A Self-Learning Manual - Institution of Engineers Mauritius

A Self-Learning Manual
Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU
Level One (Core FAQs)
Part I: Bolts and Fasteners
1. What is the difference between fasteners, bolts and screws? (BF1)
Fastener is a general term to describe something which is used as a
restraint for holding things together or attaching to other things.
The main physical distinction between screws and bolts is that screws are
entirely full of threads while bolts contain shanks without threads. However,
a better interpretation of the differences between the two is that bolts are
always fitted with nuts. On the contrary, screws are normally used with
tapped holes.
2. What is the difference between normal bolts and high friction grip
bolts? (BF2)
High friction grip bolts are commonly used in structural steelwork. They
normally consist of high tensile strength bolts and nuts with washers. The
bolts are tightened to a shank tension so that the transverse load across
the joint is resisted by the friction between the plated rather than the bolt
shank’s shear strength.
3. What are the advantages of using high strength friction grip (HSFG)
bolts when compared with normal bolts? (BF3)
HSFG bolts have the following advantages when compared with normal
bolts [47]:
(i) The performance of preloaded HSFG bolts under fatigue loading is
good because the prestressed bolts are subjected to reduced stress
range during each loading cycle when compared with unloaded bolts.
(ii) For structures adjacent to machinery which generate substantial
vibration, preloading bolts can help to avoid the loosening of bolts.
(iii) HSFG bolts are used in connections where any slight slip movement
would render the integrity of the whole structures break down.
(iv) Owing to its high tensile strength, it is commonly used in connections
which require the taking up of high flexure and the tensile stress
generated could be readily resisted by it high tensile strength.
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