Mechanics Exam 3 Review 1

Mechanics Exam 3 Review 1 - beam (variable cross sectional...

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Mechanics Exam 3 Review Equations: Definitions: Nominal Dimensions for Wood Beams a) Nominal dimensions are different from actual dimensions b) actual dimensions are usually smaller than nominal dimensions c) nominal dimensions are reduced in order to obtain the smooth surface d) 2x4 is really a 1.5x3.5 e) actual dimensions must be used in stress calculations on wood beams Built-Up Sections a) a built up section is constructed from two or more parts joined together to form a single unit b) in order to increase the moment of inertia of the member, most of the material should be placed as far away from the centroid as possible c) deep wide flanged beam is efficient in resisting moment d) rather than using several available beams, engineers will usually build up a beam using plates and angles e) wood beams can be built up using the form of a box beam section Prismatic/non-prismatic beam a) prismatic means that all the cross sections are the same throughout the beam b) non prismatic means that the cross sections are different throughout the
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Unformatted text preview: beam (variable cross sectional area). c) Since the moment in a beam usually varies along its length, the choice of a prismatic beam is usually inefficient since it is never fully stressed at points where the internal moment is less than the maximum moment in the beam d) Often used since they can be readily formed by casting, stress analysis is difficult for non-prismatic beams Fully-stressed beam a) a fully stressed beam is when the internal moment is expressed in terms of x along the beam and since sigma allow is constant, the section modulus S or the beams dimensions become a function of x. b) S=M/sigma allow Radius of Curvature a) beams that are deflected at some point have some radius of curvature. b) The radius of curvature of the arc is defined as the distance p which is measured from the center of curvature O to dx c) P is the radius curvature at the point on the elastic curve d) 1/p is referred to as the curvature...
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Mechanics Exam 3 Review 1 - beam (variable cross sectional...

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