functional variation principle

Then based on energy functional variation principle, the governing differential equations considering shear lag for theory of elasticity in box girders are established. (3) The closed-form solutions of the governing differential equations are derived from differential equation operation principle.
本文完成了下列有特色的工作:(1) 结合了薄壁杆理论和能量泛函变分原理,系统地建立了薄壁箱梁弯曲、弯扭、压弯等的剪力滞效应的弹性力学求解体系,完善了薄壁结构理论。