Designed for Forces
Form, Function, and Fashion
Arch Frame Bridges
• Weight and forces
are spread over the
entire arch.
• Date back to Roman
• Good for making
over rivers.
Cable Stayed Bridge
• Cables and
Columns work
together to support
the weight and
• Cables become very
tight when bridge is
Girder Bridge
• Columns take the
weight and stress
from the forces on
the bridge.
• Disadvantage: Many
columns must be
Rigid Frame Bridge
• Strong bridge
• Supports Weight
and Forces well
• Disadvantage:
Costly because it
takes lots of
material to build.
Suspension Bridge
• Cable and
Columns work
together to
support forces on
• Few columns
needed because of
the cables.
Truss Bridge
• Stick like framing
provides support for
weight and forces
on the bridge.
• Lower cost than
other bridges but
less decorative.
Toothpick Bridges
Your Challenge
• Build a 300-400 toothpick bridge out of standard, doublepointed toothpicks.
• Use only white glue. No wood glue, Gorilla glue, or
crazy/super glue.
• Time will be about 1 week.
• The bridge must be more than 20 cm long, but not longer
than 25 cm
• Bridge must have four sides
• Height: at least one toothpick tall
• Width: at least one toothpick wide
• You must draw a preliminary drawing of your bridge
before you start work on the bridge.
Steps of Construction
• Line toothpicks to
make the length of
the bridge.
• Note: ends of
toothpicks are
• Bundles of 3
toothpicks are
Providing Truss Supports
• Framing of bridge
should be done
using triangles.
• Triangles provide
for excellent
support when forces
are applied.
Footing of the Bridge
• Note the use of
angled supports.
• Again the
triangular design
distributes the
forces over a
greater area.