Fatigue Design Method for Reinforced Concrete Slabs of Highway Bridges

在日本，公路桥梁的钢筋混凝土板的设计都是按允许设计方法进行的。然而，从1970年左右开始，板就出现了由冲切破坏引起的开裂破坏。这些损伤已经被认为是由于重载引起的疲劳现象。通过对原滚动轮载试验结果的分析，认为疲劳破坏主要取决于轮载作用于板裂纹表面的剪应力变化。因此，作者认识到，设计时应考虑剪应力。在这种情况下，作者认为实验数据是最合适的。开展研究是为了建立设计方法。为了完成研究，需要准备车轮载荷特性。然而，要找到现有的数据是非常困难的。为此，作者提出了一种基于轮载裂纹张开测量的行车轮重测量方法。通过对主要载荷的24小时测量，准备了合适的数据。利用已有的疲劳数据和车轮载荷特性，提出了一种基于剪应力幅值的设计方法。

In Japan, the design of reinforced concrete slabs of highway bridges has been done by the allowable design method. However, since about 1970, the slabs were suffered from cracking damages inducing punching shear failures. These damages have been recognized an fatigue phenomenon due to heavy wheel loads. From the original experimental tests under running wheel loads, the author has explained that the fatigue failure depends mainly to alternation of shearing stresses acting on cracked surfaces in the slab under running wheel loads. Therefore, the author has recognized that the design should be chanced by considering the shearing stresses. In the case, the experimental data by the author seen to be the most suitable. The research was carried out to establish the design method.To complete the research, wheel load characteristics should be prepared. However, it was very difficult to find out the existing data. Therefore, the author has developed a new method to measure wheel loads under running which is based on measuring crack opening due to wheel load. Through 24 hours measuring for main load, we prepared a suitable data. Using the existing fatigue data and the wheel load characteristics, a new design method based on shearing stress amplitudes was derived.