From the genealized one, the extended principle of virtual displacements for static systems is deduced, including the classical one.

由此推得静止系统的虚位移原理（扩大），它包含古典的虚位移原理在内；

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The extended principle of virtual displacements is also proved by another method, which is used customarily to prove the classical one.

用证明古典虚位移原理的传统方法证明虚位移原理（扩大）。

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This paper presents a method of using the principle of virtual displacements directly to obtain the ordinates of the influence line for frames.

本文阐述了直接用虚位移原理计算刚架影响线纵距的方法。

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