不引入解析法中体外筋预拉力增量与梁中点振动位移成正比的假设,提出用能量法分析体外预应力梁动力特性.由于不引入解析法中的假设,梁自振频率也更准确,与数值解吻合良好.计算结果表明:解析法低估了体外筋对第1自振频率效应；高估了对第2自振频率效应；体外预应力筋对第1自振频率影响较大,对高阶的频率影响很小,可以不考虑其影响；随着体外筋面积和偏心距的增加,梁的第1自振频率也随之增加.在理论上,体外预应力能减小梁的自振频率,而体内预应力对梁的自振频率没有影响.%The assumption that the prestress increment of external tendon is proportional to the mid-span vibration displacement of a beam in the analytical method was not adopted. The energy method to analyze the dynamic behavior of an externally prestressed beam was proposed. Due to not adopting the assumption in the analytical method, the natural vibration frequencies were more accurate, and ageed well with the numerical results. The calculation results showed that the effect of external tendon on the 1st frequency is underestimated by the analytical method, and its effect on the 2nd frequency is overestimated; the influence of externally prestressed tendon on the 1st frequency is significant, but its influence on higher natural frequencies is slight and can be neglected; with increase in area and eccentricity of external tendon, the 1st frequency of the beam increases. Theoretically, external prestress can reduce the 1st frequency of a beam, but, internal prestress has no influence on the natural frequencies of a beam.
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