Research Of The Anchor Concrete Local Stress And Closure Sequence On Continuous Rigid Frame Bridge

With the rapid development of China's transportation industry,the prestressed concrete continuous rigid frame bridge has become one of the main bridge types in bridge construction due to its own superiority.In recent years,due to design defects,improper construction and disposal,resulting in this type of bridge in the construction and operation stage has been cracking,down deflection and other diseases.Therefore,it is of practical significance to carry out the research on the mechanical behavior and construction closure sequence of the area under the complex stress anchor.In the research,a(40+70+40)m continuous rigid frame bridge is taken as the engineering background.For the crack problem of 1# block webs during cantilever construction,the local space model is established by ANSYS to simulate and analyze,and the simplified strut tie model is used to calculate,trying to find out the mechanical reason of its cracking.For the change of secondary stress and linearity caused by the closure sequence of continuous rigid frame bridge,the Midas Civil finite element software is used to simulate the construction of the closure process,and the influence of three different closure tensile sequences on bridge linearity and stress was investigated.After calculation and analysis,the following conclusions are mainly drawn:(1)Through the finite element nonlinear simulation calculation of the space entity of ANSYS software and the calculation of the strut-tie-model,the results show that: the design of the steel strand and tensile force is reasonable,it will not cause local cracking of the web under anchor.The mian reason should be that the local anti-cracking steel bar is not enough,the tensile force control is improper during the construction process and excessive main tensile stress caused by insufficient concrete strength during tension.(2)For the D zone under the anchor,the concrete is complicated and does not satisfy the assumption of the flat section.And the simplified calculation and analysis are carried out by using the strut tie model,which conforms to the local force transfer relationship,simplifies the mechanical analysis of the complex force area,facilitates the local steel bar configuration,and can effectively avoid the design defects and make it more reasonable.(3)From the comparative analysis of the closure stage,completion stage and 10-year results of the completion of the bridge,it is better to stretch the side span and middle span closure section in batches than to stretch the side span closure section first,then to stretch the middle span closure section and to stretch the middle span closure section first and then to stretch the side span closure section.The scheme of first stretching the steel bundle in the closure section of side span and then stretching the steel bundle in the closure section of middle span is prone to upward deformation during closure,which has adverse effects on the line shape of the bridge.(4)The calculation results show that there is no obvious influence on the line shape and stress of the bridge for the different closure tension sequence.(5)When the actual construction process due to the period limit and so on,for the commonly used span of the three-span continuous rigid frame bridge can adopt the mid-span closure scheme,which can also meet the design and specification requirements.