San Francisco — The Golden Gate Bridge, Highway and Transportation District (District) selected HDR to provide Fracture Critical Bridge Inspection Services on select floor beams and truss members, supporting one of the world's most iconic structures.
The District performs regular bridge inspections of all its bridges on a multi-year cycle. During the inspection, all elements of the structures are investigated and their condition assessed. The Federal Highway Administration (FHWA) has developed a list of 23 compliance metrics associated with the oversight of the National Bridge Inspection Program and one of the metrics requires bridge owners to develop a plan to identify and inspect all bridge fracture critical elements. Fracture critical elements are defined as steel bridge tension members that, if they fail, could lead to the partial or complete collapse of a structure.
A Fracture Critical Plan for the Golden Gate Bridge was developed by the District. They identified all fracture critical members and performed fracture critical inspections on all readily accessible elements. However, there are a number of elements that are not accessible and require teams trained in rope access techniques to get within the arm's-length maximum distance required to perform the fracture critical inspections.
HDR used all SPRAT (Society of Professional Rope Access Technicians) certified teams with at least three years experience inspecting fracture critical bridges to perform the inspections the District couldn't do itself. Using industrial rope access techniques, we performed the inspections over a three-week time period — completing the job in one-third of the originally scheduled time. The project included the inspection of 179 truss members and 168 floor beams within the following structure units:
- South Approach Viaduct (SAV) Deck Truss Spans (Spans 4 – 6)
- Fort Point Arch Span
- Suspension Spans
- North Approach Viaduct (NAV) Deck Truss Spans (Spans 1 – 5)
The three SAV Girder Spans and select portions of the Main Cable were also inspected as an add-on to the original scope of work.
As part of the documentation requirements for this project, Element Level condition states and defect text according to the AASHTO Manual for Bridge Element Inspection were used to describe and rate the conditions of the fracture critical members inspected.