CTLGroup performed a long term performance monitoring of the retractable roof viscous-damper system movement at Safeco Field in Seattle, Washington. There are three retractable roof panels with a total of eight 800-kip viscous dampers mounted between horizontal trusses and down-turned north legs. These units act as large shock dissipaters to dampen lateral loads through the roof truss structure from wind and seismic events and minimize lateral loads transferred to the runway support structures. The long-term performance of the dampers is essential for proper roof operation. An autonomous monitoring system that would provide minute-by-minute readings was an absolute necessity. CTLGroup was awarded the contract to design, install and maintain such a system.
In August and September of 2000, a high-speed automatic data acquisition was installed in the roof operator's room to monitor movement of the retractable roof viscous damper system at Safeco Field. The system is used to monitor long-term performance of the viscous dampers on the roof structure. Sensors were installed to measure vibration, strain and displacement. CTLGroup designed, installed and initiated operation of the system. This instrumentation determines and remotely reports the percent damping in the structure by monitoring the dynamic movement of the roof panels during strong windstorms and earthquakes. Remote access to the system is through modem or internet. Results are analyzed by the stadium designer and compared with original baseline damping values to quickly pinpoint any degradation in performance.
CTLGroup is currently maintaining the system and has a recurring yearly maintenance contract with the client. The project has since helped CTLGroup develop similar long term monitoring projects.