怎樣計算物體能承受的重量？

物體能承受的重量(應該是說compressive strength吧)必須以實驗找出. 實驗會破壞物體.
ultimate compressive stress就是物體能承受的pressure. 單位是Pa(N/m^2), kPa(kN/m^2), MPa(N/mm^2), GPa(kN/mm^2), 同樣物質的compressive stress是一樣的, 如steel, 是200-400MPa, 石屎是數十MPa.
compressive strength, 即物體能承受的force. 就是depend on Area 的, 單位是N,kN,MN
stress=force/Area
所以實驗通常會找出compressive strength, 再計算ultimate compressive stress.
如知道ultimate compressive stress就可以計算出compressive strength, 即物體能承受的compressive force了.
但實驗必須確保物體會因compressive force而failure. 因物體failure 的方法有好多, 好似bending, shear, buckling, tension......其中長的物體受compression時很容易出現buckling, 即受compression影響而彎曲, 甚至折斷.