A nonlinear macromodel for simulating the in-plane behavior of unreinforced masonry (URM) infilled frames.

This study introduces the application of parallel arrangement of multiple axial springs in a nonlinear macromodel to capture the in-plane rotational behavior and predict shared axial forces between column and wall of an infilled frame under rotation. In addition, multiple failure mode of both boundary frame and infill can be simulated using the developed macromodel. A systematic arrangement of two types of elements, each with one shear spring and one axial spring, is used to replace the masonry infill panels in the numerical modeling of infilled frames. The constitutive models of the axial and shear springs are derived using the geometric properties of the infilled frame and the results of simple material tests such as tension tests of rebar and compression tests of masonry prisms and concrete cylinders. A brief summary of the experimental study and numerical simulation of a 1/2.5-scale 2-story 2-bay unreinforced brick masonry infilled frame specimen (the BF + MIW specimen) is presented, focusing on the behavior of existing vulnerable buildings in developing countries (e.g., Bangladesh). A distinct type of failure mode was observed in the BF + MIW specimen: snap-through shear failure of the column on the lateral loading side with simultaneous sliding at the beam-wall interface. The developed macromodel considers this failure mode. Another reinforced concrete frame specimen with unreinforced concrete block masonry infill is analyzed using the macromodel. Analysis results effectively approximate the overall behavior of the infilled frames and predict axial forces on columns under rotation. [ABSTRACT FROM AUTHOR]