Techniques of Geometric Shape Control for Pre-Assembling of Steel Main Girder of Erqi Changjiang River Bridge in Wuhan

To guarantee the geometric shape for erection of the steel main girder of Erqi Changjiang River Bridge in Wuhan,several techniques involved in the shop pre-assembling,survey control and geometric shape adjusting of the girder were studied.The assembling of the girder components and the pre-assembling of the girder blocks was all carried out on the assembly jig stands and 9 datum lines were set according to the geometric shape of fabrication of the girder for the purpose of positioning and measuring the girder blocks.The survey control network for the assembling was established by the method of external control and borrowing of lines.Each batch of the components of the girder blocks was positioned from the far side to the close side according to the sequence of the assembling.The matching of the late fabricated girder blocks with the early installed steel girder of the composite girder was surveyed by the calibrated steel tapes and multiple observation-set survey method.In the inspection of the pre-assembling of the steel girder,the measures of adjusting the assembling and welding procedures,redrilling the holes,strictly restricting the inspection time in shop,unifying the precision of inspection instrument were taken to eventually realize the adjusting of the geometric shape of the girder.