简要介绍了单自由度非线性保守系统作大振幅振动时周期的计算方法，并给出了几个常见典型振动问题的周期公式。
A calculation for period of a single freedom nonlinear conservative system vibrating in a large amplitude is performed, and the period formulae of some typical vibration problems are presented.
研究结果表明：在简谐地面加速度作用下，高频地震动也可以引起长周期结构产生很大的位移反应，且最大位移反应出现在结构的瞬态自由振动阶段。
It is concluded that the transient response to a high frequency harmonic ground motion can increase greatly the displacement response of structures, particularly for the long period structures.
对给定参量的非线性自由振动的相位图特性、振动周期等进行了定量及定性研究。
For the given parameters, the quantitative and qualitative analyses to the phase portrait and motion circle of the nonlinear free vibration are dealt with.
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