| Prestressed concrete cable-stayed bridges are currently one of the widely used large-span bridge types.However,due to factors such as material time-varying effects,variable load effects,and environmental factors,there are certain differences between the structural stress state and the completed bridge state after years of operation,which has affected the applicability and even safety of the structure.The cable-stayed cables also have to be replaced due to corrosion and damage.This article is based on the theory of geometric nonlinear finite element,and conducts research on the determination of reasonable completion state,finite element model correction,and cable replacement schemes for prestressed concrete cable-stayed bridges.Firstly,the existing methods for determining the reasonable completion state of cablestayed bridges are summarized.Based on the characteristics of prestressed concrete cablestayed bridges,the minimum bending energy method and the influence matrix method are comprehensively used to optimize the cable forces of the cable-stayed cables.To avoid disordering the tension of the stay cables,the selected target control amount far exceeds the adjustment amount of the tension.Therefore,the equation set established by the influence matrix method is a set of contradictory equations,which are solved using the least squares method.The focus is on studying the selection of the adjustment amount(to be adjusted cable force)and the adjusted amount(target control amount)during the cable adjustment process.The selected adjusted amount mainly includes the bending moment of the main beam that deviates greatly,the bending moment of the bridge tower control section,the displacement of the tower top,and the cable force of the entire bridge cable.The adjustment amount is selected for the cable force of the cable that is sensitive to the adjusted amount or abnormal cable force,and the adjustment amount of the adjusted amount is further quantified to avoid the blindness of cable adjustment.The proposed method was validated using a concrete cable-stayed bridge with a main span of 450 m.Then,based on the reasonable completion state of the bridge,and based on the static and dynamic load test data of the bridge beam,a finite element model correction method combining static and dynamic forces is adopted,and multi-objective optimization problems are introduced.Non dominated sorting genetic algorithm(NSGA-II)is used to solve the problem,achieving finite element model correction.After correction,the elastic modulus of the main beam and tower pier increased by 17.73% and 15.00% respectively,the bending moment of inertia of the main beam decreased by 10.0%,the bulk density of the main beam increased by 6.31%,and the elastic modulus of the cable material increased by 8.97%.The static and dynamic load calculation values of the modified finite element model are more consistent with the measured values,which can better reflect the actual stress state of the structure.Finally,based on the modified model,the cable replacement scheme for concrete cablestayed bridges is studied.Concrete cable-stayed bridges often use parallel steel wire stay cables with large cable distances.When replacing the stay cables in certain areas,it is easy to cause the tensile stress of the main beam to exceed the limit.Therefore,it is necessary to study a more reasonable cable replacement plan for concrete cable-stayed bridges.Under the principle of not changing the existing stress state,based on the sensitivity analysis results of cable replacement,considering factors such as safety,construction efficiency,and traffic,three cable replacement plans have been formulated.By analyzing and comparing the changes in cable force,deflection of the main beam,and stress of the main beam,a comprehensive plan is proposed.This plan can minimize the tensile stress of the main beam while ensuring construction efficiency,providing reference for the cable replacement construction of the bridge. |
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