If the temperature increases by 30F, how much will an unencased steel frame expand per 100 ft?

If the temperature increases by 30F, how much will an unencased steel frame expand per 100 ft?

• A. 1/16 inch
• B. 3/32 inch
• C. 1/8 inch
• D. 1/4 inch

Answer: (D)

When steel heats up, it expands in a way that is proportional to its length and the temperature increase. The typical linear coefficient of thermal expansion for steel is about 6.5 × 10^-6 per degree Fahrenheit. For a 100 ft length, convert to inches: 100 ft equals 1,200 inches. A temperature rise of 30°F gives a change in length ΔL = α × L × ΔT = (6.5 × 10^-6) × 1,200 × 30 ≈ 0.234 inches. So an unencased steel frame would expand by about 0.23 inches, which is essentially a quarter inch per 100 ft for a 30°F rise. This is why allowances are often made in steel framing for thermal expansion, and why the option closest to that value (about 1/4 inch) is the best match.

When steel heats up, it expands in a way that is proportional to its length and the temperature increase. The typical linear coefficient of thermal expansion for steel is about 6.5 × 10^-6 per degree Fahrenheit.

For a 100 ft length, convert to inches: 100 ft equals 1,200 inches. A temperature rise of 30°F gives a change in length ΔL = α × L × ΔT = (6.5 × 10^-6) × 1,200 × 30 ≈ 0.234 inches.

So an unencased steel frame would expand by about 0.23 inches, which is essentially a quarter inch per 100 ft for a 30°F rise. This is why allowances are often made in steel framing for thermal expansion, and why the option closest to that value (about 1/4 inch) is the best match.