Study On The Creep Effect On The Static Mechanical Performance Of Glulam Suspend Dome

Glulam suspend dome is a novel and reasonable of long-span steel-wood composite space structure based upon the single-layer spherical lattice glulam shell and the tensegrity system. The tensegrity systems improve the static characteristics of the glulam shell,help glulam suspend dome reduce the burden on boundary structures, increase resistance to bucking and avoid problems of excessive flexibility. Due to the creep characteristics of glulam,glulam suspend dome has a different mechanical performance from the steel suspend dome.In the paper the influence of creep effect to the structure was investigated,which also included the analysis of creep effect to the long-term mechanical performance of the structure. In addition, the influence of creep to the construction process was studied in order to find a reasonable construction procedure and method.The main content of this paper includes:Firstly, the static performance of glulam suspend dome was compared with a single-layer glulam dome of the same geometric parameters through the analysis of a typical glulam suspend dome structure.It was shown that glulam suspend dome could delay the critical time of creep buckling compared with the glulam dome,and the influence of creep effect on the structure was mainly embodied on the nodes’ vertical displacement.The deformation of the structure had an obvious increase over time,for example,the maximum displacement of the node could achieve 3.8~4.6 times the initial displacement in the fiftieth year. At the same time, creep of glulam also had certain influence on the internal force of the structure’s elements with some decrease on the rib elements while some increase on the ring elements.But as to the reaction forces, they changed little with the creep developing.Secondly, the static characteristics regardless of the creep and considering the creep of the materials both had been analyzed absolutely.The influence of the structural parameters such as rise-span ratio, heights of strut, the numbers of hoop cables and prestresses of cables on the structural characteristics were concluded,which mainly included the comparison of the structure’s deformation, radial reactions,vertical reactions and the axial force of elements.The analysis provided some advice on the bound of logical parameters of different structural parameters, which can offer some reference for more designs and constructions of glulam suspend dome,for example,1/8 and 1/6 were the better chose of the span ratio for the structure of which the span developed between 40 and 60m; the heights of strut were more appropriate with a length ranging 1/12 to 1/10 of the span; the cable prestress values in the range of 200 ~ 250 Mpa could better improve the structure’s mechanical performance;the arrangement of the cables should better be continuous.At the end of the paper,the cable-strut system of construction is simulated.The influence of different tensioning order and different tensioning methods of the construction process are compared and analyzed,in addition,the influence of the creep to the process of construction is investigated.It was shown that tensioning the cables from outside ring to inside ring and a consideration of super tension at the outer three rings which was super tensioned at a degree of 25%,15% and10% from outside to inside in turn was more reasonable.At the last,some advice was given for the creep consideration,which could provide some reference for the real construction process.