Compressive tests of mortar-filled small rectangular hollow section members for long-span roof trusses

To improve the buckling resistance of slender truss members, mortar-filled rectangular hollow section (RHS) members have been used for the diagonal and chord members in roof trusses. In this study, the compressive behavior of mortar-filled RHS members was experimentally investigated. Compressive tests of six slender truss members with a small section (i.e., 100 mm×100 mm) were performed. The thickness of RHS, use of longitudinal reinforcement, and size of cap plates were considered as main test variables. Test results showed that the governing failure mode of all truss members was flexural buckling. The effective axial stiffness and compressive strengths of truss members were significantly affected by the thickness of RHS, whereas the effects of other test variables were limited. The nominal compressive strengths calculated in accordance with the design provisions for filled composite columns of current design codes showed good agreement with the test results.