Load-Induced Fatigue Category of Hand Holes and Manholes

Current steel bridge design and evaluation practices assume that large inspection access holes, such as manhole and hand holes are presently classified as category D details. While category D is adequate for the fatigue evaluation of small open holes, such as an empty bolt holes, this has been shown to be overly conservative when the dimensions of the hole are larger. Specifically, the stress concentration of a hole decreases as the size of the hole relative to the size of the plate...
More Description

Current steel bridge design and evaluation practices assume that large inspection access holes, such as manhole and hand holes are presently classified as category D details. While category D is adequate for the fatigue evaluation of small open holes, such as an empty bolt holes, this has been shown to be overly conservative when the dimensions of the hole are larger. Specifically, the stress concentration of a hole decreases as the size of the hole relative to the size of the plate increases. In order to verify whether the reduction in stress concentration is significant enough to grant an improvement in the fatigue category, a parametric study using finite element analysis was conducted. The results of the parametric study revealed that larger holes may be reclassified as category C fatigue-prone details when certain geometrical features are met. To assist the implementation of the research findings, the current report also includes recommended modifications to the AASHTO LRFD Bridge Design Specification.