Effect of Building Height and Vertical Seismic Load Patterns on the Behavior Factor of Reinforced Concrete Frames with Rigid Masonry Infill

Abstract

In the seismic design of reinforced concrete (RC) frame structures, the interaction between the structural frame and masonry infill walls is generally neglected or treated in a simplified manner. Masonry infill walls, typically constructed from hollow clay bricks or concrete blocks bonded with low-strength mortar, may be either fully connected to or detached from the surrounding RC frame. Numerous experimental and analytical studies have demonstrated that infill walls can significantly influence the lateral strength, stiffness, and overall seismic response of RC frames.

In the present study, the nonlinear behavior of RC frame–infill systems is modeled using the equivalent diagonal compression strut approach, with the objective of quantifying the contribution of rigid masonry infill walls to the seismic performance of such structures. First, linear modal response spectrum analyses are performed to highlight the limitations of the Algerian seismic code RPA99/Version 2003 in adequately capturing frame infill interaction effects. Subsequently, the impact of masonry infill on the nonlinear seismic response of RC frames is thoroughly investigated through nonlinear static (pushover) analyses.

Based on the pushover results, the influence of building height on the bidirectional evaluation of the global seismic behavior factor (R) of RC frames with masonry infill is examined, considering several vertical distributions of lateral seismic forces. The computed values of the behavior factor are then compared with those prescribed by the Algerian seismic code RPA99/Version 2003 for fully infilled frames and frames with a soft or open story.

The results obtained from the different analyses confirm the necessity of explicitly accounting for masonry infill effects in seismic design. In particular, they underline the relevance of incorporating equivalent diagonal strut models into the Algerian seismic code to achieve a more realistic assessment of the seismic performance and behavior factor of RC frame structures with masonry infill.