This set of Building Construction Multiple Choice Questions & Answers (MCQs) focuses on “Trussed Roofs – 1”.
1. In trussed roofs, the limit of the spacing for wooden trusses is generally _______
a) 1 metre
b) 2 metres
c) 3 metres
d) 4 metres
Explanation: In trussed roofs, the limit of the spacing for wooden trusses is generally 3 metres. Trussed roofs are used when the span of the roof is greater than 5 m.
2. Trusses are used in trussed roofs to support the _________
b) Roofing material
Explanation: There are basically three elements in trussed roofs. These are rafters, purlins and trusses. The function of the trusses is to provide support to the purlins which in turn provide support to the rafters. Rafters are used to provide support to the roofing material.
3. Which of the following is used to provide end support to the common rafters in a king-post truss?
b) Ridge beam
d) Tie beam
Explanation: The components of a king-post truss are two inclined principal rafters, two struts, a lower tie beam and a king post. A ridge beam is also provided at the apex of the roof. The function of a ridge beam is to provide end support to the common rafters.
4. In a king-post truss, which of the following types of joints is used to join the king-post to the ends of principal rafters at its head?
a) Dovetail joint
b) Open and pin join
c) Pin and tenoned joint
d) Tenon and mortise joint
Explanation: Tenon and mortise joint is used to join the king-post to the ends of principal rafters at its head. A three-way wrought iron or a mild steel strap on each of its sides are provided to secure the joint.
5. In a king-post truss ________ prevent the purling from tilting.
a) Pole plates
Explanation: In a king-post truss, cleats prevent the purling from tilting. These are fixed on the principal rafters. Purlins are placed at right angles to the sloping principal rafters. These purlins are made of stout timber.
6. In a king-post truss, common rafters have the same slope as the principal rafters.
Explanation: In a king-post truss, common rafters have the same slope as the principal rafters. The function of the principal rafters is to provide support to the purlins while the function of the purlins is to provide support to the common rafters.
7. How many vertical posts are there in a queen-post truss?
Explanation: There are two vertical posts in a queen-post truss, unlike a king-post truss which has only one vertical post. These two vertical posts in a queen-post truss are known as queen posts. The tops of these queen posts are connected by a horizontal member known as a straining beam.
8. In the queen-post truss, the joint at the head is formed due to the junction of two compression members and one tension member. This tension member is __________
a) Tie beam
c) Straining sill
d) Principal rafter
Explanation: In the queen-post truss, the joint at the head is formed due to the junction of two compression members and one tension member. The two compression members are principal rafter and straining beam and the tension member is the queen-post.
9. Queen-post trusses are suitable for spans up to ______
a) 12 m
b) 25 m
c) 32 m
d) 46 m
Explanation: Queen-post trusses are suitable for up to 12 m spans. However, a combination of queen-post and king-post trusses are suitable up to a span of 18 m.
10. A mansard roof truss is named after a _____ architect.
Explanation: Mansard roof truss is named after a French architect named Francois Mansard. This type of roof is a combination of king-post and queen-post trusses.
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