The Failure Behavior And Ultimate Bearing Capacity Of A Single-bay Partal Frames Under Wind Loads

Portal frame is widely used in industrial and civil buildings.The existing studies of the portal frame design are mainly based on a once-in-a-half-century fundamental wind pressure.In this paper,based on software ANSYS,the study establishes the fineness finite element model of shell,nonlinear static calculation and nonlinear dynamic transient calculation are carried out for portal frame structure,to analyse the wind ultimate bearing capacity and wind-induced effect of portal frame.The main contents and conclusions are as follows:(1)The damage levels of the portal frame structure are categorised into four levels,namely slight damage,moderate damage,severe damage and collapse.Also,the description of the response damage status is given.Based on the results of the nonlinear static calculation,the stiffness ratio is used as the evaluation index as the boundary of different grades.The proportion of plastic strain energy in the boundary state of each failure grade presents a certain rule(2)Based on the above failure grade classification,the critical bearing capacity of different failure grades was studied.The wind load bearing capacity of the structure can still be greatly improved after yielding T Portal frame structure that design according to the standard load will collapse under once-in-5500-year strong winds.as its high safety reserve.The plastic strain energy ratio of medium failure limit is about 0.1.The plastic strain energy ratio at the critical failure limit is about 0.5.The collapse limit plastic strain energy ratio is range between 0.6 and 0.8.(3)The elastoplastic wind resistance of portal frame is studied by incremental dynamic analysis.When the wind pressure is small,the average wind response of horizontal displacement remains unchanged.When the wind pressure is large,as the plastic effect accumulates,the quasi-static displacement of the structure drifts,and the average wind response of the horizontal displacement increases.When the structure enters plasticity,the lateral stiffness of the structure decreases rapidly,and the lateral stiffness of the structure degenerates seriously under the wind load once every 500 years,losing the ability to continue to bear the load.When the wind load lasts for a long time,with the increase of the action time of wind load,the structural displacement and plastic strain energy first increase rapidly,and then increase rapidly slowly after a certain time.