BRIDGES by: 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. 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 IDENTIFY and define a problem SOLVE THE PROBLEM SOLVE THE PROBLEM ANALYZE the problem ANALYZE the problem DESIGN and propose solutions DESIGN and propose solutions REFINE their proposals REFINE their proposals

TYPES OF CIVIL ENGINEERS þ STRUCTURAL þ TRANSPORTATION þ GEOTECHNICAL þ ENVIRONMENTAL þ WATER RESOURCES

STRUCTURAL ENGINEERS Who does this?

TRANSPORTATION ENGINEERS Who does this?

ENVIRONMENTAL ENGINEERS ENVIRONMENTAL ENGINEERS Who does this?

GEOTECHNICAL ENGINEERS 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 Chemistry1 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!

KYTC Applications 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 Project Scholarship 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!!!! zBridge Material yTimber yConcrete ySteel

EQUILIBRIUM zLOADS zFORCES zMOMENTS zTORSION Summation of Forces Σ F=0 yHorizontal Direction Σ F h =0 yVertical Direction Σ F v =0

LOADS zDead Loads zLive Loads zWind Loads zSnow Loads

AXIAL LOADS zCompression ypushing or yshortening zTension ypulling or yelongating

FORCESFORCESFORCESFORCES

MOMENTS zSummation of Moments – Σ M=0 zMoment = Force * Distance

TORSION zTorsion is produced when a beam is subjected to loads which cause it to buckle and roll. zDiaphragms are inserted to eliminate torsion.

TORSIONTORSIONTORSIONTORSION

Bridge Experiment zBuild a people bridge to experiment with the forces: compression, tension and torsion yHave pairs of students face each other with palms touching and feet flat and about 0.5 m (1.5 ft) apart. yHave 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 yWhere on the bridge do students feel forces of compression and tension? yHave one person move two steps to the left. What happens to the balance of the bridge? yHow does torsion affect the stability of the bridge? yWhat forces might cause the support structure of a real bridge to rotate?

Arch Bridges Bixby Creek Bridge, Monterey, CA zArch bridges are one of the oldest types of bridges zModern arch bridges span between feet zThe structure is completely unstable until the two spans meet in the middle. zHave great natural strength.

Arch Bridges Bixby Creek Bridge, Monterey, CA zHow it works: yInstead of pushing straight down, the weight is carried outward along the curve of the arch to the supports at each end. yThese supports, called abutments, carry the load and keep the ends of the bridge from spreading yWhen supporting its own weight and the weight of crossing traffic, every part of the arch is under compression.

Beam Bridge zA beam or "girder" bridge is the simplest & most inexpensive bridge. zRarely span more than 250 feet. zIn 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. zWhen 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 zLake Ponchartrain Causeway, Louisiana zThe world's longest bridge is a continuous span beam bridge. zAlmost 24 miles long zConsists of two, two-lane sections that run parallel to one another. yThe Southbound Lane, completed in 1956, is made up of 2243 separate spans, yThe Northbound Lane, completed in 1969, is pieced together from 1500 longer spans.

Suspension Bridge Golden Gate Bridge, San Francisco, CA zAesthetic, light, and strong zCan span 2,000 to 7,000 feet -- longer than any other kind. zAlso tend to be the most expensive. zSuspends 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. yMost of the weight of the bridge is carried by the cables to the anchorages, yAnchorages are imbedded in either solid rock or massive concrete blocks.

Suspension Bridge zthe cables are made of thousands of individual steel wires bound tightly together. zSteel, which is very strong under tension, is an ideal material for cables; zA single steel wire, only 0.1 inch thick, can support over half a ton without breaking. zBecause suspension bridges are light and flexible, wind is always a serious concern

Suspension Bridge Tacoma Narrows - Bridge Oscillation zAt the time it opened for traffic in 1940, the Tacoma Narrows Bridge was the third longest suspension bridge in the world. zNicknamed "Galloping Gertie," due to its behavior in wind. yNot only did the deck sway sideways, but vertical undulations also appeared in quite moderate winds. yDrivers of cars reported that vehicles ahead of them would completely disappear and reappear from view several times as they crossed the bridge. yAttempts were made to stabilize the structure with cables and hydraulic buffers, but they were unsuccessful. yOn 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. zIn 1949 a new bridge was constructed.

Cable Stayed Bridge Clark Bridge, Alton, IL zFor medium length spans (those between 500 and 2,800 feet) zRequire less cable zAre quickly built, resulting in a cost-effective bridge and is beautiful. zCable-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. yThe difference lies in how the cables are connected to the towers. yIn suspension bridges, the cables ride freely across the towers, transmitting the load to the anchorages at either end. yIn cable-stayed bridges, the cables are attached to the towers, which alone bear the load. Parallel attachment pattern Radial attachment pattern

zThe truss is a simple skeletal structure. zindividual members are only subject to tension and compression forces and not bending forces. zTypical Span Lengths are 120 – 1500 feet zTrusses 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. zLike Beam bridges zIdeal bridge for places where large parts or sections cannot be shipped or where large equipment cannot be used. Truss Bridges

zBecause 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

zWarren Truss yThe Warren truss pattern features a series of isoceles or equilateral triangles. In contrast to the Pratt and Howe patterns, the diagonals alternate in direction. yWarren trusses are typically used in spans of between feet yThe 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

zPratt Truss yThe Pratt truss design contains a downward pointing V in the center with parallel diagonals on each side. yExcept 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.

zHowe Truss yThe 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 yIt 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

zWarren Truss zPratt Truss zHowe Truss Build Your Bridge!

Ohio River Bridge Project