*Beam Deflection (Statically Indeterminate)  -  Method of Superposition

 

Example:  Beam  AB shown below is of length L and flexural rigidity EI.  It is clamped at A

and supported by a rod at B of length H, modulus of elasticity, E, and cross-sectional area A. 

External loading consists of a uniformly distributed load, q. 

Find the axial stress in the rod.

                             

                        

 

Strategy:  Determine the deflection, ∆1, of the beam at end B in terms of q, L, and EI. 

                  Then find the defection, ∆2,  of the beam at end B in terms of T, L, and EI.

                  The net deflection of the beam must equal that of the rod.  See the figures below.

                   From the value of  T, the axial stress in the rod is just  T/A.

 

               

 

From tables for the beam   1  =  qL4/8EI   and  2  =  TL4/3EI   where  T  is the tension in the rod

For the rod   3  =  TH/AE  

        

Click here to continue this example.

 

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