Inelastic Design of Infilled Frames

This paper describes a new method of analysis and design for steel frames with concrete or masonry infilling walls subjected to in-plane forces. The method is based on data generated from previous experiments as well as results from a series of nonlinear finite-element (NLFE) analyses. The method accounts for elastic and plastic behavior of infilled frames considering the limited ductility of infill materials. The proposed method predicts the strength and stiffness of infilled frames as well as the infill diagonal cracking load. The method also allows for the major practical imperfections, such as lack of fit and shrinkage of the infill. Variations, such as infill aspect ratio and beams having different strength and stiffness from the columns, are accounted for and it is concluded that the behavior of frames with pin or semirigid joints can also be predicted. The method is further developed to model multistory infilled frames as braced frames, replacing the infills by equivalent diagonal struts.