Calculation Of Horizontal Force On The Pier Top Of Extradosed Cable-stayed Bridge And Study On Spatial Effect Of Box Girder With Wide Flange

Extradosed cable-stayed bridge is a new type of bridge structure developed slowly in the 20 th century.It is a rigid flexible bridge type between continuous beam bridge and flexible cable-stayed bridge.In the concrete design of low tower cable-stayed bridge,there are few documents about the calculation of the horizontal force of the substructure,especially the pier and abutment.In this paper,a low tower cable-stayed bridge is taken as the research object.By comparing the two methods of manual calculation of the integrated stiffness method and the establishment of the whole finite element model of the upper and lower parts of the whole bridge to simulate the horizontal force,the feasibility and accuracy of the calculation of the horizontal force of the whole finite element model are verified,and a new idea and method for the design and calculation of the horizontal force of piers and abutments are proposed.On this basis,through theoretical derivation and engineering calculation,the influence of considering elastic constraint of pier top on horizontal force distribution is discussed.In addition,the urban bridge deck is generally wide,and the wide box girder and short tower cable-stayed bridge has been widely used and developed.The wide box girder has the characteristics of wide transverse flange and thin box wall.The spatial stress distribution of the wide box girder is uneven,especially for the cable-stayed bridge with single cable plane and short tower.Because of its special boundary conditions,complex structure and numerous prestressed tendons,the three-dimensional stress of block zero is very complex.Therefore,the static analysis of the whole bridge is carried out first,and the local stress analysis of the zero block of the main beam under different construction stages is carried out,in order to verify the reliability of the project design or make up for its shortcomings.The results can provide engineering reference value for the design of similar bridges.Through the spatial stress analysis,it can be found that the vertical and horizontal stress of block zero has obvious heterogeneity.In order to quantify the nonuniformity of the transverse stress distribution,the concept of nonuniformity coefficient is put forward in this paper.The influence parameters affecting the nonuniformity of the stress distribution of the box section are selected by consulting the literature,and the uniform design is carried out and Kriging agent model is established to verify the accuracy of Kriging agent model.On this basis,the genetic algorithm(NSGA-II)with the elitist strategy is used to solve the cross-section multi-objective optimization problem in the design domain,and the Pareto optimal solution is obtained by iterative solution.Then the optimal solution set is tested and the compromise solution is selected.The longitudinal and transverse stress values of the specific section of the optimized girder are extracted,and the shear lag coefficient and the nonuniformity coefficient at the specific position of the section are calculated.It can be seen from the results that after optimization,the longitudinal and transverse stress distribution of the box girder changes in a flat shape,the shear lag coefficient and the nonuniform coefficient are reduced,and the longitudinal and transverse stress distribution is more uniform,which can achieve the purpose of section optimization.