Optimization Of Bidirectional Progressive Structure Of Segmental Prefabricated Continuous Girder Bridge

In recent years,structural optimization has been successfully applied in various fields of structural design,which can generate optimal structural topology and shape according to different objective functions and constraints.Combining bridge design and structural topology optimization opens up a new way for bridges to achieve light weight and enrich the bridge landscape.In this paper,we take the segmental precast continuous girder bridge on the South Fourth Ring Road in Zhengzhou City,Henan Province,as the engineering background,and study the optimized design of the web and bottom slab of the segmental precast continuous girder bridge by the two-way progressive structure optimization method,and prepare the corresponding optimized design procedure.It is of great significance for the future development of bridge engineering to seek a lightweight bridge with beautiful form and reasonable structure under the precondition of ensuring good structural performance of the bridge.The main research results are as follows:(1)Based on the basic theory of bidirectional progressive structural optimization,the sensitivity filtering strategy and smooth process are analyzed,the unit addition and deletion operations and convergence conditions are summarized,and the implementation method of importing the Python program into ABAQUS software to carry out segmental precast box girder optimization is proposed.Based on the results of Midas/Civil calculations,the stress characteristics of each segment of segmental precast assembled continuous girder bridges during the construction and operation periods are summarized,the segmental classification method applicable to structural topology optimization is established,and the segmental precast assembled continuous girder bridge precast segmental classification based on the ratio of shear force and bending moment is proposed,which provides a reasonable research object for the two-way progressive structural optimization of bridges.(2)The internal force calculation results are extracted in Midas/Civil under different working conditions such as self-weight,city-A lane load and temperature,and the force characteristics of each segment of segmental precast continuous girder bridge during the construction and operation periods are summarized based on Midas/Civil calculation results.The segmental classification of prefabricated sections of prefabricated continuous girder bridges based on the ratio of shear force and bending moment is proposed,which is divided into three categories: shear-dominant,moment-dominant and bending-shear sections,providing a reasonable research object for the two-way progressive structure optimization of bridges.The results of the structural optimization analysis of the classified segments show that the absolute value of the ratio of shear force to bending moment within [0-1] is classified as momentdominated segment;the absolute value of the ratio of shear force to bending moment within [2-3] is classified as bending-shear-dominated segment;the absolute value of the ratio of shear force to bending moment > 3 is classified as shear-dominated segment.The volume of the optimized segmental precast continuous bridge is reduced by 9.94% compared to the volume of the original segmental precast bridge under load in Case 1(deadweight)loading,and by 10.3%compared to the volume of the original segmental precast bridge under load in Case 2(deadweight and city-A lane loading)combination;the optimized result under the combination of self-weight and urban-A lane load is more obvious than the optimized result under the combination of self-weight and urban-A lane load,so the optimized result under the combination of self-weight and urban-A lane load is more valuable for research.The optimized results are more valuable for research.(3)Combined with the segmental prefabrication construction process and prestressing tendon linear arrangement,the main optimization result characteristics were proposed,and the optimized shapes of the web of trapezoidal and rectangular cavity and the bottom plate of rhombic cavity were established,taking into account the later prefabrication and construction problems such as lifting and transportation,and the web cavity was optimized as elliptical quadrilateral with curved instead of straight.The optimized bridge shape is formed by combining the web of elliptical quadrilateral cavity and the bottom plate of rhombic cavity.The results of structural testing and modal analysis show that under the combination of self-weight and city-A lane load,the maximum tensile stress in the span section of the optimized segmental precast continuous girder bridge is 8.9% less than that of the original girder bridge in terms of structural strength.For the shear performance of the bridge structure,the maximum shear load capacity of the optimized bridge increased by 7.65% compared with the original bridge;for the stability of the structure,the flexural critical load of the optimized bridge increased by 4.89%compared with the original girder bridge,and the results of the modal analysis of the optimized bridge met the requirements.In conclusion,the results obtained from the optimization of the segmental precast continuous girder bridge are advantageous in terms of light weight,strength,stiffness,stability performance and shear resistance.The feasibility of this optimization is verified by the above study.