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Stresses on the exterior or outside of a structure These outside EXTERNAL forces and stresses lead to INTERNAL stresses. INTERNAL FORCES or stresses that act on the materials inside the structure. What type of forces may have lead to this DEFORMATION?? Video http://www.youtube.com/watch?v=HxTZ446tbzE 1. 2. 3. 4. 5. List 5 factors which should have been considered for the Tacoma narrows Bridge DEAD load is a permanent force acting on a structure. This includes the weight of the structure itself Overtime this weight and gravitational force can cause a structure to sag, tilt, or pull apart as the ground beneath it shifts or compresses. Live load is a changing or non-permanent force acting on a structure. This includes the force of the wind and the weight of things that are in or on a structure (people roof). , furniture, and snow and rain on the Impact forces, caused by objects colliding with the structure, are another type of live load. Tension force ◦ Tensile strength Compression force ◦ Compression strength Shear force ◦ Shear strength Torsion force ◦ Torsion strength http://www.funnyordie.com/videos/be30300 653/head-crusher-vs-face-pincher-by-kidsin-the-hall-from-greatest-comedy-sketches Add Tension and Compression arrows to this diagram Steel has high tensile strength. It has strong forces pulling its particles together. A very strong tension force is needed to separate the particles and break the material. Graphite (a form of carbon) has low shear strength. Its particles are arranged in layers, but the forces between the layers are relatively weak. Because the layers slide over one another easily, graphite is slippery and makes a good dry lubricant. The layers of graphite ina pencil “lead” rub off and leave a mark on the paper when you write. Rubber has high torsion strength. Each particle is attracted in all directions to the other particles around it. The particles hold together even when a piece of rubber is twisted out of shape. 1. 2. 3. List examples of deformation that you learned about in this topic? What are the three types of forces that can be caused inside a structure? Pick a structure and draw in these forces Draw a Venn diagram showing the similarities and differences between a Live load and a dead load.
