BRIDGE EXPLORATIONSWhat 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 – EnglandCirca 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.1882-1889Scotland

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 Specifications10” 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