中文摘要：

外部对的具体结构的自然频率的分析和计算是为学习如此的结构的动态性质的底。我们 carded 外面外部简单地支持的横梁的三种类型上的动态测试，逐渐地拉横梁。当频率和相关系数在每步被测量时，然后垂直的负担被用于横梁。我们计算了自然频率和结果当对的力量在预先击碎阶段升起，显示自然频率增加，并且在裂缝以后的阶段期间显著地减少。实质的 incoincidences 在改变的频率和它的趋势的计算、试验性的结果之间存在。基于试验性的结果，我们在方程修改了僵硬和另外的参数。用修改方程计算的结果同意试验性的结果很好，因此修改方程能实际上被使用。

英文摘要：

Analyses and computations of the natural frequencies of external prestressed concrete structures are the bases for studying the dynamic properties of such structures. We carded out dynamic tests on three types of external simply supported beams, pulling the beams gradually. Then vertical loads were applied to the beams while the frequencies and related coefficients were measured at every step. We calculated natural frequencies and the results indicate that natural frequencies increase as the prestressing force rises in the pre-crack stage, and decrease significantly during the post-crack stage. Substantial incoincidences exist between the calculated and experimental results for the frequency and its tendency to changel Based on the experimental results, we modified the stiffness and other parameters in the equations. The results calculated using the modified equations agree with experimental results well, so the modified eauations can be used nractically.