in members are

unknown. The result of the first level is the most conservative.

The second level evaluation consider the ultimate strength, failure mode, and ductility

of columns. Girders are considered rigid and strong enough. The third level evaluation

consider those of the girders, too. The third level evaluation must be applied for the

buildings of which girders are expected to form yielding hinges.

The required seismic capacity index, soI , is calculated as Equation 3.2.4.

UGZEI SS 0 Equation 3.2.4

Where SE is the basic seismic capacity evaluation index, 0.8 for the first level

evaluation and 0.6 for the second and third level evaluations. Z is the zone factor, which

is a reduction factor according to the seismic activity at the site defined in Building

Standard Low in Japan. G is the soil condition factor and U is importance factor.

The Japanese central government set the target to finish the evaluation and retrofitting

if needed of 90% of the existing buildings by Y2015. The Building Standard Low of

Japan had been revised in 1981. After that, ultimate capacities of all existing buildings

need to be evaluated. Therefore, the “standard for seismic evaluation of the existing

reinforced concrete buildings” is basically applied for the existing buildings that were

designed before 1981. As of 2008, about 80% of the existing buildings were evaluated

and retrofitted if needed.

3.3 Computer analysis tools

3.3.1 Modeling of building

In order to conduct a numerical simulation to predict building behavior, building needs

to be modeled in a computer to represent its structural characteristics. There are three

levels of modeling of building as shown in Figure 3.3.1, frame model, shear vibration

model (MDoF), and shear vibration model (SDoF).

In frame model, each member such as column, girder, and shear wall are modeled to

18

one-component model, which has several springs to represent linear and non-linear

flexural, shear and axial behaviors. Figure 3.3.2 shows an example of one-component

model for girder. The model has two rigid zone at both ends of the member to represents

rigid behavior in the beam-column joint region. At the end of rigid zone, it has

non-linear springs to represent flexural behavior. At the center of the member, there is

one more non-linear spring to represent shear behavior. There are several models

proposed to represent non-linear behavior of each spring.

The shear vibration model (MDoF) is simplified model from the frame model, which has

one horizontal non-linear spring in each story to represent the non-linear relationship

between story shear and story displacement. The relationship is defined from the

results of pushover analysis, which will be mentioned later. The degree-of-freedom of

the model is equal to the number of story (Multi-Degree-of-Freedom). Therefore this

model can represent higher mode effect.

The simplest model is the shear vibration model (SDoF). The behavior of the building is

simplified down to the Single-Degree-of-Freedom (SDoF) system. The model has only

one horizontal nonlinear spring, which is defined according to the total behavior.

(a) Building

(b) Frame Model (c) Shear Vibration

Model (MDoF)

(d) Shear Vibration

Model (SDoF)

Figure 3.3.1 Modeling of Building

19

Figure 3.3.2 Example of one-component model (for girder)

3.3.2 Time History Analysis

Once the building is modeled, several kind of analysis can be conducted with the model.

Time history analysis can reproduce the response behavior of the building under an

earthquake input. During the analysis, the motion of equation is solved to calculate the

responses at each time step. Time history of input motion is needed for this analysis. If

the input motion can be defined, this analysis method is the most accurate to predict

actual behavior during an earthquake. The results is, however, depending on the input

motion. Careful attention must be paid that a different input motion can give different

results.

3.3.3 Pushover analysis

Pushover analysis gives non-linear response under the constant lateral load

distribution shape. Generally, the lateral load distribution shape (the ratio of the

amount of lateral load at each floor) is defined prior to conducting the analysis. The

amount of the lateral load is then gradually increased.

Figure 3.3.3 Pushover analysis

From the pushover analysis with frame model or shear vibration model (MDoF), the

Rotation

Rigid zone

One-Component Model

Moment Rotation spring

Shear spring

Skelton curve by using tri-linear

Rotation spring

Displacemen

Shear Shear spring

Crac Crac

Yield

Shear

EI

20

relationship between story shear and story displacement of each story can be obtained

as shown Figure 3.3.4. From this relationship, it can be discussed such as the amount of

base shear, most vulnerable story, and failure mechanism. Moreover, the damage of the

building at step by step can be checked as shown in Figure 3.3.5, and deformation and

restoring force of each member can be traced.

Sto

ry s

he

ar

Story displacement

1F

2F3F

Figure 3.3.4 Relationship between story shear and story displacement

Figure 3.3.5 yield hinge development

3.3.4 Capacity spectrum method

The response of the pushover analysis as shown in Figure 3.3.4 can be simplified down

to the SDoF system. The simplified shear force in unit of acceleration, 1 , is called

“representative acceleration”, and calculated from Equation 3.3.1. The simplified

displacement, 1 , is called “representative displacement”, and calculated from

Equation 3.3.2.

i

ii

ii Pxm

xm12

1

21

1 Equation 3.3.1

21

ii

ii

xm

xm

1

21

1 Equation 3.3.2

Where;

im Mass at i-th story

ix1 Relative displacement at i-th floor to the base of the building

iP1 Amount of lateral force acting at i-th floor

If the system is elastic, the maximum value of 1 and 1 under an earthquake are

equal to the values of the acceleration response spectrum Sa and the displacement

response spectrum Sd at the predominant period of the building as shown in Figure

3.3.6. The curve of which horizontal axis is 1 and vertical axis is 1 is called

performance curve, and the curve of which horizontal axis is Sd and vertical axis is Sa is

called demand curve. The maximum response point is the intersection between the

performance curve and the demand curve. The demand curve is usually defined from

the design spectrum.

1

1 Figure 3.3.6 Maximum response, Sa and Sd

If the performance curve shows nonlinearity, additional damping effect due to

additional energy dissipation during the non-linear response. The equivalent damping,

eqh is calculated as Equation 3.3.3 according to the Building Standard Low of Japan.

22

The viscous damping of 5% is considered.

05.01

1

eqh Equation 3.3.3

Where;

=0.20 or 0.25 according to the structural characteristics

yielding factor

The demand reduction factor due to the nonlinearity, hF is calculated as Equation

3.3.4.

eq

h hF

101

5.1

Equation 3.3.4

The maximum response can be estimated at the intersection between the performance

curve and reduced demand curve by hF . If no structural member reaches the safety

limit state such as shear failure, bonding failure, or compression failure, the structure is

evaluated safe.

Figure 3.3.7 Capacity Spectrum Method

23

4. Result of Field Investigations

Field investigation was conducted in mainly three locations, which were Sagbayan,

Tubigon, and Loon as shown in Figure 2.1.

Totally 10 buildings were surveyed from outside and 7 buildings were investigated in

detail. The investigated buildings were listed in Table 2.1.

Table 4.1 Building for investigation

Location

Sagbayan Building A: Sagbayan City Hall (Detailed Investigation)

Building B: Residential house (Detailed Investigation)

Loon Building C: Hospital No.1 at Loon (Detailed Investigation)

Building D: Hospital No.2 at Loon (Detailed Investigation)

Building E: Hospital No.3 at Loon (Detailed Investigation)

Tubigon Building F: Tubigon Presidencia Building

Others Corella high school

Canangc an integrated school

Paaralang elementrya ng Fatima Cortes

Municipal Hall at Catigbian

24

Figure 4.1 Survey root (2014/02/25) and location of the investigated building in Bohol

25

4.1 Building A: Sagbayan city hall (at Sagbayan)

4.1.1 Outline of building damage

The front view of Sagbayan city hall is shown in Figures 4.1.1 and 4.1.2. The building

has 2 stories, reinforced concrete structure with the hollow concrete brick walls. There

is the independent frame structure in the first story of main frame (see Figure 4.1.7).

The building have open ceiling space in the entrance area. Dimension of typical column

is shown in Table 4.1.1. The Spacing of hoop is 250 mm, which is relatively large. In

Japan, minimum spacing of column hoop is basically 100 mm in order to prevent shear

failure [4].

The brick walls were severely failed in shear as shown in Figure 4.1.3. Large shear

cracks and falling of concrete bricks were observed. The shells of concrete bricks broke

down partially, then the mortar in their hollow was exposed as shown in Figure 4.1.4. It

is presumed that strength of concrete brick was small or the quality of the bricks was

not good. A girder failed in torsional shear at the joint with a orthogonal beam due to

torsional moment as shown in Figure 4.1.5. Most of columns of which dimensions were

270 × 270 mm failed in shear as shown in Figure 4.1.6.

Figure 4.1.1 Before the earthquake

(from google)

Figure 4.1.2 After the earthquake: Feb.

25 2014

26

Figure 4.1.3 Damage to wall Figure 4.1.4 Damage to wall

Figure 4.1.5 Damage to girder Figure 4.1.6 Damage to column

Table 4.1.1 Dimensions of Columns

Member Longitudinal bars Hoop

Column 300×300mm 8-D19 Hoop: 2-D10@250 (90° hook)



4.1.2 Damage assessment of the building

Damage of the surveyed building was assessed according to the evaluation method

shown in Section 3.1. The plan view of the first floor and damage class of column is

27

shown in Figure 4.1.7. The hollow concrete brick walls were neglected. The residual

Seismic Performance ratio: R, was calculated 62 % as follows. As the result, the

surveyed building was judged “Moderate damage”.

%6210041

5.25100

org

j

A

AR

Figure 4.1.7 Damage class of column on the first floor

Table 4.1.2 Assessment of Damage of member

Shear column flexure column total

Number of member 42 1 43 Number of

surveyed member 40 1 41

40×1.0 1×1.0 = 41 =Aorg

Damage

class

0 ×1.0 0 ×1.0 =0 =A0

22 ×0.95 0 ×0.95 =20.9 = A1

II 5 ×0.6 1 ×0.75 =3.75 = A2

III 3 ×0.3 0 ×0.5 =0.9 = A3

IV 0 ×0 0 ×0.1 =0 = A4

V 10 ×0 0 ×0 =0 = A5

Sagbayan City Hall 1F

N

2600

4700

4100

4300

4900 2900 5800 2200 5800 2900 4900

5850

5500 4900

1800

2870

2870

3870

23001070

4300 4300

independent frame

Ⅰ

Ⅰ

Ⅰ

Ⅰ

Ⅱ Ⅰ

Ⅰ

Ⅴs

?

?

Ⅰ Ⅰ Ⅰ Ⅰ

ⅠⅠⅠⅠ

Ⅲs

Ⅴs

Ⅴs

Ⅴs

Ⅴs

Ⅱs Ⅱs

Ⅴs

Ⅴs

Ⅴs

Ⅱs

Ⅰ

Ⅱs Ⅱs

Ⅲs

Ⅴs

Ⅴs

Ⅰ Ⅰ

Ⅰ Ⅰ

Ⅰ Ⅲs

Ⅰ Ⅰ

Unit: mm

28

4.1.3 Findings and Lessons from Building A

The following remarks can be drawn from the findings from the field investigation of

Building A

As a result of damage assessment of three buildings, all surveyed buildings were

judged "Moderate damage".

It is presumed that strength of concrete brick was small since the quality of the

bricks was not good.

Since some columns do not have girders in one direction, the lateral strength could

be reduced, which may reduce the base shear coefficient.

Most of columns of which dimensions were 270 × 270 mm failed in shear

29

4.2 Building B: House (at Sagbayan)


The investigated house is shown in Figures 4.2.1, 4.2.2, and 4.2.3. The building has 2

stories, and it is reinforced concrete structure with the hollow concrete brick walls. The

first floor of this building used to be a restaurant and second floor is residence. Story

collapse at the first story took place, then the second floor fell down. Dimension of the

column was 250×250mm, longitudinal bar was 4-D13, hoop was 2-D8@220 (ps=0.0018)

and rebar hook type of hoop was 90° bend. Story height was 2500 mm. The rebound

hammer test revealed an average concrete strength of 22.0 N/mm2. Tensile test of

reinforcing bars revealed yield strength of 359 N/mm2. The plan view of second floor is

shown in Figure 4.2.4. The shape of the plan view was trapezoidal shape.

Figure 4.2.1 Exterior views of the

buildings

Figure 4.2.2 Damage to column

Figure 4.2.3 Interior views of the buildings

30

Figure 4.2.4 Plan view of the second floor

4.2.2 Base shear coefficient

The base shear coefficient of this building was calculated. The collapse mechanism of

the building was story collapse at the first story. It is assumed that the collapse occurred

due to the failure of columns. Since the first floor was collapsed and not able to be

investigated, it was assumed that the plan of first floor is the same as the second floor

plan. Dead load and live load were assumed as the follows.

[Dead load] - roof 0.2kN/m2（steel sheet roofing）

- ceiling 0.15kN/m2 (boarded ceiling)

- floor 0.2kN/m2 (boarded floor)

- reinforced concrete, concrete brick 2.4kN/m3

[Live load] 0.6kN/m2

As the result, Total weight of the building was calculated 534 kN. The compressive

strength of concrete of 22.0 N/mm2 and the yielding strength of reinforcing bars of 359

N/mm2 were applied.

The ultimate flexural strength and ultimate shear strength of columns were calculated

according to the "Standard for Seismic Evaluation of Existing Reinforced Concrete

Buildings" [3]. It was evaluated that the column should show flexural failure mode.

The base shear coefficient, which is shear capacity of first story divided by the total

weight of the building, was evaluated as 0.40. Since some columns do not have girders

in one direction as shown in Figure 4.2.3, the lateral strength could be reduced, which

may reduce the base shear coefficient. Moreover, there might be possibility that the

House 2F

N

4250

515

017

25

balcony

3350 3350 3350 1125

?

Unit: mm

x

y

31

amount of the hollow brick walls in the first story might be less than that of the second

story, since the first story was restaurant.

4.2.3 Pushover analysis

Non-linear pushover analysis was conducted. The beams and columns were modeled by

using One-component model. Non-linear shear spring was considered in modeled

column. The foundation was assumed to be fix, and the floor was assumed to be rigid.

The lateral load acted on the building according to Ai distribution calculated from the

following equation.

T

TA i

i

i 31

211

n

j

j

n

ij

j

i

W

W

1

i : Non dimensional weight

Wi : Weight of i-th story

n : Number of story of the building

T : The fundamental natural period (sec)

hT 01.002.0

h : Height of the building (m)

α : Ratio of the height of story, consisting of steel columns and girder, to entire

height h, this means that T = 0.03h for steel structure and T = 0.02h for

concrete structures.

Mass of first story (second floor) and second story (roof floor) were assumed to be 372kN

and 162kN respectively. The loading direction were x and y direction. This analysis was

conducted by using a software of " STERA3D ver.6.0" [5].

Story drift and story shear relations are shown in Figure 4.2.5. Longitudinal axis is

story shear coefficient which story shear is normalized by total weight of the building.

Figure 4.2.6 shows location of plastic hinge in the building. Story shear coefficient at the

first story is about 0.39. Story drift at the first story is considerably larger than that at

the second story, and it is found that plastic hinge develop end of column in first story.

32

these results are corresponding to story collapse at the first story of damaged building.

Figure 4.2.5 Relationship of story shear and story drift

X-direction loading

Y-direction loading

Figure 4.2.6 location of plastic hinges

4.2.4 Findings and Lessons from Building B


Building B





Story drift at the first story is considerably larger than that at the second story, and

it is found that plastic hinge develop end of column in first story. These results are

corresponding to story collapse at the first story of damaged building.

0.6

0.5

0.4

0.3

0.2

0.1

0

Q /

ΣW

0.020.0150.010.0050

Story drift (rad.)

1st-stroy 2nd-story

X-direction

0.6

0.5

0.4

0.3

0.2

0.1

0

Q /

ΣW

0.020.0150.010.0050

Story drift (rad.)

1st-stroy 2nd-story

Y-direction

33

4.3 Building C: Hospital No. 1 (at Loon)


The investigated Hospital No.1 is shown in Figures 4.3.1. The building has single-story,

and is reinforced concrete structure with the hollow concrete brick walls.

Dimension of the column was 300×300mm, longitudinal bar was 4-D19, hoop was

2-D10@200 (ps=0.0024). Dimension of the beam was 200×300mm. Story height was

3400 mm. The rebound hammer test revealed an average concrete strength of 30

N/mm2.

As for damage of columns, although cracks and falling of finishing cement mortar were

observed in most columns, the damage level of reinforced concrete columns themselves

was minor damage. A column showed falling of concrete cover as shown in Figure 4.3.6.

The brick walls failed in shear with large crack or breaking bricks as shown in Figures

4.3.7 and 4.3.8. Failure of beam-column joint was observed as shown in Figure 4.3.9.

Figure 4.3.10 shows cracks in floor slab. Slight settlement was also observed. The

column significantly separated form brick wall and sink as shown in Figure 4.3.11. Also

other column separated form brick wall sink as shown in Figure 4.3.12, and it was found

that there was no RC foundation in visible observation. It is preferable that firm RC

foundation beam is used in order to provide structural performance of column or brick

wall. Meanwhile, This building located adjacent to slope as shown Figure 4.3.13, and

crack occurred in soil of slop as shown in Figure 4.3.14.


buildings

Figure 4.3.2 Damage to column

34

Figure 4.3.3 Damage to column Figure 4.3.4 Damage to column

Figure 4.3.5 Damage to column Figure 4.3.6 Damage to column

Figure 4.3.7 Damage to wall Figure 4.3.8 Damage to wall

35

Figure 4.3.9 Damage to beam-column

joint

Figure 4.3.10 Damage to floor

Figure 4.3.11 Separation between

column and wall

Figure 4.3.12 Separation between

column and wall at the bottom of column

Figure 4.3.13 Surrounding situation Figure 4.3.14 views of the slope at the

western side of the building

separation

slope soil crack

FL

36


Damage of surveyed building was assessed according to evaluation method shown in

Section 3.1. The plan view of the first floor and damage class of column is shown in

Figure 4.3.13. The hollow concrete brick walls were neglected. Residual Seismic

Performance ratio: R, was calculated 78 % as follows. As the result, the damage level of

the surveyed building was judged "Moderate damage".

%7810028

8.21100

org

j

A

AR


(Damage class of V is determined due to failure of beam column joint)

NHospital 1

3800 5100 4500 4500 5100 3800

5300

2800

5300

Crack and Settlement

Ⅰ

Ⅰ Ⅰ

Ⅰ

Ⅰ Ⅰ

Ⅰ

Ⅰ

Ⅰ

Ⅰ

Ⅱ0

0

0

Ⅱ

0

0

Ⅱ

ⅡⅡs Ⅱ

Ⅱ

Ⅱ

Ⅰ

Ⅲ

Ⅴ

Ⅴ

Ⅴ

Unit: mm

37



Number of member 1 27 28 Number of surveyed member 1 27 28

1×1.0 27×1.0 = 28 =Aorg

Damage

class

0 ×1.0 5 ×1.0 =5 =A0

0 ×0.95 11 ×0.95 =10.45 = A1

II 1 ×0.6 7 ×0.75 =5.85 = A2

III 0 ×0.3 1 ×0.5 =0.5 = A3

IV 0 ×0 0 ×0.1 =0 = A4

V 0 ×0 3 ×0 =0 = A5

4.3.3 Findings and Lessons from Building C


Building C



It is preferable that firm RC foundation beam is used in order to provide structural

performance of column

This building located adjacent to slope as shown Figure 4.3.13, and crack occurred

in soil of slop.

38

4.4 Building D: Hospital No. 2 (at Loon)


The investigated Hospital No.2 is shown in Figure 4.4.1. The building has single-story,

and it is reinforced concrete structure with the hollow concrete brick walls. This

building has parapet made of concrete brick on the roof as shown in Figure 4.4.1. This

concrete brick parapet drop down and be inclined.

Dimension of the column was 300×300mm. Dimension of the beam was 300×400mm.

Story height was 3500 mm. The rebound hammer test revealed an average concrete

strength of 32 N/mm2.

The column at the corner of building separate from brick wall as shown in Figure 4.4.3.

The brick wall infilled RC frame and the brick wall between windows failed in shear as

shown in Figure 4.4.4 and Figure 4.4.5. As for damage of columns, although crack and

falling of finishing cement mortar were shown in most columns, reinforced concrete

column themselves were slightly damaged. These damages were similar to Building C.

Figures 4.4.7 and 4.4.8 show damage of beam. The cantilever beam was connected these

beam-column joint in order to sustain concrete brick parapet, it is presumed that much

stress applied to this beams.


buildings


buildings

39

Figure 4.4.3 Damage to bottom of column Figure 4.4.4 Damage to brick wall

infilled RC frame

Figure 4.4.5 Damage to brick wall between

windows

Figure 4.4.6 Damage to beam-column

join

Figure 4.4.7 Damage to beam Figure 4.4.8 Damage to beam

40


Damage of surveyed building was assessed according to evaluation method shown in

Section 3.1. Plan view of the first floor and damage class of column is shown in Figure

4.4.9. The hollow concrete brick walls is neglected. Residual Seismic Performance ratio:

R, is calculated 92 % as s follows. As the result, the surveyed building was judged

"Minor damage".

%9210028

8.25100

org

j

A

AR


(Damage class of III is determined due to damage of beam-column joint or the beam)



Number of member 0 28 28 Number of surveyed member 0 28 28

0×1.0 28×1.0 = 28 =Aorg

Damage

class

0 ×1.0 11 ×1.0 =11 =A0

0 ×0.95 14 ×0.95 =13.3 = A1

II 0 ×0.6 0 ×0.75 =0 = A2

III 0 ×0.3 3 ×0.5 =1.5 = A3

IV 0 ×0 0 ×0.1 =0 = A4

V 0 ×0 0 ×0 =0 = A5

NHospital 2

2940 5840 5900 5900 5900 6000

4000

4200

400

0

Ⅰ

0

Ⅰ

Ⅰ

Ⅰ

Ⅰ

Ⅰ

0

0

Ⅰ

Ⅰ

Ⅰ

0

0

0

0

0

0

0

0

Ⅰ

Ⅰ

Ⅰ

Ⅰ

Unit: mm

Ⅲ

ⅢⅠ Ⅲ

41

4.4.3 Findings and Lessons from Building D


Building D



This building has parapet made of concrete brick on the roof. The cantilever beam

was connected these beam-column joint in order to sustain concrete brick parapet,

it is presumed that much stress applied to this beams.

42

4.5 Building E: Hospital No. 3 (at Loon)


The Loon Hospital is a two-storey building located in the municipality of Loon, in the

central part of the Bohol island, at some distance from the earthquake epicenter.

The building has a complex configuration with the overall dimensions 25.0х8.0 m in the

plan. It is a two-storey building, the storey height being 3.2 and 3.0 m. The structural

design is a reinforced concrete frame consisting of columns and two-way beams. The

columns of the first floor have rectangular cross-section of 300х500 mm. The columns

grid is 3.0х8.0 m. The columns of the second floor have the section of 300х350 mm.

The floor structure consists of the two-way reinforced concrete beams and cast

reinforced concrete floor slab. The covering structure consists of the timber triangular

truss. The roof coating has four sloping surfaces and is covered by the metal fluted

sheets. The walls are made of hollow concrete blocks (the material is porous concrete)

with subsequent filling of cavities with the reinforced concrete. There is a staircase,

which is made of the wooden structures.

Overview of damage

Primary structure: there are cracks in the separate external and internal walls. The

general condition of the bearing structures is estimated as satisfactory.

Secondary structure: the internal wall of the first floor is blocked near the staircase; the

wall is ruined on the second floor. There is a crack seen in the cantilever part of the rear

façade girder. The condition of the separate filler structures is estimated as

unsatisfactory.

43

Figure 4.5.1 - Overall View of Loon Hospital

Building

Figure 4.5.3 - Flank Façade

Figure 4.5.5 - External Wall Damage

Figure 4.5.2 - Rear Façade

Figure 4.5.4 - Second Flank Façade

Figure 4.5.6 - Crack in the Cantilever

Part of Girder

44

Figure 4.5.7 - Cracks in Sidewall

Figure 4.5.9 - Damage of External Wall

Figure 4.5.11 - Blocked Wall Near the

Staircase of the First Floor

Figure 4.5.8 - Cracks under Longitudinal

Girder

Figure 4.5.10 - Failure of the Second

Floor Wall

Figure 4.5.12 - Cracks in the Partition of

the First Floor Internal Wall

45

Figure 4.5.13 - Reinforced Concrete

Cantilever Girder of the Entry Elements

(top

view)

Figure 4.5.15 - Reinforced Concrete Floor

Slab

Figure 4.5.14 - Timber Structures of the

Roof and Roof Coating


Possible cause of damage drawn from the quick assessment

The building bearing structures do not have any damages. To all appearances the basic

part of seismic load was taken up by the walls, as the most rigid elements, across the

building, as a result of which they suffered the major damages. In general the building

structure is seismically safe; however the roof construction does not have sufficient

rigidity for the perception and equal reallocation of the horizontal seismic loads, that is

the negative factor.

46

Computer analysis

The building seismic resistance was determined on the basis of analysis of design

features, which the buildings should have for their operation in the earthquake

endangered zone. The analysis was carried out based on the experience of design of

similar buildings and multiple preceding inspections and computer design models.

Design of the bearing structures was made through computer modeling. In the design

only the load-carrying capacity of the columns was taken into account, without

consideration of perception of seismic load by the walls (in the long term). Data of the

reinforcement tests carried out by the MAPUA Institute of Technology of Philippines [6]

were also included into the design. There is no data on the concrete material, therefore

in the design the light concrete type 2000 in density, grade in density on B15

compression was conditionally accepted [7][8][9].

As a result of the in-depth inspection the following was identified. The building in its

current condition is seismically safe. Reinforcement of the damaged walls is required,

inclusion of the additional vertical stiffening elements (walls, trusses, etc.) to the frame

performance is recommended. When reconstructing the roof structure establishment of

lateral braces along the roof structure for stiffening for the horizontal impacts is

recommended. In accordance with the design results, the provision of the load-carrying

capacity of the columns the minimum reinforcement of 8Ø28 mm (first level) and 8Ø22

mm (second level) is required. Otherwise the building seismic resistance will not be

considered as ensured.

The inspection was made at random, i.e. a certain part of structures is exposed to the

inspection. In this connection at the time of work performance on reconstruction and

seismic reinforcement circumstances not taken into account in this conclusion may be

identified. In such event for the correction of the decisions made it is necessary to apply

to the developers of this conclusion in order to make adequate decisions.

47

4.5.3 Findings and Lessons from Building E


Building E

In general the building structure is seismically safe.

The roof construction does not have sufficient rigidity for the perception and equal

reallocation of the horizontal seismic loads.

Reinforcement of the damaged walls is required, inclusion of the additional vertical

stiffening elements (walls, trusses, etc.).

When reconstructing the roof structure establishment of lateral braces along the

roof structure for stiffening for the horizontal impacts is recommended

48

4.6 Building F: Governmental Building (at Tobigron)


The building inspected is located in the territory of Bohol Island (Philippines).

The Tubigon Presidencia building is located in the municipality of Tubigon situated in

the north-western coastal part of the island, which is close to the epicentral area.

Function – administrative building. Age not established.

The Tubigon Presidencia building has a configuration complex in its plan and consists of

4 blocks. There is a public building adjacent to the main building, which has no

functional relation to the inspected part and is separated from it with a seismic joint

about 1 meter wide, therefore it was not included into the inspection goal. There is no

project documentation for the building.

Block 1.

It consists of a two-storey part with the plan dimensions 21.5х12.5 m, borders with

blocks 2 and 3, and entry elements with the plan dimensions 9.5х4.5 m. The entry

elements and blocks 2 and 3 are separated from block 1 by seismic joints. Storey height

is 4.0 m.

The structural design is mixed and includes the bearing walls along the perimeter and

internal timber frame.

The bearing walls are made of local blocks, the material is natural stone (limestone).

The internal frame consists of timber struts of the first floor with the section 200х200

mm (there are no struts on the second floor).

The floor structure between the first and second floors consists of longitudinal timber

struts resting against the struts and walls and wooden floor. The covering structure

consists of timber space trusses (by the time of the inspection the roof coating is

dismantled by 90 %). The roof coating material is not known.

The entry elements are made of reinforced concrete.

Block 2.

It is a staircase extension. Plan dimensions are 10.0х8.0 m. Structural design – bearing

walls bearing walls along the perimeter.

Bearing walls are made of reinforced concrete.

Stair flights and extensions are made of timber.

The roof structure is similar to block 1. At the time of inspection there is no roof and roof

coating.

49

Block 3.

It is a basement single-level structure. Plan dimensions are 8.0х3.5 m, height is 2.5 m.

It is adjacent to block 2, there are no seismic joints. Structural design is bearing walls

along the perimeter.

Bearing walls are made of reinforced concrete.

The roof structure is a cast reinforced concrete slab.

Block 4.

Its plan configuration is rectangular with dimensions 12.9х7.0 m, two-storey, floor

height is 4.0 m. The structural design is a reinforced concrete frame consisting of

columns and two-way beams.

Columns of the first floor have the rectangular (500х500 mm) and circular (500 mm)

section. The column grid is 4.3х3.5 m. Columns of the second floor are located along the

perimeter of the block, with section 350х350 mm.

The floor structure consists of two-way reinforced concrete beams and a cast reinforced

concrete floor slab.

The roof consists of triangle lean-to metal trusses. There is no roof coating at the time of

the inspection.

There are no walls at the time of the inspection, the material could not have been

determined accurately. From all appearances, the walls were made of artificial hollow

blocks (material – porous concrete) with subsequent filling of hollows with reinforced

concrete.

Characteristics of the material bearing walls were not identified.

Block 4.

The design characteristics of the basic materials accepted in the design:

- Design resistance of the reinforcement to the tension is Rs = 170 MPa.

- Modulus of reinforcement elasticity under the tension and compression is Es = 174 000

MPa (not sure).

- Design concrete resistance to the compression is Rb = 8.5 MPa.

- Initial modulus of concrete elasticity under the tension and compression is Eb = 18 000

MPa.

52

Figure4.6.1 - Overall View of Tubigon

Presidencia Building

Figure 4.6.3 - Block 1. Wall Damages


Figure 4.6. 2 - Entry Elements



53

Figure 4.6.7 Block 1. Through Cracks in

Walls

Figure 4.6.9 Block 1. Roof Coating

Dismantled

Figure 4.6.11 Block 2. Inside View

Figure 4.6.8 Block 1. Internal Timber

Frame

Figure 4.6.10 Block 2. Overall View

Figure 4.6.12 - Block 2. End Wall. Roof

Coating Dismantled

54

Figure 4.6.13 Joint between Block 2 (on

the left) and Block 1 (on the right).

No Clearance in the Seismic Joint

Figure 4.6.15 Block 3. Reinforced

Concrete Roof Slab

Figure 4.6.17 Block 4. Seismic Joint

between Blocks 1 and 4. Columns of

Console Section

Figure 4.6.14 Block 3. Overall Overview

Figure 4.6.16 Block 4. Overall

Overview

Figure 4.6.18 Block 4. Destruction of the

Concrete of the Second Floor Column

55

Figure 4.6.19 Block 4. Metal Roof

Trusses

Figure 4.6.20 Block 4. Reinforce

Concrete Frame and Cast Floor Structure


Possible cause of damage drawn from the quick assessment

Defects of individual structural elements were identified during the inspection.

Block 1.

A part of the bearing walls is collapsed. There are vertical and inclined through cracks

in the wall crossing areas and in separation walls. There are horizontal cracks in the

level of lintel blocks.

As a result of horizontal shifts clearances appeared in the wooden cover of the floor

structure. There are no linking elements in the floor structure level.

Entry elements – there are cracks in the upper part of the vertical bearing elements.

The overall condition of the bearing and enclosing structures is estimated as critical.

Damages of structures of this block made up over 50%. Only structures of timber struts

and beams of the floor structure were left undamaged. The structural design of block 1

is not aseismic on several parameters:

- Internal wooden structures almost do not bear horizontal loads, as a result all seismic

load falls at the bearing walls.

- Wooden floor and roof do not provide stiffness of the structure, as a consequence, the

walls are not connected with each other.

- The bearing walls structure does not provide the bearing capability for dynamic loads

(both on the brick material and joint), there is no masonry reinforcement, there are no

metal and reinforced concrete inclusions as well.

- Timber and soldier arches over the door and window openings also made a bad

56

showing at the time of operation in the seismic zone.

- Distance between the bearing walls of one direction is too big for such wall parameters

(another wall is required longitudinally, and at least two walls transversely).

- Also there are no vertical ties, which could bear a part of seismic load.

It is an emergency block.

Block 2

It has no significant damages. There is no clearance in the seismic joint between blocks

1 and 2, due to which there are cracks in their junction zone. The overall condition of the

bearing and enclosing structures is estimated as satisfactory.

The structural design of block 2 is seismically safe – the bearing concrete reinforced

walls operate reliably under seismic effects. However, absence of a stiff roof or

horizontal ties in the roof level may result in their excessive deformation in case of

resonance phenomena. This block is seismically safe.

Block 3

It has no damages. The overall condition of the bearing and enclosing structures is

estimated as satisfactory.

The structural design of block 3 is seismically resistant – bearing concrete reinforced

walls in combination with the concrete reinforced roof are an earthquake resistant

structural system. Seismic resistance of this block is provided.

Block 4.

All walls are removed, due to which it is impossible to assess their damages.

One of columns of the second level has significant damages – concrete in the lower third

of the column completely collapsed, the reinforcement cage bared and was partially

exposed to corrosion. Reinforcement of this column was made of 6 bars Ø 12 mm

(longitudinal reinforcement) with the total area about 6.8 cm2, lateral reinforcement Ø

6 mm is located with vertical spacing 300 mm.

At the time of the frame erection three columns of the second level were displaced more

than 0.5 m off axis to the console part.

The overall condition of the bearing and enclosing structures is estimated as

unsatisfactory.

From all appearances, the main part of the seismic load was borne by the walls along

the perimeter of the block, as the most stiff elements, as a result they suffered major

damages. In general, the block structure is seismically safe, however the columns on N

axis are displaced as to the lower columns, which is a negative factor. Vertical elements

57

should be located directly one over another, with no shifts.

4.6.3 Damage assessment of the building Computer Analysis

For block 4 the bearing structures design was made (computer design). Only the bearing

capability of columns was taken into account, without considering bearing of the seismic

load by the walls (long term). Also the design included data of the reinforcement test

performed by the MAPUA Institute of Technology of Philippines[6]. There is no data

about concrete material, therefore in the design the concrete of light density grade 2000

was provisionally accepted with compression capacity class В15 [7][8][9].

The design was made in accordance with the standards applicable in the territory of the

Republic of Kazakhstan with reference to the local ground and seismic conditions.

The area of construction is seismic – intensity 8 (tentatively). Class of soils according to

seismic properties is II (second).

Design of the building bearing structures was made using LIRA-Windows computer

system implementing the finite element method in the design. The design models are

described below.

When designing for the earthquake effects in accordance with the requirements of

Construction Norms & Regulations RK 2.03-30-2006 [7][8][9]. the following design

factors were used for the area with the estimated seismicity of intensity 8 and soil class

II (second):

- seismicity coefficient А = 0.25 (when determining the horizontal seismic

loads) and 0.18 (when determining the vertical seismic loads);

- building criticality factor К1 = 1.0;

- reduction ractor taking into account the building construction solutions К2 =

0.30;

- building height factor К3 = 1.0;

- factor taking into account the building capacity to dissipation of vibrational

energy Кψ = 1.0;

- soil conditions factor К0 = 1.0.

The design was made for the following loadings:

1 – constant;

2 – temporary (useful for the floor structure);

3 – special (seismical along axis X);

4 – special (seismical along axis Y).

According to the design results a conclusion was made that bearing capability of

58

columns does not provide seismic resistance of the block, reinforcement of the damaged

column is not enough, 8Ø28 mm (first level) and 8Ø22 mm (second level). It is necessary

either to reinforce them or include additional vertical stiffness elements into the work

(walls, ties, etc.). In the current state this block is earthquake-prone.

4.6.4 Findings and Lessons from Building F


Building F

Block 1, a part of the bearing walls is collapsed Block 2 and 3 don’t have significant

damage. Block 4, All walls are removed, due to which it is impossible to assess their

damages

There is no clearance in the seismic joint between blocks 1 and 2, due to which

there are cracks in their junction zone.

The columns on N axis are displaced as to the lower columns, which is a negative

factor. Vertical elements should be located directly one over another, with no shifts..

Bearing capability of columns does not provide seismic resistance of the block,

reinforcement of the damaged column is not enough

59

5. Conclusion for RC buildings

All findings of 6 buildings that were conducted detailed assessment are listed below

again.

Building A

It is presumed that strength of concrete brick was small since the quality of the

bricks was not good.



Most of columns of dimensions 270 × 270 mm failed in shear.

Building B



From pushover computer analysis, story drift at the first story is considerably

larger than that at the second story, and it is found that plastic hinge develop end of

column in first story. These results are corresponding to story collapse at the first

story of damaged building.

Building C

It is preferable that firm RC foundation beam is used in order to provide structural

performance of column

This building located adjacent to slope, and crack occurred in soil of slop.

Building D

This building has parapet made of concrete brick on the roof. The cantilever beam

was connected these beam-column joint in order to sustain concrete brick parapet,

it is presumed that much stress applied to this beams.

Building E

The roof construction does not have sufficient rigidity for the perception and equal

reallocation of the horizontal seismic loads.

Reinforcement of the damaged walls is required, inclusion of the additional vertical

stiffening elements (walls, trusses, etc.).

When reconstructing the roof structure establishment of lateral braces along the

roof structure for stiffening for the horizontal impacts is recommended

60

Building F

There is no clearance in the seismic joint between blocks 1 and 2, due to which

there are cracks in their junction zone.

The columns on N axis are displaced as to the lower columns, which is a negative

factor. Vertical elements should be located directly one over another, with no shifts.

Bearing capability of columns does not provide seismic resistance of the block,

reinforcement of the damaged column is not enough

Recommendation

Taking into account that these 6 buildings don’t necessarily represent all buildings in

Bohol or Philippines, however, we could draw recommendations from perspective of 1)

Structural Design, 2) Material and 3) Zoning from our investigation.

Structural Elements

Foundation:

Building without RC foundation beam, that caused the reduction of structural

performance of columns was observed. In order to secure enough strength for shear

force, it is recommended that have RC foundation beam and columns/bearing walls are

rigidly connected (Ex: reviewing structural/seismic code/standard, reviewing building

control system (interim check etc.)).

Columns:

Failure in shear in small dimension columns was observed. Also the displacement of

columns on N axis was observed. These are assumed to be caused due to lack of

principle in the building code or inappropriate practice during construction. It is

recommended that the columns have enough dimension size to sustain the earthquake

force and columns are vertically placed appropriately. (Ex: Reviewing the building

code/standard for the structural/seismic safety principle and reviewing the building

control (interim check). Reviewing seismic design force or safety factor in the structural

design)

Columns and Walls:

Crash of first floor in piloti building was observed. The crash was caused by plastic

hinge in the columns of first floor. It is recommended to have enough columns and walls

to sustain earthquake force (Ex: reviewing structural/seismic design for enough

columns and walls and balance of planning in order to avoid crash/swing of the

building).

Beam:

61

Lack of connection between beam and columns was observed. These are assumed to be

caused due to lack of principle in the building code or inappropriate practice during

construction. (Ex: Reviewing the building code/standard for the structural/seismic

safety principle and reviewing the building control (interim check). Reviewing seismic

design force or safety factor in the structural design).

Roof:

Lack of rigidity in the roof structure was observed, that caused the unequal reallocation

of the horizontal seismic loads. These are assumed to be caused due to lack of principle

in the building code or inappropriate practice during construction. (Ex: Reviewing the

building code/standard for the structural/seismic safety principle and reviewing the

building control (interim check). Reviewing seismic design force or safety factor in the

structural design).

Design:

Unbalanced design with top heavy concrete parapet that caused the damage on parapet

and beams was observed. Also, the lack of clearance between two different structures

that caused the cracks in the junction zone was observed. (Ex: Reviewing the building

code/standard for the structural/seismic safety principle and reviewing seismic design

force or safety factor in the structural design).

Material

Crash of concrete block and the exposure of mortar in the block’s hollow were observed.

This is the lack of strength of the block. It is recommended that the material is secured

to have enough strength to sustain earthquake force. (Ex: reviewing material standards

and quality control of material).

Zoning

Cracks in buildings adjacent to slope were observed. It is recommended that the

buildings are built based on the risk the location have. (Ex: reviewing the zoning code

site selection and design of foundation in building code).

62

6. Condition Assessment of Four Heritage Churches on the Island of Bohol

6.1 Church of Our Lady of the Immaculate Conception in Baclayon

Background and Description

The Church of Our Lady of the Immaculate Conception (Figure 6.1.1) is located in

Baclayon (9˚ 37’ 22” north; 123˚ 54’ 44’ east; elevation 22 metres). Founded in 1595, it is

one of the oldest churches in the Philippines and the present structure is one of the best

preserved Jesuit-built churches in the region. Construction of the present structure was

begun after 1717 and completed in 1727. The bell tower was completed in 1777. In the

19th century, a new façade with portico was added, along with a number of stone

buildings that now surround the church. Next to the church is the convento. A new wing

was added to the convento in 1872. The convento is now the Baclayon Museum.

The Church of Our Lady of the Immaculate Conception is cruciform in plan with an

octagonal dome at the crossing, an octagonal baptistry off of the west transept, and a

convento connected to the east transept (see drawings in Appendix A). The bell tower is

square in plan and is located in front of, and to the east of, the main entrance. The

exterior masonry bearing walls are composed of dressed coral stone exterior and interior

surfaces.

There are buttresses on the longitudinal walls with two levels of windows between each

buttress. The roof structure is a wood A-frame truss with 150x250 mm (6x10 inch) top

chords and a 100x200 mm (4x8 inch) horizontal center brace. There are four trusses

per bay. At each bay of the nave the walls are tied together with a horizontal wooden

250x350 mm (10x14 inch) beam. These beams also engage the base of the

aforementioned trusses.

The roofing is painted corrugated metal that simulates the appearance of Spanish tiles.

The interior walls are finished with dressed coral stone and the ceiling is

monochromatic fabric stretched over board planking. The altar ceiling is polychromed.

The floors are cement tile over a concrete slab on grade.

The church is oriented with its entrance to the south and altar to the north. It is south

southwest of the epicenter of the earthquake.

63

Figure 6.1.1. Pre-earthquake view of the church in Baclayon showing the now collapsed

portico and bell tower.

Mapping of Damages

We visually observed the following damages:

The portico at the front entrance to the church has completely collapsed, leaving

the original front façade exposed but compromised (Figure 6.1.2).

There are large diagonal cracks in the original front façade of the church (Figure

6.1.3).

The top tier and much of the middle tier of the bell tower have collapsed. At the

bottom tier, the exterior coral stone is delaminating from the rubble back-up

(Figure 6.1.4).

One of the interior pilasters collapsed into the sanctuary, revealing that it was

not keyed into the nave wall during construction (Figure 6.1.5). At least three

other pilasters are also delaminating from the nave walls (Figure 6.1.6).

The west transept gable partially collapsed, falling outward onto the roof of the

baptistry (Figure 6.1.7).

A crack map survey of the church in plan is provided in Appendix E. It reveals,

other than that described above, a series of vertical cracks through the exterior

masonry bearing walls that are typically located at corners and at window and

door openings in the wall.

64

Figure 6.1.2. Collapsed front portico. (photo: S. Kelley)

Figure 6.1.3. Cracks in the original front façade seen from the interior upper balcony.

(photo: S. Kelley)

Figure 6.1.4. Delamination of the dressed coral stones from the rubble back-up at the

base of the belltower. (photo: S. Kelley)

65

Figure 6.1.5 Collapsed interior pier in the nave. The separation is smooth except for

some stone keys indicating that the pier is not contiguous and may not have been

constructed at the same time as the nave wall. (photo: S. Kelley)

Figure 6.1.6 Partial separation of another interior pier on the nave wall. (photo: S.

Kelley)

Figure 6.1.7 Partial collapse of the west gable onto the roof of the baptistry. (photo: S.

Kelley).

66

Materials Studies

Based on petrographic studies, the wall interiors are filled with rubble stone laid in

carbonated hydrated lime with aggregate of poorly graded natural sand and pebbles

mainly composed of rounded particles of carbonate rock (limestone), coral, shells and

minor amounts of siliceous rocks/ minerals.2

2 Petrographic studies of samples removed from the bell tower performed by Laura Powers of WJE.

67

6.2 The Church of Santa Monica in Alburquerque


On June 9, 1868, Gov. General Jose de la Gandara, issued the decree establishing the

new town of Alburquerque in its civil jurisdiction. On November 14, 1868, the Fr.

Provincial of the Recollects approved the creation of the town as to its religious

jurisdiction. On June 18, 1869, the Bishop of Cebu made Alburquerque a separate

Diocesan parish. It was dedicated to Santa Monica. During this era the Augustinian

Recollect friars administered the parish.

Up to the 1880s, the parish church was a large shed with thin partition walls. The

present church of was commenced shortly afterwards, utilizing the same three-aisled

plan as the original. However, the bell tower and other upper portions were completed

during the first half of this century. The interior paintings were done by Ray Francia

circa 1932.

The Church of Santa Monica is cruciform (see drawings in Appendix B). The bell tower

is square and rises above the front entrance (Figure 6.2.1). The exterior masonry

bearing walls are composed of dressed coral stone exterior and interior surfaces. There

are interior log columns in the nave that accentuate the division between the nave and

aisles (Figure 6.2.2).

The belltower is constructed of reinforced concrete and stands on four square columns -

two in the front façade and two within the nave (Figure 6.2.3). It was noted that one of

the wood columns had also been replaced with reinforced concrete.

The roof structure is supported on simple king post trusses with 100x200 mm (4x8 inch)

chords and 100x200 mm (4x8 inch) and 100x100 mm (4x4 inch) diagonals. There is one

truss per bay.

The roofing is painted corrugated metal. The interior walls are finished with dressed

coral stone and the ceiling is polychromatic fabric stretched over board planking. The

floors are cement tile over a concrete slab on grade.

The church is oriented with its entrance to the south southwest and altar to the north

northeast. It is located south southwest of the epicentre of the earthquake.

68

Figure 6.2.1 View of the front façade of the church in Alburquerque as seen from the

southeast. Note that the upper portion of the belltower is reinforced concrete. (photo: S.

Kelley)

Figure 6.2.2 Interior view of the Church. The interior columnar supports are logs, and

the ceiling is highly decorative. (photo: S. Kelley)

Figure 6.2.3 View of the reinforced concrete belltower support columns where they

penetrate through the decorative ceiling.

69

Mapping of Damages


The church relative to other churches in the area sustained little damage and

the damage is centered at the south entrance portico.

There is significant damage to the east and west ends of the portico. Most of the

displaced elements were observed to be either reinforced concrete or stone work

that was set in hard mortar (Figures 6.2.4 and 6.2.5).

There is displacement of the voussoirs of the west arch in the portico (Figure

6.2.6).

There is cracking and displacement at many of the buttresses indicating that the

walls must have moved during the event (Figure 6.2.7)

The gable ends were constructed with wood rather than with stonework (Figure

6.2.8). This indicates that a lesson had been learned about collapsing gables

during seismic events and the details of construction had been changed to

prevent this collapse phenomenon.

There is vertical cracking on the corners of the left transept corners (Refer to

Appendix E).

Termite mud tubes were observed in the walls in the area of the portico. Termite

tubes are also present in the roof structure on the east side (Figure 6.2.9).

70

Figure 6.2.4. Concrete elements that have fallen from the façade. (photo: S. Kelley)

Figure 6.2.5. Damaged portions of the façade where concrete elements have fallen away.

(photo: S. Kelley)

Figure 6.2.6. Stone voussoirs that have become loosened on the eastern archway

leading into the south portico. (photo: S. Kelley)

Figure 6.2.7. Stonework that has become loosened at the buttress. (photo: S. Kelley)

71

Figure 6.2.8. North gable of the church that was completed with wood rather than

masonry. (photo: S. Kelley)

Figure 6.2.9. Termite mudtubes on the wooden rafters at the east side of the roof.

(photo: S. Kelley)

72

6.3 The Church of Our Lady of the Village in Corella


The following oral history was developed by Soli Rigor and Joselito H. Corpus in

interviews with villagers.

The village of Corella was formerly known as Nugas (from verb manugas, meaning from

“pounding rice” in a mortar and pestle) and was later renamed Corella, after a town in

Portugal. The parish of La Nuestra Senora del Villar was established 1884, separated

from the mother parish of Baclayon.

The site of the Church of Our Lady of the Village was originally a ricefield that was

donated by a prominent citizen of the town. The plaza was owned by the municipio

(town government) and was leased out to the church at 5 pesos per year.

Prior to construction of the church a chapel was on the site. After the establishment of

the parish, church building began and culminated in the early 20th century. The

building has not been significantly altered since its completion.

The entire ceiling was painted with murals but was whitewashed because of moisture

infiltration from the roof. Only the four evangelists remain at the four corners of the

dome of the church. The floor has the original cement tiles. The windows were altered

in the 1970s/1980s; the original window system was formerly wood frame holding

translucent capiz shells.

Since the earthquake, the church reports that cracks had appeared on the left side aisle.

The Church of Our Lady of the Village is cruciform (see drawings in Appendix C). The

bell tower is square and rises to the right of and adjacent to the narthex (Figures 6.3.1

and 6.3.2).

The exterior bearing walls are composed of reinforced concrete. There are interior

reinforced concrete columns in the nave that accentuate the division between the nave

and aisles (Figure 6.3.3).

The roof structure is supported on wood scissors trusses with an upper slope of 20

degrees. We could not measure the member sizes or truss spacing. It is assumed that

the roof trusses are wood.

73

The roofing is painted corrugated metal (Figure 6.3.4). The interior walls are painted

concrete and the ceiling is metal panels painted white. The floors are cement tile over a

concrete slab on grade. Reportedly the left (west) side of the church was constructed on

fill.

The church is oriented with its entrance to the south and altar to the north. It is

located south southwest of the epicentre of the earthquake.

Figure 6.3.1 View of the Church in Corella from the southwest. (photo: S. Kelley)

Figure 6.3.2 View of the church in Corella from the southeast. (photo: S. Kelley)

Figure 6.3.3 View of the Church from the interior. (photo: S. Kelley)

74

Figure 6.3.4 Roof above the Church as seen from the south. (photo: S. Kelley)

Mapping of Damages


There is damage to the east and west ends of the portico. The portico sustained

movements that were counter to the rest of the structure (Figure 6.3.5).

There is a large vertical crack adjacent to the belltower (Figure 6.3.6).

There are cracks along the left (west) side of the reinforced concrete arches that

connect the nave columns to the west wall (Figure 6.3.7).

There are cracks and differential settlements along the left (west) side of the

church (Figure 6.3.8).

Crack mapping is shown in 6.5.5

75

Materials Studies

Tensile testing of five samples of the steel reinforcing was performed at the Mapua

Institute of Technology in Manila under the direction of EduardoVillamor. Samples S1

through S3 were the size that would be considered number 5 bars by the Concrete Steel

Reinforcing Institute (CRSI). Samples S4 and S5 were the size that would be

considered number 2 bars by CRSI. Samples 1 through 3 met requirements of 60KSI

steel and samples 4 and 5 met the requirements of 40KSI steel. Test results are

included in 6.6

Figure 6.3.5 Damage of the portico where it meets the narthex of the church, as seem

from the east. (photo: S. Kelley)

Figure 6.3.6 Damage to the church where it meets the belltower. (photo: S. Kelley)

76

Figure 6.3.7 Cracking within the reinforced concrete arches in the left (west) aisle of

the nave. (photo: S. Kelley)

Figure 6.3.8 Cracking on the floor on the left (west) side of the nave. (photo: S. Kelley)

77

6.4 The Church of Saint Anthony of Padua in Sikatuna


The following oral history was developed by Soli Rigor and Joselito H. Corpus in

interviews with villagers.

Sikatuna was originally known Cambuyod then as Cornago, after a visiting friar’s last

name. Then the town was renamed in 1917 as Sikatuna after Datu Sikatuna.

The original chapel was constructed nearby the mercado (market), but moved to a better

location that was at the highest point in the town. The land was owned by the diocese.

The designer of the church was an engineer from Loon who had no architectural

training. Plots nearby the church were given to parishioners to re-center the town

around the church.

The construction of church began in 1900 and was completed over ten years, with

parishioners contributing sacks of cement, sand and stones. Steel rebars were

included in the original construction.

The foundation of the church is solid limestone, reportedly going down at least one

meter.

The windows were originally wood, but changed to decorated blocks in 1970s or 1980s.

The floors have been tiled twice; the ceilings have been redecorated three times, and the

roofing was installed in 1997.

The Church of Saint Anthony of Padua is cruciform (see drawings in Appendix D). The

bell tower is square and rises at the center of the entrance portico (Figures 6.4.1 and

6.4.2).

The exterior bearing walls are composed of reinforced concrete.

The roof structure is supported on wood piggyback trusses with an upper slope of 24

degrees. The top chord is a 150mm (6 inch) diameter log. The bottom chord is a

125x225 mm (5x9 inches). The diagonals are 50x100 mm (2x4 inches) and 50x200 mm

78

(2x8 inches).

The roofing is painted corrugated metal. The interior walls are painted concrete and the

ceiling is metal panels painted white (Figure 6.4.3). The floors are cement tile over a

concrete slab on grade.

The church originally had four doors and one front door entry, and after quake, the

community decided to renovate the church to include two additional doors at the right

and left sides (Figure 6.4.4). Buttresses were later additions to the original

construction; after the recent earthquake, two more buttresses were added at the nave.

Additionally, two more buttresses are planned to be constructed at the front of the

church.

The church is oriented with its entrance to the south and altar to the north. It is

located south southwest of the epicenter of the earthquake.

Figure 6.4.1. Front façade of the church in Sikatuna. The belltower is centered on the

portico. (photo: S. Kelley)

79

Figure 6.4.2 View of the church from the southwest. Notice the recently added buttress.

(photo: S. Kelley)

Figure 6.4.3. Interior view of the church. (photo: S. Kelley)

Figure 6.4.4. A doorway was being added on the east side of the nave. (photo: S. Kelley)

80

Mapping of Damages


There is significant damage to the east and west ends of the entrance portico.

The portico and belltower above sustained movements that were counter to

the rest of the structure (Figures 6.4.5 and 6.4.6).

The base of the portico columns are fractured due to rocking of the portico

(Figure 6.4.7).

The south façade of the church adjacent to the portico has also been damaged

due to the movement of the portico (Figure 6.4.8 and 6.4.9).

Crack mapping reveals vertical cracks along both sides of the nave are

included in 6.5.5

Figure 6.4.5. Damage on the east side and within the portico. (photo: S. Kelley)

81

Figure 6.4.6 . Damage on the west side of the portico. (photo: S. Kelley)

Figure 6.4.7 . Damage at the base of one of the portico columns. (photo: S. Kelley)

Figure 6.4.8. Damage on the west side of the church where it abuts the portico. (photo:

S. Kelley)

82

Figure 6.4.9. Damage on the east side of the church where it abuts the portico. (photo:

S. Kelley)

Materials Studies

Tensile testing of four samples of the steel reinforcing was performed at the Mapua

Institute of Technology in Manila under the direction of EduardoVillamor. Samples S1

through S4 were the size that would be considered number 5 bars by the Concrete Steel

Reinforcing Institute (CRSI). Samples met requirements of 40KSI steel. Test results

are included in 6.6

83

6.5 Drawings

6.5.1 Drawings of Church of Our Lady of the Immaculate Conception in Baclayon

Plan Side Elevations

Longitudinal sections.

87

6.5.2 Drawings of the Church of Santa Monica in Alburquerque

Plan Side Elevations Transverse sections

91

6.5.3 Drawings of the Church of Our Lady of the Village in Corella

Plan

Front Elevation Side Elevations Transverse section Longitudinal Section

96

6.5.4 Drawings of the Church of Saint Anthony of Padua in Sikatuna

Plan

Front Elevation Side Elevations Transverse section Longitudinal Section

101

6.5.5 Crack Map Surveys

Church of Our Lady of the Immaculate Conception in Baclayon Church of Santa Monica in Alburquerque Church of Our Lady of the Village in Corella

Church of Saint Anthony of Padua in Sikatuna

106

6.6 Tensile Testing of Steel Reinforcing

The Church of Our Lady of the Village in Corella The Church of Saint Anthony of Padua in Sikatuna

109

7. Conclusions for the churches All findings of 4 churches that were investigated are listed below Church of Our Lady of the Immaculate Conception in Baclayon Both the portico and the bell tower have collapsed and are damaged so severely that

they will need to be totally dismantled before they can be reconstructed. It is significant

that the portico was an addition to the church, and reveals that the addition was not

adequately attached to the original structure.

The masonry bearing walls appear to be undamaged other than the interior pilasters,

which do not seem to be adequately tied into the nave walls. These interior pilasters are

not part of the structure of the walls but a decorative applique. Other than the front

portico, two of the gables have collapsed at the top, revealing possible differential

movement between the walls and roof.

Any rehabilitation or reconstruction will require a seismic retrofit intervention to

strengthen the unreinforced masonry walls and tie the various elements of the

structure together (i.e. walls and roof) or to separate certain elements (i.e. sanctuary,

baptistry, bell tower). For any intervention, traditional methods and “soft” materials

should be given first consideration.

Church of Santa Monica in Alburquerque Significant damage was observed at the portico. It was observed that the stone portico

is built in tandem with a belltower that is composed entirely of reinforced concrete.

The belltower, being taller than the church nave moved independently of the church this

causing damage to the portico. In addition concrete elements that had been

incorporated into the façade also became loose and fell to the ground.

There was also significant damage at many of the buttresses. This seems to indicate

that the nave walls were in out of plane movement during the seismic event.

Termite activity was observed in the attic at the south end of the building.


strengthen the unreinforced masonry walls and tie the various elements of the

structure together (i.e. walls and roof) or to separate certain elements (i.e. sanctuary,

110

baptistry, bell tower). For any intervention, traditional methods and “soft” materials

should be given first consideration.

Church of Our Lady of the Village in Corella There was observable damage to the portico at the south end of the church. In addition

there was damage to the wall structure where it about the belltower indicating that the

tower had a period that was distinct from the church.

The church was reportedly built on fill on the west side. In this area there was

settlement that is observable on the floor on the left side of the nave. In addition the

cracking of the concrete vaults on the west side of the nave are probably related to this

differential settlement.


strengthen the damaged concrete elements and tie the various elements of the structure

together (i.e. walls and roof) or to separate certain elements (i.e. sanctuary, portico, bell

tower). For any intervention, reinforced concrete would be the appropriate material.

Church of Saint Anthony of Padua in Sikatuna

There was significant damage to the portico at the south end of the church. In addition

there was significant damage to the wall structure where it abuts the portico indicating

that the portico and belltower had a period that was distinct from the church.


strengthen the damaged concrete elements and tie the various elements of the structure

together (i.e. walls and roof) or to separate certain elements (i.e. sanctuary, baptistry,

bell tower). For any intervention, reinforced concrete would be the appropriate material.

111

Summary Taking into account that these 4 churches don't necessarily represent all churches in

Bohol or Philippines, however, we could summarize the damage and recommendation as

follows.

Cause of Damage Tightness: It is observed in the damage of inadequate tight ness between the building elements

such as interior pilasters and nave walls (Baclayon) and walls and roofs that might

cause the collapse of gables (Bacrayon).

Differential Movement: Differential movements are observed in building elements that caused the damage in

the structures such as bell tower and nave wall (Alburquerque), buttress and nave wall

(Alburquerque), tower and church (Collera) and Portico, bell tower and church

(Silatuna).

Others: There are other observation of termed activity in the attic (Alburquerque) and allegedly

built on the fill that caused the cracking in the concrete vaults (Corella).

Intervention: Rehabilitation or reconstruction will require a seismic retrofit to strengthen

unreinforced or concrete elements.

In the intervention, it should be careful to tie or separate structural elements.

It should be careful for the material/method of intervention. For some churches,

traditional methods (In this case unreinforced masonry walls with buttresses instead of

concrete) and soft materials (use of lime mortars rather than Portland cement mortars)

should be given first consideration, for others, reinforced concrete would be the

appropriate material.

112

References

[1] PHIVOLCS Seismic Monitoring Network, http://www.phivolcs.dost.gov.ph/,

(April.2014)

[2] The Japan Building Disaster Prevention Association: Guideline for Post-earthquake

Damage Evaluation and Rehabilitation, 2002. (in Japanese)

[3] The Japan Building Disaster Prevention Association: Standard for Seismic

Evaluation of Existing Reinforced Concrete Buildings, 2005.

[4] Architectural Institute of Japan: AIJ standard for structural calculation of reinforced

concrete structures, 2010. (in Japanese)

[5] T. Saito: STERA3D Technical Manual Ver. 3.3,

http://www.rc.ace.tut.ac.jp/saito/software-e.html (2014.6)

[6] Construction Norms & Regulations 2.03.01-84* Concrete and Reinforced Concrete

Structures. Moscow, 1992.

[7] CN RK 1.04-04-2002 Inspection and Assessment of Technical Condition of Buildings

and Structures. Almaty, 2002.

[8] Data on testing the material samples obtained by the MAPUA Institute of

Technology of Philippines.

[9] Construction Norms & Regulations RK 2.03-30-2006 Construction in Seismic

Districts. Almaty, 2006.

113

Annex

Mission member

UNESCO-IPRED

1. Soichiro Yasukawa (UNESCO Paris) coordinator for experts

Programme Specialist, Earth Science and Geohazard Risk Reduction, Natural

Science Sector, UNESCO, Paris

2. Mr. Ruslanzhan Sadyrov (Kazakhstan)

Institute of Seismology, Ministry of Education and Sciences

3. Mr. Kanatbay Ryskulov (Kazakhstan)

Institute of Seismology, Ministry of Education and Sciences

4. Tomoya Matsui (Japan) Toyohashi Institute of Technology

5. Koichi Kusunoki (Japan) Tokyo University (Yokohama national University

during the mission)

6. Mr. Stephen Kelly (USA) Historic Preservation Specialist (Wiss, Janney,

Elstener Associate, Inc during the mission)

UNESCO National Commission

1. Dr. Virginia A. Miralao

Secretary-General, UNESCO National Commission of the Philippines

2. Dr. Reynaldo S. Vea

Chairman, S&T Committee

UNESCO National Commission of the Philippines and

President, MAPUA Institute of Technology

3. Dr. Mario Aurelio

Head, Structural Geology and Tectonics Laboratory

National Institute of Geological Sciences

University of the Philippines, Diliman, Quezon City, Philippines

4. Engr. Bienvenido Cervantes

Professor, Civil Engineering and Environmental Division

MAPUA Institute of Technology

5. Engr. Eduardo Villamor

Professor, Civil Engineering and Environmental Division

MAPUA Institute of Technology

6. Mr. Freddie A. Blanco

Development Management Officer, UNESCO National Commission of the

114

Philippines

Bohol Partners

1. Fr. Ted Torralba

Secretary, CBCP Permanent Committee on Church Heritage (PCCH)

Archdiocese of Tagbilaran

2. Arch. Anthony Manding

Coordinator of the Diocese of Tagbilaran's Commission for the Cultural

Heritage of the Church

3. Mr. Joselito “JJ” Corpus

Heritage Conservator

4. Ms. Socorro T. Rigor

Diocese of Tagbilaran

5. Mr. Lemuel Barol

Cogon High School (Evening Class)

115

Itinerary

Date Activity

24th February AM: Team Member Meeting

PM: Field Investigation on 3 schools around Tagbilaran

: Courtesy visit to Leonardo Medroso, Bishop

: Courtesy visit to Edgardo M Chatto, Governor of Bohol

25th February AM: Field investigation on government hall (Sagbayan)

Field investigation on government hall (Tubigon)

Interview to building official at Sagbayan municipality

PM: Field investigation on government hall and houses (Sagbayan)

Site visiting of churches at Calane, Loon and Panglao

26th February AM: Visiting Catigbian looking for damaged buildings

Field investigation on government hall and houses (Sagbayan)

Site visiting at Inabanga (the fault lines)

PM: Field investigation on government hall (Tubigon)

Field investigation on hospitals (Loon)

Meeting on field investigation on church and building permission

27th February AM: Field investigation on 4 churches (Sikatuna, Corella, Baclayon

and Albur)

PM: Field investigation churches (Sikatuna, Corella)

28th February AM: Field Investigation on churches (Baclayon and Albur)

: Report to Leonardo Medroso, Bishop

PM: Field Investigation on hospictals (Loon)

29th February AM: Report to Edgardo M Chatto, Governor of Bohol

report of post-earthquake field investigation bohol ... · report of post-earthquake field...

Documents