基于映射变换法的平面预应力钢桁架整体可靠性分析

利用映射变换法建立索张拉平面预应力钢桁架任意单元失效模式可靠度指标的迭代模型,并基于点估计法得到整体结构失效概率及可靠性指标的计算公式。模型中的随机参数包括折线索单元和桁架单元的截面面积(或综合刚度)、张拉钢索的预拉力、外荷载及边界弹性约束刚度等。基于所建立的计算模型编制相应的计算程序,对工程中常见的结构形式进行分析,并对影响结果的有关参数进行讨论。结果表明,钢索张拉力标准差对结构可靠性指标的影响与杆件截面面积随机变量的分布特性有较大的关系,且当截面面积为对数正态分布时,其影响大于正态分布。其次,随机变量标准差的变化对结构可靠性指标的影响均与相关性系数ρNA有一定关系。这些结论为索张拉预应力钢结构整体可靠性设计奠定了一定的基础。

RELIABILITY ANALYSIS OF PLANAR PRESTRESSED STEEL TRUSSES BASED UPON REFLECTION TRANSFORMATION METHOD

The method of reflection transformation is used to establish the computational model of reliability index of each element of planar prestressed steel structures with elastic restraint,and reliability index of the structural system is further obtained with the method of point evalution technique.Random parameters,including areas of cross sections of all the elements,area of cables,pretension of cables,external forces and stiffness of elastic restraint are considered.Finally,some computational examples are put forward and the results are discussed.It is concluded that effect of mean square deviation of pretension of the cables,on reliability index of the structures is relevant to characteristics of distribution of random variables,and the effect of the random variables being in normal distribution is commonly less than that in logarithmic normal distribution.On the other hand, effect of mean square deviation of random variables on reliability index of the structures is also linked to relativity coefficient ρ-(NA),which lay some fundation for reliability design of the prestressed steel structural system.