Forensic Evaluation and Repair of Failures in 41-Story Granite Facade

摘要

The granite facade of a 41-story steel-framed building constructed in the early 1970s experienced multiple facade failures after 40+ years in service. A forensic investigation of the facade revealed that the approximately 3-inch thick granite facade panels were supported with a structural steel shelf angle detail similar to typical brick masonry support for cavity walls. The shelf angle support was poorly adapted for use with the granite clad facade and created reservoirs that trapped water against unprotected steel, resulting in corrosion of the steel and distress to the granite panels, and in turn formed hundreds of granite spalls that created a potentially hazardous condition around the building. In addition to the granite spalls, the window system contained significant air and water intrusion that led to staining at the window frames and moisture damage at the interior ceilings. Our work included the creation of a 3-dimensional analytical structural model to study building drift and movement; thermographic studies of the facade and windows to identify areas needing additional insulation and water management systems; and studies of both the solid granite wall areas and ribbon window areas to identify cause and origin of the granite and weather-proofing failures.