Impact of Column Shear Force on the Seismic Performance of Open Ground Storey Structures

Open Ground Storey (OGS) structures are particularly vulnerable to seismic failures due to their inherent soft storey behaviour, which reduces lateral stiffness and significantly increases shear forces in the ground floor columns. This study aims to analyze the shear forces in columns of three-dimensional (3D) OGS Reinforced Concrete (RC) frames subjected to seismic loads, focusing on the effectiveness of two Lateral Load-Resisting Systems (LLRS): the use of stiff columns at the ground floor and the implementation of shear walls in various configurations. The seismic performance of these systems is compared with conventional OGS configurations and bare frames, considering the impact of infilled frames. The results of the study reveal that infilled frames significantly reduce the shear force in columns, with a reduction of up to 70% compared to bare frames. However, the shear force in ground floor columns of OGS frames is increased by about 78% compared to fully infilled frames due to the reduction in stiffness. The inclusion of shear walls in OGS frames effectively reduces this increased shear force. The ratio of ground-floor to first-floor shear forces for the OGS model ranges from 6.25 to 8.60, which can be reduced to 0.52 to 5.74 with the provision of various types of shear walls. Furthermore, the study finds that shear forces in peripheral and corner columns of OGS frames are about 10% higher compared to inner peripheral and core columns. It also highlights that increasing the ground floor height by 1 meter induces approximately 25% higher shear forces in ground floor columns. These findings underscore the importance of optimizing shear wall placement and other structural configurations to enhance the seismic resilience of OGS buildings.