Abstract
Considering shortcomings of the current technology in controlling ground surface settlement and reducing the effect of excavation on the surrounding environment. This paper presents an experimental study on the flexural performance of composite structures of concrete-filled steel tubes, which are proposed as a new type of pipe-roof structure. It is also called as steel tube slab (STS) structure. The most important feature of this structure is that the adjacent steel tubes are connected using flange plates, bolts, and concrete in the transverse direction, forming the supporting system after pouring concrete. The main design parameters considered in this investigation are the connection type, spacing between the tubes, welding of the top flange, and thickness of the bottom flange. By conducting six flexural experiments, the failure process and crack development in the composite beams and their load–displacement curves are investigated. The results of laboratory tests show that the composite beams exhibit ductile failure. Increasing connections between the steel tubes has an obvious effect on the load-carrying capacity and flexural stiffness. The spacing between tubes can improve the flexural stiffness of STS beams, while having a limited effect on the longitudinal load-carrying capacity of the STS structure. Welding of the top flange and thickness of the bottom flange shows limited effect on the flexural performance of STS composite beams. Moreover, a series of numerical models is established to further identify the optimum tube thickness-to-flange-thickness ratio in terms of the flexural bearing capacity and stiffness. The numerical solutions suggest that the optimum ratio of the flange thickness to the tube thickness is between 1.0 and 1.25. Finally, a theoretical model for the flexural stiffness of the cross-section of this structure is also proposed, and the predicted results are found to be in excellent agreement with the test results. The research results can provide references for design and construction of STS method.
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