Scour: Why Most Bridges Fail

Yesterday the I-5 bridge spanning the Skagit River in Washington had one of its support girders hit by a truck too wide, and the whole scene of contorting metal fell into the water below. Though a number of people and their cars went into the water along with the bridge, thankfully no one was killed. The collapse of the I-5 bridge has sparked a conversation about the failing infrastructure system of the US, but failures due to girders unable to take a truck impact are hardly a common occurrence. In fact, the most dangerous thing to a bridge is that which it typically takes us over.