THE INFLUENCE OF THE SEISMIC DESIGN ON THE PROGRESSIVE COLLAPSE RESISTANCE OF MID-RISE RC FRAMED STRUCTURES

In this study the influence of the seismic design to better resist progressive collapse of mid-rise RC framed structures is investigated. A ten-storey building is designed for three distinct seismic areas (low – ag=0.08g, moderate – ag=0.16g and high – ag=0.24g) from Romania. Using the GSA criteria, a nonlinear static analysis is carried out first in order to estimate the progressive collapse resistance of the structures subjected to interior column removal. It is shown that only the model designed for high seismic area has a low potential for progressive collapse; the capacity curves provided by the nonlinear static analysis indicate that the models designed for low and moderate seismic areas collapses before the standard GSA loading is attained, unlike the model designed for a high seismic area which can sustain this load without failure. Consequently, a nonlinear dynamic analysis is carried out to validate the results ’ accuracy obtained with the static procedure. The results indicate that all the models have a low potential for progressive collapse and thus, the dynamic increase factor (DIF) of 2.0 recommended by the GSA (2003) Guidelines can be overestimated. A nonlinear incremental dynamic analysis is carried out in order to estimate with maximum accuracy the ultimate load bearing capacity of the damaged structures before collapse. The variation of DIF dependent on the level of loading is highlighted as well