1. Beam bridge Truss bridge Arch bridge Suspension bridge
Bridge Design
Beam bridge
Truss bridge
Arch bridge
Suspension bridge
Mr. Klokman
Computer / Technology
King Philip Middle School

2. Beam bridge beam supported at each end by piers.
This is why beam bridges rarely span more than 250 feet.
Pros: Easy to build; inexpensive relative
to other bridge types; used widely
in urban and rural settings
Cons: Limited span; does not allow
large ships or heavy boat traffic to pass
underneath; design generally not considered very interesting or eye-catching

3. Beam bridge
Live Load
Compression: the tendency to push or squash a material
Dead Load
Tension: the tendency for a material to be pulled apart
Beam Bridge: Forces When something pushes down on the beam, the beam bends.
Its top edge is pushed together, and its bottom edge is pulled apart.
BRIDGE BRAG
It’s the loooooooonnnnnnngest bridge in the world, and it’s a beam bridge!
The Lake Pontchartrain Causeway in Louisiana is approximately
24 miles long, and its twin spans are supported by over 9,000 pilings.

4. Truss bridge
The truss bridge... consists of an assembly of triangles. Truss bridges are
commonly made from a series of straight, steel bars.
Rigid arms extend from both sides of two piers. Diagonal steel tubes, projecting from the top and bottom of each pier, hold the arms in place. The arms that project toward the middle are only supported on one side, like really strong diving boards. These "diving boards," called cantilever arms, support a third, central span.

5. Truss Bridge Tension: the tendency for a material to be pulled apart
Compression: the tendency to push or squash a material
Truss Bridge: Forces Every bar in this cantilever bridge experiences either a pushing or pulling force.
The bars rarely bend.
This is why cantilever bridges can span farther than beam bridges.
Pros: Very strong; frequently used as a draw bridge
Cons: Difficult to construct; high maintenance; difficult to widen if necessary; generally not considered attractive
Wooden truss bridges were used as early as the 1700s, but the first metal one was completed in They are very strong and have been used for railroad bridges mainly because of the heavy loads they can support. A truss, a rigid support structure that is made up of interlocking triangles, holds up the roadbed and is set between two piers. The triangle is used because it is the only shape that is inherently rigid.

6. Arch bridge Live Load: would be the water
Dead Load: would be the stone
The arch bridge... has great natural strength. Thousands of years ago, Romans built arches out of stone.
Today, most arch bridges are made of steel or concrete,
and they can span up to 800 feet.

7. Arch bridge
Arch Bridge: Forces The arch is squeezed together, and this squeezing force is carried outward along the
curve to the supports at each end. The supports, called abutments, push back on the
arch and prevent the ends of the arch from spreading apart.
Pros: Wide range of materials can be used; considered attractive; very strong
Cons: Relatively expensive; typically designs are limited to certain sites (for example, where the ground can support
the large forces at the base of the arch; where the span-to-depth ratio of the arch is proportional; or where an arch is visually appropriate)

8. How are arch bridges built
How are arch bridges built? Building an arch bridge isn't easy, since the structure is completely unstable until the
two spans meet in the middle. For years, engineers used a technique called centering,
in which a wooden form supported both spans until they locked together at the top.
A newer method supports the spans using cables anchored to the ground on either
side of the bridge. This is how the New River Gorge Bridge in West Virginia was built.

9. Suspension bridge
The suspension bridge... can span 2,000 to 7,000 feet -- way farther than any other type of bridge!
Most suspension bridges have a truss system beneath the roadway to
resist bending and twisting.

10. Suspension Bridge Torsion: twisting material
Tension: the tendency for a material to be pulled apart
Suspension Bridge: Forces In all suspension bridges, the roadway hangs from massive steel cables, which
are draped over two towers and secured into solid concrete blocks, called
anchorages, on both ends of the bridge. The cars push down on the roadway,
but because the roadway is suspended, the cables transferthe load into
compression in the two towers. The two towers support most of the
bridge's weight.

12. Beam bridge
Truss bridge
250 feet
Longest Single Span: 350 feet (center span)
Arch Bridge
Suspension Bridge
800 feet
2,000 to 7,000 feet

13. Structures
Girders
Braces
Columns
Beams