Effects of Infilled Walls with and without Openings on Progressive Collapse Resistance of Steel Frames under Corner Column Loss Condition

Steel frames may have an inherent ability to resist progressive collapse through alternative load-resisting mechanisms, including Vierendeel, flexural, catenary, and membrane actions. Among the columns at different positions, corner column failure caused by accidental loading is more dangerous due to the relatively few alternative load-resisting mechanisms. To evaluate the effects of infilled walls with or without openings on the progressive collapse resistance of steel frames, four two-span 2-story steel frames were tested in this study. According to the test results, the solid infilled frames achieved peak loads that were over 300% greater than those of the bare frame. Relative to the bare frame, the infilled frames with solid bricks and perforated bricks increased the deflection capacities by 15% and 29%, respectively. This result was attributed to the development of effective compressive struts in the infilled walls to partially transfer the vertical loads. Thus, premature joint failure was avoided. Moreover, the failure modes of the infilled walls changed when different types of brick were adopted. The infilled walls with solid bricks showed extensive shear sliding cracks; the infilled walls with perforated bricks were relatively intact, but the compressive corners were crushed. The partially infilled frame with a 40% opening ratio still increased the load-resisting capacity of the steel frame by 90%. In addition, the efficiencies of the compressive strut models of the infilled walls under corner column loss conditions were evaluated. Based on the calculations, the width of the equivalent compressive strut provided by current US standards is recommended.