Assessment of collapse capacity of RC buildings based on fiber-element modeling
Despite the fact that structural collapse is a key contributor to seismic risk, robust procedures for the assessment of structural collapse are typically absent in seismic design documents. This paper discusses probabilistic collapse capacity assessment of reinforced concrete buildings using the New Zealand red book building as a case study. Load resisting elements of RC buildings are traditionally modelled using lumped plasticity elements at predefined plastic hinge locations which require crude approximations of several features of post-peak response, which is very important in simulating structural collapse. This paper presents a discussion on the use of fiber-based nonlinear modelling, which utilizes generic path-dependent cyclic stress-strain relationships of concrete and reinforcing steel, for prediction of RC frame building collapse. A collapse capacity distribution accounting for ground motion uncertainty is estimated using a suite of ground motions and conducting incremental dynamic analysis (IDA), i.e., gradually increasing the intensity of the ground motions until the occurrence of collapse. It is shown that the fiber model simulates the collapse mechanism of the building without the upfront assumptions required in lumped plasticity modelling; thereby making the prediction more reliable.