The Physics Of Bridges Essay Research Paper — страница 2
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most famous example of several collapses. This is an extreme example – in fact the effects of forces are never instantaneous – they always take time to propagate through the medium. As the speed of waves in structural materials is so high, we are normally not aware. Compression differs from other stresses in producing inherent instability. Tension is the opposite stress of Compression. While Tension forces pull apart, compression pull together. Torsion is not a good idea in a bridge. It is a twisting of the structure. In a long suspended span, the presence of many heavy vehicles traveling in one direction, with few on the other side, will cause the deck to twist. A long motorway over pass may support by single columns to reduce the effects on roadways below. It must then be stiff enough to transmit asymmetrical loads to the abutments without undue torsion. Bending would seem to be easy top explain, but it isn t. If you bend a long rectangular rubber eraser it tends to bend in two different axes. This effect is very small for structural materials, but we do need to remember that bending a beam causes compression on one side and tension on the other. There is a neutral surface where the length remains unchanged.