Citation: Paul, I K., S. Nakai (2022), Seismic performance evaluation of typical residential RC buildings atdifferent soil types with seismic zones in Bangladesh, Synopsis of IISEE-GRIPS Master’s Thesis.

SEISMIC PERFORMANCE EVALUATION OF
TYPICAL RESIDENTIAL RC BUILDINGS AT
DIFFERENT SOIL TYPES WITH SEISMIC ZONES INBANGLADESHIndrajit Kumar Paul1
MEE21716

Supervisor: Shoichi NAKAI2ABSTRACT
Soil site classes and seismic zones are the integral parts of building design. During the earthquake, theeffect of local soil site conditions with zone coefficient plays an important role in building vulnerability.
The Bangladesh National Building Code (BNBC-2020) recommends the guideline for design response
spectrum to reduce the vulnerability during the seismic activity. The seismic performance level of thebuildings was estimated by using the Capacity Spectrum Method (CSM) and compared with the resultsof nonlinear pushover analysis. Two maximum inter-story drift ratios of 0.5% (1/200) and 0.4% (1/250)
are used to determine building performance levels and compare it with code limitation allowable storydrift. The site classification is usually conducted using average shear wave velocity 𝑉̅𝑆 if available.
̅ may be used for site classification. In this study, 160 boreholes locations
Otherwise, the value of 𝑁
were subjected to determined average N-SPT(N30) values based on soil properties up to 30m of site
profile as per BNBC-2020. It has been observed that the two model buildings having the limited drift
angle of 1/200, are only operational in soil site classes SB and SC with a Peak Ground Acceleration(PGA) up to 0.12g. On the other hand, in both drift angles, these buildings in soil classes SB, SC, andSD with a higher PGA than 0.12g are not operational. This paper presents the maximum seismic
performance level, for example, Operetional (OP), Immediate Occupancy (IO), Damage Control (DC),Life Safety (LS), and Collapse Prevention (PC), of the two model buildings located in the different siteclasses (SB, SC and SD) of four seismic zones. Therefore, the evaluation results of the building
performance levels for the lower drift angle (1/250) are more resilient than the higher one (1/200).
Keywords: Drift angle, N-SPT (N30), Response spectrum, Performance level, Site class.
1. INTRODUCTION
The severity of the earthquake depends on the local soil condition, such as the formation period of soil,soil properties, and the nearest active earthquake fault. During the seismic activity, local geology plays
a significant role in controlling the surface effects of earthquake. In recent times Bangladesh does notexperience any high-intensity earthquakes. Bangladesh is now going through the return period of theprobabilistic Maximum Considered Earthquake (MCE) ground motion. Before 1993, Bangladesh had
no building code of its own. At present, Bangladesh has its own building code. Depending on geologicalcharacteristics and the nearest seismic fault, Bangladesh Nation Building Code (BNBC-2020) has been
divided into four seismic zones with different levels of ground motion. Each zone represents the1
2

Soil Mechanics & Foundation Engineering Division, Housing and Building Research Institute, Bangladesh.
Professor Emeritus, Chiba Univ., and Visiting Research Fellow, Building Research Institute.

1

maximum consideration of peak ground acceleration (PGA) based on other soil site classes. Most of thebuildings in our country are of RC frame structure with fill bricks masonry design by an equivalent static
method, while western world or other advanced countries are using performance-based analysis. The
design response spectrum is one of the main parameters to determine building performance. The effectof local soil conditions dominates the response spectrum. “Housing and Building Research Institute”(HBRI) has conducted sub-soil investigation work for the different infrastructure development projectsof the Bangladesh Government. There are so much sub-soil investigation data of the whole country.
Local private agencies have investigated general people's sub-soil so that they can estimate the expenses.
In most cases, the soil test report is considered not accurate. Therefore, moderate-intensity earthquakes
may severely damage our country, especially in the cities where multistoried RC masonry infill typicalresidential buildings with soft ground stories are commonly seen (Md. Arifujjaman, 2017). It isnecessary to do the building performance evaluation of the multistory typical RC residential building
based on the seismic zoning coefficient of different geological characteristics, depending on the places,soil conditions, and seismic zoning coefficient.
2. DATAFor this study, data from 160 boreholes with N-SPT values were collected from the existing soil test
report of the Housing and Building Research Institute (HBRI). These borehole locations were selected
in 160 sub-districts in Bangladesh. Measured N-SPT values were 0 to 50. Whenever the N-SPT values
exceed 50 for 300mm penetration, it was treated as refusal and further N-SPT values were not measured
for that depth as per BNBC-2020. However, measured N-SPT values were directly used here todetermine the average N-SPT (N30) up to the 30m depth.
BORE LOG
Client: BANBEISLocation
Project: Hatiya, Noakhali, Chattagram: Establishment of 160 Upazila ICT Training andResource Center for Education (UITRCE)(2nd Phase): 4(Four) Storied ICT office Building.

Building

Sample Sample
DepthType & Depth(m)No. (Thick)Soil Classification (USCS)
EGL(1.50)
1.5

D-1

3.0

D-2

3.00

4.5

D-3(3.00)

6.0

D-4

7.5

1.50
(1.50)

Light Ash, silty CLAY (CL) withpresence of rubbish.

BoreLog

Borehole No.
Boring Depth (m)G.W.L (m)R.L (m)Latitude (N)Longitude (W)Date started
Date completed::::::::

Standard Penetration
Test Values

S.P.T

0.15 0.15 0.15 0.30

0 10 20 30 40 50 60

0H/W H/W

22H/W H/W

11Light Ash, SANDY CLAY (CL)Bluish Ash/ Light Ash, N/P silty
SAND (SM).

2

34

76.00

366

12

D-5(3.00)

46

713

9.0

D-6

9.00

2336

10.5

D-7

345912.0D-845712(7.50)

1 (One)30.00
1.07 m down from EGLSame As road level22.290463
91.141151
2019/11/04
2019/12/04

Light Ash, N/P sandy SILT (ML).

510Light Ash, silty CLAY (CL).

13.5

D-9

2

2

35

15.0

D-10

12

2

4

16.5

D-11

16.50

12

3

5

18.0

D-12(3.00)

3

3

4

7

19.5

D-13

19.50

12

2

4

21.0

D-14(3.00)

22

35

22.5

D-15

3

3

5

8

24.0

D-16

24.00

44

6

10

25.5

D-17(3.00)

45

914

27.0

D-18

27.00

661218

28.5

D-195

7

101730.0

D-20

68

14

22

Light Ash, silty CLAY (CL) .

1520
Light Ash, N/P clayey SILT (ML).

22.50(1.50)

Light Ash, N/P silty SAND (SM) .
25(1.50)
28.50(1.50)
30.00

Light Ash, N/P silty SAND (SM).

Light Ash, N/P silty SAND (SM) .
Light Ash, N/P silty SAND (SM).

Figure 2. Typical bore log with SPT
N values.

Figure 1. Locations of the boreholes(▲) and two model buildings (★).

On the other hand, the target model buildings are 8-story and 5-story typical RC buildings
situated at Dhaka and Narayanganj city in Bangladesh respectively. For the analysis of 8-story modelbuilding, the superimposed dead load and live load of each floor is considered as 13.85 kN/m 2, and forthe 5-story building, it is considered as 11.73 kN/m2. Floor area for 8-story is 167.84m2 and 5-story
107.30 m2. For the analysis, the target 2 buildings were modeled in STERA_3D (Ver.11.0), which has
shown in the Figure 3 and 4.

2

Figure 4. Three-dimensional view of entire
structure (5-story model building).

Figure 3. Three-dimensional view of entire
structure (8-story model building).

3. METHODOLOGY
3.1. Site classification for the Study Area in (BNBC-2020)
The site classification has been done following the soil properties of the upper 30 meters of the site
̅=profile. Average soil properties will be determined as given in the following equations: 𝑁𝑛𝑛 𝑑𝑖∑𝑖=1 𝑑𝑖 / ∑𝑖=1 where, n= Number of soil layers in upper 30 m, di = Thickness of layer i, Ni = Field
𝑁𝑖̅ -SPT(N30) not exceeding 100(uncorrected) standard penetration value for layer i. Average 𝑁blows/0.3m was directly measured in the field without corrections of the ith formation or layer. Most of
the 160 locations can be classified as site class predominant by SD (96) and SC (61) type, apart from
̅-SPT(N30) values are within the range fromthree locations which were found to be SB type. Average 𝑁
2 to 92. However, Figures 5 and 6 shows the N30 values and site classes, respectively.

Figure 5. Location point with (N30) value.

Figure 6. Location point with site class.

3.2. Design response spectrum and pushover analysis procedure
BNBC-2020 has instructions regarding the demand spectrum of structurers for different soil categories.
In addition, this demand spectrum also emphasizes peak ground acceleration. Figure 7 shows normalized
design response spectrum in different site classes. In this study, all the plotted locations are in threedifferent site classes (SB, SC and SD) with four seismic zone coefficients (0.12, 0.20, 0.28 and 0.36) for
Acceleration Demand Response Spectrum (ADRS), where a 5% damping ratio is considered. Figure 8shows ADRS for site class SC. The selected two model buildings are in Dhaka and Narayanganj cities.

3These two locations are in seismic zone -2, whose zone coefficient is 0.20. The site classes of the modelbuilding’s locations are SC and SD, and the soil site coefficients are 1.15 and 1.35 respectively.

Figure 7. Normalized design acceleration
response spectrum

Figure 8. Acceleration Demand response
spectrums for a 5% damping ratio in 4 seismiczone and site class SC

3.3 Capacity Spectrum method (CSM)

The Capacity Spectrum Method (CSM), a performance-based seismic analysis technique, is a common
procedure for the assessment of building behavior due to ground motion. CSM is applied to assessbuilding behavior depending on several soil site classes and surface geology conditions. In thisprocedure, the resistance capacity of a building to an earthquake which is described by the capacity
curve represents the demand of an earthquake. An intersection point can be determined considering the2 𝑍𝐼
𝑆
ductility of the building. The equations required in this procedure are as follows: 𝑆𝑎 = 3 𝑅 𝐶𝑆 , 𝑆𝑑 = 𝜔𝑎2 =
2𝜋 2

𝑆𝑎 ( ) .
𝑇

3.4. Limit set of a structural model
In order to better assess the structural performance of these structures under different ground motions,five performance levels were considered. The vertical gridlines on each graph at maximum inter story
drift ratio of 0.005, 0.01, 0.015, 0.02 and 0.025 represent performance level of OP, IO, DC, LS and CP,respectively (Y.E. Ibrahim and M.M. El-Shami-2011). In this study, one more conservative drift ratioof 0.004 is considered to find the increasing performance level of these two model buildings.
3.5. Determination of performance point
To find the point where demand and capacity are equal, a point on the capacity spectrum needs to beselected as an initial estimate. Using the spectral acceleration and displacement defined by this point,
reduction factors may be calculated to apply to the 5% elastic spectrum to account for the hystereticenergy dissipation or damping. The response spectral acceleration and displacement are reduced by the1following equations: Equivalent damping ratio, ℎ𝑒 = 0.25 (1 − 𝜇) + 0.05, reduction factor of spectrum,√𝑚𝛿
1.5𝐹ℎ = 1+10ℎ , And ductility 𝜇 = 𝛿 𝑝 . Finally, the reduced demand spectrum is calculated using these𝑒𝑦Sa and (𝑆d× 𝐹ℎ ) formulas.
4. RESULTS AND DISCUSSION
In this study firstly the performance point was determined using capacity curve for each site class andfour seismic zones as shown in Figure 9 (a) and (b). After getting the results of displacement response
spectrum Sd and the story drift of each story Sdx and Sdy from pushover analysis using two drift angle
1/200 and 1/250, Figure 10 shows that for 8-story building 1st yieding point appears in the 3rd floor andthe corresponding value of target yielding point displacement Sd 6.5cm and 5.3cm in the weaker X-

4

direction, inaddition 4.3cm and 3.4cm in the weaker Y-directions for 5-story building at 1st yielding act
in the 2nd floor.

(a)

(b)

Figure 9. The performance point using capacity curve for soil class (a) SC (b) SD and zone-II (0.20g)

(b)

(a)

Figure 10. Relative displacement of each story drift Sdx (a) (1/200) for 8-story and (b) 1/250 for 5-story.

According to the result obtained, Figure 11 shows, in the both story drift angle, the 8-story structures
are not operational under all records for PGA higher than 0.12 g with soil classes SB, SC and SD; even
PGA 0.12g with soil class SD is not operational either. The 8-story model building is operational onlywith soil classes SB and SC up to PGA 0.12g. Moreover, these 8-story building can be immediatelyoccupied for all four PGA with soil classes SB and SC, but only soil class SD is immediately occupied
for PGA 0.20g and 0.12g. For soil class SD with two seismic zones 0.28g and 0.36g, these 8-story
building performance level is damage control level. However, the most important consideration is thatthese 8-story model buildings do not cross the code allowable story drift limitation. Furthermore,considering the conservative inter-story drift ratio, the 8-story model building performance level
increased from 4.11 % to 13.33% individually, for all four PGA conditions with three soil classes.

(b)

(a)

Figure 11. (a) and (b), Performance levels of the buildings with two different angles (1/200) and (1/250).
Figure 11(a) also shows the percentage variation between the two-drift angle. For example, for SC soil,
let X1 = 0.98(1/200) SD, and PGA) and X2 = 0.92(1/250) and substitute into formula =|0.98−0.92|
× 100 = 6.32%.
[(0.98+0.92)/2]
Similarly, in Figure 11 (b), the 5-story building is not operational when the story drift angle is
1/200 with soil classes SB, SC and is higher than 0.12g. Even when PGA is 0.12g with soil class SD, it5

is not operational. The 5-story model building is operational only under ground motions with PGA up
to 0.12 g including soil classes SB and SC. Only in case story drift angle is 1/250, PGA is 0.12g withsoil class SB, it is operational. For story drift angle 1/200, the 5-story building can be immediately
occupied by two 0.20 and 0.28 PGA with soil classes SB and SC, but only soil class SD immediately
occupied PGA 0.12g. It has been observed that due to the lower drift angle, the soil class SB zone 0.36g,
the performance level has changed from DC to IO. Furthermore, considering the conservative inter-story
drift ratio, the 5-story model building performance level increased from 5.44 % to 12.35% individually,
for all four PGA conditions with three soil classes.
5. CONCLUSIONS
The analysis showed that with the maximum inter-story drift angle of 1/200, the 8-story and 5-story
model buildings are only operational with soil classes SB and SC with PGA up to 0.12 g ground motion.
This operation means that negligible damage to nonstructural components of the building is expectedeven after the earthquake. On the other hand, in both drift angles of 1/200 and 1/250, these buildings insoil classes SB, SC, and SD with a PGA higher than 0.12g are not operational. In addition, that 8-story
building can be immediately occupied for all four PGA with soil classes SB and SC, but only soil class
SD is immediately occupied for PGA 0.20g and 0.12g. For soil class SD with two seismic zones 0.28g
and 0.36g, these 8-story building performance level is damage control level. Consequently, that 5-story
building can be immediately occupied for two PGA 0.20g and 0.28g with soil class SB and SC, howeverwith soil class SD only immediately occupied for PGA 0.12g. Considering the lower drift angle (1/250),
the performance level of these two model buildings will increase from 4.11% to 13.33% for 8-story and5.44% to 12.35% for 5-story by different soil site classes. In this research, it has been observed thatwhen the ground motion in our country is moderate or high intensity, this type of RC building will besafe in the location which falls in the seismic zone 1 (0.12g) with soil classes SB and SC.
Finally, the result shows that 60 percent in the study area is soil class SD (Alluvial silt /Alluvial silt and clay) predominated. Therefore, the evaluation results of the building performance levels
for the lower drift angle (1/250) are more resilient than the higher one (1/200). So, this study
recommended yield point drift angle of 1/250 from the static non-linear pushover analysis of the SDOF
system, especially in our country’s context.
ACKNOWLEDGEMENTS
I express my sincere gratitude to my thesis supervisor, Dr. Shoichi Nakai, and my adviser, Dr. Eng.
Hiroto Nakagawa, for their supervision assistance, helpful discussions, and valuable ideas throughout
my master’s studies. I also acknowledge Dr. Taiki Saito's continuous advice on using Stera_3Dmodeling and pushover analysis. I like to convey my deep gratitude to the individual study period of thetraining course on "Seismology, Earthquake Engineering, and Tsunami Disaster Mitigation" by theBuilding Research Institute (BRI) Japan, JICA, and GRIPS.
REFERENCES
ASCE., 2000, American Society of Civil Engineers, FEMA 356.
BNBC 2020, “Bangladesh National Building Code”.
FEMA. (2004), FEMA 389, Washington, D.C.
Ibrahim, Y.E., and El-Shami, M.M., 2011, IES Journal Part A: Civil and Struct. Eng., 4(4), 213-223.
Mohd Assyarul Bin Saadum (MEE20710), 2021, IISEE Synopsis, 1-6.
Mahmoud Helal SaadEldin Elawady, 2017.
Md. Arifujjaman (MEE16712), 2017.
Mohammad Tariqul Islam (MEE16714), 2017,P. Anbazhagan et al., Pure Appl. Geophys. 170 (2013), 299-318.
Q. Xue, C.-W. Wu, C.-C, Chen, K.-C. Chen., Engineering Structures, 2008. 30(6), 1535-1547.
Saito T., STERA_3D Ver. 11.0 “Technical Manual” & FEM-I, IISEE Lecture Note-2021-2022.

6