how to apply traction vectors on each node of the model?

Dear All,

I was wondering if someone experienced could reply me. I've already
analyzed a model and extracted the nodal stress tensors. Now the aim is
identifying the external model nodes and its corresponding stress
tensors and then re-apply them as a new Boundary Condition. Firstly, it
seems that I need to multiply these stress tensors (which vary node by
node) by a normal vector resulting traction vectors. But, here is the
question, how should I define these traction vectors on external nodes
as Boundary condition? On the other words, if I wanna apply these
surface traction vector as concentrated force I need to multiply
traction vectors by an area (somehow node area!?) which I don't have any
idea about it. Any suggestion is truly appreciated.