The behavior of steel plate shear walls under the effects of lateral loads depends on the stiffness of the surrounding frame members. Previous research has quantified the minimum required stiffness of columns in the middle stories of steel plate shear wall systems. As the columns of the steel plate shear wall system are subjected to both large axial forces and bending moments, use of composite columns is a viable option in this system. Among the different types of composite columns, the recently developed partially encased composite columns with built-up steel sections have some advantages over other types of composite columns and thus their performance as columns in steel plate shear wall systems needs to be studied. In the first part of this research, a numerical and analytical study has developed a new design parameter and determined the minimum required stiffness of end beams in end panels of the steel plate shear wall system. The effect of the rigidity of the frame connections on the uniformity of the tension field has also been studied in this part. The second part of this research includes two large scale tests on steel plate shear walls with built-up partially encased composite (PEC) columns. One of the test specimens was modular and the other one used reduced beam sections in the frame. The results of the tests show that the columns were stiff enough to anchor the infill plate. The PEC columns in these tests performed in a ductile manner. The overall system behavior was ductile, stable and the specimens showed good seismic behavior and redundancy. Based on the results and observations of this research, design recommendations for PEC columns used as the vertical boundary members of steel plate shear walls are provided. / Structural Engineering

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