Papers by Keyword: Initial Geometric Imperfection

Abstract: Based on the probability reliability theory, this paper proposes a modified consistent mode imperfection method, which fits the integral stability analysis of single-layer reticulated shells with the initial geometric imperfections. Nearly 1000 elasto-plastic load-deflection overall processes of four different rise-to-span ratio for Kiewitt-8 single-layer reticulated shells are analyzed by using the random imperfection mode method, the consistent mode imperfection method and the modified consistent mode imperfection method respectively. The study shows that the random imperfection mode method can assess the influence of initial geometric imperfections on structure stability more scientifically, but the calculation is quite large. By using the consistent mode imperfection method, the buckling load is not sure to be the most unfavorable, and the degree of reliability couldnt be ensured effectively. The modified consistent mode imperfection method can gain the buckling load which meets the requirement of probability reliability with less calculation. It can also assess the stability performance of single-layer reticulated shell structure more reasonably and safely.

Abstract: Based on Ježek method of computing the elastic-plastic buckling of the member under the axial compressive load and the bending moment, considering the initial geometric imperfection, the analytical expressions of calculating the ultimate load of buckling about the neutral axis with the maximum moment of inertia for a square steel tube member with flange outsides wrapped by carbon fibre are derived. Using the elastic-plastic finite element method and the theory of nonlinear buckling, the impact of the initial geometric imperfection on the square steel tube steel member wrapped by carbon fibre under the axial compressive load and the bending moment are analyzed and the numerical solutions of ultimate bearing capacity are obtained. By compared with the values of the finite element method (FEM), it shows that the analytical method in this paper is valid. Compared the reinforced effect of the carbon fibrer to the perfection member with the defect member, we find that the former is higher than the latter. The results of the example also show that the presence of initial geometric imperfection reduces the ultimate bearing capacity of the steel member to a great extent. The influence of defect member gradually decreases when the given moment rises.

Abstract: Based on Ježek method of computing the elastic-plastic buckling of the member under the axial compressive load and the bending moment, considering the initial imperfection, the analytical expressions of calculating the ultimate load of buckling about the neutral axis with the maximum moment of inertia for a square steel tube member are derived. Using the elastic-plastic finite element method and the theory of nonlinear buckling, the impact by initial geometric imperfections on the square steel tube member under the axial compressive load and the bending moment are analyzed and the numerical solutions of ultimate bearing capacity are obtained. By compared with the values of the finite element method (FEM), it shows that the analytical method in this paper is valid. The results of the example show that the presence of initial imperfections reduces the ultimate bearing capacity of the steel member to a great extent. It is also found that the influence of the initial geometric imperfection on the ultimate bearing capacity of member is smaller when the M increases.

Abstract: This article aims to shed light on the nonlinear local-distortional-global interactive behavior of web-slotted channel columns by use of the finite element method. The effects of three kinds of initial geometric imperfection based on different distortional buckling mode were evaluated. It indicates that different distortional buckling mode does little difference on the nonlinear interactive buckling behavior of web-slotted channels. Based on the extensive parametric study, some modifications were made to the traditional Effective Width Method for the practical design of web-slotted channel columns undergoing local-distortional-global interactive buckling.

Abstract: The suspended dome structure, which is a new kind of hybrid spatial one composed of the upper single layer latticed shell and the lower cable-strut system, generally has smaller rise-to-span ratio, thus the overall stability is one of the key factors to the design of the structure. The nonlinear buckling behavior of an elliptic paraboloid suspended dome structure of span 110m80m is investigated by introducing geometric nonlinearity, initial geometric imperfection, material elastic-plasticity and half-span distribution of live loads. The study shows that the coefficient of stable bearing capacity usually is not minimal when the initial geometric imperfection configuration is taken as the first order buckling mode. The unsymmetrical loading distribution and the material nonlinearity might have significant effects on the coefficient. The structure is sensitive to the changes of initial geometric imperfection, and the consistent mode imperfection method is not fully applicable to the stability analysis of suspended dome structure.

Abstract: Based on Ježek method of computing the elastic-plastic buckling of the member under the axial compressive load and the bending moment, considering the initial imperfection, the analytical expressions of calculating the ultimate load of buckling about the neutral axis with the maximum moment of inertia for an H-shaped member are derived. Using the elastic-plastic finite element method and the theory of nonlinear buckling, the impact by initial geometric imperfections on the H-shaped steel member under the axial compressive load and the bending moment are analyzed and the numerical solutions of ultimate bearing capacity are obtained. By compared with the values of the finite element method (FEM), it shows that the analytical method in this paper is valid. The results of the example show that the presence of initial imperfections reduces the ultimate bearing capacity of the steel member to a great extent. It is also found that the influence of the initial geometric imperfection on the ultimate bearing capacity of member is smaller when the bending moment increases.

Abstract: Based on Ježek method of computing the elastic-plastic buckling of the member under the axial compressive load and the bending moment, considering the initial geometric imperfection, the analytical expressions of calculating the ultimate load of buckling about the neutral axis with the maximum moment of inertia for an H-shaped member with flange outsides wrapped by carbon fibre are derived. Using the elastic-plastic finite element method and the theory of nonlinear buckling, the impact of the initial geometric imperfection on the H-shaped steel member wrapped by carbon fibre under the axial compressive load and the bending moment are analyzed and the numerical solutions of ultimate bearing capacity are obtained. By compared with the values of the finite element method (FEM), it shows that the analytical method in this paper is valid. Compared the reinforced effect of the carbon fibrer to the perfection member with the defect member, we find that the former is higher than the latter. The results of the example also show that the presence of initial geometric imperfection reduces the ultimate bearing capacity of the steel member to a great extent. The influence of defect member gradually decreases when the given moment rises.

Abstract: Nonlinear buckling analysis method using the finite element with application to Long-Span Steel Truss was studied is this paper. The finite element model of long-span complex steel truss hoisting was established and nonlinear buckling analysis of long-span complex steel truss hoisting for two hoisting points schemes was accomplished. The eigenvalues, eigenvalue buckling modes and nonlinear buckling analysis of two hoisting point’s scheme were analyzed. The results indicate that, the nonlinear buckling analysis method using the finite element is applicable approach to study the hoisting buckling problem, the buckling will be not occurring under hoisting stage only with gravity loads. The force status of long-span complex steel truss is improved under more hoisting point’s scheme and the lateral stability is strengthened.

Abstract: The elastoplastic instability of the symmetrical double-arc ring-stiffened cylindrical shell was analyzed. The critical pressure was obtained for small deflection elastoplastic buckling of the cylindrical shell under hydrostatic pressure. The critical pressure for large deflection buckling of the cylindrical shell with initial geometric imperfections was determined under hydrostatic pressure by using nonlinear large deformation theory. The effects of hoop equivalent wave number, initial geometric imperfection and the central angle of circular arc on buckling mode and critical pressure of double-arc ring-stiffened cylindrical shell were analyzed. The results showed that the hoop equivalent wave number of arc cylindrical shell had an main effect on the critical pressure of the structure, designed equivalent hoop wave number of double-arc cylindrical shell should not be approach to the hoop wave number corresponding to minimum critical pressure, and the central angle of circular arc had less effect on critical pressure of the structure.