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Improving double-layer space trusses collapse behavior by strengthening compression layer and weakening tension layer members

Progressive collapse is a chain of local failures leading to the collapse of either the entire or a part of the structure. The double-layer space trusses are susceptible to progressive collapse due to sudden buckling of compression members. The method of strengthening the compression layer members along with weakening the tension layer members is an effective method for retrofitting the double-layer space truss behavior against progressive collapse. In this study, the method is applied on offset double-layer space truss models with different support conditions, members’ geometrical imperfections, height, and shapes, and the effectiveness in increasing the structure’s ductility and load-bearing capacity is demonstrated. The results show that the method converted the sudden collapse of the structures into a beneficial gradual (progressive) collapse. More specifically, for double-layer space trusses comprising members with similar geometrical imperfection, strengthening the compression layer chords along with weakening the tension layer chords within 30%–40% will significantly improve the ductility and load-bearing capacity. In addition, the results show that the method can decrease the weight of the structures and consequently provide more economical structures.