有初始变形井架结构分析的简便方法

A simple method for analyzing structure of derrick with initial deformation

研究井架结构的折算长细比法和单肢演算法并不能真实反映井架的应力大小，也不能精确确定危险截面位置及应力分布；而有限元分析方法又没有普遍意义。为此，采用等价应力法对有初始变形的井架进行结构分析。该方法通过对没有变形的井架整体或构件的有限元模型施加一组等价力，使之产生的应力与具有初始变形时的井架应力值相一致，可以在不改变井架有限元模型的基础上，达到计算快速且结果准确的目的。实例计算表明，除井架整体稳定临界系数的相对误差为１１.７％以外，其余各项的相对误差都小于１０％。

The shortcomings of analyzing the derrick structure with conventional methods are pointed out. An equivalent stress method for the structural analysis of derrick with initial deformation is offered. By applying a group of forces on the finite element model of the derrick and its components to produce identical stresses as the stresses on the derrick with initial deformation, this method carries out rapid and accurate calculation without changing the finite element model of the derrick. A case study shows that the relative errors of the calculated values are all less than 10% except that the relative error of the critical coefficient of the derrick stability is11.7%.