Finite Element Refinement Analysis For Single-layer Reticulated Vaults With Welded Hollow Spherical Joint And Tubular Joint

As reticulate shell has the characteristics of large span and light weight，stabilityis a particularly important factor to consider in design of the shell. The single-layerreticulated vaults are widely used and the support and the joint style will have amajor impact on its stability. The most commonly used form of joint in reticulatedvaults is welded hollow spherical joints, may also tubular joint. The joints in shell areoften connected to a lot of pipes which are not in the same plane, of complex force,and the stiffness of joint is related to the loading history when it is in plastic.Therefore, the study on the relevance between joint and shell stability should notseparate the joint and shell.In this article welded hollow spherical joints and tubular joints are selected, twosupport ways are used, in order to analyse the relationship of joint and stability. Theshell181element in ANSYS is used to simulate pipes and joints, the joints are buildby actual constitute. Thereby the refinement model is not only taking into account ofthe joint stiffness, strength, and size in complex stress state, but also taking intoaccount of the bending damage which may occur on the pipe. Main contents are thefollowing components:Selected a reasonable structural model. It is showed that the material nonlinearcan’t be ignored in the calculation. Determine the mesh size of shell element. Twoforms of refinement shell element model were established, and there were acomparison between shell model and the traditional beam element model.Analyse the relationship of welded balls parameters (the ball thickness and theball diameter) and the stability. It includes the analysis of load-displacement curve,buckling model, plastic strain and stress distribution as well as the plastic history. Itis showed that the ratio of ball thickness pipe thickness greater than1.8is fine, theductility and stress distribution is reasonable.Analyse the relationship of tubular joint parameters and the stability. theanalysis process is same as above. It is showed that the ratio of main pipe thicknessand vic-pipe thickness greater than1.8is fine.Some measures are taken to strengthen the joint. For welded hollow sphericaljoints, the plan stiffening rib is the best, the crosswise stiffening rib is second, thelengthways stiffening rib is ineffective. For tubular joint, the best strengtheningmeasure is stiffening ring.