Project Type: Evaluation, Forensics, Design
The Vital Structure:
Emergency Forensic Evaluation and Design for Failed Beam, Manchester, NH
Issue
Vital Structures was called out on emergency status to this high school, due to one of the garage roof beams having reportedly failed and dropped from its support. This beam was a 30” deep steel beam which supported a plaza deck above. The failed connection resulted in the plaza deck dropping approximately 9” vertically, and tearing building waterproofing systems.
Diagnosis
Vital Structures traveled to the site to perform an emergency forensic review of the existing framing systems, failed connections, overall building geometry and also reviewed the building’s original structural design documents in an effort to determine the source of the failure. Upon review, it was determined that the failure was likely due to an error in the original design and construction when considering the slotted connection required for a building expansion joint. The limitations of the expansion joint detail resulted in fatigue of the connection, and eventually failure.
Solution
As part of Vital Structures’ scope of services, we provided the city with a repair design for the new joint and connection system. As the original framing design of the building did not appear to sufficiently accommodate thermal expansion and contraction of the plaza deck above, Vital Structures provided the owners with a redundant design which addressed the failed system, but also had a secondary system in-place to protect pedestrians and cars in the garage below, should there be a systematic failure at another location.