Research On The Construction Control Technology Of Xiangjiang River Sanchaji Self-anchored Suspension Bridge

Self-anchored suspension bridges are increasingly appreciated by engineers for their merits such as aesthetic appearance and high adaptability to the land form and geology. It has become a more competitive design scheme in small and medium-span bridges in cities. Sanchaji Bridge is the largest span steel box girders self-anchored suspension bridges with twin towers with steel box girders in Asia at present, which lies in Changsha city, Hunan province. What's more, it adopts a new construction method that thrusting the steel box girders, and then erecting the main cable system; lifting the steel box girders and installing the suspenders, finally, dumping the steel girders to bridge, so the construction control of this bridge has the following features and difficulties: large span, large deformation and small permissible error. Based on the construction control of Sanchaji Bridge in Changsha, the paper studied the theory and method of construction control in self-anchored suspension bridge with steel box girders. The main contends cover the following aspects:(1) The paper studied the linear control method of pushing the steel box girders along the vertical curve. The top pushed steel box girders under the force of gravity would cause rotation of the end beam and compression of the end point, considering the new assembled beams on the pushing platform as a rigid-body rotation and movement to position, meanwhile, mending their manufacturing errors and deformations, and concerning about the stress level of the steel box girders, the safety of the steel guided beams and the structural stability of the temporary piers, etc. in the process of pushing the steel box girders, which would control the linear and the safety when it pushed the steel box girder along the vertical curve.(2) The paper studied the control method of positioning the benchmark strands in self-anchored suspension bridge, as we know the linear of the benchmark strands would be much impacted by temperature, partial volume pre-saddles and saddle higher-parabolic, etc. The paper explored the changing law of benchmark stands linear under the effected of various factors, a method that the ratio of the length and span is relatively stable was raised to control the benchmark strands position, which would control the entire rope line. (3) The paper studied the control method of dumping steel box girders in self-anchored suspension bridge. It ensured that the lifting height and grading program of lifting the steel box girders, and the suspenders vertical displacement by which could improve the internal forces of the suspenders. Lifting against steel girders the inverse construction -- dumping steel girder to bridge, it was certain that the steps of set-beam construction and the pushing quantity of the saddle under the levels-beam construction, which ensured the safety and smooth when the system was conversed.