Interaction Effects Of Steel Portal Frames Under Wind Loads

At present, the light-weight steel portal frame structure is widely used in industrial buildings. As steel portal frame structures are usually light-weighted and flexible, they are very sensitive to wind loads. So far, analysis of portal frame structure mainly adopts the plane frame model. When subjected to wind loads, the main lateral stiffness is provided by transverse portal frame. The calculation of strength and stability are based on single purlin and neglects the influence that rigid frame and roof cladding exert on it. However, the portal rigid frame is composed of tie bar, purline, bracing, roof and wall made of profiled steel sheet, and these components work together when loads are applied. Therefore, the plane flame and single purlin calculation cannot reasonably reflect the actual performance of the portal frame structure. The study of the interaction of the components of lightweight steel portal frame structure is quite necessary.Five models are created using ANSYS software, a general FEM software, in this study. They are plane frame model, independent purline model, space skeleton model, complete model and roof model respectively. The simulation method and equivalent model of roof, purline tray and knee-bracing are explored as well.Then using the time-history data of gable roof from the aerodynamic database of low-rise building in Tokyo Polytechnic University, the thesis carries out a series of static analysis on averaged wind loads of the plane frame model, space skeleton model and complete model. The time-history analysis of the three models under fluctuating wind load is also provided in this thesis, thus obtaining the influence law that the average and extremum wind response obey. Through the analysis of average wind response, displacement and extreme stress value of main frame, the influence mechanism that substructure and envelop enclosure exert on main frame is obtained. Besides, based on the wind load specified in Technical specification for steel structure of light-weight buildings with gabled frames and Load code for the design of building structure, the influence of the substructure and enclosure on the main structure is analyzed, and comparison between the data of wind tunnel and the conclusion in this thesis is carried outUtilizing the data of wind tunnel, the time-history analysis under fluctuating wind and static analysis under average wind load of purline model, space skeleton model, and roof model are conducted and the average wind response and its extremum of purline in the above models are analyzed. Based on the loads specified in the Technical specification for steel structure of light-weight buildings with gabled frames and Load code Jor the design of building structure, the thesis studies the influence that main frame and roof sheathing exert on purline, and then contrasts the results with the data of wind tunnel.