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A d v a n c e d S t r u c t u r e s S e t
C o m m o n T r u s s B r i d g e s
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Common Truss Bridges
Warren Bridge
The Warren Bridge (Figure 17) is a simple type of bridge consisting of a series of triangles. However, a simple
Warren Bridge is not practical for supporting a deck (road bed). Vertical members can be added to support the
deck. Additional verticals can support an upper deck.
To make a free-standing bridge, begin by laying out one side of the bridge on a table. Then build the other side of
the bridge. Join the two sides of the bridge attaching the floor beams and the top cross beams. Use additional
members as piers to support the bridge. (Figure 18).
Different Scales
It is possible to build bridges of two different
scales. Figure 19 shows a Warren with Verticals
built to two different scales.
In spanning a particular distance, why wouldn’t
you use the smaller scale bridge and add more
panels? An examination of the forces in the mem-
bers of each size bridge will give the answer. If
the smaller and larger bridges have the same num-
ber of panels and experience the same load, the
forces in any member of the smaller bridge is the
same as the same member in the larger bridge.
Each additional panel is submitted to larger
forces. This can be explored using load cells. See
the section on
Measurement of Static and
Dynamic Loads
Figures 20 and 21 show different bridges. Investi-
gate how the forces in these bridges differ from
the Warren.
Figure 18: Free-standing
Warren bridge
Figure 17: (Top) Warren bridge (Middle) Warren
with deck verticals (Bottom) Warren with verticals
#4
#5
#3
#3
#3
#4
#3
#3
#4
#5
Figure 20: (Top) Pratt. (Bottom) Howe
Figure 19: Smaller and larger scale Warren with verticals
#3
#4
#5
#3
Figure 21: Free-standing Howe