Full-scale Experimental Research And Analysis On Mechanical Performance Of Arch Shed Structure

In China,the structure of plastic greenhouse is widely used because of its light skeleton,low construction cost and good heat preservation and moisture retention,which can reach the production mode of early spring and late autumn.At the same time,this kind of structure is sensitive to wind load and snow load due to its large span,small cross-section of members and light skeleton.In recent years,the collapses of greenhouses caused by wind and snow disasters have occurred frequently,bringing serious economic losses to people.In addition,because the plastic greenhouse structure belongs to agricultural buildings,the latest ?Code for Structural Loads of Agricultural Greenhouse ?(GBT 51183-2016)is only aimed at the provisions of structural design and load values,but lacks in-depth research on its safety and durability.In view of the widespread application of plastic greenhouses and their vulnerability to wind and snow disasters,this paper has carried out a full-scale experimental study on the mechanical properties of the structure of the arched shed.The finite element software has been applied to establish an overall arched shed model and to study the influence of wind load and snow load on the structure of the arched shed and the critical buckling load under different load conditions.The main work includes the following aspects:(1)Taking the overall rise-span ratio of the structure,the vault height of the arch shed and the shoulder height as influencing factors,three groups of full-scale arch shed skeleton specimens are designed.The span of the three groups of specimens is 8m,and the ridge heights are 3m(GP-1),3.4m(GP-2)and 3.8m(GP-3),respectively.Each group of specimens consists of three arch bars and internal connecting bars.In the test,vertical load was used to replace the uniform snow load on the structure,and the graded loading test of three groups of full-scale specimens was completed.The results show that under the action of vertical concentrated load,the maximum deformation relation of the three arch sheds is GP-1 > GP-2 > GP-3.The working systems of the three under vertical load are: GP-1 structure is similar to arch truss structure system,GP-2 structure is equivalent to arch action system,GP-3 structure is inclined beam working system.The weak position of the structure under vertical load appears at the one fourths of span.(2)According to the arch action stress system corresponding to GP-2 structure proposed in the physical test,a simplified stress model corresponding to this kind of load is established.By comparing the internal force calculation results of the simplified model with the physical test results,it is found that both almost match with each other,and the analytical calculation method of GP-2 structure working system is established.(3)Through finite element analysis software,the overall models of three kinds of arch shed structures are established,and the influences of wind load and snow load in different return periods on the mechanical performance of the arch shed structures are studied respectively.The analysis data show that the maximum deformation of the structure is located at one fourths of span of the windward side of the arch shed,and the maximum stress is located at the root of the arch shed.Comparing the influence of wind load and snow load on the mechanical performance of the structure in different return periods,it is found that the structure is more seriously affected by wind load,indicating that the structure is more sensitive to wind load.(4)Compared with the influence of snow load on the deformation of the arch shed in different return periods,the wind load in different return periods has a greater influence on the deformation gap between the windward side and the leeward side of the arch shed.With the increase of wind load,the structure is subject to the reverse suction of wind load greater than the pressure of snow load,and the leeward side of the structure is more obviously subject to the leading role of wind load.(5)Through the nonlinear buckling analysis of the whole arch shed model under different load conditions,it is found that the structure is more prone to buckling instability under dead load+half-span snow load than under dead load+full-span snow load.Finally,the ultimate bearing capacity of the structure under the action of dead load+full span snow load is determined to be the highest,while the bearing capacity under the action of dead load+full span snow load+full span wind load is the lowest,indicating that the structure is more prone to damage under the combined action of wind and snow load.The research results in this paper can provide theoretical reference for wind and snow load research of arch shed structure.