Development of Fatigue Check Program of Highway Bridges

公路桥梁经常受到重型汽车的影响，对桥梁的次要构件产生了一定的疲劳问题。特别是在20世纪60年代和70年代日本经济快速增长期间和之后，卡车的成员和重量都有所增加。与铁路桥相比，公路桥梁在卡车荷载作用下对构件的应力范围较小，传统上不考虑疲劳设计。然而，近年来许多公路桥梁都出现了疲劳开裂现象，因此对桥梁进行疲劳评估显得十分必要。采用直方图记录仪对几座公路桥梁进行了使用应力测量，并采用Miner累积损伤规则计算疲劳损伤。结果表明，公路桥梁主要构件的服务应力范围相对较小，存在的可能性很小。然而，在经历疲劳裂纹的几个细节的使用应力范围显示出相当高的应力范围，因此剩余疲劳寿命短。

Highway bridge are subjected to heavy truck traffics, which causes some fatigue problem to the secondary member of the bridges. Both the member and the weight of the trucks increased , especially during and after the rapid economic growth in Japan in 1960's and 1970's. The highway bridges were traditional not designed for fatigue because the truck loading caused relatively small stress range to the members, compared with the railroad bridges. However, the fatigue cracking were observed recently in many highway bridges, and assessment for fatigue seems necessary.Service stress measurement were carried out on several highway bridges by histogram recorder, and fatigue damages were computed using the Miner's cumulative damage rule. The result revealed that the service stress ranges in main members of the highway bridges were relatively small and a very little chances seemed to exist. However, the service stress ranges in several details which experienced fatigue crackings showed rather high stress ranges, and hence short remaining fatigue lives.