Abstract
This study analytically investigated the behavior of reinforced concrete frames with masonry infills. For the analysis, VecTor2, a nonlinear finite element analysis program that implements the Modified Compression Field Theory and Disturbed Stress Field Model, was used. To account for the slip behavior at the mortar joints in the masonry element, the hyperbolic Mohr–Coulomb yield criterion, defined as a function of cohesion and friction angle, was used. The analysis results showed that the lateral resistance and failure mode of the infilled frames were significantly affected by the thickness of the masonry infill, cohesion on the mortar joint–brick interface, and poor mortar filling (or gap) on the masonry boundary under the beam. Diagonal strut actions developed along two or three load paths on the mortar infill, including the backstay actions near the tension column and push-down actions near the compression columns. Such backstay and push-down actions increased the axial and shear forces of columns, and ultimately affect the strength, ductility, and failure mode of the infilled frames.
Highlights
Reinforced concrete moment frames with unreinforced masonry infills have been used in many existing buildings such as school and government facilities in Korea
By performing nonlinear analysis, the force transfer mechanism and failure mode of the infilled frames varying with the thickness of the masonry infill and poor mortar filling on the masonry boundary under the beam, were investigated
This study focused on failure mode and force transfer mechanism depending on: (1) relative stiffness and strength between the masonry infill and adjacent columns and (2) poor mortar filling on the masonry boundary under the beam
Summary
Reinforced concrete moment frames with unreinforced masonry infills (or infilled frames) have been used in many existing buildings such as school and government facilities in Korea (see Fig. 1). The first approach is to separately model brick units, mortar joints, and interfaces, considering failure mechanisms (Lourenco and Rots 1997; Mehrabi and Shing 1997; Stavridis and Shing 2010; Zhai et al 2017). This study investigated the behavior of infilled frames through nonlinear analysis by VecTor2 For this purpose, the DSFM for masonry (Facconi et al 2014) that accounts for the orthotropic behavior of brick units and the slip behavior on the mortar joint–brick interface was reviewed. By comparing the distributions of cracks and diagonal struts on the masonry infill at various loading stages, the effects of such diagonal strut actions on the masonry infill-frame interaction and column shear failure were studied
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