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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.

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Space trusses under certain conditions may be prone to snapthrough buckling. The sudden reduction of the load carrying capacity of a single critical compression member, or a group of compression members, may lead to the snap-through buckling of the compression chord of the structure. This temporary loss of equilibrium due to snap-through normally results in a dynamic force being applied to each node associated with the snap-through. In this paper a methodology based on energy methods is presented to determine the dynamic snap-through response of truss structures. Member failure is taken into consideration by carefully following the buckling load-displacement response of the member. It is assumed that the structure is subjected only to static gravitational loading. A one degree of freedom, simple three bar truss, is used to describe the approach. Finally, this method has been used to perform the snap-through buckling analysis of two double layer grid structure providing a load-displacement behaviour from each structure variation to that obtained from a conventional static analysis.