Research On Shape Forming Process And Load Behaviours Of A New Post-Tensioned And Shaped Dome

The post-tensioned and shaped space trusses is a new space structural system. Compared with the traditional space trusses, the assembly of the new space trusses can be finished wholly at ground level and it improves validly the stability behavior of single-layer shells because of the use of out-of plane web members, so the new space structrual system will have the important advantage in the future application. Based on the research on the post-tensioned and shaped dome, a new single-chorded plane space truss formed dome with post-tension is put forward firistly in this paper, through model tests and nonlinear finite element analysis, the shape forming process and load behaviors is studied. The paper mainly does work as follows:Though simulating the shape forming process of post-tensioned and shaped dome by nonlinear finite element analysis, the post-tensioning method and joint connections in the new single-chorded plane space truss as well as the forming shape of dome are studied. It lays a theoretical foundation for the design and manufacture of experimental model.A single-chorded plane space truss experimental model of post-tensioned and shaped dome is finished and the shape forming test and ultimate load test are carried out. Results showed that the single-chorded plane space truss model in this paper has very good deformability and it can form dome with more rise-to-span ratio by means of a post-tensioning technique, the forming shape of dome can be controled by the gaps which are given in certain bottom chords, the post-tensioning forces and member forces produced in the shape forming process are small and the bending stress is much larger in comparison with the axial stress in the member forces, the post-tensioned and shaped single-chorded dome has satisfactory utimate load capacity with ductility-type failure and the instability failure has not happened.In the test model, a new type joint connection of one-way hinge is put forward for achieving pure-hinge connection; In the shape forming test, because of the little post-tensioning forces, a new type loading method of twisting nut for drawing wire is put forward in stead of jack tensioning for solving the questions, such as super-tensioning and the nonuniform rate of loading; In the loadtest, a new type vertical loading system of multiple-point fixed pulley is put forward for solving the questions, such as more loading points and larger vertical force at one loading point. Results showed that these improvement methods that are put forward in this paper are rational and correct, they ensured the test processes to be successful and gathering the fine test data.Then an thorough computer modeling test using various finite element models with geometry and material nonlinear taken into account is carried out on a set of influencing factors, such as the stiffness of joint connections, the size of joint, the eccentricty of joint and support connections, the member forces produced in the shape forming process, etc. Lots of useful conclusions are drawn form computer modeling.In the finite element analysis, by adding individual beam elements to model the connector between top joints and chords in finite element model, based on the experimental model, the factors affecting the shape forming process of dome, such as the bending stiffness of duckbilled connector and the size of top joints, can be taken into account; A whole and continuous analysis method is put forward for solving the question of applying the member forces produced in the shape forming process to the finite element models of load analysis.The nonlinear stability of single-chorded domes is analyzed. The factors affecting the stability of single-chorded domes are taken into account, such as the thickness of shells, the ratio of rise to span, the connections between botttom chords and bottom joints, the stiffness of chords takeing the place of top post-tensioning wires, members forces, etc. Lots of useful conclusions are drawn.Last, the overall conclusion is drawn and the prospect of f...