New Method for Fatigue Design of Bridges

The present American Association of State Highway and Transportation Officials' (AASHTO) fatigue specifications, and earlier versions of these specifications, have generally resulted in conservative bridge designs. However, the specifications originated before much information was available on the actual stresses in bridges and on the variable-amplitude fatigue behavior of bridge members; therefore, they do not accurately reflect the fatigue conditions that actually occur. A new method of designing highway bridges against fatigue is presented. This method more accurately reflects actual conditions and would permit the engineer to design for any desired weight distribution and volume of traffic. Although the development of some parts of the method are complex, the method is simple to use and could be incorporated into the AASHTO specifications as illustrated in the paper.