3423 Categorization of Details

The following is a brief simplified overview of the categorization of fatigue details. In all cases, the applicable specifications should also be checked. Several reports have been published that show a large number of illustrations of details and their categories in addition to those in AISC and AASHTO specifications [33,34]. Also, the EC3 [20] and the British Standard BS 7608 [21] have more detailed illustrations for their categorization than AISC or AASHTO specifications. A book by Maddox [9] discusses categorization of many details in accordance with BS 7608, from which roughly equivalent AASHTO categories can be inferred (using Table 34.1). In most cases, the fatigue strength recommended in these European standards is similar to the fatigue strength in the AISC and AASHTO specifications. However, there are several cases where the fatigue strength is significantly different; usually, the European specifications are more conservative.

There have been very few, if any, failures that have been attributed to details with fatigue strength greater than Category C. Most structures have many Category C or even more severe details, and these

will generally govern the fatigue design. Therefore, only Category C and more severe details will be discussed in depth.

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