| Single-box multi-chamber box-girder because of its unique advantages is widely used in bridge engineering design.In the current study,some problems in the shear failure mechanism of box-girder still not been studied deeply,such as shear distribution,the web of single box multi cell box-girder webs’ damage process and features,etc.need further analysis.Aiming at the problems existing in the research,it has important practical guiding significance on the shear design of the new bridges and existing bridges’ inspection and reinforcement that study webs’shear distribution law of single box,multi cell box-girder of the stress-strain relationship and web shear failure mode.The shear force behavior of single-box multi-chamber box-girder is analyzed considering the distribution law of web shear force.The following research contents are mainly results and conclusions in this paper.(1)This paper introduces the analysis theory and finite element theory of concrete box-girder.At the same time,it simply introduces the analysis theory of MIDAS/FEA finite element software,and summarizes the commonly used nonlinear analysis models of MIDAS/FEA when defining reinforced concrete members.(2)In order to research the distribution laws of single-box multi-chamber box girder in different supporting conditions,webs’ number and its thickness,numerical simulation for single-box multi-chamber box girder was carried out by using 3D finite element analysis software,Midas/FEA.Using the post-processing "The Sum of the Internal Forces in Local Directions" to extract the shear value of each web in box girder and comparatively analyze,the concept "increasing coefficient of shear force η" is put forward.The results show that when there are double supporting conditions in box-girder,the increasing coefficient of shear force η is the largest.When the webs fewer,the difference of increasing coefficient of shear force between the side webs and the middle-webs(or secondary webs)is smaller,and η increases with the increase of webs.The variation of the webs’ thickness has little effect on the distribution of shear force,and the method of adjusting the webs’ thickness is proposed according to the result of η.(3)A single box four cells box-girder 3D simulation model is established based on material nonlinear analysis by MIDAS/FEA,then extracted analysis results are as follows:a.Based on load-displacement curves of girder’ s webs at different locations,the vertical displacement of Web girders with load is analyzed,and the cracking load and shear capacity of box-girders are obtained.b.According to the principal tensile shear stress of concrete in compression zone and principal stress angle,the sequence of web cracking is determined,the average angle of fracture is also obtained.c.According to the stress change state of the stirrup,the conclusion is that when the concrete is cracked,the stirrup has a greater contribution to the shear resistance of the beam element.d.According to the strain distribution of the roof steel bar,we can draw that when the box-girder is subjected to shear failure,the shear force value of the side web is higher than the secondary side web plate.e.The development process of cracks in box-girder and the shear stress of the web are analyzed,by extracting the process of the crack development in the box-girder. |
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