Force-displacement relationship modelling of masonry infilled walls with openings in hinged steel frames

Seismic behaviour of masonry infilled frames has attracted extensive attentions from researchers, and it was found that infills normally experienced a diagonal compression under lateral loading. Infill was therefore assumed as an equivalent diagonal strut in structural response estimations of infilled frames, and a force-displacement curve was adopted to describe the mechanical properties of the strut. However, the influences of infill aspect ratio, vertical load acting on the surrounding frames, and opening were not systematically addressed in establishing the force-displacement relationship of infills. To investigate the effects of these influential parameters on the lateral responses of infilled walls including initial stiffness and strength, detailed three-dimensional finite element (FE) models of masonry infilled hinged steel frames are developed in ABAQUS in the present study, and a wide parametric study with respect to various aspect ratios, vertical loads, and opening sizes and locations is performed. A generalized force-displacement relationship model of infilled walls is proposed based on regression analyses of numerical results. The efficacy of the proposed model is examined by using the existing experimental test results, and it shows that the model can accurately predict the lateral stiffness and load carrying capacity of infilled walls and thus has great potential applications in structural designs and analyses for masonry infilled steel frames.