BRIDGES
BRIDGE EXPLORATIONS
What makes bridges stay up
What makes bridges fall down
Different types of bridges
You will design and construct a bridge
You will test your bridge’s load capacity

Beam Bridges

The Tarr Steps – England
Circa 1000 B.C.
KOCHER VIADUCT, AUTOBAHN, GERMANY
185 m HIGH, 1128 m LONG
Top of beam is in compression and bottom is in tension.
The middle of the beam is neutral – the middle is in neither compression or tension.
Making a beam stiffer:
I Beams move most of the beams material away from the neutral axis which is underutilized.
This results in a stiffer beam.
Arch Bridges
PONT DU GARD, FRANCE, 63 BC-13 BC 47.4 m HIGH
Arches are made of wedge-shaped stones in compression. Without the keystone the two sides of the arch will fail.

The wedged stones at the bottom must be prevented from moving outwards using abutments (stones anchored into the soil).
MOSTAR BRIDGE, YUGOSLAVIA 1566-1567
27.3 m SPAN, 19 m HIGH
Cabin John Bridge, Washington D.C.
RHINE RIVER, BONN- BUEL, 1948
FRANCIS SCOTT KEY BRIDGE, WASHINGTON, DC
HEILBRONN, AUT0BAHN, GERMANY
Truss Bridges

A truss is a hinged triangle
TENMON BRIDGE, KUMAMOTO PREFECTURE, JAPAN
SPAN 100 + 300 +100 m 42 m CLEARANCE, 1966
Why are trusses so common?

The members are in either experiencing compression or tension; the members are not bending.

Trusses can be arranged into many shapes.
Truss Bridge with a moveable center section.
Cabin John Bridge, under construction
using timber false work
Cantilever Truss Bridge
Cantilever is a beam supported at only one end.
Cantilever Bridges
The Forth Rail Bridge – c.1882-1889
Scotland

One the worlds most massive bridges.
Suspension Bridges
Akashi-Kaikyo Bridge 3911 m
http://www.youtube.com/watch?v=kuWHIAOxcLA&feature=PlayList&p=B7C0C5CE439D8D7C&playnext=1&playnext_from=PL&index=11
Cable is made by running spools of smaller cable back and forth across the towers. This is called spinning the cable.
Cable Stay Bridges
Kaohsiung County, Taiwan
Øresund Bridge between Denmark and Sweden
Relatively inexpensive to construct – no large cables need to be spun over towers. Able to span large distances.
What kind of Bridges?
MARACAIBO BRIDGE, VENEZUELA, 1957
FEHMARNSUND BRIDGE, 248 m SPAN
Combination arch and beam.
GANTER BRIDGE DESIGNED BY CHR. MENN
Engineering Design Process
Problem Statement
Problem Analysis
Design Specifications
Brainstorming / Idea generation
Idea Selection
Implementation

Problem Statement
What is the maximum load a short paper bridge can carry?

Problem Analysis
How will structure carry loads?

How is failure likely to occur?

What can be done to prevent failure?

Design Specifications

10” minimum span

1” max. bearing at abutment

Tape is connector only.

Bridge cannot be taped to the abutment.

Materials: Three 2”X12” strips (cut from heavy poster paper)

Idea Generation & Selection

Brainstorming

Minimize judgment

Combine ideas

Select final idea based on best fit for Design Specifications


Implementation

Construct bridge

Test bridge

Review and evaluate design