Can anyone show me the procedure for plotting the tension force curve in the bolts as a function of the load applied to the beam?

I know that i have to take the value of the stress S33 and multiply it by the surface area of the stem, but I don't know where to take this stress from, do i have to look for the node with the maximum value or take the average stress values over the whole stem if yes? which part of the stem.

Another thing, the value of the stress multiplied by the surface area at the beggening of loading should normally be equal to the value of the bolt pretension force which is equal to 250kn, why on some nodes do I find this value whereas other nodes greatly exceed the value of the pretension force?

as you can see in the screeshot, the first step is for bolt pretensionning and >second step is loading, the nodes were taken randomly from the surface pointed by an arrow.