Seismic Performance Assessment of RC Buildings with Variable Soft Storey Configurations and Infill Masonry Using Nonlinear Pushover Analysis

https://doi.org/10.46610/JOCCE.2025.v011i01.002

Abstract

Reinforced Concrete (RC) buildings with infill masonry walls are a prevalent construction practice in seismically active regions such as Nepal. However, rapid population growth has driven a surge in residential construction, often bypassing essential design considerations, including seismic safety. This oversight leaves many buildings susceptible to significant damage, even during low-intensity ground shaking. A critical factor influencing a building's seismic performance is the presence and placement of soft stories floors that are comparatively weaker or more flexible than others in the structure. These soft storeys can dramatically affect structural behavior during seismic events.

Structural engineers frequently resort to increasing the dimensions of beams and columns to address these vulnerabilities. While this approach enhances structural capacity, it often results in inefficient and overly conservative designs. This study evaluates the seismic performance of RC buildings with varying soft storey levels and in fills masonry configurations through nonlinear pushover analysis using finite element simulations. The analysis compares bare frames, structures with different percentages of infill masonry, and fully infilled models.

Key structural responses analyzed include base shear, performance points, deflection, storey drift, and hinge formation stages. The results reveal that increasing the quantity of infill masonry enhances performance points and base shear while reducing displacement. Storey drift ratios displayed sharp peaks at certain levels, followed by reductions. Capacity curves for frames with 25%, 50%, 75%, and 100% infill illustrated considerable variations in structural response. Fully infilled frames demonstrated higher base shear capacities but reduced roof displacements at the collapse stage compared to partially infilled frames.

These findings underscore the critical role of infill masonry quantity and soft-storey positioning in seismic design. By addressing these factors, engineers can achieve a more effective balance between structural safety and design efficiency in reinforced concrete buildings.