Load Redistribution and Remaining Fatigue Life of Steel Built-Up Members Subjected to Flexure Following a Component Failure

Built-up steel girders have been shown to be resistant to total member collapse in the event that a single component fails from brittle fracture or from fatigue. However, accurate methods to determine the remaining capacity of members with partially failed cross sections have not been addressed. Because the failure of a single component represents a localized failure, a simple flexural stress calculation of a member cross section, using only the remaining components, does not represent the actual member capacity. Additionally, a traditional linear stress distribution over the height of a flexural member is not accurate due to the load transfer, engagement of mechanical fasteners, and remaining portions of unfailed components. This paper will present the methods used in determining the localized stress distribution as well as how to estimate the appropriate levels of stress in partially failed built-up steel members. Results of experimental fatigue tests are presented along with an analytical parametric study investigating the localized stresses near a partially failed component. This information is critical in determining the strength capacity of members who have experienced a failure in one of the components, as well as determining the remaining fatigue life of built-up girders subjected to vehicular loads.