Performance Based Analysis Of R.C.C. Buildings

Abstract

Earthquakes are known to produce one of the most destructive forces on earth. It can be originated number of natural or human induced events and causes loss of life and property and shakes the moral of the people. Earthquake cannot be stopped but people can be prevented from them, as earthquakes don’t kill human beings but the buildings do. A historical approach of building design is using “factor of safety” to account for uncertainty in Earthquake demand and building capacity, because of lack of knowledge on earthquake demand. Also the seismic design of building structures is based on the concept of increasing the resistance capacity of the structures against earthquakes by employing, shear walls, braced frames or MR frames. In the past decade, India has seen major earthquakes of the world, recently one being Bhuj earthquake 2001. The building which appeared to be strong enough, found crumbled during Bhuj earthquake. During this earthquake, most buildings were found deficient to meet the requirement the present day codal provisions. To avoid major disasters, existing building can be retrofitted to strengthen them. But before that building should be analyzed for their strength and performance. The seismic design should be such that it prevents loss of life, ensure continuity and minimize damage to the property. Performance Based Seismic Engineering is the modern approach to earthquake resistant design. It is an attempt to predict the buildings with predictable seismic performance. In one sense, it is limit-states design extended to cover complex range of issues faced by earthquake engineers. The thesis is an attempt to understand the basic fundamentals and procedures of Performance Based Analysis of R.C.C. buildings. The analysis was performed on new as well as existing R.C.C. buildings and the performance of buildings in future earthquake was obtained. The software used for performing Nonlinear Static Analysis (Pushover Analysis) is ETABS 8.11. Two kinds of new R.C.C. buildings were taken for analysis: G+4 and G+10 to cover the broader spectrum of low rise & high rise building construction. Different modeling issues were incorporated through eight various models for G+4 and G+10 R.C.C. building. Also, parametric study of infill walls in terms of its location was done in G+4 R.C.C. building models. Out of eight models, five models were of G+4 building and three of G+10 building. An existing building selected for its performance study in future earthquake was Shivshakti Apartment, located at Vasna, Ahmedabad. It’s a G+4 residential building constructed about 12 years back in 1993 without lift core and a water tank at its top. An existing building has already suffered an earthquake of magnitude 7.5 (Bhuj Earthquake, 2001). The performance of an existing building was thought to be obtained by once without consideration of infill contribution and twice, with consideration of infill contribution. Hence, two G+4 R.C.C. building models were developed and analyzed for Nonlinear Static Analysis (Pushover Analysis) to obtain its performance for future predicted earthquake. Number of results obtained through the Nonlinear Static Analysis were studied and conclusions were made. Also, the sequence of formation of hinges at different stages to define its overall performance were studied. Comparisons between different developed building models in term of displacement were plotted and influence of storey drift were also plotted.