Research and Application on Equivalent Method of Aluminum Alloy Gusset Joints

Single layer aluminum alloy reticulated shells based on gusset joints are widely used in long-span spatial structures.At present,the spring element method is used to simulate the mechanical properties of the gusset joint single-layer aluminum alloy reticulated shell.Although the spring element method is accurate,the modeling method is complex and not easy for engineers to use.Therefore,this paper takes the equivalent method of gusset joints as the research object,uses the equivalent beam element to simulate the mechanical properties of gusset joints,gives the calculation formula of the equivalent method,and verifies the effectiveness of the method through numerical simulation and quasi-static test.Then using this method,the effects of the length of the joint domain and the camber height on the slab joints are analyzed.Through the early compression and bending tests,it is found that the load-displacement curve of gusset joints under the axial force and bending moment includes four stages:elastic stage,bolt slip stage,hole wall pressure stage and failure stage.Therefore,under the bending moment or axial force,the load-displacement curve of gusset joints is approximately a four fold line model.Although the four fold line model can be realized by using the spring element method,it also has cumbersome calculation and difficult modeling.In order to simplify the calculation,the equivalent beam elements are used to simulate the gusset joint,and the four fold line model is transformed into the double fold line model according to the principle of equivalent yield load and equivalent yield displacement.Based on the deformation mechanism of gusset joints,the deformation mechanism under the separate action of axial force and bending moment is deduced,and the calculation method of equivalent beam element is proposed based on the equivalence principle.In single-layer aluminum alloy reticulated shells,the joints often bear the effects of axial force and bending moment (eccentric force) at the same time.In order to verify the effectiveness of the equivalent method under eccentric force,the gusset joint and the corresponding equivalent beam element model are established,and then the same eccentric force is applied.The axial force-axial deformation curve and moment-rotation curve of the gusset joint model and the corresponding equivalent model are extracted respectively.By comparing the curves of the two models,it is found that the axial deformation and bending deformation of the equivalent beam under different eccentric forces are very consistent with the gusset joints.At the same time,in order to verify the accuracy of the equivalent method under quasi-static load conditions,a group of quasi-static test results are quoted,and the corresponding equivalent analysis model is established.it is found that the equivalent method can be used to simulate the mechanical properties of gusset joints under reciprocating load.In conclusion,this method can be used to simulate gusset joints under different working conditions.Using this equivalent method,a numerical analysis model is established to analyze the effects of joint domain length and camber height on slab joints.The results show that:1) the increase of joint domain length has a certain weakening effect on the overall stiffness of the structure,and the weakening effect is gradually decreasing,but has little effect on the bearing capacity.2) With the increase of camber height,the stress state of the joint changes,and the bearing capacity and stiffness are significantly improved.In the structural design of single-layer aluminum alloy reticulated shell with gusset joints,the length of joint area and camber height should be reasonably selected.