Effect Of Geometric Imperfections And Local Damage On In-plane Stability Of Steel Arch

Arch structure has been widely applied in engineering practice due to its beautiful shape and good mechanical properties.Its stability has always been valued by academic circles.However,due to the deviation of the arch axis due to improper design and construction error,the geometric defects of the arch structure,as well as the local damage caused by environmental corrosion in the external corrosion environment,have a great influence on the stability of the arch structure.In view of this,this paper derives the nonlinear stability theory of the circular arc arch under the condition of initial geometric imperfections,combines the common steel pipe parabolic arch in the actual project.The experimental verification and finite element simulation are used to study the plane stability bearing capacity of the parabolic arch with local damage under axial pressure and bending.As follows:（1）The uniform defect mode method assumes that the distribution of geometric defects caused by the deviation of the axis of the arch is an anti-symmetric geometric defect and a positive symmetrical geometric defect.By considering the axial strain and curvature of the defect,the energy method is used to consider the defect in the energy equation of the buckling of the arch surface,and the equilibrium differential equation with geometric defects is obtained.The principle of energy variation and the perturbation method are used to solve the equilibrium differential equations with geometric defects,and the nonlinear stability curves of arc arches under the action of concentrated forces are considered and the nonlinear stability curves of the arcs with anti-symmetric and positive symmetry are considered.Tracked its deformation and instability in the entire stress process,and the calculation results have been verified by the finite element method.（2）Based on the local damage to the elastoplastic stability test of the steel arch structure in plane,this paper uses the large general finite element software Ansys to establish the parabolic arch model of the partially damaged steel tube,combines the nonlinear defect stability theory of the arch structure derived in this paper,and analyses the positive and anti symmetric buckling modes of the arch structure.Then the influence of main damage location,depth and length of damage on ultimate bearing capacity is studied.（3）For different span-span ratio and slenderness ratio models,considering the influence of geometric nonlinearity and material nonlinearity,the in-plane nonlinear stability bearing capacity of a parabolic arch with local damage under full-span vertical uniform loads is studied.Combining with the calculation method of axial load column’s stability bearing capacity in China’s steel structure specification and the modified regularized slenderness ratio concept proposed by Pi et al,a formula for calculating the stability factor of steel pipe parabolic arch under axial compression is proposed.（4）Through the numerical simulation of the parabolic arch of steel tube under different loads,the stable design formula of the parabolic arch of steel tube under the action of pressure bending is proposed.This formula introduces the correction factors eta and beta of the damage location and damage degree,and also correction factors such as sagittal ratio,slenderness ratio,and initial defects affecting axial and bending moments are also considered?_{a n} and?_am,and can effectively evaluate the stability of the parabolic arch of steel pipe.Finally,the correctness of the design formula is verified by the test results of the local damage of the arch structure.