Stability And Joint Local Stress Analysis Of Wide Continuous Steel Truss Arch Bridge

Continuous steel truss arch bridge has a beautiful shape,complex staggered bars and obvious spatial effect.In recent years,high-strength materials and thin-walled structures have been used widely,and the span has been increasing,so the stability and stress concentration problems of structures are prominent.This article takes the wide continuous steel truss arch bridge under construction in Liaocheng City as the research object,establishes the whole bridge model and joint local model respectively,and studies its static performance,stability and joint local stress.The main work and achievements are as follows:(1)The finite element model of the wide continuous steel truss arch bridge was established by using Midas/Civil,and the model was modified and optimized based on the influence matrix method.Taking geometric displacement and stress state as the control object,a group of optimal bridge cable forces were solved after several iterative calculations,and the accuracy of the model is verified by comparing the calculated and measured values of cable force,which provides the calculation basis for the static performance,stability and joint local stress.(2)The static performance of the wide continuous steel truss arch bridge is analyzed under the condition of bridge completion.The structural displacement and stress data were obtained through field monitoring,and the accuracy of the reference model was verified by comparing the measured and calculated values under the single action of dead load.Then,its static response under the single action of dead load,moving load,temperature and different load combinations was analyzed.At the same time,the static response of the bridge was studied by adjusting the influence parameters such as the span ratio and boom characteristics,and the static response of the arch rib,main longitudinal beam and boom was analyzed.(3)The theory of arch bridge stability is discussed and the linear elastic stability analysis and nonlinear stability analysis of wide continuous steel truss arch bridge are carried out.The results show that the transverse distance between the arch ribs is large and the transverse connection is strong.The horizontal connection and beam of the bridge can improve its transverse stiffness to a great extent,so that it has good spatial stability.The unstable members of the structure are all wind braces or arch ribs,and the instability modes are mainly antisymmetric instability outside the arch rib surface,local instability outside the arch rib surface,local instability of wind braces and positive symmetric instability outside the arch rib surface.Parametric analysis is carried out from two angles of structural member failure and member stiffness change,and the influence of suspender,wind brace and arch rib on the stability of the whole bridge is studied,and the main factors affecting its stability are found out,which can provide a certain reference for similar bridge design,monitoring and operation.(4)The local analysis method and related theories are briefly introduced.Using Midas/FEA to establish a refined model of B2 joint which is the most complex joint of all bridge members.B2 joint is a new type of welded integral joint,its appearance is simple but the internal structure is relatively complex,through welding and arch rib upper and lower chord rod,belly rod,beam and other rods into a whole.The joint is large and irregular structure,the stress state is very complex.The results show that the overall stress level of B2 joint is not high under the most unfavorable load conditions in the selected construction stage and bridge operation stage.The stress distribution of each component is more uniform,and it is in the elastic stress state.In addition to the local stress concentration,the Von Mises stress value in most areas of the joint is less than 200 MPa,lower than the allowable tensile stress of the material,so the design of the joint is reasonable.