Question

why do Engineers use PIN connection support during calculations but does not use it in actual. What is the effect of this?

Answer 1

Pin joints basically carry horizontal and vertical loads, but not any moments. So it is more of a hypothetical joint which only carries load but no moment, but yet constraints that turn in a direction. This gives ease of calculation but it cannot exist in actual. Effect is that no paper calculations of joints can be as it used in reality, hence, we have to big factor safeties while actual design. But while doing that we don't consider moment restraint contributed by the joint, whereas in actual it does, hence there are no negative effects of doing so.