,so basically what you said is that there is no difference (or are very close to each other) in the directions where the actual load will travel through the part and the directions of the Maximum principal stress within the part? And why should we ignore the directions of minimum principal and only be concerned about maximum principal? Or we should take into account the directions of that principal stress whose magnitude in greater than other?nAnd also, speaking my mind out right now, I actually never understood that how does the trusses in a bridge, or somewhere else, understands that they are supposed to carry only the axial forces. For instance, have a glance on the picture below.nconsider JOINT A. There are two reaction forces i.e. Ha and Ra are acting on joint A. Can't the force Ha or Ra be taken completely by the inclined member so that it bends as well Why do we assume that the members only take forces along the axial directions?