Research On Arch-rib Line Shape Control And Optimization For Rod Tensile Force Of Tied Arch Bridge With Steel Box Ribs

Steel box tied arch bridge has the characteristics of tight,strong,large spanning capacity and good seismic performance.Therefore,in recent years,it stands out in the long-span bridges designing.The safety and reliability of such bridges could be extremely influenced by selecting and controlling of the line shape,determining of the reasonable finished state and setting rob tensile forces.On the basis of Jin Ji Da Dan River Steel box tied Arch Bridge,with the method of finite element analysis,the line shape of the rid,constructing state control and rob tensile force optimization were studied.The main work and conclusions are summarized as follows:1.Using the finite element software to establish the overall bridge model,the inner forces distribution of completion state gained by several commonly used arch rib lines are compared and analyzed.The research shows that the effect of dead load on arch rib alignment is much greater than that of live load.Besides,the line obtained by the Cubic spline interpolation has the best result of inner forces distribution.Overall,the parabola or catenary are well used as arch rib alignment.2.The thesis introduces the basic principle of camber setting and common algorithms.Combining with the project example,with different algorithms,the cambers are set on the models.Using the error assessment method of estimation bias and root mean square error(RMSE)to judge the quality of the results.It is shown that iterative method and proportional setting of thrust impact line are suitable for steel box tied arch bridges.3.Making use of unknown load-factor method to calculate the cable force of steel box tied arch bridge constructed by cable-stayed and buckling-hanging method.Taking the vertical deflection of bare arch as the control objective,linear function as the objective type,the calculated cable force can adjust the arch rib segment to the desired manufacturing alignment.And then the control of arch rib alignment is realized by adjusting construction cable force.4.Through the finite element software Midas/civil,the original state vectors of bending moment,displacement and the influence matrix of rod are obtained.After the step,structural strain energy can be calculated.The influence direction and magnitude of rob force changing on structural parameters under completion state are judged.5.By choosing appropriate constraints,the optimization models are established with the objective functions of bending moment,displacement and strain energy respectively.The KT equation method is used to solve the optimization problems with the help of MATLAB programming.The comparison of the completed bridge state under the force of the original design and calculating results is analyzed.The results illustrate that optimum ranges of displacement,bending moment and strain energy is 9.4%,23.5% and 25.7% respectively by optimizing the rob force.Based on the finite element analysis,the article discusses the alignment control of arch rib and the optimization of rob force of tied arch bridge with steel box ribs,and puts forward many constructive suggestions for the design and construction of this kind of bridge,which provides a basis for further optimization of arch bridge design.