Rapid Visual Screening Survey

International Conference on Enhancement of Urban Disaster Resilience

(under the UNU Grant for Global Sustainability Project)

Organized by:

Yangon City Development Committee (YCDC)

Yangon Technological University (YTU)

Myanmar Engineering Society (MES)

Graduate School of Global Environmental Studies (GSGES), Kyoto University

Chapter (I) Introduction

1.1 General

Myanmar is prone to different ranges of natural disaster includingearthquake. Several earthquakes of different magnitudes happened inthe past around the country such as the Magnitude 8.0, May 23, 1912Maymyo earthquake, the March 23, 1839 Ava (M~7.5) Earthquake,May 5, 1930 (M-7.3) Bago Earthquake and July 16, 1956 (M-7.0)Sagaing Earthquake (source; Dr. Myo Thant). The most recentdamaging Chauk Earthquake happened in 2016 caused 3 peopledead and several pagodas were damaged and collapsed in Baganarea.

Earthquake don’t Kill people but unsafe buildings do.

Therefore, it is important to know the seismic hazards of existingbuildings

1.5 Expected Outcomes

• To get GIS database for Screen area,

• To Identify if a particular building requires further evaluation (Tier-2 detailed analysis),

• To increase awareness among screen area regarding seismic vulnerability of buildings.

1.6 Implementation Programm

Data Presentation

Data Entry to QGIS Map

Digitizing the map using QGIS Software

Data Analysis

Data Compilation

Field Observation

Determination of Cutoff Score

Acquiring Soil Information

Determination of Benchmark Buildings

Preparation of RVS Forms

RVS sheet per Seismicity

Calculate Seismicity

Chapter (2)Literature Review

2.2 International Practice in RVS

RVS can be very valuable to prioritize the buildings to be furtherstudied so that technical and other resources could be mosteffectively utilized. The procedure involves side walk surveyeither without entering the building or doing so for a shortduration only (15-45 minutes). RVS is useful when the number ofbuildings to be evaluated is large, since even non-engineers maycollect data and assign scores. However, uncertainty and nonavailability of the details can result in widely differinginterpretations of the criteria by different individuals leading toinconsistent results.

2.3 RVS Methodologies in USA

• A number of guidelines were developed by the federal emergencymanagement agency (FEMA) in the USA for seismic riskassessment and rehabilitation of buildings. These includes

1. FEMA 154 in 1989 and revised in 1992,

2. FEMA 154(2002) developed as second edition

3. Developed as third revised version of FEMA 154 in 2015 Januaryfor rapid visual screening of buildings.

• FEMA-154 has been used not only in America but also widely inEurope (2.4 RVS in Greece) as well as in Asia (2.5 RVS in India)

• In this Study, FEMA-154 Third Edition established in 2015 Januaryhas been used

Chapter (3)Theoretical Approach to

Seismic Risk Management

3.1 General

Seismic risks management ofexisting buildings is mainly influencewith dealing three steps: ScreeningPhase (1), Numerical Evaluation (2)and Detailed Analysis to assesseither the life safety or immediateoccupancy performance level of thebuilding. Screening Phase (Tier 1)uses a Rapid Visual Screening(RVS) methodology, while tier (2)and tier (3) needs more detailed andsophisticated analysis. In this study,Rapid Visual Screening assessmenthave been adopted to know collapseprobability of existing buildingsaccording to FEMA-154.

Basic Information

Step 1: Rapid Visual Screening

Step 2: Numerical Evaluation

Step 3: Detail Analysis

Earthquake Risk Mitigated Building

Not OK

OK

Not OK

OK

Retrofit Design

3.2 Rapid Visual Screening of Buildings for Potential Seismic Hazards (RVS Procedure)

• Screening PhaseTier (1)

• Evaluation PhaseTier (2)

• Detailed Evaluation PhaseTier (3)

3.3 Uses of Rapid Visual Screening Results

The main purpose of RVS results is to knowthe current situation of existing buildings inrelation to seismic hazard and other relatedhazards so that the building owner canknow his/ her building requiresstrengthening or retrofitting measures. Thebuildings can be identified according to RVSscores. The scoring system provided ineach building with a numerical score can beused as a prioritization tool in vulnerabilityassessment. (FEMA 155, Third Edition)

3.4 Instructions of Filling Data Collection Form Level (I)

• Seismicity

• Building Identification

• Photograph

• Occupancy

• Sketch

• Soil Type

• Falling Hazards

• Comments

• Building Type

• Modifiers

• Final Score

• Evaluation Required

Wai Yar Aung M.S (CM)-6 12

3.5 Instructions of Filling Data Collection Form Level (II)

Chapter (4)Analysis for Rapid Visual Screening Assessment

4.1 Introduction

In this chapter, the proposedselected areas in Yangonregions are evaluated withrapid visual screeningassessment and digitized withQGIS. For this study, ByaneKwet Thit Ward in TarmweTownship and Pzundaung ward(2) in Pazundaung Townshipare selected. Before Observingat selected areas, the followingparameters are required.

1. Seismicity of YangonRegion

2. Choosing data collectionform according to seismicityregion

3. Soil Type

4. Determination ofBenchmark Building

4.2 Seismicity of Yangon Region

Ranges of acceleration of gravity inhorizontal direction for moderately highseismicity region areSpectral Acceleration Response, Ss(Short-period or 0.2 seconds) = 0.50 g≤ Ss < 1.00 gSpectral Acceleration Response, S1(Long-period or 1.0 second) = 0.20 g≤ S1 < 0.40 gGround motion for 0.2 Sec SpectralResponse acceleration for 2% Ss andMotion for 1 sec spectral responseacceleration at 2% of Yangon are 0.77 and0.31 accordingly. Therefore, Yangon lieswithin Moderately High Region.

Seismicity

Region

Spectral Acceleration

Response, Ss (Short-

period or 0.2 seconds)

Spectral Acceleration

Response, S1 (Long-

period or 1.0 second)

Low Ss < 0.25 g S1 < 0.10 g

Moderate 0.25 g ≤ Ss < 0.50 g 0.10 g ≤ S1 < 0.20 g

Moderately High 0.50 g ≤ Ss < 1.00 g 0.20 g ≤ S1 < 0.40 g

High 1.00 g ≤ Ss < 1.50 g 0.40 g ≤ S1 < 0.60 g

Very High Ss ≥ 1.50 g S1 ≥ 0.60 g

Note: g = acceleration of gravity in horizontal

direction

4.3 Choosing data collection form according to seismicity region

There are five different types ofLevel 1 and 2 Data Collection Form,representing different seismicityregions; Very High, High, ModeratelyHigh, Moderate and Low. The basisscores and score modifiers vary withseismicity regions. According toseismicity, the selected areas arelies in the Moderately high seismicityregion, Therefore, for this study,Moderately High Seismic datacollection form is used. The followingfigure are the sample data collectionform according to the FEMA-154pwhich was used to know the seismicperformance existing buildings.

4.4 Soil Information

• There are various sources of datafor the soil conditions at a site,including geotechnical engineeringreports. If soil maps of the area arenot available, soil type can beestimated based on average shearwave velocity in the top 30 metersof soil, VS

30.

• According to the probabilisticseismic hazards map of Yangon,Yangon lies between within 340m/sec to 200 m/s. Therefore, soiltype for Yangon region is Type D(Stiff Soil) as per FEMA soilClassification.

Figure showing Vs30 Contour map of Yangon City, Yangon Region (Ref: Probabilistic Seismic Hazard Map of Yangon, Yangon Region, Myanmar)

4.5 Determination of Benchmark building

In Myanmar, Seismic design provision onlystarted to apply after CQHP (Committee forQuality Control of High rise building ConstructionProjects) had established in 2002. Seismicresistant design for buildings more than 8 storieswas initially adopted in 2002 with the formation ofCQHP (Committee for Quality Control of High-rise Buildings Construction Projects). Later in2009, YCDC (Yangon City DevelopmentCommittee) adopted seismic detailingrequirements for all buildings in Yangon includinglow-rise buildings. Therefore, buildings before2002 can be assumed as pre-code and thesebuildings were not considered as earthquakeresistant buildings and buildings after 2009 canbe assumed as post benchmark buildings can beassumed as the building with compulsory seismicdetailing.

Building Type Seismic Design

Provision

Code Note

RC Frame,

Brick Infilled

2002 UBC97 9 story and above

All building 2016 MNBC 3 story and above

Table showing benchmark year of the corresponding building type

4.6 Field Survey Case Study Areas

(1). Pazundaung Ward (2), Pazundaung Township

2. Byane Kwet Thit Ward, TarmweTownship

Pre-Screening Data

Seismicity Region Yangon (Ss : 0.77 , S1 : 0.31) Moderately High Seismicity

Building Age Pre Code : Before 2002 , lower

than 9th story before 2008

Post Benchmark : After 2002

(10th story above for after

2008)

Soil Type PSHA Map Yangon Soil Type SD (Stiff Soil)

Determine Cutoff Score N=2 (default) Below N=2 unsafe (detailed

evaluation required)

Chapter (5)Comparison of Analysis

Results

5.2 Comparison of number of buildings with its occupancy

In this section number of buildings and itsoccupancy of Pazundaung Ward (2) inPazundaung Township and Byane Kwet ThitWard in Tarmwe Townhip is comparedbased upon moderately high seismicity andsoil type (D). In Pazundaung Ward (2), total199 buildings are located but for ByaneKwet Thit Ward there are only 142 buildings.As both of the wards are located in desnsepopulation areas, the common buildingoccupancy types that are observed in fieldsurveyed was residential buildings mostly 6to 8 stories multi family apartments buildingswhich observed 171 residential buildings inPazundaung Ward (2) and 137 buildings inByane Kwet Thit Ward. The following chartshowing the distribution of buildingsoccupancy in both selected wards.

5.3 Comparison of Building Typology in PazundaungWard (2) and Byane Kwet Thit Ward

Common building typology in selectedwards is reinforced concrete with masonrybrick infill (C3) with 242 out of 341 buildings.Another buildings typology that can only beobserved in Pazundaung ward (2) ascompared to Byane Kwet Thit Ward isUnreinforced masonry brick buildings (URM)with 26 out of 341 buildings which were builtsince 1939 accordingly. Other buildingtypology that are also observed inPazundaung ward (2) and Byane Kwet ThitWard are Brick Noggin without propercompartment (BN1) with 39 out of 341buildings, Single storyed wood building with23 out of 341 buildings and multi storyedwood buildings 9 out of 341 buildings.

5.4 Comparison of building age in Pazundaung Ward (2) and Byane Kwet Thit Ward

According to the surveyed results, buildingage of existing buildings in Pazundaungward (2) can be classified into threecategories; (1) Old buildings (build morethan 50 years which buildings are overdesign life (50 years), (2) Pre-code buildingswhich buildings have no adoption of seismicdetailing and (3) post code buildings whichbuildings are buildings with proper seismicdetailing. Old buildings can be found only inPazundaung ward (2) which has overdesign life and. Moreover, PazundaungWard (2) and Byane Kwet Thit Ward haspre-code buildings with more than 50% andPost code buildings are few with less than50%. The chart below show the number ofbuildings according to buildings inPazundaung Ward (2) and Byane Kwet ThitWard.

5.5 Comparison of Structural Irregularity in Byane KwetThit Ward and Pazundaung Ward (2)

In Pazundaung Ward (2) 24 buildings has beensuffered soft story irregularity. This situationmostly arises in buildings located along the side ofa main street. The ground stories, which have levelaccess from the street, are employed as a street sidestore or a commercial space whereas residencesoccupy the upper stories. These upper storiesbenefit from the additional stiffness and strengthprovided by many partition walls, but thecommercial space at the bottom is mostly left openbetween the frame members, for customercirculation.

In Byane Kwet Thit Ward, 43 buildings have beensuffered short column vertical irregularity effect asmany pre-code buildings in Byane Kwet Thit Wardare built mezzanine floor which shorten the maincolumns in mezzanine floor as compared to othertypical columns because mezzanine floor slab hasbeen added between typical floor levels. The chartbelow show the number of buildings that have beensuffered vertical irregularity effect in PazundaungWard (2) and Byane Kwet Thit Ward

5.6 Comparison RVS results of Pazundaung Ward and Byane Kwet Thit Ward

Pazundaung Ward (2) Byane Kwet Thit Ward

(1) Brick noggin buildings without compartments has average

score 1.17 lower than safety level (n=2) and has collapse

probability 7.2 %

(1) Brick noggin buildings without compartments has average

score 1.215278 lower than safety level (n=2) and has

collapse probability 6.1 %

(2) Unreinforced Masonry Building (URM) has average score 1

lower than safety level (n=2) and has collapse probability

10%

(2). There are no unreinforced masonry buildings observed in

Byane Kwet Thit Ward

(3) Reinforced Concrete with masonry brick infill has average

score 1.37 lower than safety level (n= 2) and has collapse

probability 4.3%

(3). Reinforced Concrete with masonry brick infill has average

score 1.23875 lower than safety level (n= 2) and has collapse

probability 5.77%

(4) Single Wood Story buildings has average score 3.38 higher

than safety level (n=2) and has collapse probability 0%

(4) Single Wood Story buildings has average score 3.903 higher

than safety level (n=2) and has collapse probability 0%

(5) Multi Wood Story buildings has average score 3.1 higher

than safety level (n=2) and has collapse probability 0%

(5) Multi Wood Story buildings has average score 3.7 higher than

safety level (n=2) and has collapse probability 0%

Chapter (6)Conclusion and

Recommendation

6.2 Conclusion

After conducting Rapid Visual Screeningassessment of selected two wards, the mapwhich show seismic performance of exitingbuildings with the guidelines of FEMA 154paccording to collapse probability have beenestablished with the use of Qgis software.Existing buildings in Pazundaung ward (2)and Byane Kwet Thit ward are divided intothree categories,

(1) Good seismic performance which RVSScore greater than 2 ( 0% collapseprobability),

(2) Moderate seisimic performance whichRVS score is between 1 and 2 ( 0% to10% of collapse probability).

(3) Low seismic performance which RVSscore is less than 1 ( more than 10%collapse probability).

42

78

2224

135

40

0

20

40

60

80

100

120

140

160

Low Seismic

Performance

moderate Seismic

Performance

High Seismic

Performace

Num

ber

of

Buil

din

gs

Seismic Performance of existing buildings (FEMA-

154)

Byane Kwet Thit Ward Pazundaung Ward

Seismic PerformanceRed Low Seismic performance 24

Yellow

Moderate Seismic

Performance 135

Green High Seismic Performance 40

Seismic PerformanceRed Low Seismic performance 42

Yellow

Moderate Seismic

Performance 78

Green High Seismic Performance 22

6.3 Recommendation

Existing buildings which has low seismicperformance should be made Tier (2)deficiency based evaluation according tothe guidelines of ASCE 41-13 andRetrofitting guidelines in Myanmar.Moreover, brief explanation of Tier (2) andTier (3) analysis are introduced for furtherstudy.

Step (2) Numerical Evaluation

(1) Pseudo Seismic Force

(2) Story Shear Force

(3) Spectral Acceleration

(4) Fundamental Period

(5) Drift Ratio

(6) Shear Stress in concrete framecolumn

(7) Axial stress in moment frame atbase subjected to overturningforce.

UNU-GGS Project Team Members

Thanks You !!