Seismic Behavior of an Isolated Base Reinforced Concrete Building For Short and Long Duration Earthquakes

This paper studies the structural behavior of a reinforced concrete building originally seismically deficient when subjected to seismic excitation before and after using base isolation bearings of different properties. The building is a three-story typical residential building. The base isolation bearings have two values for the horizontal shear stiffness in the two directions which are 104 and 193 kN/m. Dynamic nonlinear time history analysis is conducted under three natural earthquakes of short durations and three natural earthquakes of long durations all of which are matched to the design response spectrums of the Eurocode-8, Egyptian loading code ECL201-2012, Saudi loading code SBC301-18, and ASCE7-22 code for different seismic zones. The study is made using commercial software called SeismoStruct. The project studies the effect of base isolation properties and earthquake duration on the building structural properties in terms of maximum building top acceleration, maximum building top displacement, and maximum building inter-story drift. It is found that the maximum acceleration, and consequently the maximum induced seismic forces, is equally reduced for short and long duration earthquakes and this reduction is similar for both types of base isolations. The maximum top displacement is equally reduced with the two types of base isolations and the reduction is little larger for long duration earthquakes. The inter-story drift is reduced and this reduction is higher for the case of long duration earthquakes. Base isolations type 1 and type 2 produced similar inter-story drifts’ reductions.