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WBS BASIC Help index |
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WOOD BEAM SIZINGTM Deflection
Deflection is the measure of the amount the beam will sag under load. In general, we ignore the deflection caused by dead loads (every beam has a permanent deflection) unless it is extreme and would cause a problem with finishes. But the deflections caused by live loads may be a problem. Under excessive deflection, the beam may feel too springy underfoot or plaster finishes may crack. MEASURING DEFLECTIONThe conventional measure of deflection is given, for example, as 1 in 360, meaning that a beam spanning 30 feet, actually deflects 1 inch at the center under the total live load (1 inch in 360 inches). WBS DEFLECTION PANEL
In this example, the beam is deflecting 0.27 inches under live load, which is a 1 in 442 deflection over the beam span. Under total load, the deflection is
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