Prestress Optimization And Construction Simulation For Long-span Saddle-shaped Cable Net Structures

The saddle-shaped cable net structure is a late-model spatial structure composed of bearing cables and stable cables.It has been widely used in recent years because of its reasonable load transfer and beautiful structural style.On the basis of reviewing relevant literatures,the problems of morphological analysis,prestress optimization and construction simulation analysis are studied in this paper.The main contents are summarized as follows:(1)The inverse iteration method is used for morphological analysis,and its applicability is verified by examples.The difference of cable force distribution in initial state between considering dead weight and not considering dead weight is compared.On this basis,the parameter analysis is carried out,and the influence of typical structural parameters on the results of morphological analysis is discussed.The research shows that the influence of dead weight on the cable force distribution can not be ignored,so the dead weight should be considered in the morphological analysis of saddle-shaped cable net structure.Compared with the bearing cable,the similar cable force distribution in initial state can be obtained by applying a smaller prestress to the stable cable.Therefore,tensing stable cable has advantages over the bearing cable in construction.Based on the variation law of cable force reflected by the change of geometric parameters,it is reasonable for the sag-span ratio to be 1/16~1/10,the rise-span ratio to be 1/38~1/30,and the sag-rise ratio to be not less than 3 in engineering design.(2)Plant growth simulation algorithm(PGSA)is applied to the prestressing optimization of saddle-shaped cable net structure.The limitations of the algorithm are analyzed,and three corresponding improvement strategies are put forward,that is,merging cable grouping,introducing growth space optimization method and adding iterative termination judgment mechanism.Based on it,the reasonable value of the optimization parameters in the improved algorithm is discussed.The result shows that,compared with the original PGSA,the search ability of the improved algorithm is improved,the iteration times is reduced,and the result is closer to the optimization objectives,which verify the improved algorithm is applicative in the prestress optimization of saddle-shaped cable net structure.Considering the optimization effect and efficiency,it is reasonable for the growth space optimization factor to be 0.5~0.8 and the growth step size to be 25kN~50kN for the prestress optimization of similar structures.(3)The construction simulation analysis of saddle-shaped cable net structure is carried out by reverse disassembly method,and the differences of tensing bearing cables and stable cables,single stage and multistage tension and different tension sequence are compared.The result indicates that compared with tensing bearing cables,the tension force and overtension range are smaller when tensing stable cables,and the vertical displacement of the central point of the structure changes more gently.Secondly,compared with single stage,multistage tension has the advantages of smaller tension force,smoother variation of cable force and displacement,but it increases the construction process at the same time.Therefore,the influence of the magnitude of tension force and workload should be considered comprehensively to select construction scheme.Besides,a reasonable tension sequence can reduce the overtension range and the maximum displacement,which is beneficial to the forming of the structure.For similar structures,when the force of the stable cable in initial state is small,tensing stable cables is suggested and single stage tension should be adopted in engineering.