五、某些基本原理及近似计算方法在本部分中将要介绍一些基本原理及近似计算方法,以了解结构动力学的基础及具体应用方法。1.能量原理我们只研究保守系统(即不考虑阻尼)的情形。在(一)中,已由达朗倍尔原理得到了单质点体系的动力平衡方程Ma~2y/dt~2+ky=F(t)(y=0)由此易引出具有广泛意义的能量守恒原理。将上式两端乘以(?)=dy/dt,积分,得到 V. Some Basic Principles and Approximate Calculation Methods In this section, we will introduce some basic principles and approximate calculation methods to understand the basics of structural dynamics and specific application methods. 1. Energy Principles We only study conservative systems (ie do not consider damping). In (1), the dynamic equilibrium equation of single-point system has been obtained by the Darang-Del principle. Ma~2y/dt~2+ky=F(t) (y=0) It is easy to derive energy with extensive significance. Conservation principle. Multiply the two ends of the equation by (?)=dy/dt and integrate to get