Discipline-Specific Technical Knowledge
What depth questions look like
Discipline-Specific Technical Knowledge tests the design and analysis methods of your chosen branch-for example structural concrete, machine design, power systems, or process control. The exam expects you to combine material behavior, code equations, and constructability, not just plug into a formula.
Core rules (structural concrete example)
- Whitney stress block: a = A_s f_y / (0.85 f'_c b).
- Nominal moment: M_n = A_s f_y (d − a/2).
- Strength reduction factor φ = 0.9 when the section is tension-controlled (ε_t ≥ 0.005).
- Check β₁: 0.85 for f'_c ≤ 28 MPa, reduced by 0.05 per 7 MPa above 28, not below 0.65.
Worked example
b = 300 mm, d = 500 mm, A_s = 1000 mm², f_y = 420 MPa, f'_c = 28 MPa. a = (1000)(420)/(0.85 × 28 × 300) = 420,000/7,140 = 58.8 mm. c = a/β₁ = 58.8/0.85 = 69.2 mm. ε_t = 0.003(d − c)/c = 0.003(500 − 69.2)/69.2 = 0.0187 > 0.005, so φ = 0.9. φM_n = 0.9 × 1000 × 420 × (500 − 29.4) = 1.779 × 10⁸ N·mm ≈ 178 kN·m. The strain check matters: if ε_t were below 0.005, φ would drop and the capacity would be lower.
Traps
- Using d instead of d − a/2 in the moment arm.
- Mixing N·mm and kN·m at the final step.
- Assuming φ = 0.9 without verifying tension-controlled behavior.
- Ignoring minimum reinforcement or bar spacing and cover checks that a depth question may also require.