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Homework Help: Beam Design

  1. Dec 5, 2011 #1
    Hi,

    Calculate the dimensions of a solid rectangular beam using the information below:

    Max Bending Moment= 8280Nm

    Ze = 36cm^3

    Allowable Stress = 230MPa

    d = 2b

    Stress = moment/section modulus
     
  2. jcsd
  3. Dec 5, 2011 #2
    Where are your workings? Where is it you're having problems?
     
  4. Dec 5, 2011 #3
    Sorry I did this on my phone and I didn't have time to finish it.

    I have the following:

    230 = 8280/36cm^3 The problem I have is am not sure where or how to go about finding the dimensions from here.
     
    Last edited: Dec 5, 2011
  5. Dec 5, 2011 #4

    PhanthomJay

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    what's the section modulus formula for a rectangular beam?
     
  6. Dec 5, 2011 #5
    Z= I/y with y being depth/2.

    But I can't see how this will help. Sorry.
     
  7. Dec 5, 2011 #6

    PhanthomJay

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    Yes, Z= I/(d/2), so what is I in terms of the base (b) and height (d), for a rectangular cross section?
     
  8. Dec 5, 2011 #7
    Firstly thank you for your help and patience.

    ((b*d^3)/(d/2) = b*d^2/6

    Z = b*d^2/6

    Z * 6 = b*d^2

    But I still have two unknowns and one equation.
     
  9. Dec 5, 2011 #8

    PhanthomJay

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    you mean (bd^3/12)/(d/2) = b*d^2/6
    No, you have 2 unknowns and 2 equations....the one that was given you....in your original post..

    d = 2b
     
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