Experimental Research And Finite Element Analysis On Steel Braced Frame Structures With Random Imperfections

Compared with the traditional method of calculating length coefficient design, advanced analysis and design method for its accurate, rapid and practical advantages are widely used in multistory and high-rise steel frame structure stress analysis and design. At present domestic and foreign research focus on advanced analysis method generally focused on how to accurately considering the ultimate bearing capacity of structure under the influence of nonlinear factors, this stage of deformation characteristics of the structure under is less. But studies have shown that, according to the bearing capacity limit state design framework, high soft steel frame lateral often beyond the overall structure of serviceability limit state, the actual bearing capacity is controlled by the structure deformation of the performance. The deformation performance of the structure is affected by various nonlinear factors, especially the influence of initial geometrical imperfections of the structure is particularly prominent, and now the various countries and regions specification in consideration of initial geometric imperfections of the size, direction and distribution forms are not clear and unified, cause defects in accordance with the specification requirements to one side to decorate more high-level framework, of initial lateral may not meet the requirements of the whole structural perpendicularity, and structural components of real defect size and direction in a random distribution of contradiction. According to the above two major problems, this paper carried out the following work:For six layers braced frame structure with first order elastic analysis, the approximate second-order elastic analysis as well as advanced analysis method to carry on the design, compare the different design methods of the structure of the ultimate bearing capacity, the internal force and the final deformation situation, analysis shows that the superiority of advanced analysis and insufficiency of the present calculation method.The scaled test of two span double-layer steel frame and braced frame structure, focusing on the influence of initial geometric imperfections on the deformation property. The test measured before the initial defect frame beam column distributed feedback to self consider the finite element and the random initial defect model, from the test results and the finite element analysis results are in good agreement with the consideration of contrast, prove the correctness of the finite element model of random initial imperfections.Each of the 6,12,20,and 30 layers steel braced frame structure random defect model of advanced analysis of the whole process by using the finite element software, using Monte Carlo method and Latin hypercube sampling technique to simulate the layout frame random initial defects,and comparison of various domestic and international standard method considering the initial imperfections, key study on the deformation behavior of the structure.Results indicate that the ultimate deformation of steel braced frames are proportional to the size of the initial imperfections, the braced frame deformation considering random initial imperfections are closed to the results of ideal frames without imperfection, in the advanced analysis of tall and flexible structures can not consider. Advanced analysis of high-rise steel braced frame structures, the calculation of ultimate bearing capacity often does not meet the requirements of serviceability limit and failure, structural design ultimately controlled by the displacement limit, and it brings forward a kind of applicable to high soft steel frame-support structure, based on the deformation properties of practical advanced design method.