ME or MEng Master of Engineering Master of Civil Engineering 5 — Questions and Answers
Question 1: In the context of environmental engineering, the term 'BOD5' refers to:
- Biological oxygen demand measured over 50 days
- Biochemical oxygen demand measured over 5 days at 20°C (Correct answer)
- Baseline oxygen deficit in a stream 5 km downstream
- Biological oxygen demand at 5°C temperature
Correct answer: Biochemical oxygen demand measured over 5 days at 20°C
BOD5 is the standard measure of organic pollution—the amount of oxygen consumed by microorganisms decomposing organic matter in a sample over 5 days at 20°C.
Question 2: A prestressed concrete beam is post-tensioned. The primary advantage of post-tensioning over pre-tensioning is:
- Lower material cost
- Tendons can be curved to follow the moment diagram, reducing eccentricity losses (Correct answer)
- Higher ultimate strength of tendons
- Elimination of all shrinkage losses
Correct answer: Tendons can be curved to follow the moment diagram, reducing eccentricity losses
Post-tensioned tendons can be profiled (draped) to align with the bending moment diagram, optimizing prestress efficiency throughout the beam length.
Question 3: The 'rational method' formula Q = CiA is used to estimate:
- Average annual groundwater recharge
- Peak stormwater runoff from small watersheds (Correct answer)
- Sediment yield from agricultural fields
- Baseflow contribution from wetlands
Correct answer: Peak stormwater runoff from small watersheds
The rational method estimates peak discharge Q where C is the runoff coefficient, i is rainfall intensity for the time of concentration, and A is watershed area.
Question 4: According to ASTM standards, the Standard Proctor compaction test uses a hammer energy of approximately:
- 12,375 ft-lbf/ft³ (Correct answer)
- 56,000 ft-lbf/ft³
- 600,000 ft-lbf/ft³
- 1,800 ft-lbf/ft³
Correct answer: 12,375 ft-lbf/ft³
The Standard Proctor test (ASTM D698) applies approximately 12,375 ft-lbf/ft³ of compactive energy, while the Modified Proctor uses ~56,250 ft-lbf/ft³.
Question 5: In steel connection design, a 'slip-critical' bolt connection is required when:
- The connection is in a low-seismic zone
- Slip would be detrimental to serviceability or the connection is subject to fatigue loading (Correct answer)
- Using A307 bolts in simple shear
- The connection is on a non-primary member
Correct answer: Slip would be detrimental to serviceability or the connection is subject to fatigue loading
Slip-critical connections are required where joint slip would affect alignment, serviceability, or structural integrity, and in connections subject to fatigue or load reversal.
Question 6: The 'Unit Hydrograph' method in hydrology assumes that:
- Rainfall is uniform only in mountainous watersheds
- Direct runoff response is linearly proportional to excess rainfall depth (Correct answer)
- Base flow and direct runoff cannot be separated
- Storm duration does not affect peak discharge
Correct answer: Direct runoff response is linearly proportional to excess rainfall depth
The unit hydrograph principle assumes a linear, time-invariant watershed response where excess rainfall of different depths produces proportionally scaled hydrographs.
Question 7: In seismic design, the concept of 'ductility' in structural systems is important because:
- It increases the elastic modulus of the material
- It allows structures to absorb and dissipate seismic energy through inelastic deformation (Correct answer)
- It reduces the natural period of the structure
- It eliminates the need for base isolation
Correct answer: It allows structures to absorb and dissipate seismic energy through inelastic deformation
Ductile systems can undergo significant inelastic deformation without collapse, dissipating earthquake energy and allowing use of reduced seismic design forces.
ME or MEng Master of Engineering Master of Civil Engineering 5
In the context of environmental engineering, the term 'BOD5' refers to: