What windspeed was the existing bridge designed to withstand?
The existing bridge was designed to withstand 50-70 mph winds. Why do you close the bridge to traffic during severe windstorms? We close the bridge to traffic in order to open the drawspan, which relieves pressure on the bridge from wind and wave action during windstorms. The criteria for closing the bridge to traffic and opening the drawspan is 50 mph gusts sustained for 15 minutes. When a 40 mph gust is sustained for one minute, a warning alarm alerts crews to come to the bridge for inspection and monitoring. As with all WSDOT bridges, our experienced crews can close the bridge anytime they deem it unsafe, or when there is a potential for damage. You can check current conditions at the SR 520 bridge on the Web. What repairs and retrofits have been made on the current bridge? 2006 – Replaced drawspan anchor bolts sheared off during storms earlier in the year. The anchor bolts hold the drawspan closed. 2000 – Emergency repairs to column damage. 1998 – Seismic retrofit, cable post tensi
