Development of Structural Design Method of Ultra-Thin Whitetopping with High Strength Concrete

超薄白色面层最初是在北欧和美洲开发的，用于修复严重车辙的沥青路面，此后这种方法在世界各地推广。在日本，这种方法已经在几个地点进行了试验，并收集了性能数据。性能数据表明，白顶结构能够承受至少5年以上的中等交通条件。另一方面，超高强纤维增强材料(UFC)已被开发并应用于几种实际结构。由于-UFC具有非常致密的基质和含有短纤维，与传统混凝土相比，它具有优异的力学性能和耐久性。结合这两种技术，高强混凝土超薄白顶结构应运而生。在这种方法中，将在工厂中在非常好的固化条件下预制的厚度为30 mm的1.0m×1.7m的板材放置在现有的ASPH…上高强混凝土板的抗弯强度可达40 Mpa以上，远高于普通混凝土板。通过灌浆面板之间的间隙，将面板与沥青层粘合在一起。为了合理地进行高强混凝土管的结构设计，必须对结构的受力性能有一个透彻的了解。虽然高强混凝土面板具有很高的抗弯强度，但由于交通荷载的作用，面板中的应力预计会非常高，并且强烈依赖于下面沥青层的刚度和厚度。此外，由于沥青层比面板厚得多，沥青层的粘弹性性质不容忽视。为了建立HSCWT的结构设计方法，本文在HSCWT足尺试验路面上进行了加速加载试验，并对其长期性能进行了研究。采用三维有限元分析方法对试验进行了模拟，分析了高强混凝土短管的结构特点。在载荷试验和有限元计算分析的基础上，讨论了一种结构设计方法。本文的研究成果总结如下：(1)加速加载试验：HSC-WT的试验路面是在加速加载设备上建造的，承受大约150,000~200,000次的移动轴载。从试验结果可以看出：面板之间的接缝形成了未粘结区域，这可能会导致面板支撑力较弱，并促进非常细小的表面开裂。面板底面的石头和硬币纹理类型有效地增强了粘结，而孔洞型纹理在界面形成了气孔，削弱了粘结。交通负荷对HSCWT的长期性能没有造成严重的问题。(2)有限元分析基于动力三维有限元加载试验结果，并将计算结果与实测值进行对比，识别出沥青层的粘弹性参数。通过3DEFM加载试验的动力分析，研究了HSCWT的力学行为。在夏季荷载试验中，沥青层的粘性较低，而在冬季荷载试验中，沥青层的粘性较高，粘弹性参数和加载速率对高强混凝土面板的应力影响很小。影响最大的是墙板与灌浆层之间的界面状况，在保证界面粘结良好的情况下，墙板内的应力远小于高强混凝土墙板的强度。结构设计方法在加速加载试验和有限元分析的基础上，建立了高强混凝土水工混凝土结构的力学设计方法。在此过程中，用三维有限元计算下垫层的拉伸应变，并利用沥青混合料的疲劳曲线由拉应变估计沥青层的疲劳损伤。研究发现，不仅沥青层的粘度对沥青层的疲劳寿命有显著影响，车速也是影响沥青层疲劳寿命的重要因素。较少

Ultra-Thin White-topping was originally developed in Northern Europe and America to rehabilitate severely rutted asphalt pavement Since then this method has been spread around the world. In Japan, this method has been tried in several sites as a trial and performance data have been collected. The performance data revealed that the white-topping structures is able to withstand at least medium traffic conditions for more than 5 years. On the other hand, Ultra High Strength Fiber Reinforced (UFC) has been developed and applied on several actual structures. Because-UFC has a very dense matrix and contains short fibers, it has excellent mechanical properties and durability compared with conventional concrete. Combining these two technologies, Ultra-thin white-topping structure with high strength concrete (HSCWT) was developed. In this method, 1.0m by 1.7m panels with a thickness of 30mm, which are prefabricated in a factory under very good curing conditions, are placed over an existing asph … More alt pavement The flexural strength of the HSC panels is more than 40MPa, which is much higher than normal concrete slabs. The panels are bonded with the asphalt layer by grouting the gap between them. For rational structural design of the HSCWT, mechanical behavior of the structure should be thoroughly understood. Although the HSC panels have very high flexural strength, the stresses in the panels due to traffic loads are expected to be very high and strongly depending upon the stiffness and thickness of the underlying asphalt layer. Furthermore, since the asphalt layer is much thicker than the panels, the visco-elastic nature of asphalt layer could not be ignored.In this study, in order to establish the structural design method for HSCWT, accelerated loading tests were conducted on full scale test pavement of HSCWT and long-term performance was investigated. 3DFEM analysis was performed to simulate the tests and address the structural features of HSCWT. Based on the analysis of loading tests and FEM calculations, a structural design procedure was discussed. The results of this study are summarized in the following.(1) Accelerated loading tests.Test pavements of HSC-WT were constructed on an accelerated loading facility and were subjected to moving axle loads about 150, 000 to 200, 000 times. From the test results, following remarks can be made :● Unbonded area developed from joint between panels, which might cause weak support for the panels and promote very fine surface cracking.● Stone and coin texture types on the bottom face of the panel effectively enhanced the bonding, while hole type of texture formed air void at the interface and weakened the bonding.● No serious problems under traffic loads raised on long term performance of HSCWT, as long as a sound bonding was ensured at the interface between the panels and the asphalt layer.● Joint reinforcement with underlying panels was not good measure.(2) FEM analysisBased on analysis of the loading tests with dynamic 3DFEM and comparison of the computer results with the measured data, visco-elastic parameters of the asphalt layer were identified. Mechanism behavior of HSCWT was investigated based on dynamic analysis of the loading tests with 3DEFM. Following remarks can be made :●For the summer loading test, low viscosity in the asphalt layer was identified, while for winter loading test, relatively high viscosity was identified.●Stresses in HSC panel was affected very little by visco-elastic parameters and loading rate. The most significant effect was the interface condition between the panel and grout.●Stresses in the panel much less than the strength of HSC panel if good bonding at the interface was ensured. Therefore the fatigue of the panel would not be an issue in the structural design of HSC-WT.(3) Structural design methodBased on the results of the accelerated loading tests and FEM analysis, a mechanical design procedure for HSCWT was developed. In the procedure, tensile strains in the underlying asphalt layer are calculated with 3DFEM and fatigue damage of the asphalt layer is estimated from the tensile strains using fatigue curve of asphalt mixture. It was found that not only viscosity of asphalt layer but also vehicle speed significantly affects fatigue life of asphalt layer. Less