Abstract: For cavein failure mode is apt to occur in hollow steeltube joint. In order to avoid this kind of failure, chord is grouted to increase the cave-in bearing capacity. Experiment was carried out on cave-in bearing capacity of 15 groutedsquare-steel tube and influence of some factors on cave-in bearing capacity of grouted-square-steel tube was analyzed, such as ratio of length of branch tube to length of chord tube, characteristics and value of axial force acting on chord. In addition to these factors in model experiment, influence of factors such as thickness of chord's wall panel, strength of hardened grout and strength of chord steel was analyzed in simulated experiment. Based on model experiment and simulated experiment, mechanical properties of grouted-square-steel tube in cavein failure mode was analyzed and the formula of cave-in ultimate bearing capacity of grouted-square-steel tube was established. It can provide basic data for spreading encased steel truss-concrete composite beam.

Key words: grouted-square-steel tube, cave-in ultimate bearing capacity, simulated experiment, model test