Research On Calculation Method Of Ultimate Bearing Capacity Of Circular CFST Truss Joints

Steel tube truss structure has good mechanical performance and beautifulshape. It has been widely used in industrial buildings, long-span structures,offshore platform, bridge structures. Tube connections are the key part in steel tubetruss structures. There are a large number of experimental and theoreticalresearches on joints of steel tube truss, but there is still lack of systematic designmethod of joints of circular concrete-filled steel tube (CFST) truss.The ultimate bearing capacity of circular CFST truss joints are studied bytheoretical analysis, experiments and numerical calculation. The specific work isexpressed as follows:(1) When the branch section is circular or rectangle, the calculation methodsof ultimate bearing capacity of circular CFST Y-joint was proposed. The failuremechanism of the CFST Y-joint under tension or compression or bending wasdiscussed. Reasonable mechanics models were established based on the failuremodes. The calculation methods of the circular CFST Y-joint of ultimate bearingcapacity of tensile or compression or bending, were verified by the tested results.Finally the ultimate bearing capacity design formula of circular CFST Y andX-joint were suggested.(2) When the branch section is circular or rectangle, the calculation methodsof ultimate bearing capacity of circular CFST K-joint was proposed. The failuremechanism of the CFST K-joint under tension or compression or bending wasdiscussed. Reasonable mechanics models were established based on the failuremodes. The calculation methods of the circular CFST K-joint of ultimate bearingcapacity of tensile or compression or bending, were verified by the tested results.Finally the ultimate bearing capacity design formula of circular CFST K andN-joint were suggested.(3) The calculation methods of ultimate bearing capacity of semi-tubular jointor CFST semi-tubular joint was proposed. The failure mechanism of semi-tubularjoint or CFST semi-tubular joint under tension or compression or bending wasdiscussed. Reasonable mechanics models were established based on the failuremodes. The calculation methods of the semi-tubular joint or CFST semi-tubularjoint of ultimate bearing capacity of tensile or compression or bending, were verified by numerical calculation. Finally the ultimate bearing capacity designformula of semi-tubular joint or CFST semi-tubular joint were suggested.