Design of High-Low Legs Gantry Crane for South Main Bridge of Xiazhang Sea-Crossing Bridge

The south main bridge of Xiazhang Sea-Crossing Bridge is a composite girder cablestayed bridge with span arrangement of(135+300+135)m.It was planned to use the gantry crane to hoist the precast deck slabs,stay cables and other components,with the heaviest component weighing up to 25t.To ensure the smooth progress of the hoisting,the high-low legs gantry crane made of Q235Bsteel and with a weight of 10twas designed.The high leg of the crane is72.5mlong,and the low leg 5.1m,which are all formed of steel tubes by assembly and welding.The two bailey truss main beams spanning 36mwere each composed of three blocks of bailey trusses.The ANSYS software was used to analyze the deformation and stress of the bailey truss main beams.According to the analysis,the maximum stress was 154.7MPa,the maximum downwarping in the midspan was 73.4mm,and the strength and stiffness of the Bailey truss main beams could meet the requirements.The calculation of the anti-overturning of the gantry crane showed that the longitudinal overall stability coefficients of the gantry crane was 10.9,the transverse overall stability coefficient was 1.72,greater than the value of 1.2stipulated in the code,and the overall stability of the gantry crane could match the requirements.The stability safety coefficient of the high leg calculated by the MIDAS software was 10.04,and the critical load of the most unfavorable chord members was far greater than the design load,which indicated that the structural design of the high-low legs gantry crane was safe and rational.