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Building Our Bridge to Fun!

Explore the world of bridges through hands-on activities building two types of bridges with different materials and measuring deflection using LEGO sensors. Learn about the forces, materials, and history of bridges while engaging in a creative engineering project.

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Building Our Bridge to Fun!

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  1. Building Our Bridge to Fun! Civil Engineering in the Classroom

  2. Main Goals of this Activity • Learn about how bridges are used and why we need them • Identify forces acting on a bridge • Hands-on activity: build two type of bridges (with two type of materials) • Measure deflection of a span using LEGO ultrasonic sensor • Gather data (load vs. deflection)

  3. Introduction What is a bridge? Why do we need build bridges? Water supply Traffic Crossing rivers or water bodies

  4. Engineering for bridges Construction Materials: • Concrete • Steel • Wood • Stone • Brick Bridges are structures to provide passage over water, roadways, and more!

  5. Engineering for bridges: History • Primitive People: • Logs • Slabs of Rocks • Intertwined Vines or Ropes • Roman Empire—First Great Bridge Builders • Timber Truss Bridges • Masonry Arch Bridges • Nineteenth Century • Modern Long Bridges • Moveable Bridges • Europeans • Followed Roman Empire style until iron and steel was used

  6. Engineering for bridges: Primitive Bridges Rock Bridges Rope Bridges Log Bridges

  7. Engineering for bridges: Loads Primary Loads acting in a bridge Weight of the bridge DEAD LOAD Traffic: cars, trucks, people LIVE LOAD Wind, snow Dynamic: earthquake and vibrations

  8. Engineering for bridges: Primary forces Tension: magnitude of the pulling force that acts to lengthen an object, usually by a string, cable, or chain. Compression: a pushing force that acts to shorten the thing that it is acting on. Opposite to tension.

  9. Engineering for bridges: Primary forces Demo: Use a sponge to represent a beam. When loaded with weight, the divots (holes) on top _________ and the divots (holes) on bottom _________ Conclusion: close open compression tension compression The top of a beam experiences __________. The bottom of a beam experiences _______. tension

  10. Engineering for bridges: Type of Bridges Fixed Moveable Other • Beam bridge • Truss bridge • Continuous truss • Arch bridge • Cantilever • Suspension • Cable-Stayed • Swing bridge • Bascule bridge • Vertical lift bridge • Bailey bridge • Pontoon bridge

  11. Type of Bridges: Fixed Truss Bridges Beam Bridges • Beam bridge strengthened by trusses • A truss is a structure joined to form triangles with tie rods • Lighter than ordinary beam sections of equal length • Useful for longer bridges • Two parallel beams with flooring supported by piers • Used for highway over and underpasses or small stream crossings

  12. Type of Bridges: Fixed Continuous Truss Bridges Simple Truss Bridges

  13. Type of Bridges: Fixed Arch Bridges Aqueduct • One or more arches • Masonry, reinforced concrete or steel • Roadway on top of arches or suspended by cables • Spans can be longer than beam or truss

  14. Type of Bridges: Fixed Cantilever Bridges Suspension Bridges • Roadway hangs from vertical cables supported by overhead cables chained between two or more towers • Longest spans, costly and challenging to design • Highly susceptible to winds and swaying • Cables can be up to three feet in diameter • Double-ended brackets supporting a center span • Shore end of each cantilever firmly anchored • Center supported by pier

  15. Type of Bridges: Fixed Cable-Stayed Bridges • Suspended by cables that run directly down to roadway from central towers • Less costly than suspension • Quickly constructible • Spans must be limited in length

  16. Type of Bridges: Moveable Swing Bascule Vertical Lift • Central span turned 90 degrees on pivot pier placed in the middle of the water way • One or two sections are not supported by piers • Balanced on one end by counterweights • Section jack-knifes up to allow passage of ships • Most common type of highway drawbridge • Central span extends between two towers • Balanced by counterweights

  17. Let’s start building our bridges: Two Designs: a. A three-span beam bridge made with paper b. A simple truss bridge made of spaghetti (recommended) or any other design is also welcome

  18. Paper Bridge:

  19. Spaghetti Bridge: • Identify tension and compression forces • Learn how to strengthen a single beam bridge • Measure deflection using a LEGO MINDSTORMS EV3 ultrasonic sensor

  20. THANK YOU !

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