Research On Optimization Methods Of Resonable Completed State And Resonable Constructing State For Cable-Stayed Bridge With Steel Box Girder

Determination of reasonable completed state and reasonable constructing state are always critical and core of issues during design and analysis process of cable-stayed bridge with steel box girder. On the basis of summarization on structure characteristics, construction characteristics and existing research results, took large span cable-stayed bridges with steel box girder as background, systematical researches on optimiazaiton method of reasonable completed state and reasonable constructing state for cable-stayed bridge with steel box girder were conducted through the combination of mathematical optimization method and finite element method. Practical methods of construction control and error adjustments for cable-stayed bridge with steel box girder were also discussed. The main contents were as follows:(1) The combination of multiplier path following method and finite element method was proposed to optimize reasonable completed state for cable-stayed bridge with steel box girder, in which sum of bending energy of girder and pylon was taken as objective function, and vertical displacements of girder, horizontal displacements of pylon, normal stresses of girder and pylon, cable forces and their distributional uniformity were taken as constraint conditions. Impacts of changing range of constraint conditions on optimization results were also analyzed through example analysis. The application of this method could avoid the arbitrariness of artificial adjustment of cable forces under dead load. Mechanics as well as deformation characteristics of cable-stayed bridge with steel box girder could be fully taken into account by taking sum of bending energy of girder and pylon as objective function, and the reasonable completed state of cable-stayed bridge with steel-box girder could be obtained simply and efficiently.(2) Combined multiplier path following algorithm with finite element method, influence of structural parameters, such as support form between girder and pylon, length ratio of side span to main span, ratio of pylon height(above the deck) to main span length, number and arrangement of assistant piers on completed state of cable-stayed bridge with steel girder were analyzed respectively.(3) The combination of multi-objective optimization algorithm with forward iteration finite element method was proposed to determine the reasonable constructiing state for cable-stayed bridge with steel box girder, in which differences of vertical displacements of girder, horizontal displacements of pylon, bending moments of girder and pylon, and cable forces between the results gained from forward iteration finite element method and the reasonable completed state were taken as objective functions. Impacts of selection of objective function on optimization results were analyzed through example analysis. Theoretical and comparison analysis results showed that this method was simple, effective, and not only can avoid the randomness of artificial adjustment of cable tensions during construction process, but also mechanics as well as deformation characteristics of cable-stayed bridge with steel box girder could be fully taken into account.(4) Combined geometric nonlinear theory with finite element method, influences of cable sag effect, P-Δ effect respectively, and comprehensive effects of the three types of geometric nonlinearity on constructing state of cable-stayed bridges with steel box girder were analyzed respectively.(5) According to the characteristics of construction and construction contol, control principle, contents, implementation process, and the precision of control objectives of geometry control method for cable-stayed bridge with steel box girder were elaborated. An improved weighted least squares method was proposed to minimize the construction deviation. Took large span cable-stayed bridges with steel box girder as examples, construction control and error adjustments were carried out, thus the feasibility and effectiveness of the method could be verified.