Knowing contractors who are majority basketcases when it comes to quality, REs try to use the fear factor to ensure compliance which usually resulted as a futile and causing cracks in relationship throughout the project. Shouting, cursing and evwn threats are action which is out of the pretext of a good project management; moreover such actions is outdated.

I have no problem in most of the projects i supervised. I get resistance in the first 5 or 6 months and eventually turn around. What is the right approach?

When every time a contractor shows the inability to comprehend the needs of a test, keep cool and open the specification and make references. Secondly, explain to them why such test is beneficial in validating their claim rather than to suffer during the maintenance period or in any even of opening up due to inconclusive result. Second, i often mix around with contractor's QAQC team. In a friendly manner and in impromptu basis, i quizzed them on the reason behind each step or procedures for QAQC. I gave them the technical reasons behind it and somehow i bait them into craving to learn more.

When these sub-ordinates learned more each day, it would likely be smooth execution instead of having big boss who have no clear reason to even to start a conversation; worst, an argument.

These are some of the soft skills you need at site. Humane skills to show authority indirectly and a leadership by example even if they are at the opposite site. It is called transformational leadership to be exact.