平面框架有限元程序，可计算线性和非线性（几何、材料非线性）问题，来自《杆系与箱型梁桥结构分析及程序设计》一书，是学习fortran和非线性很好的例子-Plane finite element program frame, can be used to calculate the linear and nonlinear (geometry, material nonlinear) problems, from the rod and box girder bridge structure ana