Research On The Mechanical Performance Of Arc-edged Square Steel Tube Frame Plastic Greenhouse Under Full Dynamic Wind Loa

The facility agriculture in China has developed more than half century and has become more and more advanced.The greenhouse diversified in materials and structures.In the past,people pay more attention to the economy of plastic greenhouses,while the current farmers and owners are more and more inclined to use the greenhouse with high safety,good durability and excellent cost performance.In the recent years,a new type of greenhouse appeared in the market,that is arc-edge-square-steel pipe plastic greenhouse.The greenhouse skeleton is a single-member structure,in which the right angles in rectangular square steel pipes are made blunt,and the skeleton is bend into arch.At present,it was been more and more widely used in the cold area in north of China.At present,domestic and foreign scholars are calculated in accordance with the "Agricultural Greenhouse Structural Load Code"(GB/T51183-2016)and "Building Structural Load Code"(GB50009-2019),when they research wind resistance performance of greenhouses.The wind vibration coefficient is set to 1,because of the small height of the greenhouse.Thus,due to the pulsating wind load is not take into account,the seriously damage of greenhouses and skeletons occur in the practical engineering.In this background,this paper conducts numerical simulation of the pulsating wind acting on the greenhouse by the same analytical method as civil engineering houses.Analyze the mechanical performance of arc-edge-square-steel pipe plastic greenhouse based on the combined pulsating wind and average wind(i.e.full dynamic wind load).Following research work was mainly carried out in this paper:Firstly,the testing of the structural performance of square steel pipe skeleton plastic greenhouses under gust effects was carried out,and the boundary conditions of the greenhouse skeleton support were identified,providing a basis for finite element analysis.An ABAQUS finite element model of the arc-edge-square-steel pipe plastic greenhouse was established,and static wind loads were applied to the model.Compared with the finite element calculation results with the field test results and verified the correctness of the finite element model.According to previous scholars’ experience and conclusions in simulating pulsating wind speed time histories,the Davenport spectrum for pulsating wind speed was utilized.The Shiotani correlation coefficient,considering the longitudinal and vertical positions of the greenhouse as independent variables,was selected.The AR model(autoregressive model)in linear filtering method was implemented in MATLAB program to simulate the pulsating wind speed time history.By comparing the simulated wind power spectrum with the target power spectrum,the correctness of the pulsating wind speed time history simulation has been verified,providing a loading basis for subsequent research.The full dynamic wind speed time history curve was obtained by adding the simulated pulsating wind speed and the average wind speed calculated according to the "Building Structural Load Code"(GB50009-2019).Thus,the full dynamic wind pressure time history curve was obtained,as the load input.Using ABAQUS finite element software to analyze the mechanical properties of single skeleton,five skeletons and fifty skeletons of arc-edge-square-steel pipe plastic greenhouse under full dynamic wind load.Compared with the stress distribution and deformation value of the greenhouse skeleton under the wind load of the code.Giving the safety evaluation of the arc-edge-square-steel pipe plastic greenhouse.The analysis results show that: under the wind load of the code,the stress of the greenhouse and the skeletons does not exceed the elastic limit,and the deformation is within the allowable range.Under the full dynamic wind load,the stress of the greenhouse and skeleton exceeds the elastic limit and enters the plastic stage,which does not meet the safety requirements of the greenhouse structure.