【作者】 符媛媛；

【导师】 赵峰；

【作者基本信息】 武汉科技大学 ， 结构工程， 2009， 硕士

【摘要】 预应力网壳结构已成为现代钢结构工程中最具有发展潜力的结构体系之一,钢拉索是此种结构的核心构件。通过张拉预应力索在结构中引入初始应力,扩大了构件的弹性工作范围,提高结构的承载力和刚度,使结构产生与荷载作用相反的变形,可以改善结构的受力性能。拉索引入的初始应力值的确定是非常重要的。但在进行结构分析时,拉索的预拉力值不易控制,本文就如何有效地控制拉索预拉力值做了以下研究。分别用等效荷载法、初始应变法和降温法对网壳结构的拉索预应力值进行了分析研究,提出了等效荷载法忽略拉索单元刚度矩阵对结构整体刚度矩阵的贡献,不能有效的反映结构的真实受力情况;初始应变法和降温法分析网壳结构时,拉索单元和网壳杆件始终作为整体进行非线性分析,能真实反映结构的受力情况。预应力网壳结构应用初始应变法和降温法分析拉索预拉力值是比较适合的。结合张弦双层预应力网壳结构的实际工程,采用初始应变法、降温法对拉索预拉力值进行了分析研究。采用初始应变法时,只要改变拉索单元中以实常数定义的初始应变量就可以使索内力值趋近设计预拉力值;采用降温法确定拉索预拉力值时,计算精度不如初始应变法高,且在受外荷载作用时,分析过程比较复杂。两种方法比较用初始应变法来确定预拉力控制值效果更好。指出初始应变法确定拉索预拉力控制值仍存在不足之处,主要体现在计算量大,循环迭代次数较多。为了解决减少计算量和迭代次数的问题,本文提出了一种新的控制拉索预拉力值的方法,即改进的初始应变法。运用数值分析的方法,结合史蒂芬森(Steffensen)迭代法将初始应变法的迭代公式改进,给出了改进后的初始应变法的迭代公式,并运用牛顿差值公式,近似模拟出一条简单的拉索索内力与索应变关系函数,并代入迭代公式,可以得出满足工程精度的预拉力控制值。与未改进的初始应变法作分析比较,改进方法可以实现确定拉索预拉力控制值的方法从电算向手算转移,而且这方法有更好的收敛性,运算效率更高。更多还原

【Abstract】 Nowadays the prestressed lattice steel structure is one of the most popular and potential structures, and in this kind of structure cable is the important construction member. After prestressed lattice applied in structure, prestressing could improve its flexible scope, increase its capacity and stiffness, cause a reverse deformation, and improve its stress state. Determination of the prestress value applied by lattice is very important. Carrying out structural analysis, the value of pre-tension lattice is often difficult to determine, revolving how to correctly determine the value of pre-tension lattice, following works are put forward.Several methods of determination the prestressed value are researched, the paper puts forward that using the equivalent forces method lattice element stiffness matrix is ignored, the station of the real force on the structure can not be effectively reflected, that using the initial strain method and the reducing temperature method to analyze the prestressed structures, the cable unit and shell bar is always analyzed as a whole, and the whole process can be conducted by a unified non-linear analysis, the station of the real force on the structure can be truly reflected, these two methods are better methods to analyze the value of pre-tension lattice.Combining Large-scale Reticulated Shell Structure, value of pre-tension lattice can be determined using the initial strain method and the reducing temperature method. Using the initial strain method, as long as the real constant defined by the initial strain is changed, internal force of lattice is increasingly closer to the design value of pre-tension lattice; Using the reducing temperature method, calculation accuracy is not high comparatively. Subject to external loads, the analysis process is more complicated. Comparison of two methods,using the initial strain method to determine the value of pre-tension lattice is better.Some deficiency which is a large quantity of calculation and loop iterations is pointed out using the initial strain method. In order to solve the problem, a new method to determine value of pre-tension lattice is put forward, That is, improved the initial strain method. Combination of Stephenson iterative method, the iterative formula of initial strain method is improved, the new the iterative formula is put forward. Using Newton’s formula, a simple Function of relationship with internal force and tension strain is analogously simulated. Putting this function into the new iterative formula, the value of pre-tension lattice meeting the engineering precision is obtained. Comparing with the results before; this method has good computational efficiency and convergence.更多还原