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Table of Contents Content Standards Lesson Title Objectives Guiding Questions Materials Activities References Handouts Title Page Forces and Loads Loads Static Loads Dynamic Loads Live Loads Dead Loads Tension Compression Tension and Compression (Images) Shear Shear (Image) Torsion Torsion (Images)

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Standards Standards for Technology Education Construction Systems WVEIS 2424 Standard 7: Forces and Loads (2424.S.7) Students will identify and examine the forces and loads acting upon structural elements. Forces and Loads Objectives Students will: Differentiate between the forces that act on structures (tension, compression, shear, and torsion), and determine which forces are present in various structural elements Differentiate between static, continuous dynamic, and impact dynamic loads, and give examples of each.

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Forces and Loads George Washington Bridge, NYC Lesson Title

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Objectives After performing several small activities and studying with the handouts the students will be able to distinguish between different forces that are present in various structural elements and will have basic knowledge of different loads that act on structures.

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Guiding Questions Which forces have you already heard of? Where do loads on structures come from? Why is it important that Engineers understand the basic principles of physics? Can you think of a simple, every day example where we can find tension and compression? Do you know of any structures that have collapsed?

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Materials Rubber band for each student Marshmallow for each student Handouts –(alternatively the applicable slides can be presented in form of a PowerPoint presentation)

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Activities Tension: –Students are to link their hands together and pull. They will feel tension. –Let students stretch a rubber band. They see tension in action. The rubber stretches, and the band gets longer. It's in tension. Compression: –Have students put their hands together and push hard. They will feel tension –Give each student a marshmallow to put on the table in front of them. As they push it down with their hand, the marshmallow gets shorter because it is in compression.

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References –http://www.adl.gatech.edu/classes/dci/structur/dci08.html –http://www.answers.com/topic/shear-stress?cat=technology –http://www- geology.ucdavis.edu/~GEL1/W03_verosub/G1Hwebsite/buildinggroup/ Andrews/challenges.html –http://www.enm.bris.ac.uk/research/nonlinear/tacoma/tacoma.html

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Forces and Loads George Washington Bridge, NYC

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Forces and Loads Forces that act on structures are called loads Loads on structures come from three main sources: –Structure weight –Occupants or users –Natural elements

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Loads Two main categories: – Static Loads The effect of the load on a structure – Dynamic Loads The permanence of the load

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Static Loads –Static loads change slowly or are motionless –Static loads can include: The weight of the structure The weight of its occupants Any furniture or machinery

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Dynamic Loads Change rapidly or move unpredictably Dynamic loads can include: –Wind –Waves –Earthquakes –Traffic over a bridge

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Live Loads Anything not permanently attached to the structure Can be moved or changed over time Live loads from natural elements: –Snow, Winds, earthquakes, water Live occupant loads: –People, Furniture, Machines

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Dead Loads Weight of the structure itself Includes all structural elements and components, such as –Roof –Walls –Floors –Foundation

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TENSION- The Pulling Force Stretches materials apart Look for materials in tension in: –Rope and suspension bridges –Telephone wires –Tents –Steel cables supporting a full elevator

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COMPRESSION - The Pushing Force Compression pushes materials Look for materials in compression in: –Pyramids –Telephone poles – Arch bridges

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Tension and Compression

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SHEAR – The Sliding Force Shear causes parts of a material to slide past one another in opposite directions

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A road destroyed by shear

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TORSION – The Twisting Force Torsion is the force that twists a material

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Tacoma, Washington, 1940 Torsion movement, twisting motion

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