The Key Parts Of The Force Analysis And Risk Assessment In Walking-Type Incremental Launching Construction Of Ultra-Wide Steel Box Girder

In order to better solve the problem of complex structural stress in the construction of ultrawide steel box girder step jacking,this paper uses the background of the Weimin Yellow River Bridge Wei project.First introduces the research status of the jacking method,the construction principle of the jacking and the construction scheme of the bridge.Then verifies the stability of the jacking platform and the temporary pier.The dynamic simulation analysis of ejection is realized by establishing the ejection model by the finite element program Midas/Civil,and the dynamic simulation analysis of the ejection is realized,and the force of the main girder under various working conditions is obtained.Finally,the mixed finite element local model under the unfavorable conditions is established by ABAQUS to explore the stress change law in the supporting area of the steel box girder.The risk assessment method is used to evaluate the potential risks in the jacking process.It provides guidance for the construction and safety management of step jacking of bridges of the same type,the main contents are as follows:(1)Using the beam element theory,the finite element model of the rod system is established for construction simulation analysis,which can know the deformation of the main beam and the general change law of the internal force in the jacking process,and the typical unfavorable working conditions in the whole process of ejection can be determined by using the deflection of the guide beam,the temporary pier support force and the internal force of the main beam as the control indicators.(2)By simulating a variety of falling beam modes by jacking support,the results show that the multi-supported jacking beam body can effectively reduce the supporting force size of the most unfavorable pier,thereby improving the force state of the structure,and the research conclusion can provide an important reference for the selection of the falling beam mode in the jacking construction.(3)Based on the typical unfavorable working conditions,the finite element software ABAQUS is used to establish a beam-shell-solid-contact hybrid finite element local model,and the stress in the support area of the steel beam is analyzed Condition and stability.For the phenomenon of large stress on the steel beam plates,three improvement schemes are proposed:increasing the welding corner stiffening ribs,locally thickening the junction of the bottom web of the steel box girder,and changing the contact area between the beam body and the pad.At the same time,the effect of unsynchronized jacking on the local stress of the steel box girder was explored,to get the safety control threshold of the jacking construction out of synchronized,which can provide an important reference for the top thrust construction of similar bridges.(4)Based on the analytic hierarchy method and the fuzzy comprehensive evaluation method,the risks that may occur in the jacking construction are evaluated,and then corresponding control measures are taken according to the weight value of each risk factor,so as to reduce the probability of potential risks in the construction.