Abstract
Performed analysis of the initial geometric imperfections influence on the stability of the open C-shaped bars. Test tasks were solved in MSC Nastran, which is based on the finite element method. Imperfections are given in different formulations: the general stability loss of an ideal bar, of wavy bulging of walls and shelves, of deplanation of a bar. To model imperfections, has been developed a program which for the formation of new coordinates of the nodes of the "deformed" model, the components of a vector similar to the form of stability loss are added to the corresponding coordinates of the middle surface of the bar. In this way, you can set initial imperfections in the forms of stability loss of the bar with different amplitude. Researches made with different values of the imperfection amplitude and eccentricity of applied efforts. All tasks are performed in linear and nonlinear staging. The conclusion is made regarding the influence of initial imperfections form and imperfection amplitude on the critical force in nonlinear calculations. It was found that the most affected are imperfections, which are given in the form of total loss of stability. It was revealed the influence of the imperfection amplitude on the magnitude of the critical force for such imperfections. The influence of imperfections amplitude given in the form of wavy bulging walls and in the form of deplanations is not affected on the value of the critical force.
Highlights
The appling of thin-walled steel constructions in building allows to solve a wide range of problems
In the test tasks without eccentricity, the first form of stability loss for the ideal bar occurs in the form of a wave-like bulging of the wall and shelves (Fig. 3)
Was researched the influence of imperfections specified in the form of a general stability loss was investigated, which, for that the bar was fifteen (the first was in the form of wave-like bulging of the walls – see Fig. 7(a) and Fig. 7(b)
Summary
The appling of thin-walled steel constructions in building allows to solve a wide range of problems. Thin-walled cold-formed profiles with an open cross-section have another feature - susceptibility to local deformations that occur during the manufacture, transportation, installation or operation of elements Such defects can significantly affect the stability loss of the element, and, lead to structural violations. In the test tasks without eccentricity, the first form of stability loss for the ideal bar occurs in the form of a wave-like bulging of the wall and shelves (Fig. 3). This form is transformed by the above method into initial defects with different amplitudes for nonlinear calculations. The graph is divided into two parts: linear and nonlinear calculations
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