Proceedings of the 2nd International Conference on Civil Engineering for Sustainable Development (ICCESD-2014), 14~16 February 2014, KUET, Khulna, Bangladesh, ISBN: 978-984-33-6373-2 (CD-ROM)
STRUCTURAL PERFORMANCE INVESTIGATION BASED ON SIMPLE ASSESSMENT PROCEDURE AT CUET CAMPUS Abul Khair1, Ram Krishna Mazumder*2 Nazmus Sakib3 Md. Abdur Rahman Bhiyan 4 and Md. Jahangir Alam5 1
Civil Engineering, Chittagong University of Engineering and Technology, Bangladesh, e-mail:
[email protected] 2 Institute of Earthquake Engineering Research, Chittagong University of Engineering and Technology, Bangladesh. e-mail:
[email protected] 3 Civil Engineering, Chittagong University of Engineering and Technology, Bangladesh, e-mail:
[email protected] 4 Institute of Earthquake Engineering Research, Chittagong University of Engineering and Technology, Bangladesh. e-mail:
[email protected] 5 Civil Engineering, Chittagong University of Engineering and Technology, Bangladesh, e-mail:
[email protected] ABSTRACT Bangladesh is situated in the seismically moderate risky zone due to its geographical location. Presences of exiting fault lines surroundings the country are capable to produce damageable earthquake. Frequently occuring light earthquakes in last couple of years make us aware about its future risk. In proposed Bangladesh National Building Code (BNBC) Second Edition seismic map, Chittagong city is quite subtancial to earthquake with a seismic zoning coefficient of 0.28. One of the leading technical universities of the country, Chittagong University of Engineering and Technology (CUET) campus is located about 27 km far from the heart of the Chittagong city center. This study was undertaken to prepare a structural database and to ivestigate the seismic safety of the structures by applying a two-level based simple assessment technique. Rapid screening procedure (RSP) was peformed in the first tire of assessment. Then Structural Inegrity Check was performed for the academic and administrative buildings in the second tire. Structural information database was prepared and presented in Geographic Information System (GIS). Most of these buildings performed well in the both level of assessments. Keywords: Assessment, CUET, Rapid Screening Procedure, Performance, Vulnerability. 1. INTRODUCTION Bangladesh is situated in a moderate seismic region in the world seismic map according to Global Seismic Hazard Assessment Program (GSHAP, 1992). An earthquake of even medium magnitude can produce massive destruction in major urban areas of the country, especially Dhaka, Sylhet and Chittagong. Recent earthquakes in India, Pakistan and Myanmar make us aware about the future risk of this region. Great Inidan Earthquake in 1897 with a Richter Local Magnitude 8.7 is the previous large event triggered at Shillong near the SylhetMeghalaya border area. No earthquake occurred in these faults for many years, which means huge strength has gathered underground that could cause serious earthquakes in Bangladesh and its neighboring areas any time. There exist few faults in this region that can cause strong earthquake in the country. One of them is the Dauki fault at the bordering area of Sylhet–and the other one is Sitakunda-Taknaf fault at Chittagong coastal area. However, a recent study conducted in Comprehensive Disaster Management Program (CDMP) proposed five earthquake scenarios where each scenario was set as a maximum possible earthquake (Mw) occurring within a fault zone. These five major fault zones are named as Madhupur fault, Dauki Fault, Plate Boundary Fault -1, Plate Boundary Fault -2 and Plate Boundary Fault -3 (as shown in Figure 1). A special earthquake scenario where a magnitude-6 earthquake is occurring beneath Chittagong city was recommended during the study (CDMP, 2009). The scenario of falt parameters for the Chottagong city was shown in Table 1.
2nd International Conference on Civil Engineering for Sustainable Development (ICCESD-2014)
Figure 1: Earthquake Fault Model in Bangladesh, (CDMP, 2009). Table 1: Earthquake Scenario Parameters for Chottagong city area. Case
Coordinate of Epicenter
Mw
Depth to top of
Dip
Fault
fault (km)
Angle
type
Description
Latitude
Longitude
1
21.1
92.1
8.5
17.5
30°
Reverse
Plate Boundary Fault -1
2
23.8
91.1
8.0
3
20°
Reverse
Plate Boundary Fault -2
3
22.4
91.8
6.0
25
90°
Reverse
M w 6.0 beneath the city
Chittagong University of Engineering & Technology (CUET) is one of the leading technical institutions in the country which is located by the side of the Chittagong-Kaptai road and about 27 kilometers off from the Chittagong city center. This region falls into zone number 2 in the Bangladesh National Building Code (BNBC 1993) with a seismic coefficient of 0.15 g. This map was based on Peak Ground Acceleration (PGA) considering a return period of 200 years. In proposed Bangladesh National Building Code (BNBC) Second Edition seismic map, the concept of Maximum Credible Earthquake (MCE) has been inreoduced where MCE is correspond to a return period of 2475 means 2% probability of exceedance in 50 years. In this new seismic map, CUET falls into zone number 3 with a coefficient of 0.28 g. It has been felt necessary to prepare a structural database of existing buildings at CUET campus. This study was undertaken by the Institute of Earthquake Engineering Research (IEER) to assess the seismic safety of existing structures by applying two-level based seismic vulnerability assessment techniques. First tire includes simple walkdown assessment by visualizing the structural vulnerability parameters. In the second tire, buildings were assessed by checking their structural integrity. 2. METHODOLOGY The medthod was originally generated by Ozcebe et al. In 2006. It is very important to identify seismically vulnerable building before taking any strengthening measure. To survey all buildings in detail level is neither feasible nor possible, Rapid Screening Procedure is widely accepted before considering any structural detail level of investigation. To evaluate the seismic condition of the existing buildings, two level risk assessment procedures applied based on the structures level of importance in terms of building use. Mainly two major types of structures are presence at CUET. One type is Reinforce Concrete (RC) frame structures with masonry infill and another is Unreinforced Masonry Buildings (URM) with flexible or rigid diaphragm. For a RC building, Turkish simple screening procedure (Ozcebe et al., 2006) was followed. This procedure contains three level of assessment whre only RC building can be analyzed. Detail structural assessment wasn’t performed due to insufficient informations (eg., destructive, non-destructive tests results). Rapid Visual Screening (FEMA 154) was applied for masonry structures.
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2nd International Conference on Civil Engineering for Sustainable Development (ICCESD-2014) 2.1
Turkish Method
2.1.1
Tire 1 Assessment
A street survey procedure based on simple structural and geotechnical parameters that can be observed easily from the sidewalk. The time required for an observer for collecting the data of one building from the sidewalk is expected about 20 minutes. The parameters that are selected for representing building vulnerability in this study are the following: 1) The number of stories above ground (1 to 7) 2) Presence of a soft story (Yes or No) 3) Presence of heavy overhangs, such as balconies with concrete parapets (Yes or No) 4) Apparent building quality (Good, Moderate or Poor) 5) Presence of short columns (Yes or No) 6) Pounding between adjacent buildings (Yes or No) 7) Local soil conditions (Stiff or Soft) 8) Topographic effects (Yes or No) The intensity of ground motion at a particular site predominantly depends on the distance the causative fault and local soil conditions. As there exists a strong correlation between Peak Ground Velocity and the shear wave velocities of local soils, in this study the PGV is selected as to represent the ground motion intensity. The intensity zones are expressed accordingly, in terms of the associated PGV ranges. Zone I : 60
