Nonlinear Buckling Analysis Of Complex Steel Frames

Steel constructions are widely used in modern building for their remarkable advantages such as lightweight great intensity quality, well anti-seismic behavior, high industrialization degree, quick construction velocity, etc. Buckling analysis is a vital step in the design of steel constructions. In recent years, because of the application of high intensity materials, and the development of precise modeling and analysis technology, steel constructions develop quickly with more light weight, more large span, and more complex structure shape. These changes make the buckling analysis more important and complicated, so that the geometrical nonlinear and material nonlinear must be considered in the buckling analysis for getting more accurate simulation to reveal the real buckling behavior of steel constructions.However, the present design code of steel structure just solve the buckling problem of structural elements, such as columns and planes, and usually take account of the local buckling analysis of frame columns instead of global stability of the whole steel frames. It is an appropriate method when used in the common regular steel frames, but might bring error when used in the analysis of complicated space steel frame and can not provide meaningful ideas for the practical constructions.In this paper, the buckling characteristics of the steel frame structure are introduced. With deeply study of ultimate bearing load considering both the geometrical nonlinear and material nonlinear, a complex non-regular steel frame structure is analyzed to research its ultimate bearing load and buckling behavior by the common element code ANSYS. By accurately modeling and proper calculation technology, the load displacement curves and ultimate bearing load are obtained, which can show the safety storage and overload capacity, and provide assistance for the structure design and safe usage. Moreover, according to the result of bi-nonlinear analysis results, the plastic zone development of the important components is described, so is the critical place in the structure design.In fact, both of the theory and the code application of the nonlinear buckling analysis are not perfect at present. ANSYS is one of the few codes which can support nonlinear buckling analysis. However it is not an easy task but has many difficulties in the analysis process, which requires much experience and attempt. So some useful advices are offered in the field of nonlinear buckling analysis in ANSYS for the structure designers.