RectangularBeam:

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   Calculates the tensile and shear stresses acting on a rectangular beam
   and the design factor of safety for the material used.
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   Form:
   [sigma, tau, FOS] = RectangularBeam( d, V, M, yS)
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   ------
   Inputs
   ------
   d          (1,1)  Data structure
                     .w          (1,1)  Width (m)
                     .h          (1,1)  Height (m)
                     .t          (1,1)  Thickness (m)
   V          (1,1)  Shear Force (N)
   M          (1,1)  Bending Moment (N*m)
   yS         (1,:)  Yield Stress (Pa)

   -------
   Outputs
   -------
   sigma      (1,1)  Flexural stress (Pa)
   tau        (1,1)  Shear stress (Pa)
   FOS        (1,1)  Factor of Safety

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   Reference: 

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