Research On Mechanical Properties Of Key Connection Joints In Metal Roof System

In recent years,the metal roofing system of construction has developed vigorously in our country.However,in typhoon and non-typhoon areas,there are different degrees of metal roof wind damage cases,and it is found that there are joint failures,and the connection of key nodes in the metal roof system is often the cause of damage.At present,there are few researches on the mechanical properties of the key connections of the metal roof system.This paper takes the Zhuhai Airport extension Project-Terminal T2 as the background,and several connection modes of the key nodes of the metal roof system as the research object.Pay attention to three connection modes in a key node: weld connection,L-support connectors,self-drilling screw connection,and carry out laboratory simulation tests in order to restore the failure form of each connection under external load.First of all,pay attention to the weld connection and L-support connectors of the continuous welding metal roofing system,and then extend to the most common connection,self-drilling screw connection,in the metal roofing system,and carry out the related mechanical experimental research.The main research work and conclusions of this paper are as follows:1.The pull-out test of self-drilling screw connected on aluminum alloy substrate was carried out,and the pull-out tests of 198 connected specimens were completed with the variables of drilling mode,substrate thickness,pitch and screw diameter.The results show that the drilling mode has a certain influence on the specimen with small pitch,and the pull-out capacity of the connected specimen drilled manually is small.The pull-out capacity of selfdrilling screw connection on aluminum alloy substrate is positively correlated with substrate thickness,pitch and screw diameter.The calculated value of pull-out capacity of connection specimen is compared with the experimental value,and an improved formula is obtained.It can be used to calculate the pull-out capacity of self-drilling screw connection on aluminum alloy substrate.2.The pull-out test of self-drilling screw connection on steel substrate was carried out,and the tests of 120 specimens were completed.The results show that the pull-out capacity of the connection between self-drilling screw and steel substrate is mainly affected by substrate plate thickness,pitch and screw diameter.Among them,the thickness of the substrate has a significant effect on the pull-out performance of the specimen,and the pull-out capacity increases with the increase of the thickness of the substrate.The pitch has an obvious effect on the pull-out performance of the specimen,and the pull-out capacity increases with the increase of the pitch.The screw diameter has an effect on the pull-out capacity of the specimen,but the effect is not very obvious.The pull-out capacity increases with the increase of screw diameter.3.The peeling test of weld joint was carried out,and two working conditions of welding between two plates and support and two plates without support were analyzed,and the comparative tests of 6 specimens were completed.The results show that when the weld joint is subjected to external load,the base metal is the first to tear failure,and the weld joint has better bearing capacity.Comparing the plate-to-plate connection with the connection between plate and support,it is found that the bearing capacity of the two is close,indicating that there is no obvious weak part in the weld joint.4.The tensile test and shear test of L-support connectors carried out and the mechanical tests of 54 L-support connectors were completed with the thickness of L-support stainless steel gasket and the number of drilling screws as variables.The results show that when the L-support is under tension,the failure occurs near the screw hole,and the L-support is deformed and then torn,and when the stainless steel gasket has the same thickness,the more screws are drilled into the L-support,the greater the tensile capacity is.When the number of screws are the same,the larger the thickness of the L-support gasket is,the greater the tensile capacity is.When the L-support is subjected to shear,the failure form is that the L-support is torn after shear deformation,and the shear capacity of the L-support connector is better when the number of drilling screws is larger,and the greater the thickness of the gasket is.