NEW 375 lecture04 - one plate to another through its own...

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BEARING STRESS A compressive normal stress that is produced by the compression of one surface against another surface. In other words, bearing stresses occur on the surface of contact between two interacting members.
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Bearing Stresses σ b1 σ b1 σ b2 σ b2 σ b1 > σ b2 P
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Bearing Stresses Consider a wood column bearing on a styrofoam base plate, which in turn, bears on a concrete footing. Which bearing stress is most critical?
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Bearing Stresses Stryofoam base plate crushes
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EXAMPLE : TWO TIMBERS FASTENED TOGETHER WITH A BOLT
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LOOK AT FREE BODIES OF TIMBERS: BEARING STRESS Bearing Bolt b A P = σ 1 b 2 b 1 b 2 b 2 b 1 b
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LOOK AT FREE BODIES OF BOLT BEARING STRESS Bearing Bolt b A P = σ 1 b 1 b t t TENSILE STRESS Bolt Bolt t A P =
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EXAMPLE : HOW MANY FAILURE MODES COULD BE CONCERNED? Square headed bolt Square plate with square hole
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MODE 1 . TENSILE MODE 2. BEARING C t A F = σ Bearing b A F = F F
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MODE 2: BEARING b σ
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b σ b MODE 2: 3-D BEARING STRESS
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MODE 3: SHEAR (a) (b)
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3a: SHEAR POSITION 1 (a) τ τ
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3b: SHEAR POSITION 2 (b) τ
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Special Case of Bearing Stress When a bolt connects one or more plates subjected to axial force, it transmits force from
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Unformatted text preview: one plate to another through its own surface and the surface of the hole. Special Case of Bearing Stress • There is the case that the stress on the hole surface be higher than the allowable stress for the given material, causing a bearing failure. • The value of the stress on the hole surface, i.e. the bearing stress can be calculated in an approximate way as follows: d t P A P b ⋅ = = σ P Factor of Safety Factor of Safety = F.S. = ultimate load allowable load • ultimate load – the load at which a structural member or machine component is expected to fail. • allowable load - the maximum load a structural member or machine component will be allowed to carry under normal conditions of utilization. • NOTE: The ultimate load capacity should be considerably larger than the allowable load....
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NEW 375 lecture04 - one plate to another through its own...

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