【摘要】 针对预应力混凝土构件的正截面疲劳开裂机理与静力开裂机理的差异.指出了影响疲劳开裂的两个主要参数,即预应力钢筋的有效预应力值与混凝土抗拉疲劳强度随着重复荷载次数增加而逐渐降低,且其降低的程度不可忽略.在混凝土轴心拉-拉与拉-压疲劳试验的基础上得到了疲劳强度折减系数的计算公式,并推导出考虑了疲劳荷载作用而产生的预应力损失增量的计算公式.指出对于大多数允许出现拉应力而不允许出现裂缝的预应力混凝土构件,混凝土的抗拉疲劳强度折减系数应采用由拉-压疲劳试验得出的结果,不可简单地套用规范取值.最后给出了正截面疲劳抗裂分析的实用验算方法,为预应力混凝土构件的疲劳抗裂设计提供了依据,并可为制订有关设计规范所参考.更多还原

【Abstract】 The difference of mechanism between normal section fatigue crack resistance and static crack resistance for prestressed concrete members was analyzed.The decrease in two main parameters affecting fatigue cracking,namely the effective prestress and the tensile fatigue strength of the concrete, with the increase of cyclic number was found unnegligible.The calculation formula for fatigue strength reduction factor was established based on fatigue tests of concrete under uniaxial tension-tension and tension-compression and the calculation formula for increase in prestress losses caused by fatigue load was derived.For most prestressed concrete members in which tensile stress was permitted while cracks were unallowed in service phase,it was indicated that fatigue strength reduction factor should apply the result from fatigue tests of concrete under tension-compression instead of the value provided by the code.At last the practical checking method for analyzing fatigue crack resistance of normal sections was given which can provide the evidence for design of fatigue crack resistance for prestressed concrete members and is suitable for incorporation into relevant design codes.更多还原