Internal Redundancy of Mechanically Fastened Built-Up Steel Axially Loaded Multicomponent Members

Abstract

Full-scale fracture tests on mechanically fastened steel built-up tension members have shown that these members can be resistant to complete member fracture when a single component suddenly fractures. This characteristic of built-up steel members is referred to in this research as cross-boundary fracture resistance (CBFR). A comprehensive finite-element model-based parametric study, calibrated to the after-fracture static load redistribution behavior of the experimental fracture specimens, was also performed to study the after-fracture load redistribution behavior of multicomponent built-up steel members. Simplified closed-form solutions were developed for engineering analysis of built-up members to evaluate for internal member redundancy and estimate safe inspection intervals that are based on the fatigue life of the member in the assumed faulted condition. An internally redundant member is defined as a primary steel bridge member in tension, or with a tension element, which has redundancy within the cross section, such that fracture of one element will not propagate through the entire member and is discoverable by the applicable inspection protocol.