Civil Engineering Interview Questions Part – 18




Question No. 01
General Specification for Civil Engineering Works (1992 Edition) Clause 15.09 specifies that tying wires for reinforcement adjacent to and above Class F4 and F5 finishes should be stainless steel wires. Why?
Answer: If plain steel tying wires are used for reinforcement adjacent to Class F4 and F5 finishes, it poses the problem of rust staining which may impair the appearance of exposed concrete surfaces. The rate of corrosion of plain steel tying wires is similar to normal steel reinforcement. However, for tying wires with very small diameter, upon long exposure it stands a high chance of rusting completely and this rust will stain the formwork and significantly affect the concrete finish. Therefore, stainless steel tying wires are specified for locations in the vicinity of high quality off finishes to avoid rust staining by corroded typing wires. Note: Tying wires are wires used for fixing and connecting steel reinforcement bars.

Question No. 02
Which architectural movement is also known as Jazz Moderna?
Answer: Art nouveau

Question No. 03
Should raking piles of a bridge abutment be placed under an embankment?
Answer: For a bridge abutment to be supported on raking piles with different orientations, the movement between the ground and the pile group is difficult to predict. For instance, if some of the raking piles of the bridge abutment are extended beneath an embankment, then the settlement of embankment behind the abutment may cause the raking piles to experience severe bending moment and damage the piles as recommended by Dr. Edmund C Hambly (1979).

Question No. 04
In designing of access ramps for drainage channels, why should the direction of access ramps be sloping down towards downstream?
Answer: In the design of access ramps, the direction is normally specified to be sloping down towards downstream so as to avoid the occurrence of over-shooting of flowing water for supercritical flow in case of aligning the ramps in the reverse direction of channel flow.
Note: Access ramps refer to ramps used for maintenance vehicles during routine maintenance of channels.

Question No. 05
What is the difference in application between open stirrups and closed stirrups in concrete beams?
Answer: Open stirrups are provided principally to resist shear forces in concrete beams and they are applied in locations in which the effect of torsion is insignificant. U-shaped stirrups are placed in the tension side of concrete beams in which shear cracks would occur. However, when concrete beams are designed to resist a substantial amount of torsion, closed stirrups should be used instead.



Question No. 06
How do you convert wind speed into force?
Answer: Thermometer

Question No. 07
Why are voids filled with lightweight infilling material in raft foundation of pumping stations?
Answer: To reduce the dead load and hence to reduce the settlement of pumping stations, the voids inside the raft foundations are filled with light material. If instead concrete is placed inside these voids, it poses severe thermal cracking problem and drastically increases loads to pumping stations. The use of general fill is also not desirable because its self-weight is comparable to that of concrete. On the contrary, if these voids are left vacant, water may penetrate into these voids during future operation and increases the dead load of pumping stations during its normal operation. Therefore, lightweight infill material, which is non-water-absorbing and non-biodegradable, is designed inside these voids to avoid ingress of water and to reduce the dead load of the structure.

Question No. 08
Nowadays, most flap valves are made of HDPE. What are the advantages of using HDPE when compared with cast iron?
Answer:
(i) It has no reaction with sewage and seawater and does not suffer from the corrosion problem associated with cast iron.

(ii) No protective coating is required and it is almost maintenance-free.
(iii) HDPE flap valves require very low opening pressure in operation (like 5mm water level difference). For cast iron flap valves, due to its own heavy self-weight, the required opening pressure of cast iron flap valves is higher than that of HDPE flap valves. This criterion is essential for dry weather flow conditions.
However, the pressure resistance of HDPE flap valves is not as good as cast iron flap valves. For instance, a typical 450 mm wide HDPE flap valve can only withstand about 5 m water column.

Question No. 09
Does brick grows bigger every year?
Answer: Usually bricks do not grow, but since stuff gets all over, it looks like it grows.

Question No. 10
Are diaphragms necessary in the design of concrete box girder bridges?
Answer: Diaphragms are adopted in concrete box girder bridges to transfer loads from bridge decks to bearings. Since the depth of diaphragms normally exceeds the width by two times, they are usually designed as deep beams. However, diaphragms may not be necessary in case bridge bearings are placed directly under the webs because loads in bridge decks can be directly transferred to the bearings based on Jorg Schlaich & Hartmut Scheef (1982). This arrangement suffers from the drawback that changing of bearings during future maintenance operation is more difficult. In fact, diaphragms also contribute to the provision of torsional restraint to the bridge deck.


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