Steel Structures - Trusses

1. Consider following figure of a purlin which is continuous over the supports of span L
Moment {M_x} due to loads W₁ and W₂ will be
(a) ({W_1} - {W_2}\cos \theta )\frac{{{L^2}}}{{10}}
(b) ({W_2}\cos \theta )x\frac{{{L^2}}}{{10}}
(c) ({W_1} + {W_2}\cos \theta )\frac{{{L^2}}}{{10}} 
(d) ({W_2}\sin \theta )x\frac{{{L^2}}}{{10}}

2. In above question, {M_y} is
(a) ({W_1} - {W_2}\cos \theta )\frac{{{L^2}}}{{10}}
(b) ({W_2}\cos \theta )x\frac{{{L^2}}}{{10}}
(c) ({W_1} + {W_2}\cos \theta )\frac{{{L^2}}}{{10}} 
(d) ({W_2}\sin \theta )x\frac{{{L^2}}}{{10}}

3. The section chosen for purlin must have extreme fibre stress within permissible bending stress {\sigma _{bc.bt}}  which is given by
(a) \frac{{{M_x}}}{{{Z_x}}} - \frac{{{M_y}}}{{{Z_y}}}  
(b) \frac{{{M_x}}}{{{Z_x}}} + \frac{{{M_y}}}{{{Z_y}}}  
(c) \frac{{{M_x} + {M_y}}}{{{Z_x}{Z_y}}} 
(d) \frac{{{M_x} - {M_y}}}{{{Z_x}{Z_y}}} 

4. The economic spacing of a roof truss depends upon the
(a) cost of purlins and cost of roof covering
(b) cost of roof covering and dead loads
(c) dead loads and live loads
(d) live loads and cost of purlins (IES 2000)

5. Effective length of a rafter member between two nodes at a distance L, perpendicular to the plane of truss is
(a) 2.00L
(b) 0.85L
(c) 1.50L
(d) 1.00L (GATE 1997)

6. Which of the following material is not used in making trusses?
(a) Wooden struts 
(b) Metal bars
(c) Channel 
(d) Concrete (SSC J.E. Exam 2018)

7. What is the major difference between truss and beam?
(a) Beam can’t transmit load in vertical direction while truss can
(b) Truss can’t transmit load in vertical direction while beam can*
(c) Beam can’t transmit load in axial direction while truss can
(d) Truss can’t transmit load in axial direction while beam can (SSC J.E. Exam, 2018)

8. Which of the following elements of a pitched roof industrial steel building primarily resists lateral load parallel to the ridge?
(a) bracings
(b) purlins
(c) truss 
(d) columns (GATE 2003)

9. Which one of the following is a compression member?
(a) Purlin
(b) Boom
(c) Girt
(d) Tie

10. To minimize the total cost of a roof truss, the ratio of the cost of truss to the cost of purlins shall be
(a) 1
(b) 2
(c) 3
(d) 4

Answers

    1. (c)    2. (d)    3. (b)    4. (a)    5. (b)
    6. (d)    7. (b)    8. (a)    9. (b)    10. (b)

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