Regarding the use of steel vs. high-grade aluminum (what we use) in construction:

– strength refers to the maximum load a material can bear without bending and loosing its shape, and the stiffness refers to the yielding properties of a material, and how much it can bend under a load or when pressure is applied.

– the parameter to quantify stiffness is called the Modulus of Elasticity. The relative stiffness of steel versus aluminum has no stiffness advantages over each other, as both of the materials can withstand and bear extreme pressure and tons of load. Aluminum beats steel, as its bending density is about 1/3 of the density of steel, and the advantage of thickness offsets the 1/3 in strength, making aluminum more dent resistant than steel of the same weight.

-the tautness or tensile strength of high-grade aluminum is in same ratio as high-grade steel. If we compare steel versus aluminum used as construction material, the specific gravity for stainless steel is 7800 ton/m, and aluminum is 2700 kg/m3.

The overall point to be kept in mind is that an aluminum structure can be made with the same or greater strength, and still be much lighter than a similar structure in steel. In simple terms, aluminum is structurally more “efficient” than steel.