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修订后的美国AA SHTO LRFD桥梁设计规范和AA SHTO阶段预制混凝土桥梁设计与施工规范,采用基于变形的体外预应力筋极限应力计算公式代替了原来的基于粘结折减系数的体外预应力筋极限应力计算公式。本文剖析了这一转变的原因,并针对美国桥梁规范体外预应力筋极限应力计算公式中,较为繁琐的中性轴高度计算进行了简化。在此基础上,建议了与我国现行公路桥梁规范材料分项系数相适应的体外预应力筋极限应力计算公式,并给出了计算示例。
Revised American AA SHTO LRFD bridge design code and AA SHTO phase prefabricated concrete bridge design and construction code, based on the deformation of the external prestress tendon ultimate stress formula instead of the original based on the bond reduction coefficient of prestressed tendon limit Stress calculation formula. This paper analyzes the reasons for this change, and simplifies the more complicated calculation of the neutral axis height in the calculation formula of the ultimate stress of prestressed tendons in American Bridge Code. On this basis, the calculation formula of the ultimate stress of external prestressing tendons, which is suitable for the sub-component coefficient of the current highway and bridge materials in China, is proposed and an example of calculation is given.