Comparison Between Common Seismic Codes Used in Nepal and Eurocode 8: Study Case Analysis of RC Building

Abstract

Earthquake risks and vulnerability to building structures have been identified by many countries and thus seismic analysis and design have become an integral part of their structural design process. Nepal has also recognized the necessity of seismic design following the past major earthquakes. It has developed the Nepal National Building Code (NBC) in 1994 AD but the implementation was very late. Most of this code was directly derived from the Indian code as the technology and construction practices in both the countries were similar. Due to this, engineers mostly preferred to use Indian Code directly rather than Nepal code. However, the code developed for Indian scenario and site condition may not be suitable for Nepalese context as Nepal is more prone to Earthquakes than India. This suggests a necessity to evaluate and compare both codes against much advance and developed code like Eurocode. The aim of this thesis is to do a comparative study between the three seismic codes namely Nepal code (NBC 105, 1994), Indian Code (IS 1893-1, 2002) and Eurocode 8 (EN1998-1: 2004) with a case study of a RC building located in Kathmandu, Nepal. The input parameters like materials, member size, soil type and ground motion were considered same for all three contexts in order to get fair results. In addition, the effect of infill masonry walls in lateral load resisting capacity of the building was also checked in the building with these codes. The research was carried out first by discussing the seismic analysis procedures (linear static and dynamic) outlined in the three codes. Then the analysis procedures introduced in the respective codes were compared and contrasted considering how they handle the major effects, characteristics of the structures and geotechnical considerations etc. To get a better comparative view a RC building was analysed and designed in ?ETABS? software using linear static and dynamic procedures according to all three codes. The performance of the building under the parameters like base shear, storey displacement, interstorey drift and reinforcement demands on the concrete members were compared for all three codes. A static nonlinear (pushover) analysis process was also carried out to get accurate performance level of the existing building. The results showed that Eurocode has given highest base shear and drift values in many cases. It also made clear that the Indian and Nepal code lacks in addressing many issues like consideration of structural irregularity, infill walls, P-delta effects, non-linear analysis etc. The research showed that the study building was under performance in damage limitation and global behaviour for Eurocode and the pushover analysis verified it. Thus, a retrofitting intervention using all steel buckling restrained braces (BRB) was suggested for the study RC building after which a fair behavior factor close to code recommendation was achieved. A significant improvement in the ductility and strength of the structure was obtained using steel BRB solution.

Earthquake risks and vulnerability to building structures have been identified by many countries and thus seismic analysis and design have become an integral part of their structural design process. Nepal has also recognized the necessity of seismic design following the past major earthquakes. It has developed the Nepal National Building Code (NBC) in 1994 AD but the implementation was very late. Most of this code was directly derived from the Indian code as the technology and construction practices in both the countries were similar. Due to this, engineers mostly preferred to use Indian Code directly rather than Nepal code. However, the code developed for Indian scenario and site condition may not be suitable for Nepalese context as Nepal is more prone to Earthquakes than India. This suggests a necessity to evaluate and compare both codes against much advance and developed code like Eurocode. The aim of this thesis is to do a comparative study between the three seismic codes namely Nepal code (NBC 105, 1994), Indian Code (IS 1893-1, 2002) and Eurocode 8 (EN1998-1: 2004) with a case study of a RC building located in Kathmandu, Nepal. The input parameters like materials, member size, soil type and ground motion were considered same for all three contexts in order to get fair results. In addition, the effect of infill masonry walls in lateral load resisting capacity of the building was also checked in the building with these codes. The research was carried out first by discussing the seismic analysis procedures (linear static and dynamic) outlined in the three codes. Then the analysis procedures introduced in the respective codes were compared and contrasted considering how they handle the major effects, characteristics of the structures and geotechnical considerations etc. To get a better comparative view a RC building was analysed and designed in ?ETABS? software using linear static and dynamic procedures according to all three codes. The performance of the building under the parameters like base shear, storey displacement, interstorey drift and reinforcement demands on the concrete members were compared for all three codes. A static nonlinear (pushover) analysis process was also carried out to get accurate performance level of the existing building. The results showed that Eurocode has given highest base shear and drift values in many cases. It also made clear that the Indian and Nepal code lacks in addressing many issues like consideration of structural irregularity, infill walls, P-delta effects, non-linear analysis etc. The research showed that the study building was under performance in damage limitation and global behaviour for Eurocode and the pushover analysis verified it. Thus, a retrofitting intervention using all steel buckling restrained braces (BRB) was suggested for the study RC building after which a fair behavior factor close to code recommendation was achieved. A significant improvement in the ductility and strength of the structure was obtained using steel BRB solution.