Behavior of Masonry-Infilled Nonductile Reinforced Concrete Frames

TLDR

Older masonry‑infilled reinforced concrete frames were originally designed for gravity loads with insufficient lateral resistance, so they fail to meet current seismic codes and often rely on overly conservative designs because infill panels were not considered in the original lateral load calculations. This study investigates the seismic behavior of masonry‑infilled RC frames, a common building type in high‑seismic zones. To assess vulnerability, the authors performed an experimental program on five half‑scale, single‑story laboratory models with varying bay numbers. The tests showed that infilled RC frames possess significantly higher ultimate strength, residual strength, and initial stiffness than bare frames while maintaining ductility, and that the number of bays influences peak and residual capacity, failure mode, and shear stress distribution.

Abstract

This paper presents research on the behavior of a type of building popular in high seismic zones with a lateral-load-resisting system consisting of masonry-infilled reinforced concrete (RC) frames. Older buildings of this type typically were designed for gravity loads in combination with insufficient or no lateral loads, therefore they do not meet current seismic code requirements. Also, the participation of infill panels in the lateral load resistance of RC frames was not recognized in the original design, often resulting in an overly conservative design. In an attempt to determine the seismic vulnerability of this type of structure, an experimental program was carried out to evaluate the behavior of five half-scale, single-story laboratory models with different numbers of bays. The results indicated that infilled RC frames exhibit significantly higher ultimate strength, residual strength, and initial stiffness than bare frames without compromising any ductility in the load–deflection response. Furthermore, the number of bays appears to be influential with respect to the peak and residual capacity, the failure mode, and the shear stress distribution.