体外预应力索自由长度分析

转向块(锚固端)间的体外预应力索可能产生独立于梁的振动,若其频率与梁的固有频率接近,就可能发生共振。当频率相近时,改变梁的截面特性或体外索的正常使用应力都不是好的解决办法,而通过改变体外索的约束长度来改变其固有频率,在经济、效果及可行性方面,都不失为一个理想的方法。体外索的无侧向支承的自由长度不应过大,根据常见桥梁频率和我国钢绞线的使用情况,体外索可控制在12m之内,这样桥梁和体外索的自振频率就相互错开,也就避免了共振问题。

Analysis on Unconstrained Length of Externally Prestressed Cable

The externally prestressed cable among the turning blocks(anchoring end) may produce the vibration independently from the girder.If its frequency is closing to the inherent frequency of the girder,the sympathetic vibration will cause.It is not the good solving method to change the section characteristic of girder or the normal using stress of external cable when the frequencies are closing.The ideal method can yet be regarded in the aspects of economy,effect and feasibility to change the restricted length of the external cable so as to change its inherent frequency.The unconstrained length of non-lateral support for external cable should not be over long.Based on the common bridge frequency and the using condition of steel strand in China,the external cable can be controlled within 12 m.In this way,the natural vibration frequencies of bridge and external cable will stagger,and also avoid the sympathetic vibration.