Unified tri-linear theoretical model for masonry infilled RC frames subjected to out-of-plane lateral loads

Abstract

The out-of-plane (OOP) behavior of infill walls has received minimal attention in the past due to the lack of reliable analytical solutions. To solve this issue, the research article proposed a simplified tri-linear theoretical model to comprehend the OOP behavior of masonry infills considering different performance levels (cracking, peak, and ultimate). This study was mainly categorized into four main parts. Firstly, it involved determining the OOP deflection field and arching mechanism of masonry infills through the advanced digital image correlation technique to form a solid foundation for theoretical investigations. Secondly, the principle of mechanics was employed to derive the OOP cracking load and the corresponding deflection. Thirdly, the OOP peak load capacity was calculated by applying the principle of minimum potential energy and considering material constitutive laws. Finally, geometrical calculations were utilized to determine the peak and ultimate deflections, making it a comprehensive and rigorous study. Upon analyzing the DIC deflection field, it was observed that the RC frame surrounding the infills effectively constrained their deflections along the boundary edges. This indicated that the assumption of hinge supports as boundary conditions were reasonable. Theoretical investigations revealed that the peak load capacity of the wall was significantly influenced by the contact length between segments in the OOP direction, which was roughly 44.8 % of the wall thickness at the peak point. Additionally, the OOP deflection after cracking depended on the wall's slenderness ratio, height, peak compressive strain, and crushing strain. It was found that the developed theoretical tri-linear model fairly predicted the OOP performance of infills (slenderness ratios range from 8.42 to 28.81) with less error in comparison to the previously developed theoretical models.