Form-finding And Vertical Seismic Response Study Of Long-span Spatial Truss String Structure

Long-span spatial truss string structure is a new form of prestressed spatial structure. It comprises the compressed top chord truss and the tensile bottom chord cable connected together through the compressed strut, in which the cable is prestressed to produce the structure a inverted arch. After the roof load is generated, the structure basically returns to the prestressed spatial structure in initial shape. Because of its reasonable force characteristics, it has been applied more in engineering practice at home and abroad.In order to better apply the long-span spatial string truss structure, an analysis model is set up by the geometric nonlinear finite element method. Using ANSYS FEM, the paper analyzes the form-finding of the string truss structure, the free vibration characteristic and the vertical seismic behavior, and researches the structural dynamic characteristic influenced by the various parameters. The main works are completed as follows:(1) The introduced method of the prestressed cable is discussed. Based on the previous research results, a new calculation method of the string truss structure suitable for form-finding is put forward, which is named equivalent decreasing temperature inverse iteration method, by which the prestress of bottom chord cable is identified, a truss string form-finding analysis is completed, and the geometric zero state and initial prestressed state distribution of structure are obtained. Differences between the results of the string truss structure under linear and non-linear method are compared and analyzed.(2) The free vibration characteristic of string truss structure is analyzed. The free vibration characteristics of structure influenced by a large amount of parameters is studied, which are rise-span ratio, sag-span ratio, number of struts, value of prestress, etc. The law of free vibration characteristic is finally summarized.(3) Using the time history analysis method, systematic analysis of dynamic response of string truss structure under vertical seismic is done. Vertical seismic behavior of the structure influenced by various parameters is studied, which are rise-span ratio, sag-span ratio, number of struts, value of prestress, etc. The reasonable values of all parameters are obtained. These conclusions can be used as reference for engineering designers.