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Homework Help: Cantilever beam

  1. Jan 22, 2006 #1
    A cantilever beam is loaded by a uniform shear stress T on its upper surface. How to calculate the stress and deflections at the end of the beam?
  2. jcsd
  3. Jan 22, 2006 #2


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    You can use [itex] EI \frac{d^{3} \nu}{dx^{3}} = V [/itex] as long as the cross section of the beam is constant. Where [itex] \nu [/itex] is the deflection.
  4. Jan 23, 2006 #3
    In this formula V is the vertical shear on a cross section. Applied shear (T) is horizontal on the upper surface. Why should they be equal?
  5. Feb 16, 2006 #4


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    Hello, it depends on the cross section of your beam. Could you tell us which profile you are using? is it a composite beam?
  6. Feb 17, 2006 #5
    Rectangular cross-section. The crossection will only affect I, in the formula. We can just keep it as I, so we don't have to worry about the cross-section.
  7. Feb 18, 2006 #6


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    The shear stress would induce a tensile stress in the beam with maximum tensile stress at the fixed end and only shear at the free end. Since the shear load is only on the upper surface, it is unbalanced, so it would induce a bending moment in the beam.
  8. Feb 20, 2006 #7
    you can take a uniform force.. find the center of it. and just put in the Fr for it.. and that makes calculations simple.
  9. Feb 26, 2006 #8
    To make sure I understand what you have; a constant rectangular cross section with a uniform horizontal force applied only along the top surface of the section and perpendiular to the longitudinal axis of the beam, and the beam has one end fixed and one end free.

    Your deflection can be broken into components of that induced by horizontal shear, bending moment and torsional moment. The shear and bending moment would give translational displacements and the torsional moment generates rotational displacement about the long. axis of the beam. Usually, the bending moment will give the significant deflection of a real world beam and the shear and torsional deflection are often minimal in comparison and sometimes ignored. But you certainly cannot ignore the stresses which they produce.

    The stresses will be from the direct shear, torsional shearing, and tension and compression from the bending moment. Your highest stresses will be at the fixed end.
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