Comparison and Selection of Construction Schemes for Vertical Rotation of Basket Handle Arch of Lancang River Bridge

Lancang River Bridge is a concrete-filled steel tube(CFST) steel frame reinforced concrete railway basket handle deck arch bridge with the calculated length of main span being 342 m.The bridge is located over the V-shape deep valley where the relative height difference is up to 1 204 m.According to the design,the arch ribs of the bridge were required to be erected by the vertical rotation method.The weight of the rotation and lowering of a half arch rib would be up to 2 500 t.In the light of the characteristics of the bridge and the topography conditions at the bridge site,two kinds of the constructions schemes of integral vertical rotation and two-time vertical rotation were proposed.Through comparison and selection,it was decided that the scheme of the two-time vertical rotation was to be adopted.The scaffoldings for assembling of the arch ribs were arranged on the mountain side,making a good use of the specific conditiions there,a half arch rib was assembled in two segments and to be rotated in place in two times.The key techniques of the adopted construction scheme included those of the intermediate hinge setting in the central part of the half arch,the strut-and-tie structure for horizontal force transferring in the first time rotation and the negative angle rotation that was dynamically and synchronously controlled by computers.