Concrete, Steel & Wood: Properties and Tests

• Steel tension test: yield strength (0.2% offset where there is no clear yield point), ultimate strength, and ductility as percent elongation. Toughness is the area under the whole curve.
• Wood: strength depends on grain direction and moisture content; it is far stronger parallel to the grain, and drier wood is stronger.
• Fatigue: repeated stress below the static strength can fail a member; steel shows an endurance limit, below which it survives indefinitely.

Worked: one cylinder, three numbers

A 6 in × 12 in cylinder fails at 120,000 lb. A = π × 6²/4 = 28.27 in², so f′c = 4,240 psi. Then E_c = 57,000 × √4,240 = 3.71 × 10⁶ psi and f_r = 7.5 × √4,240 = 488 psi.

A companion cylinder split on its side fails at 45,000 lb: 2 × 45,000/(π × 12 × 6) = 398 psi, about a tenth of the compressive strength, which is the usual proportion.