Study On Buckling Stability Of Stiffened Plate In Double Steel Plate Concrete Immersed Tunnel

With the construction of the first double steel plate concrete immersed tunnel in China,the double steel plate concrete composite structure,which has many advantages such as high bearing capacity,large rigidity and good ductility,has become a hot research object for domestic experts and scholars.At present,the research on out of plane bending,in-plane shear,in-plane axial compression and local buckling of surface steel plate of double steel plate concrete composite structure is mainly carried out in China,but the research on out of plane pressure and in-plane axial compression of double steel plate concrete composite structure is less.In fact,in the construction stage,the immersed tube tunnel of double steel plate concrete composite structure mainly bears concrete side pressure.In this paper,the buckling stability of the double steel plate concrete composite structure under concrete lateral pressure and inplane axial pressure is studied.The main contents and conclusions of this paper are as follows :(1)Based on the review of the classical buckling theory of plates,the theoretical formulas of buckling and post buckling of isotropic plates under uniaxial compression,lateral pressure and combined load are introduced in detail.It can be seen from the derived formula that under the small deflection assumption,the lateral pressure has little effect on the linear critical buckling load of the uniaxial compression plate.(2)The linear buckling eigenvalue analysis and explicit nonlinear dynamic analysis of isotropic plates are carried out by using abaqus finite element software.Through the comparison between the finite element simulation results and the theoretical formula values,the finite element simulation results are in good agreement with the theoretical formula values,which shows the correctness of the finite element simulation.(3)For the stiffeners in the double steel plate concrete composite structure,the linear eigenvalue buckling and nonlinear dynamic finite element method are used to analyze the effects of concrete pouring speed,types of transverse stiffeners,height thickness ratio of transverse stiffeners and the number of stiffeners on the buckling and post buckling of stiffeners.The results show that the nonlinear buckling load of stiffened plate decreases with the increase of concrete pouring speed.The buckling resistance of L-stiffened plate is better than that of T-stiffened plate and flat steel stiffened plate.The linear and nonlinear buckling loads of L-stiffeners increase with the increase of the height thickness ratio of transverse stiffeners.Increasing the number of transverse stiffeners can effectively increase the nonlinear buckling load,while increasing the number of vertical stiffeners can improve the ultimate bearing capacity of stiffeners.(4)In this paper,the buckling and post buckling analysis of a typical compartment in a double steel plate concrete composite structure immersed tunnel is carried out by using the linear eigenvalue buckling and the banks finite element method under the combined load of the concrete side pressure as static load and the roof pressure as live load.The results show that the overall buckling of the compartment is prior to the lateral buckling of the local transverse and vertical stiffeners.