The First Bridge

To engineers, the Tacoma Narrows were more of an economic challenge than an technological challenge. A bridge here would cut at least 40 miles off the trip between Tacoma and Bremerton. But traffic estimates were low. In 1932, the federal government refused to give financial support for a bridge for that reason. It took major lobbying to get the money. Even then, though, it was only $3 million. So the state scrapped its first design - $11 million - and turned to Leon Moisseiff. Moisseiff, a well-regarded designer and researcher, calculated that a considerably lighter deck -stiffened only by a thin plate girder, not a deep truss - would do, thus cutting the cost to only $6.4 million. Everyone knows what happened: less than a year into its life, the bridge began to twist violently in a 40 mph wind, and soon collapsed. The disaster - which took no human lives - shocked the engineering community and did a lot to shape American bridge building. The bridge was replaced with a very conservative design in 1950.

 

 

  • built: 1940
  • carries SR 16 across the Tacoma Narrows
  • engineers: Leon Moisseiff
  • total length 1.4 mi.
  • types (maximum span): suspension (plate girder deck) (2800 ft.)
  • visuals available:

 

 

 

 

 

crosses:

Tacoma Narrows


overall length:

5000 ft.

# of spans:

3

maximum span:

2800 ft.

# of maximum spans:

1


tower height:

425 ft.

clearance:

 


type:

suspension (plate girder deck)

structural material:

steel

tower material:

steel

deck material:

 

pier material:

 

foundation type:

 


carries:

2 highway lanes, sidewalk