【作者】 姚芳；

【导师】 张文福； 张云峰；

【作者基本信息】 大庆石油学院 ， 防灾减灾工程及防护工程， 2005， 硕士

【摘要】 网架结构是一种典型的大跨度空间结构形式,广泛应用于各类大跨度建筑,但由于使用条件的变化而使网架的荷载增加或挠度增大,经检查和验算结构的强度、刚度及稳定性不能满足要求,又由于受资金和材料资源的限制,全部拆除重建是不可能的,就要求对原有网架结构进行加固或修复,体外预应力技术便是一种简单易行且行之有效的方法。预应力钢结构的提出和应用已经历了将近半个世纪,而预应力钢网架的应用,还只是近二十年的事。像钢筋混凝土一样,现代预应力技术与大跨度空间网架结构相结合而形成的预应力网架结构——一种现代的杂交空间结构可提高整个结构的刚度、减小结构挠度、改善内力分布及降低应力峰值,它的投资少,具有明显的技术经济效果,是一种有广泛应用和发展前景的大跨度空间结构体系。本文主要研究平板型预应力加固网架结构的动力特性及竖向地震作用。主要研究工作为: 第1 部分.本部分采用分解刚度法对预应力网架进行静力分析,推导出预应力网架挠度的计算公式,并对有限元理论一般原理及有限元分析软件ANSYS 的功能、典型分析问题的过程进行了简要的介绍。给出了确定网架有限元模型几何参数应遵循的一般原则,并依据《网架结构设计与施工规程》中网架内力计算算法编制了计算周边简支条件下正放四角锥网架内力和杆件截面F90 程序,从而确定采用ANSYS 进行网架计算所需的单元实常数。编制了生成正放四角锥网架节点、单元编号及约束信息的F90 程序,实现了用命令流输入的方法生成正放四角锥网架的有限元模型,为后面研究网架自由振动规律及竖向地震响应奠定了基础。通过算例比较分解刚度法与ANSYS 计算结果,表明本文采用ANSYS 软件建立网架有限元模型的方法是正确的,同时也证明了利用分解刚度法计算预应力网架挠度在精度方面是比较高的。第2 部分.给出了预应力网架固有振动频率的分解刚度法,推导出预应力网架频率计算公式。阐述了ANSYS 模态分析的实现过程,并对模态分析所采用的子空间迭代法原理进行了简要的介绍。通过对分解刚度法和ANSYS 模态分析的比较,表明了分解刚度法作为一种简化的计算方法,其精度是比较高的,同时也证明了采用ANSYS 软件进行网架自振特性研究的可靠性,在此基础上采用分解刚度法对预应力网架固有振动特性进行了研究。通过对几百种预应力网架自由振动频率的分析,得出了预应力加固网架自由振动频率的回归公式,确定了预应力加固网架自由振动频率的影响因素。第3 部分.本部分主要对预应力正放四角锥网架结构的竖向地震作用进行了研究。介绍了网架在地震作用下的几种计算方法,对水平地震反应谱的确定及如何利用水平地震反应谱确定竖向地震反应谱进行了阐述,并对竖向地震反应谱的数值进行了转换,这也是利用ANSYS 软件进行竖向地震反应谱分析的关键。该部分还简要的阐述了利用ANSYS 软件进行谱分析的步骤,并结合具体实例给出了利用ANSYS 软件进行谱分析的命令流语句。在此基础上本文对Ⅱ类场地上的预应力正放四角锥网架进行的地震作用分析,得出了预应力正放四角锥网架的竖向地震内力分布规律。第4 部分.在前面工作的基础上,建立了计算预应力加固正放四角锥网架竖向地震内力的实用计算方法,并进行了验证。更多还原

【Abstract】 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.更多还原