Research On Load-bearing Performance And Applicable Span Diameter Of Top-bearing Aluminum Alloy Arch Bridge

The arch bridge structure has always been an indispensable form in bridge engineering,and the development of science and technology has constantly refreshed the span diameter of arch bridge,and the completed Pingnan Three Bridges have refreshed the maximum span diameter of arch bridge to 575 m.With the increase of span diameter,the excessive lifting weight of sections in the construction process has been a painful point limiting the development of arch bridge span.Aluminum alloy material has high specific strength and superior anti-corrosion performance.Compared with steel arch bridge of the same strength,aluminum alloy material can significantly reduce the selfweight of the structure.Therefore,it is worthwhile to investigate the feasibility of using aluminum alloy as a load-bearing material in arch bridge structures to improve the applicable span diameter of arch bridges by reducing the lifting weight of sections during construction.In this paper,the stable load-bearing performance and the applicable span diameter of the top-bearing suspended chain line aluminum alloy arch bridge are studied in depth through finite element analysis,and the main contents and conclusions are as follows:(1)Based on the engineering example of domestic top-bearing steel box arch bridge,the trial design of aluminum alloy top-bearing arch bridge was carried out,and the force performance of the whole bridge was analyzed by MIDAS software,and the results showed that the stiffness,strength and overall stability of the whole bridge meet the specification requirements.(2)The finite element software ANSYS was used to study the ultimate load carrying capacity of aluminum alloy main arch and its damage pattern,and to investigate the influence of strain hardening index and initial geometric defects in material parameters,and the influence of vector-to-span ratio,arch axis coefficient and width-thickness ratio in structural parameters on the ultimate load carrying capacity of the arch bridge.The results show that: the ultimate live load coefficient after nonlinear analysis is 30.81%lower than that of linear elastic analysis,and the double nonlinearity must be considered in the load carrying capacity analysis;the damage form of both aluminum alloy arch bridge and steel arch bridge is large in-plane deformation against symmetric instability;the strain hardening parameter is within the range of ±60% suggested by Stein Hardt,and the n value can be temporarily taken as f0.2/10;the initial defect within L/500 has little effect on the ultimate load carrying capacity of the structure;for large span aluminum alloy box arch bridge,the recommended sagittal-to-span ratio is between 1/5 and 1.For large span aluminum alloy box arch bridge,it is recommended that the sagittal-to-span ratio should be within the range of 1/5 to 1/4;the arch axis coefficient is too large to lead to the decrease of the ultimate bearing capacity of the structure,so it is recommended that the value of the arch axis coefficient of aluminum alloy top-bearing arch bridge should be between 1.3 and 1.6;the width-to-thickness ratio in the project is within the limit of aluminum alloy,so it is recommended to take a smaller value.(3)The applicable span of aluminum alloy upper bearing arch bridge under material strength,stiffness,overall stability,construction feasibility and material processing limits was studied by ANSYS,and compared with Q345 steel arch bridge.The results show that: Under the same segmental lifting weight,when the aluminum alloy box section is2.88 times the section of the arch bridge,the applicable span of the aluminum alloy arch bridge is 700 m under the action of 1.2 times the arch ring weight.When the building weight on the arch is converted to 2.0 times of the material density of the main arch ring,the applicable span of the aluminum alloy arch bridge is 592 m.The maximum applicable span of aluminum alloy arch bridge is about 50% higher than that of steel arch bridge under different material density conversion times of main arch ring,that is,aluminum alloy material can increase the span of arch bridge.