Papers by Keyword: Initial Imperfection

Abstract: The stability analysis of an imperfect slender web subjected to the shearing load is presented, a specialized code based on FEM has been created. The nonlinear finite element method equations are derived from the variational principle of minimum of total potential energy. To obtain the nonlinear equilibrium paths, the Newton-Raphson iteration algorithm is used. Corresponding levels of the total potential energy are defined. The peculiarities of the effects of the initial imperfections are investigated. Special attention is paid to the influence of imperfections on the post-critical buckling mode. Obtained results are compared with those gained using ANSYS system.

Abstract: The stability analysis of a slender web loaded in compression is presented. The non-linear FEM equations are derived from the variational principle of minimum of potential energy. The peculiarities of the effects of the initial imperfections are investigated using user program. Special attention is paid to the influence of imperfections on the post-critical buckling mode. Stable load-displacement paths are investigated. The FEM computer program using a 48 DOF element has been used for analysis. FEM model consists of 4x4 finite elements. Full Newton-Raphson procedure has been applied.

Abstract: Glass has got important role in modern architecture not only because of its transparency, interior lighting and for aesthetical function but nowadays also more often for its load bearing function. Design of structural glass elements is limited by the lack of knowledge and standards, especially in case of stability problems of beams or columns. Slender glass beams with rectangular cross-section tend to fail because of instability.

Abstract: Based on Ježek method of computing the elastic-plastic buckling of the members 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 and 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 H-shaped steel member and 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 two kinds of steel members to a great extent. It is also found that the influence of the initial geometric imperfection on the ultimate bearing capacity of members is smaller when the bending moment increases.

Abstract: Nonlinear finite element upheaval buckling model of buried offshore pipelines under HT/HP is built using ABAQUS. The petroleum is defined as uniform flow; temperature field of offshore pipelines produced in the process of petroleum transportation is obtained by heat transfer analysis; offshore pipelines are buried in trench of sandy seabed, interaction between seabed and offshore pipelines is defined as friction, seabed interaction with offshore pipelines will limit the movement of offshore pipelines; coupled fluid-structure analysis for three phase model of oil-pipe-soil is conducted to obtain stress under HT/HP. Initial imperfection of pipeline is introduced to calculate upheaval buckling of buried offshore pipeline under HT/HP. Through numerical analysis, the axial force of pipelines under HT/HP is obtained and thus resulted in upheaval buckling.

Abstract: To reveal the harm of member initial stress on space frame structure, several models which are different in initial imperfection methods, material computational models and upper optimized stress ratios are employed to do nonlinear finited element analysis. It finds that the initial stress method and Marshall model are more accurate to simulate. When design the space frame structure, it must be avoided to optimize the cross section excessively in pursuit of economic factors.

Abstract: A large number of column-bracing systems for the horizontal braces unlocated at middle of columns with fixed-ended column base were modeled and analyzed by second-order analysis using finite element method, in which the random combination of the initial imperfections between columns and horizontal braces was well considered by Monte Carlo method. According to the analysis results, two kinds of instability modes of column-bracing system have been found, probability density function of the horizontal bracing forces unlocated at middle of columns with fixed-ended column base is established based on probability statistics, and the design formula of horizontal braces unlocated at middle of columns are also proposed.

Abstract: The ultimate compressive strengths of high performance steel (HPS) plate system stiffened longitudinally by closed stiffeners have been investigated by the nonlinear finite element analysis. Both conventional and high performance steels were considered in models following multi-linear strain hardening constitutive relationships. Initial geometric imperfections and residual stresses were also incorporated in the analysis. Numerical results have been compared to compressive strengths from Eurocode 3 EN 1993-1-5 and FHWA-TS-80-205. It has been found that although use of Eurocode 3 EN 1993-1-5 and FHWA-TS-80-205 may lead to highly conservative design strengths when very large column slenderness parameters are encountered

Abstract: Considering actual steel structures as research background, with emphasis on the effect of initial imperfections, the bending stability of stiffened plates was analyzed by ANSYS finite element. The results show that the moment of stiffening rib are different with the angle changing, and the ability of channel steel is more reinforced than L angles steel. With the thickness of the plate simply supported on four sides decreasing, the influence of imperfection becomes more obvious and the initial imperfection decreases the deflections of the skew plates. Finally through the comparative analysis with monitoring results, the numerically simulated results have a certain reference value.

Abstract: The stability and the potential seismic capacity of the double-layer elliptic paraboloid latticed shell roof structure of a stadium was analyzed and evaluated, performing by Midas Gen software. Firstly, the seismic response spectrum analyses and the linear time-history analyses were carried out respectively on two different analysis models: the integral structural model containing the lower support structure and the single latticed shell model. The seismic response characteristics and the potential seismic capacity of the models were compared and evaluated. Secondly, based upon the real detailed design of the stadium, the static stability of the latticed shell was analyzed, considering both the geometrical non-linearity and the initial imperfection. Thirdly, the influence of the effects of the vertical ground motion upon the latticed shell structure was studied. The analysis method adopted and the conclusions obtained can be used as references for the future similar engineering projects.