The effects of concrete stiffness and strength on the seismic response of RC frame buildings

This paper is concerned with the effects of concrete material properties on the seismic response of reinforced concrete frame buildings. In particular, the influence of concrete stiffness and strength on the dynamic seismic response of RC buildings is assessed. A series of nonlinear dynamic time-history analyses of model RC frame buildings are conducted. A range of concrete stiffness and strength are examined and under a number of earthquakes of different amplitude, duration and frequency content. It is shown that concrete stiffness is more dominant factor affecting the dynamic seismic response of reinforced concrete structures than concrete strength. Moreover, it is shown that the direction of the applied earthquake motion also affects the dynamic response of the framed building, especially in cases of irregular structures with differential stiffness in different directions. It is also observed from the response spectra that the applied seismic load resonates with the dominant mode of building vibration in the direction of the applied seismic load. This may suggest that real recorded earthquake motions from instrumented concrete buildings may be processed to identify their dynamic modal characteristics.