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 Bridges
Cantilever is a beam supported at only one end.
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=kuW
HIAOxcLA&feature=PlayList&p=B7C0C
5CE439D8D7C&playnext=1&playnext_f
rom=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