Wind-load And Wind/Snow Resistant Safety Analysis Of Light-weight Steel Portal Frame Structures

Light-weight steel portal frame structures have been widely used in industrial buildings in the eastern coastal area of China. As steel portal frame structures are commonly large-spanned, light-weighted and flexible, their wind resistant capacities are relatively low. However, the eastern coastal area of China is the region that suffers from typhoon attacks frequently, wind-induced failures are the main failure modes for this type of structures. Consequently, analysis of the wind resistant behaviors and ultimate load-carrying capacities for the light-weight steel structures is of importance to the building design.Wind load distribution characteristics of portal frame industrial building which is considered as a kind of low-rise buildings are firstly examined in this paper. The wind pressures on the surface of a typical existing portal frame industrial building located at the eastern coastal area of China is determined by means of the wind-tunnel model test technique, in which the cases of wall closure and opening in the single side gable wall are taken into account. The wind loads obtained from the test are compared with those calculated from the currently applied load code/specificatipon.Secondly, the wind-resistant safety levels of typical light-weight steel portal frame structures under strong wind loading are investigated. The wind loads under the most unfavorable wind directions obtained from the test data and the corresponding loads determined from the load code for building structures and the technical specification for steel gable frame structures are applied to the unfavorable frame of the building. Nonlinear load-capacity analyses are then performed for the frame using the refined plate/shell finite element method, through which the wind-resistant safety factors and the wind-induced ultimate limit-state failure modes can be found. Meanwhile, the effects of initial imperfection and wall openings on the ultimate load-capacities of the frame are discussed. Aiming at the problem that the wind-resistant safety redundant degrees of the frame are relatively low, a simple and effective beam-column connection enhancement measure is proposed, by which the safety levels of the frame could be considerably improved and the sensibility of the frame to initial imperfections could be reduced.Snow load is another main control load for light-weight steel industrial buildings. In the final part of the paper, the typical portal frame steel industrial building discussed above is also taken as an example here, and the snow load combination currently used is determined from the current load code of China. Nonlinear load-capacity analyses are then carried out for the frame mentioned before using the refined finite element method. The corresponding snow-resistant safety factors and the ultimate limit-state failure modes of the frame are then found through the analyses. The obtained results are discussed and also compared with those under the action of wind load.