Civil Engineering PE Basic Civil Engineering PE 3 — Questions and Answers
Question 1: A retaining wall must resist an active earth pressure. Using Rankine's theory with φ = 30° and γ = 120 pcf, the active pressure coefficient K_a is:
- 0.500
- 0.333 (Correct answer)
- 0.750
- 0.289
Correct answer: 0.333
K_a = (1−sin φ)/(1+sin φ) = (1−0.5)/(1+0.5) = 0.5/1.5 = 0.333 for φ = 30°.
Question 2: Which type of flow is characterized by a Reynolds number less than 2,000 in pipe flow?
- Turbulent flow
- Transitional flow
- Laminar flow (Correct answer)
- Critical flow
Correct answer: Laminar flow
Laminar flow occurs when Re < 2,000, where fluid moves in smooth parallel layers with no lateral mixing.
Question 3: In a triangular traffic flow diagram, what is represented by the slope of the line from the origin to any point on the flow-density curve?
- Flow rate
- Density
- Space mean speed (Correct answer)
- Travel time
Correct answer: Space mean speed
The slope of the line from the origin to any point on the q-k curve equals q/k, which by the fundamental equation equals space mean speed (u_s).
Question 4: The modulus of elasticity (E) for structural steel per AISC is:
- 25,000 ksi
- 29,000 ksi (Correct answer)
- 33,000 ksi
- 57,000 ksi
Correct answer: 29,000 ksi
AISC specifies E = 29,000 ksi (200 GPa) as the modulus of elasticity for all structural steel grades.
Question 5: A concrete mix design has a water-cement ratio (w/c) of 0.45. Increasing the w/c ratio to 0.60 will primarily:
- Increase compressive strength
- Decrease workability
- Decrease compressive strength (Correct answer)
- Increase unit weight
Correct answer: Decrease compressive strength
Higher w/c ratios produce more porous cement paste with lower compressive strength per Abrams' water-cement ratio law.
Question 6: In highway design, the stopping sight distance (SSD) depends on which two primary components?
- Grade and curve radius
- Brake reaction distance and braking distance (Correct answer)
- Speed and pavement friction only
- Horizontal and vertical alignment
Correct answer: Brake reaction distance and braking distance
SSD = brake reaction distance (driver perception-reaction time × speed) + braking distance (kinematic braking equation).
Question 7: Which consolidation parameter represents the rate at which excess pore water pressure dissipates in a saturated clay?
- Compression index (C_c)
- Coefficient of consolidation (c_v) (Correct answer)
- Preconsolidation pressure (σ'_p)
- Void ratio (e)
Correct answer: Coefficient of consolidation (c_v)
The coefficient of consolidation (c_v) governs the rate of consolidation settlement by controlling pore water pressure dissipation.
Civil Engineering PE Basic Civil Engineering PE 3
A retaining wall must resist an active earth pressure.
Using Rankine's theory with φ = 30° and γ = 120 pcf, the active pressure coefficient K_a is: