In Massachusetts, we celebrate Patriots Day on the third Monday in April.  This is a local holiday commemorating the battles of Lexington and Concord from the Revolutionary War.  Traditional ways of celebrating include watching an early afternoon Red Sox game at Fenway Park.   For those places of work not off for the day, vague illnesses seem to strike the office – fortunately nothing too serious, but enough to require an unscheduled day off.

The iconic Patriot’s Day event is the Boston Marathon.  As the Red Sox game winds down, tens of thousands of runners complete the course from Hopkinton, up Heartbreak Hill, passing Fenway Park to the downtown finish line. The Marathon has about everything you can want in a 26 mile long race for both the runners and spectators. 

The only thing missing, I think, is a good bridge somewhere along the route.  Planners for the NY Marathon have addressed this deficiency by closing the Verrazano Bridge and starting the race there. 

Likewise, Charleston South Carolina has a 10K charity race crossing the Cooper River Bridge.  This race has outlasted the original bridges crossing the river.  The course moved to the newly constructed Ravenel Bridge, requiring some readjustments since the new cable-stayed bridge deck is taller than the ones it replaced.

 
Several road races cross bridges.  A nice bridge in the middle of the run is a big lure for charity events.  Another popular 10K race crosses the Ben Franklin Bridge between New Jersey and Pennsylvania.

For most bridges, vehicular traffic and not pedestrians are the governing live load case.  You would think that sizing the bridge for heavy trucks would be sufficiently conservative.  Not that it should matter, but runners and especially marathoners are probably below average in weight for their size. 

But apparently you can fit a lot more people on a bridge than cars.  If the people are strolling instead of running, the density can result in a substantial load.  This is what happened for the 50th anniversary of the Golden Gate Bridge. 

During the celebration walk in 1987, the throngs of appreciative pedestrians were so great that the span’s graceful arch flattened out.  Twenty five years later, planners for the 75th anniversary decided that a celebratory bridge walk was not such a good idea.