【作者】 左志武；

【导师】 王选仓；

【作者基本信息】 长安大学 ， 道路与铁道工程， 2010， 博士

【摘要】 冲断是连续配筋混凝土路面(CRCP)的最主要的病害,主要发生在密集裂缝处,与平均裂缝间距和平均裂缝宽度没有相关性,论文研究了温降和干缩作用下横向裂缝的纵向分布,在此基础上进行冲断预估,具有重要的理论意义和使用价值。对耒宜高速、G210铜川段、山西省道孙吴线二级公路和粤赣高速四条公路的CRCP进行了路况调查,发现冲断占到影响行车的病害的90%以上,而且这四条路密集裂缝处的冲断分别占到各条路冲断总量的100%、44%、50%和63%,说明应该以冲断作为CRCP的设计指标,而且应该根据横向裂缝的纵向分布进行冲断预估。根据钢筋与混凝土间的粘结滑移本构关系及地基摩阻力的线性分布假设,建立了CRCP温降和干缩应力的计算模型与应力平衡微分方程,并求得CRCP在降温和干缩条件下混凝土和钢筋的应力及位移计算公式,采用有效弹性模量法考虑了混凝土的应力松弛。分别采用CPS4单元和B21单元对混凝土和钢筋进行离散,采用水平弹簧单元模拟钢筋与混凝土之间的粘结滑移,采用水平和竖向弹簧模拟基层与混凝土板之间的关系,对参数取值进行了论证,建立了CRCP有限元模型。对CRCP在降温作用下的应力应变进行了分析,并给出了应力和应变的云图。参数敏感性分析表明,混凝土弹性模量、地基摩阻力系数和混凝土热膨胀系数是温降和干缩作用下CRCP计算分析的主要参数,需要考虑它们的变异性来预估CRCP的横向裂缝的纵向分布。采用Monte-Carlo的方法,考虑混凝土强度和基层摩阻力的变异性以及平均气温逐月变化,以凝结温度与月平均气温之差的月变化作为环境荷载,采用自编程序对CRCP横向开裂进行了预估。分析表明混凝土横向开裂在100天左右趋于稳定,并对裂缝间距进行了统计,在此基础上对裂缝宽度进行了分析。确定了将非线性温度分布转化为线性温度分布的计算公式,提出了将湿度梯度转化为温度梯度进行计算的分析方法。采用有限元软件建立了车辆荷载、温度梯度和湿度梯度作用下CRCP应力分析模型,其中充分考虑了裂缝间的传荷能力、基层与面层间的摩阻系数的影响,并进行了钢筋等效和厚度等效。通过参数敏感性分析确定四个重要结构参数：传荷系数、裂缝间距、温度梯度和板厚。对参数取不同的值进行研究,给出不同传荷能力下的诺谟图。给出了冲断预估程序,根据密集裂缝间距计算出CRCP顶部临界横向拉应力后,根据损伤线性累积定理可预估出是否会发生冲断,进而结合横向裂缝纵向的非均匀分布可以确定出冲断的数量。改变混凝土组成、基层类型、钢筋防护方法、纵横向钢筋的夹角、纵向钢筋的埋置深度、主动控制裂缝间距等因素,修筑了11个CRCP试验段,测试了混凝土的抗压强度、抗拉强度、抗弯拉强度、抗压模量和抗弯拉模量,调查了各试验段裂缝发展状况,进行了FWD测试,并对比分析了各因素对于CRCP性能的影响。结果表明：混凝土材料、纵横向钢筋的夹角和基层类型对于密集裂缝的影响大于混凝土面板和基层之间的夹层的影响,1～5m的主动控制裂缝间距可以有效防止自然裂缝的产生。另外,对于车辆荷载和环境荷载作用下CRCP的应力应变进行了测试。结果表明,在进行环境荷载作用下CRCP应力应变分析时,混凝土与钢筋不是完全粘结的,裂缝处不能采用固定或自由边界条件,测试出的裂缝处钢筋的应力可以直接体现在裂缝处边界条件中；在车辆荷载和环境荷载作用下,CRCP内的混凝土和钢筋的测试结果与理论分析结果比较接近,说明理论分析模型比较合理。更多还原

【Abstract】 Punchout is the main distress of continuously reinforced concrete pavement, and often occurs at cluster cracks. It is not relative to average crack spacing and average crack width. In the dissertation, the distribution of transverse cracks along pavement longitudinal direction because of temperature drop and shrinkage is studied, then punchout is predicted on this basis. That study has important theoretical significance and practical value.Field investigations are carried out on the CRC pavements along several highways which include Leiyi Expressway,210 second class highway, Sunwu second class highway and Yuegan Expressway. Results show that the punchout is up to 90% of the distress which affect riding safety and comfort and the number of punchouts in cluster cracks regions in each of these four highways is 100,44,50 and 63 percent of the total number of punchout in each highway, respectively. So punchout should become one design index of CRCP and punchout prediction should be based on the longitudal direction of transverse cracks.According to the bond-slip constitutive relation between the reinforced bar and concrete and the linear calculation model between the subgrade and concrete, the equilibrium differential equations are established for the analysis of the stress caused by temperature drop and shrinkage in CRCP. The analytic solution is derived and the formula is provided to calculate the CRCP stress and displacement under the temperature drop and shrinkage. The creep of concrete is accounted for by effective modulus method. The finite element model is established. The concrete slab is discretized by CPS4; reinforcing steels are modeled by B21; and the bond slip between concrete and the steel bar is modeled by horizontal springs, the underlying layers are modeled by vertical springs, and the frictional resistance at the interface between concrete and base is modeled by horizontal springs. Analysis on the stress and displacement of CRCP under temperature drop is carried out and the contours of the stress and displacement are given. Sentivity study show that, elasticity modulus of concrete, bond-slip coefficient between concrete and base and expansion coefficient of concrete are key parameters. Their variation should be accounted for when the longitudal distribution of transverse cracks is predicted.Using Monte-Carlo method, considering the variation of the concrete strength and bond-slip coefficient between concrete and base, the longitudal distribution of transverse cracks is predicted, in which, the average air temperature is changed monthly, and the temperature load is also changed monthly relative to setting temperature. Analysis show that the growth rate of transverse cracks will become very small in approximately 100 days. Crack spacing is counted, and crack width is analyzed accordingly.The formulas used to get the equivalent linear temperature from the nonlinear temperature distribution are established and the method of transforming moisture gradient to temperature gradient is proposed. Considering the effects of load transfer efficiency (LTE) at the transverse cracks and the friction coefficient between banes course and concrete slab, the mechanical response analysis is carried out on the CPCP under temperature gradient, moisture gradient and vehicle load, in which the equivalent slab thickness and equivalent steel concept are used.Considering the changes of load transfer coefficients of the cracks, crack spacing, temperature gradient and slab thickness, the stress nomograms of CRCP under vehicle load and temperature gradient are given. The procedure of punchout prediction is given. When the critical transverse stress on the top of CRCP is calculated out in cluster cracking region, it can be determined whether the punchout will occur. Then the number of punchout can be predicted according to the longitudal distribution of transverse cracks.Eleven test sections were designed and constructed, in which concrete material, base, the erosion prevention of steel, the angle between transverse steel and longitudinal steel, the depth of longitudinal reinforcement, and the distance of cracks active controlled varied. The compressive strength, tensile strength, flexural strength, compressive modulus and flexural modulus of concrete were tested. The cracks in early age were surveyed and Falling Weight Deflectometer tests were carried out. Results show that, concrete material, the angle between transverse steel and longitudinal steel and base have more effects on cluster cracking than the separating layer between concrete slab and base does, and active crack with the spacing of 1 m to 5 m can prevent the occurrence of natural cracks between active cracks. For CRCP systems under environmental loads, the strains and stresses in CRCP in early age due to environmental loads were measured. Results show that, when analysis on the early age behavior of CRCP under environmental loads, the steel is not completely bonded with concrete, the perfectly free or restrained boundary condition across cracking is not true, and the longitudinal steel strains across cracking will help develop proper boundary condition across cracking. On the other hand, for the CRCP under vehicle loads and environmentalloads, the test results of concrete strains and steel strains are much closer to the theoretical analysis results which illustrate that the theory analysis models are reasonable.更多还原