EVALUATION OF SEISMIC COLLAPSE CAPACITY OF FRC FRAME STRUCTURES BASED ON THE METHODOLOGY OF EQUIVALENT SDOF SYSTEMS

In order to assess the seismic collapse capacity of building structures rapidly, an evaluation procedure is presented in the paper, which is based on the methodology of the equivalent single-degree- of-freedom (SDOF) model proposed by Adam. Firstly, static nonlinear analysis was conducted on a Fiber Reinforced Concrete (FRC) structure (the multi-degree-of-freedom (MDOF) system) by means of Pushover method; thereby a base shear-roof displacement curve was obtained. On the basis of this base shear-roof displacement profile, the relationship between the force and the lateral displacement of the structure was derived. According to this relationship and the function of lateral displacement of the MDOF system, the relevant parameters of the equivalent SDOF model were determined. The seismic collapse capacity of the equivalent SDOF model was then assessed, and the result was translated from the equivalent SDOF domain into the domain of the MDOF system, and then was compared with the median collapse capacity of the MDOF system based on the IDA method. An 8-story framed structure of normal concrete and an 8-story fiber reinforced concrete framed structure were analyzed respectively. The results show that it is feasible and conservative to use the equivalent SDOF model to assess the overall seismic collapse capacity of a MDOF system. The results using the lateral parabolic distributing load mode are more close to the median collapse capacities than those using the lateral inverted triangle distributing load mode, and the results of using the displacement shape vector corresponding to the peak point of load on the Pushover curve of the MDOF system are reliable. When other conditions are identical, the seismic collapse capacity of the frame with fiber reinforced concrete is higher than that of the frame with common concrete.