Bridge Lecture Spring 2011x - Idaho State University

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Oct 29, 2013 (3 years and 11 months ago)

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Idaho State
University

ENGR 1120

BRIDGE STRUCTURES


Arya Ebrahimpour (Dr. E), Ph.D., P.E.

Professor and Chair

Department of Civil & Environmental Engineering

Whitebird Bridge, Idaho

Bridge Uses and Types


Bridges are designed for trains, pedestrians, road
traffic, pipelines or waterways for water transport.
An aqueduct is a bridge that carries water,
resembling a viaduct (a long bridge).


Types of bridges:


Beam or girder


Truss


Arch


Cantilever


Suspension


Cable
-
stayed

2

The I. B. Perrine Bridge at Twin Falls, Idaho

Beam or Girder Bridges


Beam or girder bridges are horizontal beams supported at
each end by piers. The earliest beam bridges were simple
logs that sat across streams and similar simple structures.


In modern times, beam bridges are large steel girder or
reinforced concrete box girder bridges.

3

I
-
5 & State HW14 Interchange
following the 1994 Northridge
Earthquake (
Photo
: USGS
).

A log bridge

A plate girder bridge (top) and a concrete
girder bridge (bottom)

Forces on a Beam Bridge

4

Source: Building Big: Bridges From PBS http://www.pbs.org/wgbh/buildingbig/bridge/index.html

Truss Bridges


Composed of connected elements. They have a deck and a
lattice of pin
-
jointed (or gusset
-
joined) girders for the sides.


Assumptions: Members are pin
-
connected and are in
tension or compression.


Early truss bridges were made of wood, and later of wood
with iron tensile rods. Modern truss bridges are made
mostly with metals.

5

Continuous under
-
deck truss bridge

A single track railway bridge converted to pedestrian use and pipeline

Forces on a Truss Bridge

6

Source: Building Big: Bridges From PBS
http://www.pbs.org/wgbh/buildingbig/bridge/
index.html

Elements of a simple truss bridge

Arch Bridges


An arch bridge is a bridge with abutments at each end
shaped as a curved arch.


The weight of the bridge is thrust into the abutments at
either side.


A viaduct (a long bridge) may be made from a series of
arches, although other more economical structures are
typically used today.

7

The Alcántara Bridge, Spain (built103
-
106 AD)

Double arch stone bridge, Japan

Arch Bridge Forces

8

Source: Building Big: Bridges From PBS http://www.pbs.org/wgbh/buildingbig/bridge/index.html

Cantilever Bridges


A cantilever bridge is a bridge built using cantilevers,
structures that project horizontally into space, supported on
only one end.


Small footbridges: the cantilevers may be simple beams.


Large cantilever bridges: designed to handle road or rail
traffic use trusses built from structural steel, or box girders
built from prestressed concrete.

9

Prestressed Concrete cantilever bridge

Forth Bridge, Scotland, 1890

Parts of a suspended
-
span cantilever truss bridge

Suspension Bridge


A type of bridge in which the deck is hung below suspension
cables on vertical suspenders. Modern bridges of this type
date from the early 19th century.


The longest suspension bridge is the 3,900

m (12,800

ft)
Akashi Kaikyo Bridge in Japan with the longest span of
1,990 m (6,500

ft).

10

A simple suspension footbridge

Golden Gate Bridge , 1937. Total length 8,981

ft
(2,737

m), longest span 4,200

ft (1,280

m)

Suspender cables

Suspension Bridges

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Source: Building Big: Bridges From PBS http://www.pbs.org/wgbh/buildingbig/bridge/index.html

Cable
-
stayed Bridges


A cable
-
stayed bridge is a bridge that consists of one
or more columns (normally referred to as towers or
pylons), with cables supporting the bridge deck.


Optimal for spans longer than cantilever bridges and
shorter than suspension bridges.

12

Sunshine Skyway Bridge, Florida, 1987

5.5

miles (8.9

km), longest span 1,200

feet (366

m)


Millau Viaduct in
France, 2004

Total length 2,460

m (8,071

ft), longest span 342

m
(1,122

ft)

West Point Bridge Designer


Web site
:
http://bridgecontest.usma.edu/download2010.htm

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These members will fail and have to
be increased in size

Diameters increased from
160 mm to 180 mm.

West Point Bridge Designer

14

Bridge with initial member
sizes

Bridge after increasing
sizes of the three members

shown on previous page

Johns Hopkins Bridge Designer


Web site: http://www.jhu.edu/virtlab/bridge/truss.htm

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Johns Hopkins Bridge Designer

16

Notice what happens to the member forces
on the right truss, when the height of the
bridge is decreased from 4 units to 2 units.

Some Sources


Building Big: Bridges From PBS
http://www.pbs.org/wgbh/buildingbig/bridge/index.html


ABCD's Bridge Design
http://abcdpittsburgh.org/kids/kids.htm


Balsa Bridge Building Contest

http://www.balsabridge.com/



17

The I. B. Perrine Bridge at Twin Falls, Idaho

Structures Classes in CE Program


General Education (including Physics and Chem.)


Additional Math


Engineering Core Courses (basic mechanics, etc.)


Civil Engineering Courses


Structural Analysis, Steel and/or Concrete Structures, and lab


Basic Geotechnics, Geotechnical Design, and lab


Surveying, Transportation Engineering


Fluids, Hydrology, and Hydraulic Design


Water and Waste Water Quality and Intro. to Environmental Engineering


Technical Electives and Senior Design (one year)


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Will take the structures
sequence after Statics and
Mechanics of Materials

Tech. Electives in Structures:

Wood Structures, Prestressed
Concrete, Composite Materials,
and Advanced Mechanics of
Solids

Research in Structural Engineering


Research Interests


Earthquake Engineering and Structural Vibrations


Advanced Composite Materials


Opportunities in Undergraduate Research

Collapse of the parking structure, Cal State
University
-
Northridge campus
(Photo:
USGS
).

I
-
5 & State HW14
Interchange (
Photo: USGS
).

Computer model of a 4
-
span bridge on three shake tables.

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ASCE Student Bridge Team


ASCE Student Chapter


Steel Bridge Design (computer modeling
and hands
-
on)


Pacific Northwest Competitions: ISU, Boise
State, UI, WSU, etc.


National Society of Professional
Engineers (NSPE)

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2002 ASCE Steel Bridge Competitions Held at
the University of Idaho

2010 PNW ASCE Conference


Excellent performance by students at the 2010
ASCE Pacific Northwest Student Conference


Among 19 engineering schools: 2nd place in
Steel Bridge Competition; 1st place in
Environmental Design Competition; and 1st
place in Surveying Competition.


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