The Study On Mechanical Properties And Design Method Of Aluminum Alloy Single-Layer Reticulated Shell Based On Flower-Gusset Composite Joint

Single layer aluminum alloy reticulated shell has many advantages,such as light weight,corrosion resistance,beautiful shape and so on.In recent years,it has been widely used in long-span spatial structures.Because of its simple structure and convenient installation,plate joint has become one of the most commonly used joint forms of single-layer aluminum alloy reticulated shell.However,the flange of H-shaped aluminum alloy beam is only connected through the upper and lower cover plates,while the web of H-shaped beam is not connected,resulting in insufficient shear bearing capacity and in-plane axial bearing capacity of the joint,and prone to instability failure,which can not meet the requirements of long-span aluminum alloy reticulated shell.Based on the existing joints,this paper proposes a new type of Flower-gusset composite joint(FGC joint for short),carries out a series of static and quasi-static full-scale experimental studies,and comprehensively grasps the mechanical characteristics,failure mechanism,stiffness characteristics and hysteretic performance of the new joint.The design method and skin effect of single-layer aluminum alloy reticulated shell with FGC joints are studied.The main research results are as follows:(1)Through 7 groups of static comparative tests,the compressive,flexural and shear properties of FGC joints and traditional plate joints are studied respectively.The test results show that the axial stiffness and bearing capacity of the new joint are 2.1 times and 1.36 times that of the plate joint,respectively.The shear capacity and shear stiffness are increased by 47% and 73% respectively,and the flexural capacity is increased by 20%.According to the test results,the reliability of the simplified model of the new joint is verified,and the determination method of the main geometric dimensions of the new joint is put forward through the analysis of the load transfer mechanism.(2)Five groups of composite bearing capacity tests of FGC joint are carried out,the force transfer mechanism and failure mode of the joint under the combined action of in-plane and out of plane loads are revealed,and the simplified calculation formula of composite bearing capacity of the joint is given.(3)Through parametric analysis,the effects of cover plate thickness,bolt clearance and other main factors on the semi-rigid characteristics of FGC joints are studied.A static stiffness model of FGC joints considering the effects of axial force and bolt clearance is proposed.Through a large number of finite element analysis results,the relevant formulas are modified and fitted,and compared with two groups of joint bending tests with different axial force and bolt clearance.The results show that the static stiffness model is basically consistent with the experimental results,and the model can be used for the stability analysis of single-layer aluminum alloy reticulated shell.(4)The pseudo static test results of five groups of FGC joints show that the energy dissipation capacity of the joint is 1.8 times that of the traditional plate joint,and its hysteretic curves are S-shaped,including four stages: elastic stage,bolt slip stage,hole wall pressure stiffness degradation stage and failure stage,and there is no strength degradation stage.(5)The hysteretic performance test and finite element analysis results of FGC joints under out of plane bending moment show that with the increase of bolt clearance,the bolt slip stage in the joint skeleton curve is longer and longer,but it has no effect on the bending stiffness and bending moment of other stages.The preload of the bolt only affects the initial bending moment in the slip stage,and has little effect on other stages.The hysteretic stiffness model of FGC joints is proposed through theoretical analysis,and the experimental results are effectively verified.(6)Based on the design idea of the combination of direct analysis method and elastic-plastic whole process analysis method,a set of stability design method of single-layer aluminum alloy reticulated shell with FGC joints is proposed.Based on the equivalent principle of ultimate bending moment,axial force and flexural stiffness,an equivalent beam element simulation method of FGC joint suitable for stability analysis is proposed,and the whole process of stability design is shown in detail based on Midas and ANSYS software.(7)the performance-based seismic design method of single-layer aluminum alloy reticulated shell and the equivalent beam element simulation method of FGC node based on the principle of equal energy dissipation and ultimate moment are proposed.(8)Through theoretical analysis and experimental research,a simplified calculation formula of equivalent flexural stiffness considering honeycomb panel skin effect is proposed,which provides a theoretical basis for the stability analysis of this kind of grid structure in the future.