Gravitational Acceleration

My personal structure will sag - even more.

It depends on the safety factor in the design.

I think if you increase gravity by the same amount as your safety factor, your structure will hold...just not as reliable. Yes, it will be more prone to sag.

Since F=mg, your load will be multiplied by the same factor you increase gravitational acceleration.

My structure did not even survive the normal G.

If G is reduced for a period of time (in a spacecraft) the bone structure will loose strength. Likewise the bone structure will increase in strength if subjected to bigger stress.

if from the beginning, the gravitational acceleration of the earth was already four times what we have now, all the structures will be designed based on the actual forces acting on the structures. dead load & live load is different due to the difference of gravitational accelaration (Weight = mass X accelaration due to gravity). even the evolution of all living things is different.

but if there's a sudden change of gravitational accelaration, four times the normal, almost all the structures will collapse. even the pyramid which will not be affected by sagging like the beams, there is a tendency that the structure will sink or tilt due to failure on foundation.

just imagine what will happen to us if our testicles suddenly weigh four times the normal, hehehe .

i remember somebody asked me "why we cannot feel the rotation of the earth where the speed on the surface we're standing is 16,642 kph approx. (1 rotation = 24hrs, radius = 63567 kms)? it is because we are here since birth, since sperm i should say.