Structural Health Monitoring
Design and installation of structural health monitoring system
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The Challenge
- Original air-supported roof replaced in 1998, but needed a way to monitor loads (snow) on the roof
The University of Northern Iowa’s multi-purpose indoor facility is a 424-ftdiameter domed structure. The UNI-Dome has a seating of approximately 16,500 for sporting events and 25,500 for concerts. The original UNI-Dome was a cable-restrained low-profile air-supported roof with compression ring built in 1976 at a cost of $7.5 million. Three times in its history, the dome encountered difficulties that caused the roof fabric to sag, accumulate water, and subsequently tear.
In 1998, a hybrid roof system was installed to replace the air-supported roof. Stainless steel standing seam roof panels supported by structural metal deck and bar joists formed the skin of the peripheral area of the roof (75% of the roof area).
The Solution
Geocomp personnel designed and installed a structural monitoring system for the roof members to measure excessive or eccentric snow loads on the roof skeleton. The structural monitoring system includes wind speed, direction sensors and strain gages placed on key structural elements near the top of the roof on the central ring beam system. Strain gages were placed on ring beam structural elements to identify stresses that may approach levels where maintenance staff may be required to visually inspect roof conditions for excessive snow loads.
The strain gages connect to a data logger that issue an alarm if assigned response values for calculated stresses are exceeded for any sensor. The system is accessed remotely for software modification or data retrieval. This system provides continuous, real-time evaluation of the roof structure’s response to high winds, snow-melt or uneven snow accumulation. The system was integrated into the university’s building control system. In 2015, Geocomp performed on-site servicing and replacement of system components to assure a reliable and long-functioning system for its original intended use.
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