I am analyzing the beam with simply supported ends . in this case i have made use of enforced but without ticking the Fy option . i am getting the warning message of instability. then is it necessary to take care of the structure or not. It is the book problem.
Notice that the title on top of those boxes says "Release". So, those items that you tick are free to displace. Those that you don't tick are restrained.
can anyone suggest what happens when i tick the forces & moments in the fixed but support option.
Hi,
When you use enforced, the program applies a very stiff spring along the degree of freedom that is restrained. Thus, that degree of freedom is an active one in the stiffness matrix and hence solved for, except, its value will turn out to be zero during the calculations.
When you treat it as FIXED, that d.o.f is eliminated from the stiffness matrix, and is treated as a known value of zero, and thus not calculated.
From a numerical standpoint, they both produce the same result. However, enforced has some advantages such as it is suitable for solving support settlement problems when plates and solids are present in the model. The FIXED support does not lend itself easily to such problems.
As per your suggestion i have made changes and i got no warnings. I have also analyze the structure with enforced but with the same condition and it showed no warnings. I want to know what is the real difference between the fixed and enforced but support.