Effect of Soft Storey Location on Seismic Performance of Reinforced Concrete Building

Abstract

Reinforced concrete frames with masonry infill walls are a popular form of construction in seismic regions worldwide. The typical multi-story construction in Ethiopia comprises reinforced concrete frames with hollow concrete block masonry infill. Due to space requirements for meeting-hall, game zones, large reception rooms, open shopping areas, parking areas, the infill walls are removed or very large doors and windows are provided in reinforced concrete buildings. Unreinforced masonry infill wall panels may not contribute towards resisting gravity loads, but contribute significantly, in terms of enhanced stiffness and strength under earthquake loading. But the irregular distribution of infill crates soft storey; which is more affected by earthquake load. It is important to study the effect of irregular distribution of infill wall on the seismic performance of reinforced concrete buildings. This research determines the effect of soft storey location on seismic performance of reinforced concrete building with infill using pushover analysis. A typical office and shopping use building located in severe seismic Zones of Ethiopia is analyzed and designed according to ESEN-2015 and Euro Code. Effect of soft storey location on seismic performance has been studied with the help of (G+7, G+10) total of 16 building models with soft storey at different locations. The infill was modeled using the equivalent diagonal strut and soft storey is modeled by removing in-plane diagonal struts. To study the effect of soft storey location on seismic performance of reinforced concrete building pushover analysis for lateral loads was done using ETABS 2017 software. The comparison of these models for different earthquake response parameters like pushover curve, target displacement and base shear at performance point, Story displacement, storey shear, storey drift and seismic performance assessment are carried out. Building with soft storey at the top has good seismic demand resistance. Depending on the stiffness ratios for soft storey considered; the base shear resistances of the buildings increase by (23-39) % when soft storey located at the top than buildings soft storey at the bottom. The roof displacement of the building is the maximum displacement for exciting earthquake and converges at one point for buildings with soft storey at different locations. Buildings soft storey at the top has maximum storey shear which is increased by (21-68) % than buildings soft storey at the bottom level. The maximum drift ratio of the buildings decreases by (43-51) % and buildings soft storey located at top than bottom. Similarly, the base shear resistance at performance point is maximum and target displacement decrease by (17-36) %