Fatigue retrofits of the I-435 Missouri River Bridge

Abstract

The I-435 Bridge over the Missouri River at Kansas City, Missouri, consists of twin twogirder structures. Inspections by the Missouri Department of Transportation (MoDOT) in 2003 detected numerous cracks at the floor beam and lateral member connections throughout the 30-year-old bridge. An initial evaluation suggested that many of the cracks were the result of distortion-induced stresses. No evidence of unstable crack extension was observed. A comprehensive fatigue study was subsequently carried out to investigate the extent and cause of cracking and to evaluate possible long-term retrofit solutions. Based on the study findings, a retrofit plan was implemented that addressed details susceptible to distortion-induced cracking, end restraint cracking, and crack growth from embedded defects. Large-hole and loosening type retrofits were utilized to reduce the possibility of crack extension. The installed retrofits will significantly extend the remaining fatigue life and facilitate ease of inspection of this critical infrastructure link.