Research On Wind Uplift Resistance For Aluminum Roofing Systems Of Large Span Structures

Since metal roofing system was introduced,the aluminum roofing system has been widely used in a variety of large-span structures because of its advantages of lightweight,wonderful appearance and convenient construction.Most of the aluminum roofing sy stems are assembled,and their common forms are lapping assembly type,self-tapping screw type,upright locking edge form,etc.The wind damage investigation has shown that under the strong wind,due to its complex structure,the weak stiffness of some roofing systems can easily cause local wind damage and even extend to the neighboring areas causing the whole roof to lift up.There are few studies on the ultimate bearing capacity,force transmission mechanism and failure mode of lap assembly aluminum roofi ng system currently,and there is a lack of research on the weak links in the system and their mechanical properties,damage modes and practical calculation methods,so it is necessary to carry out more in-depth research on the wind damage resistance of such roofing system.In this paper,taking the assembled aluminum alloy roofing system of Hangzhou Asian Games E-sports Pavilion as the object,the main conclusions are as follows:(1)The full process loading test simulating the wind load on the roof was ca rried out by using the foot-rule model test method,and the evolution of the displacement and strain of the roof panels and supports during the loading process was measured to investigate the damage deformation and failure mode of the roof system.The results show that the wind damage of the roof system starts from the plastic deformation of the L-shaped transition node between the central roof panel and the secondary purlin,and gradually expands to the surrounding nodes,resulting in the pull-off failure of the roof unit.(2)Numerical simulation of the roof footprint model was carried out by the nonlinear finite element method,and the development curves of stress,deformation and displacement of each component were obtained,and parametric analysis of the wind bearing capacity of the roof system was carried out.(3)In view of the L-shaped adapter node connecting the roof panel and secondary purlin is the weak link of this kind of roof system,to clarify the force transmission mechanism and damage and failure mode of this key node,three groups of node specimens were selected and the bearing capacity tests of flexural and shear resistance were carried out,and the finite element method was used to compare and analyze the force performance of the node;the influence of the thickness of the adapter plate,material strength and bolt slots on the bearing capacity of the node was investigated.Parametric analysis was carried out on the effects of adapter plate thickness,material strength and number of bolt slots on the bearing capacity of the node.The study shows that the reason for the first yielding failure of the adapter node is that the stress concentration around the bolt slots of the plate connecting the secondary purlin is too large,resulting in the yielding bulge of the slots;the plastic hinge will appear at the bolted part and the L-shaped corner in the process of stressing the plate,thus changing the force transmission path of the plate and forming excessive plastic deformation.The connection form of the adapter node and the thickness of the plate are the key factors to determine the tensile bearing capacity of the node;changing the single-hole sliding slot of the L-shaped adapter into a double-hole sliding slot bolt connection can effectively reli eve the stress concentration at the slot edge,while increasing the thickness of the plate can effectively increase the node stiffness;both can reduce the risk of failure of the sliding slot bulge and bolt pull-off,and obviously improve the wind resistance of the node and even the whole roof.(4)According to the transmission mechanism and damage mode of L-shaped adapter node,a simplified calculation model of the node in tensile condition is established,a formula for calculating the tensile load capacity of the node based on two-stage plastic development is proposed,and a design discriminant formula to ensure that the node is in plate damage rather than bolt failure first is derived.These methods and equations provide an effective means for the design verification of such roof transition nodes.