The use of modern technologies in Civil Engineering is increasing in recent years. Due to the different aesthetic needs of people, the building of different shapes and sizes is in practice. Such building structure is more susceptible to seismic force. Numerous methods have been followed to reduce the severe effects. The shape of a building is one such method which changes the structural behavior. The objective of this research is to compare seismic properties of the seismic region of Nepal using Nepal, India, Bangladesh and China building codes provision for the same building structure with variations in the shape of a structure. Four different shapes of buildings are considered in the study and a comparison is made between different shapes of buildings against the effect of lateral loads due to the earthquake. Computer-Aided Design (CAD) is carried out to perform the relative comparison between different country building codes provision and focus on the effect due to building shape variation. In this study, countries along the Himalayan arc are chosen for a review of different seismic codes. A model RC building of four different shapes located in Nepal is analyzed by using Nepal Buildings Code (NBC 105, 1994), Indian Code (IS 1893-1, 2016), Bangladesh Code (BNBC 1993: 2014), and China Code (GB 50011: 2010). The responses of the building under the parameters like Response Spectrum Curve, base shear, time period, and absolute displacement are compared for all four codes. Based on the design base shear, China code showed a higher value compared with other codes because the design horizontal seismic force coefficient, base shear, and absolute displacement of China code are maximum than other codes. On varying the shape of a structure for base shear estimation, a similar pattern is observed. Hence, it can be concluded that shape has a negligible effect on the base shear of the structure.
Earthquake is a great challenge in the field of civil engineering, which causes severe damage and suffering to the human being such as collapsing many structures, trapping or killing persons, blockage of transport systems, animal hazards, etc. However, as designers, civil engineers play a key role in minimizing damage through proper structural design and making a useful decision by understanding earthquakes, behavior of building materials and reinforced concrete structures [
Seismic building codes are guidelines for the design and construction of buildings and civil engineering works in seismic areas. The reason is to protect human lives from the worst conditions that occur during an earthquake, to limit damage and to sustain operations of important structures for civil protection. Different codes use different load and material factors (or strength reduction factors) to design the members, and therefore the strength actually provided in the different codes may not correspond to the same pattern as the design base shear. Furthermore, as noted above, the drift may govern the design in many cases, resulting in further discrepancies in the actually provided strength [
1) To compare analysis output in terms of response spectrum curve, seismic coefficient, storey drift, and base shear;
2) Code comparison on response to an earthquake, with the effect of building shape variation (rectangular, L-shape, box, and octagonal).
This thesis is primarily a numerical study of the effect of building shape on the response to an earthquake. Four different shapes of buildings are considered in this study and a comparison is made between different shapes of buildings against the effect of lateral loads due to the earthquake. Building shape “
The building considered in the study is taken from the building which is in practice for the office and barrack block of Nepal Police. This structure is widely used throughout the country’s police station. Building features used for the study are listed in
Properties of materials use for the building structure are listed in
Loading parameters and their standard value are listed in
Following methods are used in the analysis of all shape of structure (rectangular. L-shape, box, and octagonal) [
・ Equivalent Lateral Force (Static) method;
・ Response Spectrum (Dynamic) method.
Parameters | General Description |
---|---|
Type of building | Office Building |
Structure system | RCC frame structure; Special moment resistant frame |
Plinth area | Rectangle shape : 185.62 m2 L-shape : 132.78 m2 Octagonal shape : 110.94 m2 Box shape : 196 m2 |
No. of storey | 4 (Four) storey + Stair cover |
Floor to floor height | 3.3 m |
Types of Slab | 125 mm thick; Two-way Slab, 150 mm thick staircase slab |
Types of Beam | Rectangular main beam (350 mm × 450 mm) Rectangular secondary beam (225 mm × 350 mm) |
Types of Column | Rectangular column(400 mm × 400 mm) |
Parameters | General Descriptions |
---|---|
Concrete | M20 |
Steel grade (fy) | Fe500 |
Compressive strength of brick (fb) | 17.5 N/mm2 |
Parameters | General Descriptions |
---|---|
Self-weight of Building | As per Software (ETABS) |
Floor finish | 1.5 kN/m2 |
DL wall (225 mm) DL wall (125 mm) | 10 kN/m2 5 kN/m2 |
Live load floor | 3 kN/m2 |
Live load staircase | 3 kN/m2 |
Live load Roof | 1.5, 0.75 kN/m2 |
Partition wall load | 1 kN/m2 |
Earthquake Load | as per codes adopted |
The following assumptions and basic characteristics were considered to model building in ETABS software:
1) Column and beam elements are modeled as line elements whereas the floor slabs and concrete walls are modeled as shell elements.
2) All the joints (Beam-Column, Column-Foundation, etc.) are considered to be rigid joints.
3) Frames are connected by means of rigid diaphragms in a horizontal plane at each floor level.
All floor loads were applied to the deck which distributes uniformly the load to the beams.
The model building was analyzed using four different codes and the same parameters (like same soil condition, same PGA, same building member size, material, etc.) which was present in the actual site. In this way total of 32 cases were studied: four different shapes of the building, each with a different country code (Nepal, India, Bangladesh, and China), and each building was analyzed in two different methods: static method and dynamic method (response spectrum method). Different parameters required to calculate the base shear by different countries’ codes are calculated and summarized in
A response spectrum curve is generated for dynamic analysis (Response spectrum method). The respective code has their respective response spectrum curve and their equation. Using those equations, the period and acceleration are generated which is used to define the response spectrum function on software. The response spectrum curve of pre-defined four different codes of practice is presented graphically in
Earthquake Parameters | NBC 105: 1994 | IS 1893: 2016 | BNBC 1993: 2014 | GB 50011: 2010 |
---|---|---|---|---|
Seismic Zone Factor (Z) | 1 | 0.36 | 0.15 | Intensity 8 |
0.2 to 0.3 | ||||
Importance Factor (I) | 1 | 1.2 | 1 | η = 1 |
Response reduction/performance Factor (R/K) | K = 1 | 5 | 5 | γ = 0.9 |
Soil Type | II | Medium | SC-dense or medium | For II, Tg = 0.4 |
Time period of building structure depends on the height of the structure. Different county code has a different formula to calculate the building time period.
Design Horizontal seismic force coefficient parameter is mainly dependent on the time period of the structure. Time period depends on the height of structure [
Design base shear has a vital role in the seismic analysis as it influences all the analysis parameters of the structure. The comparison of the design base share is also the major objective of this study. In this section, the base shear force obtained from static and dynamic methods is compared along with the comparison between manually calculated and software-derived base shear [
In this analysis, as shown in
Based on
Base shear for the rectangular shape model is calculated by using three procedures i.e. manually, by using ETABS and by using SAP which is presented in
Parameters | NBC 105 | IS 1893 | BNBC 1993 | GB-50011 |
---|---|---|---|---|
Building Time Period | T = 0.06 H a 4 | T = 0.075H0.75. | T = Ct(hn)m | 0.1 * No of storey |
Different shape Building with same Height (Time Period) | 0.491 | 0.614 | 0.581 | 0.5 |
Parameters | NBC 105 | IS 1893 | BNBC 1993 | GB-50011 |
---|---|---|---|---|
Design Horizontal seismic force coefficient | CZIK | A h = Z I S a 2 R g | S a = Z I C R | α = ( T g T ) γ η 2 α max |
Different shape Building with same Height | 0.08 | 0.103 | 0.08 | 0.11 |
Model cases | NBC 105:1994 | IS 1893:2016 | BNBC 1993:2014 | GB 50011:2010 | ||||
---|---|---|---|---|---|---|---|---|
Static | Dynamic | Static | Dynamic | Static | Dynamic | Static | Dynamic | |
Rectangle | 819.1 | 60.0 | 1112.2 | 644.3 | 819.1 | 2039.9 | 1139.1 | 712.0 |
L-shape | 640.6 | 41.8 | 869.3 | 478.8 | 640.5 | 1518.1 | 890.7 | 530.0 |
Octagonal | 607.7 | 48.0 | 855.5 | 565.1 | 607.7 | 1732.5 | 845.1 | 604.2 |
Box | 812.7 | 42.2 | 1097.0 | 812.6 | 812.6 | 1360.9 | 1130.1 | 552.6 |
Model cases | NBC 105:1994 | IS 1893:2016 | BNBC 1993:2014 | GB 50011:2010 | ||||
---|---|---|---|---|---|---|---|---|
Manually | Software | Manually | Software | Manually | Software | Manually | Software | |
Rectangle | 834.2 | 819.1 | 1126.2 | 1112.2 | 834.2 | 819.1 | 1136.6 | 1139.1 |
L-shape | 653.4 | 640.6 | 882.0 | 869.3 | 653.4 | 640.5 | 898.4 | 890.7 |
Octagonal | 614.8 | 607.7 | 830.0 | 855.5 | 614.8 | 607.7 | 845.3 | 845.0 |
Box | 826.6 | 812.7 | 1115.9 | 1097.1 | 826.6 | 812.6 | 1147.0 | 1130.1 |
Codes | Manually (kN) | ETABS (kN) | SAP (kN) |
---|---|---|---|
NBC 105:1994 | 834.20 | 819.09 | 866.94 |
IS 1893:2016 | 1126.18 | 1112.20 | 1171.43 |
BNBC 1993:2014 | 834.20 | 819.08 | 867.73 |
GB 50011:2010 | 1136.55 | 1139.09 | 1205.69 |
The inter storey drift ratio is an important parameter to be considered in finding out the performance of a structure. Codes define the limit of the drift ratio for the performance level of the structure. For better performance of the structure minimum drift ratio is required. Storey drift ratio is linked with absolute displacement; finally, it has an effect on the performance of structure [
The building has four different shapes considered in the study and a comparison is done between these buildings against the effect of lateral loads due to the earthquake. A computer-aid analysis is carried out to perform the relative comparison between building code provisions of different countries with a focus on the effect of the building shape. From a comparative study of four different codes on earthquake response analysis of RC structure which lies on the same Himalayan belt, the following conclusions are drawn:
1) Based on the design base shear, China code showed a higher value compared with other codes because the design horizontal seismic force coefficient of China code is maximum than other codes. Since NBC, IS and BNBC use response reduction but Chinese standard doesn’t use a response reduction factor, it has a maximum horizontal seismic coefficient.
2) On varying the shape of a structure for base shear, a similar pattern was observed. Hence, it can be concluded that shape has a negligible effect on the base shear of the structure.
3) From the comparison of the time period, it can be concluded that code provision time period of a building is different in different four codes and varies from 0.491 to 0.614. Based on the time period, India has a higher value while Nepal has a lower one.
4) The distribution of base shear at different floor levels is linear in Nepalese code and Chinese code but is distributed in a parabolic pattern in Indian code and in linear interpolation in Bangladesh code. Among predefined codes, IS 1893:2016 and BNBC 1993:2014 have provisions to scale up the base shear in dynamic analysis results if it is less than the static base shear. However, NBC 105:1994 and GB 50011:2010 are silent on this. In this study, the scale factor is greater than one as per India, Nepal and Chinese codes but less than one as per Bangladesh building code. So, dynamic base shear is not required to scale up according to BNBC.
5) Among the three procedures used in this study, maximum base shear is obtained from SAP analysis followed by a manual method and from ETABS analysis respectively.
6) Maximum drift for structure is given by Chinese standard followed by Indian standard, NBC and BNBC respectively.
I would like to express my warmest gratitude to my supervisors’ generous assistance, patience, perseverance, high-quality editing and recommendations. They also motivate and encourage me to accomplish the tasks within a given time. I am greatly indebted to the authors of books, thesis, papers and guidelines that I have gone through extensively to conduct this study.
The authors declare no conflicts of interest.
Adhikari, D., Adhikari, S. and Thapa, D. (2022) A Comparative Study on Seismic Analysis of National Building Code of Nepal, India, Bangladesh and China. Open Access Library Journal, 9: e8933. https://doi.org/10.4236/oalib.1108933