National Steel Bridge Alliance

Span to Weight Curves

The Steel Span to Weight Curves are the quickest way to determine the weight of steel per square foot of bridge deck for straight, low skew, plate girder bridges.  The Curves are organized by span arrangement (1, 2 or 3 or more span bridges) and girder spacings.

To use the graphs first determine the bridge span arrangement, then, utilizing the maximum span, find that value along the "x"-axis.  Draw a line straight up until reaching the curve.  Follow that line over to the "y"-axis to find the steel weight per square foot of bridge deck.

The curves are great for comparing various span arrangements and girder spacings.  With some additional information the weight per square foot can easily be converted to a potential dollar value for the steel superstructure.  The curves are based upon over 800 preliminary designs the NSBA has done through the years. In each instance the design was optimized for economics and is based upon standard AASHTO loading.


Download the Span to Weight Curves