Wrigley Field: Forensic Investigation and Structural Analysis of the Friendly Confines

During the 2004 baseball season, instances of concrete falling from the upper stands of Wrigley Field were reported, generating local and national media coverage. Several engineering firms were retained by the Chicago Cubs to determine the cause of the falling concrete, develop appropriate remedial measures, and review the general condition of the stadium structure. This paper describes the investigation and structural analysis carried out by the authors. Structural analysis of the grandstands, on-site strain and vibration measurements during a crowded baseball game, and laboratory testing did not reveal any systemic structural deficiencies. The cause of the falling concrete was attributed primarily to corrosion of metals embedded in chloride-contaminated concrete near joints, thermal movements restrained by welded connections, and unintended concrete-to-concrete contact between precast sections. Recommendations for remedial action were provided. The case study underscores the value of forensic engineering techniques to isolate structural performance problems and to develop appropriate and practical remedial solutions.