BRIDGESBRIDGESby: Tom Wright, P.E.

and Jennifer Hall, P.E.

Engineers are problem solvers.

→Use available technology to solve

→Rely on creativity and academic skills

→Use math, science, and computers It is very important to note that even though the tasks are very different, many of the methods used are common to all engineers.

THE ENGINEERING PROCESS:IDENTIFY and

define a problem

SOLVE THE

PROBLEMANALYZE

the problem

DESIGN and propose solutions

REFINE their proposals

TYPES OF CIVIL ENGINEERS STRUCTURAL TRANSPORTATION GEOTECHNICAL ENVIRONMENTAL WATER RESOURCES

STRUCTURAL ENGINEERS

Who does this?

TRANSPORTATION ENGINEERS

Who does this?

ENVIRONMENTAL

ENGINEERS

Who does this?

GEOTECHNICAL

ENGINEERS

Who does this?

WATER RESOURCE ENGINEERS

Who does this?

How to become an engineer!

• Education is the key:

• High School Courses

• College Courses

How to become an engineer!

UL, UK, and Western are good schools. You can think BIG. If you want to go to a nationally ranked engineering school, start planning NOW. Find out which school is right for you

Which has a strong program in the field you are interested in? How do you stack up against the admission criteria? How does location and cost of the school factor into the equation?

How to become an engineer!• U of L’s Requirements:

• 23 ACT comp. score (1060 comp. SAT)

• 23 ACT math (530 SAT math)

• 3.0 HS GPA

• High School Education:• 4 Yr English 1 Geometry

• 2 Yr Algebra 1 Advanced Math

• 1 Chemistry 1 Physics

How to become an engineer!

Suggested High School Education: Additional Chemistry

Computer Class

Graphic Class

Tips:Take as much math and science as possible

Take ACT and SAT in your junior year

Consider Co-Op Schools

Look for scholarships

How to become an engineer!

KYTCApplications accepted for UK, Western, Ky State, and UL

Summer Job and stipend while in school

Check out state website: personnel.ky.gov

Louisville River Bridges ProjectScholarship program

Maurice Sweeney

Scholarships!

College Tips:Make connections

Use campus resources

Study Schedule

Don’t Overextend yourself

Meet the faculty

Get involved in activities

How to become an engineer!

BRIDGES!!!!BRIDGES!!!!Bridge Material

Timber Concrete Steel

EQUILIBRIUMEQUILIBRIUMLOADSFORCESMOMENTSTORSION

Summation of Forces Σ F=0

Horizontal Direction Σ Fh=0

Vertical Direction Σ Fv=0

LOADSLOADSDead LoadsLive LoadsWind LoadsSnow Loads

AXIAL LOADSAXIAL LOADSCompression

pushing or shortening

Tension pulling or elongating

FFOORRCCEESS

MOMENTSMOMENTSSummation of Moments – Σ M=0

Moment = Force * Distance

TORSIONTORSIONTorsion is produced when a beam is subjected to loads which cause it to buckle and roll.

Diaphragms are inserted to eliminate torsion.

TTOORRSSIIOONN

Bridge Experiment

Build a people bridge to experiment with the forces: compression, tension and torsion Have pairs of students face each other with

palms touching and feet flat and about 0.5 m (1.5 ft) apart.

Have students slowly move their feet back while keeping their palms touching until the bridge feels balanced and they cannot back up any further without falling over.

Bridge Experiment

Where on the bridge do students feel forces of compression and tension?

Have one person move two steps to the left. What happens to the balance of the bridge?

How does torsion affect the stability of the bridge?

What forces might cause the support structure of a real bridge to rotate?

Arch Bridges Bixby Creek Bridge, Monterey, CA

Arch bridges are one of the oldest types of bridges

Modern arch bridges span between 200-800 feet

The structure is completely unstable until the two spans meet in the middle.

Have great natural strength.

Arch BridgesBixby Creek Bridge, Monterey, CA

How it works: Instead of pushing straight

down, the weight is carried outward along the curve of the arch to the supports at each end.

These supports, called abutments, carry the load and keep the ends of the bridge from spreading

When supporting its own weight and the weight of crossing traffic, every part of the arch is under compression.

Beam BridgeA beam or "girder" bridge is

the simplest & most inexpensive bridge.

Rarely span more than 250 feet. In its most basic form, a beam bridge consists of

a horizontal beam that is supported at each end by piers. The weight of the beam pushes straight down on the piers.

When a load pushes down on the beam, the beam's top edge is pushed together (compression) while the bottom edge is stretched (tension).

Beam Bridge

Lake Ponchartrain Causeway, Louisiana The world's longest bridge is a continuous

span beam bridge. Almost 24 miles longConsists of two, two-lane sections that run

parallel to one another. The Southbound Lane, completed in 1956, is

made up of 2243 separate spans, The Northbound Lane, completed in 1969, is

pieced together from 1500 longer spans.

Suspension Bridge Golden Gate Bridge, San Francisco, CA Aesthetic, light, and strongCan span 2,000 to 7,000 feet

-- longer than any other kind. Also tend to be the most expensive. Suspends the roadway from huge main

cables, which extend from one end of the bridge to the other. These cables rest on top of high towers and are secured at each end by anchorages. Most of the weight of the bridge is carried by the cables to

the anchorages, Anchorages are imbedded in either solid rock or massive

concrete blocks.

Suspension Bridgethe cables are made of thousands of

individual steel wires bound tightly together.

Steel, which is very strong under tension, is an ideal material for cables;

A single steel wire, only 0.1 inch thick, can support over half a ton without breaking.

Because suspension bridges are light and flexible, wind is always a serious concern

Suspension BridgeTacoma Narrows - Bridge Oscillation

At the time it opened for traffic in 1940, the Tacoma Narrows Bridge was the third longest suspension bridge in the world.

Nicknamed "Galloping Gertie," due to its behavior in wind. Not only did the deck sway sideways, but vertical undulations also

appeared in quite moderate winds. Drivers of cars reported that vehicles ahead of them would

completely disappear and reappear from view several times as they crossed the bridge.

Attempts were made to stabilize the structure with cables and hydraulic buffers, but they were unsuccessful.

On November 7, 1940, only four months after it opened, the Tacoma Narrows Bridge collapsed in a wind of 42 mph -- even though the structure was designed to withstand winds of up to 120 mph.

In 1949 a new bridge was constructed.

Cable Stayed Bridge Clark Bridge, Alton, IL

For medium length spans (those between 500 and 2,800 feet) Require less cable Are quickly built, resulting in a cost-effective bridge and is

beautiful. Cable-stayed bridges may look similar to suspensions bridges—

both have roadways that hang from cables and both have towers. But the two bridges support the load of the roadway in very different ways. The difference lies in how the cables are connected to the towers. In suspension bridges, the cables ride freely across the towers, transmitting

the load to the anchorages at either end. In cable-stayed bridges, the cables are attached to the towers, which alone

bear the load.Parallel attachment pattern Radial attachment pattern

The truss is a simple skeletal structure. individual members are only subject to tension

and compression forces and not bending forces. Typical Span Lengths are 120 – 1500 feet

Trusses are comprised of many small beams that together can support a large amount of weight and span great distances. The design, fabrication, and erection of trusses is relatively simple.

Like Beam bridges Ideal bridge for places where large parts or

sections cannot be shipped or where large equipment cannot be used.

Truss Bridges

Because the truss is a hollow skeletal structure, the roadway may pass over or even through the structure allowing for clearance below the bridge often not possible with other bridge types

Truss Bridges

Warren Truss The Warren truss pattern features a series of isoceles

or equilateral triangles. In contrast to the Pratt and Howe patterns, the diagonals alternate in direction.

Warren trusses are typically used in spans of between 150-300 feet

The most common truss. For smaller spans, no vertical members are used lending the structure a simple look. For longer spans vertical members are added providing extra strength

Truss Bridges

Truss BridgesPratt Truss

The Pratt truss design contains a downward pointing V in the center with parallel diagonals on each side.

Except for those diagonal members near the center, all the diagonal members are subject to tension forces only while the shorter vertical members handle the compressive forces. This allows for thinner diagonal members resulting in a more economic design.

Howe Truss The Howe truss pattern features an upward

pointing V formed by the central diagonals with parallel diagonals on either side. Unlike the Pratt pattern the diagonals will be in compression when loaded

It is the opposite of the Pratt truss. The diagonal members face in the opposite direction and handle compressive forces. This makes it very uneconomic design for steel bridges and is rarely used.

Truss Bridges

Warren Truss

Pratt Truss

Howe Truss

Build Your Bridge!

Ohio River Bridge Project

Ohio River Bridge Project

Ohio River Bridge Project