Treadway Bridge


STEEL TREADWAY BRIDGE from  Simbach, Germany, to Braunau, Austria, replaces the one destroyed by retreating Germans, May  1945. The United States Army in World War II-The Technical Services- Engineers- Volume 1

One of the things that had the Engineers pulling their hair out in the war was the ever increasing weights of military vehicles.  In 1938, a 12 ton capacity was considered sufficient for bridging equipment at the division and corps level. By 1943, the Engineers faced the need for bridges to bear weights of 35 tons or more.

Take a look at the treadway bridge. How would you increase its capacity? The simple answer is to make each float bigger, and thus more buoyant. That’s what the Engineers did. That worked from the capacity point of view, but imposed two penalties. First, the larger floats were more difficult to transport to the crossing site, requiring more and larger trucks in the divisional and corps trains.

Secondly, and from the Corps of Engineers point of view, worse,  every required increase in capacity meant that previous equipment was obsolete, and production had to be shifted to new equipment. The iron law of mass mobilization calls for freezing a design as early as possible. Having to constantly switch designs slowed the accumulation of stockpiles of bridging equipment, and meant that bridging companies rarely had sufficient stocks on hand for realistic training before deploying overseas.

Further, in the early years of the war, there were a plethora of bridge types available. Each needed its own special skills for emplacement. While the total number of bridge designs authorized didn’t really decline, by the end of the war, as a practical matter, most bridging was done with either the steel treadway bridge shown, or semi-fixed Bailey bridges adopted from Great Britain.

3 thoughts on “Treadway Bridge”

  1. You have to do things, increase the size of the float to increase buoyancy, and you have to increase the size of the spans bridging the floats. It’s a double hit. There are tricks to fool mother nature with the spanning units, to a point, but the floats have to get bigger.

    You can see what I mean with the spanning units by considering a plank. If you lay it flat with the wide part horizontal, it will bend more under a given load, then if the load is applied with the wide dimension vertical. That trick is played with steel beams, but to increase the moment capacity of the beam, you have to get more of its mass away from the centroid of the shape. Since they already play that trick, it means you will have to increase the amount of steel to make it work for larger loads, to prevent such things as web crippling, which is a form of failure similar to Euler buckling in a column.

  2. The M2 treadway bridge was probably the best assault bridge of its era but it did have stability problems and inevitably, as you increase the float size you increase drag.

    Great post, fantastic to see posts on subjects other than the fast expensive shooty stuff!

    Covered pontoons and bailey bridges in the links below

Comments are closed.