Study On The Stability Of Glulam Single-Layer Spherical Reticulated Shell

Glued timber is a natural ecological material,which has attracted much attention due to its green environmental protection,light weight,beautiful appearance and good seismic performance.With the development of manufacturing technology,glulam structure is no longer restricted to the traditional structural form,and is widely used in space reticulated shell structures.Unstable failure is the main failure mode of laminated timber reticulated shells,and the stability problem is a key problem for single-layer timber reticulated shells.However,in the current domestic research on the stability of timber reticulated shells,the research on the nonlinear effects of joints and materials is still relatively scarce,and there is no nonlinear reduction coefficient suitable for timber reticulated shells.Based on this,this paper takes the glulam single-layer spherical reticulated shell as the research object,summarizes the connection forms of shell nodes,and establishes the semi-rigid mechanical model of shell nodes constructed by one of the nodes.Then,the static analysis and natural vibration characteristics of the reticulated shell structure are carried out,and then the parametric analysis of the stability performance of the reticulated shell is carried out.Factors such as joint semirigidity,initial geometric defects and material nonlinearity that affect the stability of reticulated shells are discussed.Finally,the plastic reduction factor and the stability safety factor suitable for the wooden reticulated shell structure are proposed for the reference of the subsequent structural design.The specific research content of the paper is summarized as follows:(1)The research status of reticulated shell structure is analyzed and summarized(Chapter 1).The development background of the glulam reticulated shell structure is described in detail,and the engineering cases of long-span timber structure are introduced.The research status of reticulated shell joints and the stability performance of reticulated shell are systematically reviewed.The inconsistencies in the existing research are pointed out,and the research content and technical route of this paper are put forward.(2)The connection structure of the glulam reticulated shell joints is briefly described,and the mechanical model of semi-rigid joints is established(Chapter 2).It is pointed out that the common joint forms of the glulam reticulated shell mainly include steel-filled plate joint,steel sandwich plate joint and rebar-planting joint.Then a new type of steel-filled plate joint is selected,and its structural characteristics are briefly described.The mechanical properties of the joint are analyzed and verified,and the simulation method of the semi-rigid joint in the overall model of the glulam reticulated shell is clarified.(3)The parametric model of the glulam reticulated shell is created,and the modal analysis and static analysis of the single-layer reticulated shell structure are carried out(Chapter 3).Based on the parametric modeling idea of APDL,the model parameters and element type of the glulam reticulated shell structure are clarified.According to the static analysis and comparison of reticulated shell structure under different bar section sizes,the selection of the optimal section is realized.The natural vibration frequency and vibration mode of the structure are obtained through the modal analysis of the glulam reticulated shell.At the same time,the variation law of the natural vibration frequency under different parameters is studied.The similarities and differences between the modal analysis and the buckling analysis are proved by comparing the computer theory.(4)The stability theory of reticulated shell structure is explained,and the influencing factors of stability performance of plywood reticulated shell are analyzed(Chapter 4).The analysis results show that the existence of initial defects will greatly reduce the overall stiffness and stability bearing capacity of the glulam reticulated shell structure,and it is most reasonable to take L/300 as the introduction value of initial defects.And the stable ultimate bearing capacity of the glulam reticulated shell has a positive correlation with the cross-sectional area and the rise-span ratio of the reticulated shell members,and an inverse correlation with the span.The semi-rigid joint has a general weakening effect on the stability bearing capacity of reticulated shells,but it is relatively insensitive to the change of surrounding supporting conditions.(5)The double nonlinear stability analysis of the glulam reticulated shell is carried out(Chapter 4).Through the parametric analysis and comparison of hundreds of glulam reticulated shell structures only considering geometric nonlinearity and considering geometric material double nonlinearity,the plastic reduction coefficient value of the glulam reticulated shell is determined.Then based on the partial coefficient design method of probability,the value of stability safety factor suitable for the glulam single-layer spherical reticulated shell is proposed.