Answer / Explanation
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If the gap between C and the rigid wall at D is  initially 0.15 mm, determine the support reactions at A and  D when the force is applied. The assembly  is made of A36 steel
Procedure
Recalling the the equation of equilibrium and referencing the free body diagram of the assembly,
Therefore, ∑fₓ  = 0 ,
where, 20 ( 10³) - Fₐ - Fₙ = 0 --------------equation (1)
Now, recalling the compatibility equation, while utilizing the superposition method,
Therefore, δₓ - δfₓ 
= 0.15  = 200(10³)(600) ÷ π/4
(0.05²)(200)(10⁹) - [ Fₐ (600) / π/4
(0.05²)(200)(10⁹) + Fₐ (600) π / 4
(0.05²)(200)(10⁹) ] 
Solving this further,
We get: Fₐ = 20365.05 N
  Which is equivalent to = 20.4 kN.
Now, substituting the answer (Fₐ) into equation (1)
                 Fₙ = 179634.95 N 
                         = 180 kN