Research On Tension Method And Forming Process Of New Reticulated Spherical Shell Integral Forming By Post-tensioning

Partial double-layer reticulated spherical shell integral forming by post-tensioningis a new space structure system of shared innovation between installation technology ofreticulated shell and structural concept. The tensioning principle is that reasonablearrange tensioning bottom chord bars with reserved gaps at inter-node of lower chords(i.e. the length of chord is shorter than the inter-node’s, and the length differencebetween them is the reserved gap’s value.), using the characteristic of lowerout-of-plane bending stiffness of single-chorded plane space truss. Then tension thestretching wire by stretching equipment, eventually, the plane space truss is changedinto reticulated shell with space curved surface by gradually closure of reserved gaps.The new structure can realize target that reticulated shell’s assembling and tensioningare accomplished on the ground, and effectively prevent reticulated shell frominstability by using out-of-plane webs, which also has better overall stiffness andbearing capacity for the forming structure combine organically with tension pre-stress.As a result, the new structural system has good prospect and is worth further deepresearch.According to previous researching results and considering post-tensioning wholestructure’s features, a reasonable new structural model of single-chorded partialdouble-layer plane space truss on the basis of traditional K6type Kiewitt reticulatedspherical shell for shape forming processing is provided eventually in this paper, bycomparing advantages and disadvantages of several kinds of structure forms. Detailedstudies have been conducted on different tensioning methods and forming processes ofpartial double-layer plane space trusses. Nonlinear finite element software ANSYS11.0is used to simulate above process. Research contents and results are listed as follows: Comparable study on the features of tensioning methods of both multi-bars tensionand single bar tension are carried out from mechanism condition of post-tensioningforming, forming shape’s predictability, magnitudes of post-tension force and forminginitial stress to deformation compatibility between single layer and double layer inresearch of post-tensioning forming methods respectively. Analytical results show thatboth of the tensioning methods satisfy mechanism condition, but only multi-barstensioning has predictability of forming shape and has less post-tension force andforming initial stress than single bar tension’s, also having better compatibledeformation between single layer and double layer, all of which indicate multi-barstensioning is a more reasonable post-tensioning methods.At first, influence of geometric thickness of plane space truss H on forming frommulti-angle is studied as well as the influences of different finite element models,gravity, material’s elastic-plastic and different connection types on forming respectively.At last, the most reasonable tensioning model is obtained in the research of formingprocessing. For the new plane space truss model provided in this paper, analysesindicate that gravity and material nonlinearity should not be considered in the study offorming shape parameters of post-tensioning overall structure, just consideringgeometric nonlinearity. However, both the geometric and material nonlinearities andgravity should be included in the model in the research of forming post-tension forceand initial stress based on actual situation.Research works and relevant conclusions are summarized in this paper, and futuredirection and prospect for study work is provided at last.