"If you have mass resting on top of another structure the mass is not accelerating. Therefore does not produce a net downwards force as acceleration is 0. F=M*0."
This is where your case is flawed. The mass is always being acted upon by acceleration. The strucural integrity of the building applies an opposing force, once its gone no opposing force therefore movement.
If your case was true you and I would weigh nothing when we step on the scales. And I dont know about you but I am not moving when I am on the scales.
Weight is a measure of force.
A lack of movement does not imply a lack of force. Once the resistance to the acceleration is removed , ie catastrophic failure, you will have movement because.
so I dont have to try again, you need to try and understand. Good luck but in the end it doesnt matter, the laws of physics will not change because you dont understand them.
