Question

Q-4

Part I - What is the number of board feet for the following: 100 each 2”x 4 “x 10’-0”

a) 780 b) 667 c) 600 d) 1000

Part II - The raise and the span of a roof is 10’ and 60’ respectively, the run and the length of rafter are:

a) 5’ and 36’ b) 30’ and 31.65’ c) 6’ and 33.6’ d) 10’ and 31.65’

Part III - Which of the following is another name for metal joists?

a. Wire beams b. Closed web steel joists c. Strand joists d. Open web steel joists

Answer 1

Part I)

Ans:

We know that 1 board feet = 144 cubic inch volume

Therefore , we have 100 pieces of 2" x 4" x 120"

Hence volume in cubic inch

= 100x2x4x120

= 960000

Therefore number of board feet

= 960000/144

= 667

Hence option (b) 667 is correct answer

Part II)

Ans:

Rise of roof =10'

Span of roof = 60'

As the crown of roof will be at the centre of span we have to provide two rafter o(right hand side and on the left hand side of crown) as an hypotenuse

•Length of rafter by hypotenuse rule

30P+10

= 31.65'

Length Rafter Rise ko IE Ron: Span CScanned with CamScanner

• Horizontal projection of rafter is know as Run and vertical projection of rafter is know as Rise

Therefore run of rafter = 30'

Therefore, answer to the part II is option (b)

Part III)

Ans:

Metal joist is also know as "Open web steel joist"