Problem in finite element method using direct stiffness method

[chiraganand]

Hi,

This is a sample problem from logan finite element method. I have attached the problem and solution given in the book. As per the problem i first derived the stiffness matrix and den putting the boundary conditions started solving for the forces. I am stuck as three forces are unknown but when i checked the book it says the force at third node is zero. Can someone tell me why this force is assumed as zero?

 

[rock.freak667]

F3x = 0 since only one applied force is present in the problem at node 4. So F4x = 5000 lb.

 

[chiraganand]

F3x = 0 since only one applied force is present in the problem at node 4. So F4x = 5000 lb.

But shudnt there be a reaction at 3rd node