Dynamical Behaviors And Seismic Analysis Of External Prestressed Reinforce Double Layer Space Grids

Double layer space grids is a kind of typical large span space structure form, it has been used in various large span constructions. But with the enhance of need for large space of human being, conventional double layer space grids structure form can't satisfy need of deflection and force, improvement of conventional double layer space grids structure form is very necessary, the application of prestressed technology is feasible measure. The presentation and application of prestressed steel structure has come through about half a century, but the application of prestressed double layer space grids is merely twenty years. As well as reinforced concrete, applying prestress on double layer space grids can arrive at the aims of enhance of load carrying capacity and rigidity. At the same time, it reduced deflection of structure. The rule of free vibration and seismic design way of prestressed reinforce double layer are studied in this paper. Part 1. In this part prestressed double layer space grids is discussed,static behaviors of prestressed reinforce double layer space grids by split rigidity method as well as ANSYS Finite element theory is analyzed,functions of ANSYS software and typical analysis process are introduce in this part.Principals of how to ensure geometry parameter of space grids finite element model are given and F90 program to calculate member force and chord section is developed according 《Space Grid design and construction code》(SGDC code)so as to determine the real constant ANSYS needed.To create finite element model of PSGs, program to create node,element number and restriction information is compiled also. Comparison between split rigidity method and ANSYS is carried out, and results show that the method to create PSG finite element model by ANSYS is correct and the simplified method given by split rigidity method to calculate bending deflection is of high accuracy in precision. Part 2. Split rigidity method and ANSYS modal analysis are used in the calculation of natural vibration. The frequency formula of prestressed reinforce double layer space grids is deduced. Comparison results show that, as a simplified method split rigidity method is accurate in precision. It also proved the study of natural vibration property of space grids adopt ANSYS software is reliable. The dynamic properties of prestressed reinforce double layer space grids are studied through natural vibration analysis. Through natural vibration frequencies analysis of 400 prestressed double layer space grids, simplified formula of fundamental frequency is also presented by using multivariate linear regress statistical. The general rule of prestressed reinforce double layer space grids is achieved and influence factors for prestressed reinforce double layer space grids are determined. Part 3. Vertical seismic actions of prestressed reinforce double layer space grids is studied in this part and calculation method of seismic action is introduced. The method of how to determine vertical seismic spectrum by horizontal seismic spectrum is introduced also in this part. Vertical seismic spectrum curve values are transformed so that it can be adopted by ANSYS spectrum analysis. The procedures of spectrum analysis are given. Through the seismic action analysis of prestressed reinforce double layer space grids on Ⅱground, we achieve the distribution rule of seismic internal force coefficients. Part 4. A practical calculation method for prestressed reinforce double layer space grids is determined, and testifying is also carried out.