Shall reversible moisture movement be taken into account in estimating movement for movement joints?
Answer: The size of concrete is affected by changes in atmospheric humidity: moisture causes expansion while drying causes shrinkage. Such moisture movement is reversible. This is totally different from drying shrinkage in which concrete slowly loses moisture during hardening, thus causing irreversible shrinkage. In fact, the variation of humidity and the estimated reversible moisture movement is not significant (about 30%) and therefore, its contribution to movement does not justify for movement joints as suggested by MN Bussell & R Cather (1995).
Question No. 02
Which is stronger solid steel rod or hollow steel pipe?
Answer: On a per pound basis, steel pipe is stronger in bending and is less likely to buckle in axial compression.
Question No. 03
For long slender structures like beams, propping is required after removal of formwork. Why?
Answer: After concreting, the time at which striking of formworks should not be too long, otherwise it would affect the colour of concreted structures. For long span concrete structures, when they have attained sufficient strength to support their self-weight, creep deflection may occur in these structures if propping is not provided after the removal of formwork. Therefore, re-propping is carried out after removing formwork and these props should not be allowed to stand too long because creep loads may overstress them.
Note: Propping refers to provision of false-work to support slabs and beams during their gain in concrete strength after concreting.
Question No. 04
In joints of precast concrete bridge segments, what are the functions of applying epoxy adhesive?
Answer: Epoxy adhesive is applied in these joints for the following purposes according to International Road Federation (1977):
(i) It seals up the joints completely between precast concrete segments to protect the pre-stressing tendons;
(ii) By filling voids and irregularities along the segment joints, it helps to reduce stress concentrations otherwise it will be developed; and
(iii) It helps in transferring of shear between the joints in case a large single shear key is used.
Question No. 05
What is aggregate?
Answer: Aggregate is the component of a composite material used to resist compressive stress.
Question No. 06
What are some structures that may be subjected to fatigue?
Answer: Bridges, hydraulic presses, burners trains
Question No. 07
In concrete pavement, why is the requirement of 95% by mass of quartz grains are specified in contract?
Answer: In General Specification of Civil Engineering Works (1992 Edition), in Clause 10.09 it states “Fine aggregate of concrete shall be natural river -deposited sand consisting of at least 95% by mass of such specification is to control the quality of river sand. As quartz is a durable and hard material, using a high percentage of quartz in aggregates of concrete can enhance the strength and durability of the surface texture of concrete carriageway. In addition, such specification requires a high percentage of quartz content, thereby reducing the probability of presence of impurities like shell.
Question No. 08
What are moment of inertia and its importance in civil engineering?
Answer: The moment of inertia measures the opposition any kind of body will have against a certain momentum (along that same axis) trying to rotate that body.
Question No. 09
What is the difference in application of surface-protecting fenders and energy-absorbing fenders?
Answer: Surface-protecting fenders are fenders that induce high reaction forces to berthing structures for the energy absorbed while energy-absorbing fenders are fenders which transmit low impact to berthing structures for the energy absorbed (Carl A. Thoresen (1988)). In fact, the principal function of fenders is to absorb the berthing energy and transmit a force to the structures without damaging them. Therefore, in open berth structures, it is desirable to use energy-absorbing fenders to reduce the loads acting on the relatively flexible structures. On the other hand, for solid berth structures the usage of surface-protecting fenders is adequate because they are capable of taking up large berthing loads.
Question No. 10
What is the absolute pressure scale?
Answer: Absolute pressure is calculated from a vacuum (0 PSI) and atmospheric pressure is14.7PSIaor 14.7 PSI above a vacuum 1 PSI on a tire pressure gauge is called 1 PSIg = 15.7PSIa 10PSIg =24.7PSIa 100PSIg = 114.7PSIa etc.