Design of Steel Structures Mcqs

Q:

Live load for roof truss should not be less than

A) 0.4kN/m² B) 0.2kN/m²
C) 0.75kN/m² D) 0.8kN/m²
 
Answer & Explanation Answer: A) 0.4kN/m²

Explanation: The live load for roof truss should not be less than 0.4kN/m². For roof slopes ≤ 10⁰ and access provided, the live load to be taken is 1.5kN/m² of plan area. For roof slopes > 10⁰ and access is not provided , the live load to be taken is 0.75kN/m² of plan area.

View Answer Discuss

28
Q:

Which of the following load combination is not considered for design of roof trusses?

A) Dead load + crane load B) Dead load + wind load
C) Dead load + earthquake load D) Dead load + live load + wind load
 
Answer & Explanation Answer: C) Dead load + earthquake load

Explanation: Earthquake loads are not significant for roof trusses because of the small self weights. The following load combinations can be considered : (i) Dead load + snow load, (ii) Dead load + partial/full live load, (iii) dead load + live load + internal positive air pressure, (iv) dead load + live load + internal suction air pressure, (v) dead load + live load + wind load.

View Answer Discuss

41
Q:

Which of the following is true for economic spacing?

A) cost of trusses should be equal to twice the cost of purlins B) cost of trusses should be equal to twice the cost of purlins minus cost of roof coverings
C) cost of trusses should be equal to the cost of purlins plus cost of roof coverings D) cost of trusses should be equal to twice the cost of purlins plus cost of roof coverings
 
Answer & Explanation Answer: D) cost of trusses should be equal to twice the cost of purlins plus cost of roof coverings

Explanation: For economic spacing of roof trusses, the cost of trusses should be equal to twice the cost of purlins plus cost of roof coverings. This equation is used for checking the spacing of trusses and not for design of trusses.

View Answer Discuss

26
Q:

The economic spacing of roof truss depends on

A) cost of purlins only B) cost of purlins and cost of roof covering
C) dead loads D) cost of roof covering and dead loads
 
Answer & Explanation Answer: B) cost of purlins and cost of roof covering

Explanation: The economic spacing of the truss is the spacing that makes the overall cost of trusses, purlins, roof coverings, columns, etc. the minimum. It depends upon the relative cost of trusses, purlins, roof coverings, spacing of columns, etc. If the spacing is large, the cost of these trusses per unit area decreases but the cost of purlin increases. But if the spacing of trusses is small, the cost of trusses per unit area increases. Roof coverings cost more if the spacing of trusses is large.

View Answer Discuss

43
Q:

The minimum recommended rise of trusses with Galvanised Iron sheets is

A) 1 in 12 B) 1 in 6
C) 1 in 10 D) 1 in 18
 
Answer & Explanation Answer: B) 1 in 6

Explanation: The pitch of truss depends upon the roofing material. The minimum recommended rise of trusses with galvanised iron sheets is 1 in 6 and with asbestos cement sheets is 1 in 12.

View Answer Discuss

40
Q:

What is the maximum vertical deflection allowed for a gantry girder where the cranes are manually operated?

A) L/500 B) L/700
C) L/600 D) L/800
 
Answer & Explanation Answer: A) L/500

Explanation: The vertical deflection of gantry girder where the cranes are manually operated should not exceed L/500, where L is the span of gantry girder. The maximum vertical deflection allowed for a gantry girder where the cranes are travelling overhead and operated electrically upto 500kN is L/750 and operated electrically over 500kN is L/1000. When gantry girders carry moving loads such as charging cars, the deflection should not exceed L/600.

View Answer Discuss

31
Q:

The bending moment due to dead load of girder is maximum at

A) one-third distance at span B) two-third distance at span
C) end of span D) centre of span
 
Answer & Explanation Answer: D) centre of span

Explanation: The bending moment considered in the design of gantry girder are the bending moment due to maximum wheel loads (with impact) and the bending moment due to dead load of the girder and rails. The bending moment due to dead loads is maximum at the centre of span.

View Answer Discuss

28
Q:

The maximum wheel load is obtained when

A) crane crab is farthest to gantry girder B) crane crab is closest to gantry girder
C) crane crab is not attached D) crane crab is at mid span
 
Answer & Explanation Answer: B) crane crab is closest to gantry girder

Explanation: The maximum wheel load is obtained when crane crab is closest to gantry girder. The crab in such position on the crane girder gives maximum reaction on the gantry girder. The vertical reaction of crane girder is transferred through its two wheels on to the gantry girder. Therefore, the maximum wheel load is half of this reaction. This maximum wheel load is then increased for impact and used for design of gantry girder.

View Answer Discuss

27