水泥混凝土路面设计极限状态方程的探讨

STUDY ON THE FORMULA OF THE CONCRETE FATIGUE IN CEMENT CONCRETE PAVEMENT DESIGN

水泥混凝土路面结构设计标准是行车荷载疲劳应力与温度疲劳翘曲应力之和不超过水泥混凝土材料的极限弯拉疲劳强度,现行水泥混凝土路面设计规范(JTG-D40-2002)的设计极限状态方程γr(σpr+σtrr)≤fr中的极限应力与疲劳应力等部分指标力学概念有误,如方程中存在荷载力与温度力的概念不统一,极限应力与疲劳应力概念有误且不统一及疲劳修正系数修正有误等问题,通过对设计方程中各项指标及系数的力学原理研究,对设计极限状态方程进行了修正,采用国内研究的几个主要水泥混凝土试验疲劳方程,通过进一步的力学原理分析及设计疲劳方程对比研究,得出了比较合理的水泥混凝土路面设计极限状态方程修正公式,即γr(σpr+σtr)≤f't=fr/kr(σpr=krkcσps,σtr=ktσtm),并且用算例进行了对比设计,取得了比较满意的设计结果,研究得出了现行规范公式设计板厚偏小的结论,为水泥混凝土路面板的断裂提供了一定理论依据,研究结果论证了修正公式的正确性。

The design standards of the cement concrete pavement are that the vehicle fatigue stress and the temperature fatigue stress are less or equal to the maximum fatigue strength of the concrete. There are some incorrect mechanical concepts on the maximum stress and the fatigue stress in the design fatigue formula of γr（σpr＋σtr）≤fr in the specifications of cement concrete pavement design for highway （JTG-D40-2002）. The formula have some inconsistencies, for example, the vehicle load and the temperature load are inconsistent, the mechanical concepts on the maximum stress and the fatigue stress are incorrect, and the fatigue coefficients are incorrect. Through mechanical and comparative research on the design indexes and the fatigue coefficients in the formula, the formula has been modified, and the paper has put forward the modified formula based on several important concrete fatigue formula in China, i.e. γr（σpr＋σtr）≤fr=fr/kf（σpr=krkcσps,σtr=k1σm）.Meanwhile, the comparative design has been finished between the specification formula and the modified formula, and it is concluded that the thickness of the concrete slab by current design is relatively small, explaining the occurrence of concrete slab cracking.