Unit 4 力法和位移法.pdfVIP

2013/10/29 Unit 4 Description of the Forceand Displacement Method 力法和位移法的描述 Description of the Force Method  degree 次（数）  inconsistency 不一致  Indeterminate 不确定的  magnitude 大小  Release 释放  corresponding to  Determinate  variation  provided 只要…才  Eliminate：  readily 轻易的 ⇒exclude，kill  redundant 多余的  Superposition 叠加 1 2013/10/29 力法基本思路小结  根据结构组成分析，正确判断多于约束个数——超静定次数。  解除多余约束，转化为静定的基本结构。多余约束代以多余未知 力——基本未知力。  分析基本结构在单位基本未知力和外界因素作用下的位移，建立 位移协调条件——力法典型方程。  从典型方程解得基本未知力，由叠加原理获得结构内力。超静定 结构分析通过转化为静定结构获得了解决。 1.First of all, the degree of statical indeterminacy超静定 is determined. Anumber of releases 放松次数equal to the degree of indeterminacy is now introduced, each release being made by removal of an external or an internal force. The releases must be chosen so that the remaining structure is stable and statically determinate. 2 2013/10/29 However in some cases the number of releases can be less than the degree of indeterminacy, provided只要 the remaining statically indeterminate structure is so simple that it can be readily analyzed. In all cases, the released forces, which are also called redundant forces赘余力, should be carefully chosen so that the released structure is easy to analyze. 2. The releases introduce导致 inconsistencies in displacements, and as a second step these inconsistencies or “errors” in the released structure