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1975年部颁铁路工程技术规范第二篇桥涵,对于预应力混凝土受弯构件正截面强度的计算,保持了1961年部颁预应力钢筋混凝土铁路桥梁结构设计暂行规范所规定的计算图式,但材料的计算强度取值有所改变。受压区混凝土平均应力由0.875月降到0.7月,即等于混凝土的棱柱体强度R_a。预应力钢筋的计算强度,由极限强度R_v~i降到0.9R_v~i界限配筋的控制条件改为x≤0.4h_0。为了与61年规范协调,其强度安全系数k也作了相应的调整,降低了
In 1975, the second bridge and culvert for technical specifications of the Ministry of Railways, for calculation of the normal section strength of prestressed concrete flexural members, maintained the calculation formula stipulated in the Interim Provisions for Design of Pre-stressed Reinforced-Concrete Railway Bridges in 1961 The calculated value of the material has changed. The average compressive stress of concrete from 0. 875 to 0. 7 months, that is equal to the concrete prism strength R_a. The calculated strength of prestressing tendons is reduced from the ultimate strength R_v ~ i to the limit of 0.9R_v ~ i, and the control condition of reinforcement is changed to x≤0.4h_0. In order to coordinate with the 61-year norms, the strength safety factor k has also been adjusted accordingly, reducing