beam bridges - Edublogs

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26 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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BRIDGES

History and Development

Purpose of Bridges


Used to follow favorite paths


Crossing streams


Early Bridge Materials

These led to a
“clapper
bridge”. This
was someone
using stepping
stones,
another
person
placing logs
on top.


A fallen tree


Early bridges were created by materials easily
handled


Forests tendrils and twine/vines


Stepping
-
stone path across shallow stream


Stone, brick, and clay



http://www.ask.com/wiki/East_Dart

Roman Bridges 1
-
2 AD


Two important
contributions


Used arch design (a
structure that can
support more weight that
a flat surface)


Discovery of natural
cement


Made bridges stronger


Long
-
standing





http://theconstructor.org/structures/history
-
of
-
bridges/5491/

Asian Bridge Contributions


The Great Stone Bridge
was built about 1300
years ago.


Used a cantilever
design


Simple


Long
-
spanning



© Christopher Liu/ChinaStock Photo Library

Timber Cantilever bridge design

http://mytechnologyworld9.blogspot.com/2009/04/worlds
-
35
-
most
-
notable
-
bridges.html

The Renaissance

Leonardo
da

Vinci and Galileo developed
theories about strength of building materials
which helped architects understand how to
make strong structures from lightweight
materials.

Metal Development


200 years ago the first cast
-
iron bridge was built it
was the Iron Bridge at
Coalbrookdale

in England

http://www.dailymail.co.uk/news/article
-
1041617/Incredible
-
bulk
-
pumps
-
iron.html

Steel Development


Many new bridge designs were created and tested.


The Britannia Tubular Bridge, completed 1850


First used rectangular tubes


Used wrought iron

http://www.gorge.org/images/bridges/

Old design, but improved by engineers who knew enough about math and science

Truss bridge

http://www.trussbridges.org/tag/truss
-
bridges/

More metal was added to the truss bridges which led to the design of suspension
bridges. The Brooklyn Bridge is one of the famous bridges built during that time.

Suspension Bridge

Brooklyn Bridge (photo by Seemann, courtesy of morguefile.com)

In recent times, (last 100 years)


Engineers began using concrete for bridges.


A new method called “
prestressing
” prevents concrete
from cracking


Most new bridges today are made from
prestressed

concrete and steel.

http://www.nrc
-
cnrc.gc.ca/eng/projects/irc/galvanic
-
cathodic.html

Basic Types of Bridges


1. Beam


A. flat across


B. Supported at two ends if short


C. Supported by additional piers in middle if long


D. Weight evenly distributed along surface

Types

of
Beam

Bridges

Types of Beam Bridges


1. Clapper Bridge


2. Floating pontoon
bridge


3. Truss Bridge


4. Cantilever Bridge

http://www.globalarchitectsguide.com/library/Beam
-
bridge.php

Basic Types of Bridges (cont’d)


2. Arch


A. Arching across


B. Main weight at end supports



http://visual.merriam
-
webster.com/transport
-
machinery/road
-
transport.php

Basic Types of Bridges (cont’d)


3. Suspension

http://www.kollewin.com/blog/bridge
-
structures/

Deciding on bridge design


1. Length of bridge


2. Purpose of bridge


3. How strong is the riverbed earth below


4. Effect of bridge supports for needed job


5. Effects of weather on it


Bridge Engineer’s Goal


To design the strongest,
safest, most long
-
lasting,
and economical bridge
possible.

The physics of it

How Bridges Work

The beam bridge….



consists of a horizontal
beam

supported at
each end by
piers
. The
weight of the beam
pushes straight down on
the piers. The farther
apart its piers, the
weaker the beam
becomes. This is why
beam bridges rarely
span

more than 250
feet.

http://www.brighthub.com/engineering/civil/articles/65074.aspx?image=167894

Beam bridge continues


Forces

When something
pushes down on the
beam
, the beam
bends
. Its top edge is
pushed together, and
its bottom edge is
pulled apart.

http://www.pbs.org/wgbh/buildingbig/bridge/beam_forces.html

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
.

http://www.pbs.org/wgbh/buildingbig/bridge/truss_forces.html

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.

http://www.pbs.org/wgbh/buildingbig/bridge/arch_forces.html

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 transfer the
load

into
compression

in the two towers.
The two towers support most
of the bridge's weight.

http://www.pbs.org/wgbh/buildingbig/bridge/susp_forces.html

http://www.pbs.org/wgbh/buildingbig/bridge/challenge/indexp.html?1


http://
www.pbs.org/wgbh/buildingbig/bridge/webography.html


Website practice & information

Building Bridges Project

Construction Companies


There will be groups
of 4
-
5 students.


Each student will have
a specific job to
perform.


There is no trading
jobs once they have
been decided.


Once in your groups:


Decide on company
name and logo


Decide who is going to
complete what job.


Complete the schedule
worksheets.

Project Director


Keeps schedule


Makes sure all company members do their jobs


Keeps daily journal


Document company’s progress


Record any problems & solutions


Signs and approves building plans, checks, and
order forms


Project Director continued


Makes sure construction sight is neat and organized


Cleans up site and stores bridge each day


Cleans out and keeps glue container each day


Keeps manila envelope with all company records
(files it at end of class)


DOES NOT build, draw plans, do accounting, or
perform any duties listed for other company
members.


Accountants


Responsible for the:


Balance sheets


Checks


Helps carpenter build
bridge

Architects


Duties include:


Adhering to the bridge building code


Draw rough drafts on scratch paper first


Use the graph paper to draw exact size of:


Side view


End view


Road bed


Top view of the bridge

Architects continued


Estimate the number of toothpicks to order before
bridge is built


Keep up
-
to
-
date inventories during construction


Order building
-
plans paper from warehouse


Bridge plans are due on day 4

Carpenter


Builds bridge according to architect’s plans


Consults with architect during building process


Supervises company members that help with
building


Uses wax paper on top of graph paper to keep
original plans clean


Transportation Chief


Helps carpenter build the bridge


Delivers checks


Picks up supplies from warehouse (the only one
allowed to due business with the warehouse)


Does not write checks or performs any duties listed
for other company members



*If a 4 person group, this will be done by the
carpenter.

http://www.pbs.org/wgbh/buildingbig/bridge/index.html

http://theconstructor.org/structures/history
-
of
-
bridges/5491
/

http://
mytechnologyworld9.blogspot.com/2009/04/worlds
-
35
-
most
-
notable
-
bridges.html




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