预应力混凝土桥梁正截面疲劳抗裂性能分析

Analysis on Fatigue Crack Resistance of Normal Section of Prestressed Concrete Bridge

针对预应力混凝土桥梁正截面疲劳开裂问题,指出了在设计方面,混凝土的抗拉疲劳强度和预应力损失是影响桥梁疲劳抗裂性能的关键因素。通过双轴定侧压下的混凝土拉-压疲劳试验得到了较单轴受力状态下更为符合实际的混凝土抗拉疲劳强度的折减系数计算公式,推出了考虑疲劳徐变引起的预应力损失公式。在此基础上,修正了疲劳荷载作用下预应力混凝土桥梁的开裂弯矩计算公式和抗裂验算方法,为今后桥梁规范修订提供参考。

Aiming at the issue of fatigue cracking of normal section of prestressed concrete bridge,the tensile fatigue strength of concrete and prestressing loss are pointed out to be key factors of influencing the fatigue crack resistance of bridge in the matter of design. Through the compression fatigue test of double- axis constant confining pressure,the calculation formula of reduction factor that meets the actual tensile fatigue strength of concrete under the homotaxial stress state is obtained,and the formula of prestressing loss caused by consideration of fatigue creep is deduced. On this basis,the calculation formula of cracking moment of flexure and method of crack resistance checking computations of prestressed concrete bridge under the effect of fatigue loading are corrected, thus providing reference for the future bridge specification revision.