Compute the normal stress

Consider the I-beam cross-section:

The table below has the geometric properties for different specifications for a steel beam:

Designation h (in) w (in) Ix (in^4) Iy (in^4)
S24 x 80 24 7 2,100 42.2
S20 x 96 20.3 7.2 1,670 50.2
S20 x 86 20.3 7.06 1,580 46.8
S20 x 75 20 6.385 1,280 29.8
S20 x 66 20 6.255 1,190 27.7
S18 x 70 18 6.251 926 24.1
S18 x 54.7 18 6.001 804 20.8
S15 x 50 15 5.64 486 15.7
S15 x 42.9 15 5.501 447 14.4
S12 x 50 12 5.477 305 15.7

For the beam designations indicated below, determine the maximum normal stress $\sigma_x$ assuming that the maximum moment is equal to $M_{max} = 4 \times 10^5 \rm\ lb \cdot in$.

Designation $\sigma_x$
S15 x 42.9
S12 x 50
S20 x 75
S18 x 70

Correct answer

Student view placeholder

In student views this area is used for assessment and score info.
Tools

Staff information

Question

QID:
Title:
Compute the normal stress

Variant

Started at:
2026-09-19 07:02:55 (CDT)
Duration:
0s
Show/Hide answer 
{
  "sigma1": 6.7114093959731544,
  "sigma2": 7.868852459016394,
  "sigma3": 3.125,
  "sigma4": 3.8876889848812093
}
This box is not visible to students.
History
dec frac
rad deg