Research On The Ultimate Bearing Capacity Of Arch Bridges Considering The Action Of The Stiff Skeleton

The arch bridge was able to make a great breakthrough in terms of span,the strong skeleton concrete arch rib plays an important role.The steel pipe concrete stiff skeleton is not only used as a support for pouring the outer concrete of the arch rib,but also becomes a part of the structure in the following construction process and in the bearing after the arch is formed.The calculation of the section load capacity of a concrete arch bridge with a strong skeleton is not just a simple superposition of the load capacity of the outer concrete part and the steel pipe concrete part of the strong skeleton.It is significant to research the design theory of concrete arch bridges with stiff skeleton by considering the load bearing capacity of the arch section of the stiff skeleton.In this thesis,the factors affecting the bearing capacity of the cross-section of the concrete structure of stiff skeleton are analyzed with the help of finite element software,and the corresponding bearing capacity calculation formula is proposed.The main research and finding of this thesis are as follows:(1)The effect of the action of the stiff skeleton on the bearing capacity of the arch section of reinforced concrete arch bridges is discussed,and the main factors affecting the ultimate bearing capacity of the stiff skeleton reinforced concrete arch section are the initial stress of the stiff skeleton and the bond slip of the steel pipe and concrete.(2)The initial stresses generated in the stiff skeletal concrete arch bridge are divided into steel pipe initial stresses and core concrete initial stresses.The larger the initial stress of steel pipe,the smaller the ultimate load bearing ability of the stiff skeleton concrete structure;while the ultimate load bearing capacity of the stiff skeleton concrete structure will increase slightly with the increasing of the initial stress of core concrete.Among them,the load bearing capacity of the outer package concrete part will be reduced by the initial stress of steel pipe and almost not affected by the initial stress of core concrete;the loadbearing ability of the core concrete part within the pipe decreasing with the increasing of the initial stress of steel pipe and increasing with the increasing of the initial stress of core concrete;the load-bearing capacity of the steel pipe part of the strong skeleton decreases marginaly with the increasing of the initial stress of core concrete.(3)Factors affecting the bonding slip between the strong skeleton steel pipe and concrete are the strength of the outsourced concrete material and the thickness of the outsourced concrete.Among them,the greater the strength of the outsourced concrete,the better the bonding performance between the strong skeleton steel pipe and the outsourced concrete;bonding performance is also enhanced with the increase in the thickness of the outsourced concrete,but with the increase in the thickness of the outsourced concrete,its effect on the bonding strength tends to stabilize.(4)By introducing the discount factor of the ultimate bearing capacity of outsourced concrete considering the initial stress of steel pipe and the discount factor of the ultimate bearing capacity of stiff skeleton concrete considering the bond slip,the calculation formula given in the specification(T/CECS 663-2020)is modified,and the formula of the ultimate bearing capacity of arch bridge considering the action of stiff skeleton is proposed and verified by examples.