Research On Construction Control Of Long-Span Steel Box Basket-Handle Arch Bridge

The main aims of construction control of long-span steel box basket-handle arch bridge are to make the line shape and the internal force of the completed bridge meet the requirement of the design and the standard codes to the maximum extent, as well as to ensure the satefy during the construction. Base on Ningbo rail transit arch bridge, the largest span basket-handle arch bridge with a main span of 220m in China, this thesis investigated the simulation analysis during key construction stages by forward analysis, the calculation of foundation settlement for beam-arch simultaneous construction, the comparison of theoretical and measured results for the arch rib and tie beam, the parameter sensitivity analysis, the pre-camber setting, the calculation of final and in-construction suspender force, and cable force measurement by frequency method. The main work is as follows:(1) This thesis has described the development of long-span steel box basket-handle arch bridge, as well as the commonly used construction and calculation methods, and summarized the structural characteristics and construction control theory of basket-handle arch bridge.(2) This thesis has calculated foundation settlement by strain ratio and discussed the determination of settlement depth, given that adopting full framing and steel pipe support in soft foundation for the beam-arch simultaneous construction induces more difficulty of construction and higher requirements of foundation.(3) This thesis has simulated in-construction and complete-construction stages by using MIDAS Civil for the scheme of beam-arch simultaneous construction, and calculated the stress and deformation during key construction stages by forward calculation method, which provides the theoretical guidance for construction monitoring.(4) This thesis has illustrated the accumulative stress state of key sections in different construction phases through the comparative analysis of theoretical and measured stresses of key sections of tie beam and arch rib, and preferably controled the actual linear shape and contributed to the realization of the ideal design state, and verified the accuracy of the present analysis method through the comparative analysis of computed and measured linear shape of tie beam and arch rib in key construction phases.(5) This thesis has done sensitivity analysis of the parameters that induce the structural state error, introduced in detail the pre-camber setting of arch rib and analyzed the calculation results and applicability of various pre-camber setting methods by taking Ningbo rail transit basket-handle arch bridge as an example, and determined the unstressed length of suspenders.(6)To determine the final and in-construction suspender force is an important task for basket-handle arch bridge. Usually, the final suspender force should be firstly determined, and the in-construction force is then calculated according to the construction program by setting the final force as a goal. This thesis has introduced the elastically supported continuous beam method and the minimum strain energy method for determining the complete bridge state, calculated the final suspender force by strain energy method, and obtained the in-consideration suspender force based on reverse sequence method, influence matrix method, and simple iteration. The results show that its final state is very close to the design and this study has a reference for similar arch bridges in calculating suspender force.(7) Presently, using frequency method to measure the suspender force is usually based on string theory for which the boundary condition is hinge joint and the influence of bending stiffness is ignored, therefore a relatively large error is induced for the measurement. Taking Ningbo rail transit basket-handle arch bridge as an example, this thesis has proposed a method that can reduce the test error through revised suspender length that equals to 0.9 and 1.1 times the distance from shock absorber to anchorage, which provides a reference for cable force test of similar arch bridges.