General Equilibrium Problems (example continued)

 

Example:  (continued)

 

Examination of the FBD shows that the unknown reactions are Ax, Ay, and By.

Note:  The pin support offers two reactions whereas the roller only a vertical reaction.

 

 

Next write and solve the equations of equilibrium to determine the support reactions.

They are:    ΣFx = 0,  ΣFy = 0,  ΣMconvenient point = 0

 

          ΣFx = 0  gives    Ax   =  0

 

       ΣFy = 0  gives   Ay  - 120  -  180  +  By  =  0

 

Pick the convenient point to sum moments to be point A.

 

Counterclockwise  Σ MA = 0  gives   By (12)  - 120 (6)  -  180 (8) = 0

 

which yields  By  =  180 kips  and from the second equation of equilibrium

 

                      Ay  =  120 kips   (results)

 

Note:  Integration could have been used to determine the distributed loading

           on the beam.

 

 

  Return to Notes on Statics


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