The influence of different concrete classes on the seismic response of a seismically isolated building

In this study, an eight story seismically isolated building representing a mid-rise type building was employed to investigate the effect of usage of different concrete classes (C20, C25, C30, C40, and C50) on the seismic response of a seismically isolated building. The prototype fixed base buildings were converted to seismically isolated buildings by introducing rubber isolators at base level. Analyses were conducted by using two different isolation systems (QW5Tb3 and QW10Tb3).The modelling of conventional fixed base prototype seismically isolated buildings and their modal analyses were conducted on finite-element program SAP2000, whereas, modelling of seismically isolated buildings and nonlinear time-history analyses were conducted using 3D-BASIS program. Floor accelerations, Story shears and inter-story drift ratios were the key structural responses considered. The analysis results showed concrete strength have significant effects on the seismic behaviour of the structures. Seismically isolated buildings with isolation system having 5% characteristic strength, C40 and C50 concrete buildings showed less first floor accelerations as compared to the lower concrete class buildings. In addition, isolated buildings with C40 and C50 concrete showed much more inter-story drift ratio values at each floor level as compared to isolated buildings with C20, C25 and C30 concrete which showed values very close to one another.