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SDOT’s instrumentation consultant, BDI, measured crack depths on the sides of the box girders where they meet the deck and also used ultra-sonic pulse echo imaging and ground penetrating radar to help in understanding if there is any weakness in the steel rope that holds the bridge in compression.
On April 22, SDOT’s design consultant, WSP, provided an estimate of rate of crack growth as well as a critical failure projection. WSP also continues work on a decision tree to inform the question of whether or not to replace or repair the bridge.
SDOT also is installing additional structural health instrumentation (such as crack-width gauges, strain gauges and high-resolution cameras). This is mostly complete and will allow for a clearer definition of the condition of the bridge, and which path to pursue.
I’ve asked how the rate of crack growth informs the question of whether or not to replace or repair the bridge, and about the critical failure projection.
Road/Traffic Update
SDOT paved and reconfigured the 5-way intersection below the West Seattle Bridge last weekend; average daily traffic on the low bridge is down to 6,480 vehicles per day, approximately the same as the baseline. Here is the most recent traffic data we’ve received, with West Marginal and Idaho, and Highland Park and Marginal showing significantly higher than usual volumes:
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