Monday, September 21, 2020

Steel Structures - Compression Members

1. The numbers of battens should be such that the member is divided into not less than
(a) two parts longitudinally
(b) three parts longitudinally
(c) two parts transversely
(d) three parts transversely

2. The effective length of battened column should be increased by
(a) 10%
(b) 15%
(c) 20%
(d) 25%

3. Spacing of battens C, from centre to centre of end fastening should be such that the slenderness ratio of the lesser main component is
(a) C/r_{\min }^c \le 50
(b) 0.7 x slenderness ratio of compression member as a whole
(c) lesser of (a) and (b)
(d) greater of (a) and (b)

4. Thickness of battens (t) will be
(a) equal to l/50
(b) greater than l/50
(c) smaller than l/50
(d) none of these
where l is distance between inner most connecting line of rivets or welds.

5. Battens should be designed to carry bending moment and shear arising from a transverse shear V where
(a) V = P/100
(b) V = 2.5P/100
(c) V = 5P/100
(d) none of these
where P is total axial load on compression member.

6. The thickness of rectangular column base as per IS:800-1984 is given by
(a) t = \sqrt {\frac{1}{{{\sigma _{bs}}}}w\left( {{a^2} - \frac{{{b^2}}}{4}} \right)}
(b) t = \sqrt {\frac{2}{{{\sigma _{bs}}}}w\left( {{a^2} - \frac{{{b^2}}}{4}} \right)}
(c) t = \sqrt {\frac{3}{{{\sigma _{bs}}}}w\left( {{a^2} - \frac{{{b^2}}}{4}} \right)}
(d) none of these
where t is slab thickness in mm, w is load on underside of base in MPa, a is greater projection of the plate beyond the column in mm, b is lesser projection of the plate beyond column in mm, bs is permissible bending stress in slab bases = 185 MPa for all steels.

7. The thickness of a square slab base plate under a solid circular column is
(a) t = \sqrt {\frac{{90W}}{{16{\sigma _{bs}}}}x\frac{B}{{(B - {d_0})}}}  
(b) t = 10\sqrt {\frac{{90W}}{{16{\sigma _{bs}}}}x\frac{B}{{(B - {d_0})}}}  
(c) t = 20\sqrt {\frac{{90W}}{{16{\sigma _{bs}}}}x\frac{B}{{(B - {d_0})}}}
(d) none of these
where W is total axial load in kN, B is length of side of cap or base in mm, d0 is diameter of the reduced end(if any) of the column in mm.

8. For moderate loads and bending moments, and good soil beneath the footing, the most suitable base is
(a) slab base
(b) gusset plate
(c) base plate
(d) none

9. For bases subjected to load and bending moment tension is not developed, when eccentricity is
(a) < L/2
(b) < L/3
(c) between L/3 and L/6
(d) < L/6

10. A column base is subjected to moment. If the intensity of bearing pressure due to axial load is equal to stress due to moment, then the bearing pressure between the base and concrete is
(a) uniform compression throughout
(b) zero at one end and compression at the other end
(c) tension at one end and compression at other end
(d) uniform tension throughout (IES 1999)

Answers

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

Sunday, September 20, 2020

Steel Structures - Compression Members

1. Battening is provided where compression member is subject to
(a) axial loads
(b) eccentric loads
(c) shear stresses
(d) bending stresses

2. For lacing an engineer can recommend
(a) flat bars
(b) angles
(c) channels
(d) any of the above

3. For battening, an engineer can recommend
(a) channels
(b) angles
(c) tubular sections
(d) plates

4. The following observations relate to designing of laced column
1. Single lacing system on opposite planes shall preferably be in the same direction so that one is shadow of the other
2. Lacing bar should only be flat angle channels generally
3. The slenderness ratio of the lacing bars for compression shall not exceed 1980.
4. Laced compression members are to be provided with tie plates at ends.
Of these observations
(a) 1, 2, 3, 4 are correct
(b) 1,3, 4 are correct
(c) 2 and 3 are correct
(d) 1, 4 are correct (IES 1993)

5. The angle of inclination of the lacing bars should not exceed 
(a) 300 to 600
(b) 400 to 700
(c) 500 to 800
(d) none of these

6. The slenderness ratio of lacing bars should not exceed
(a) 100
(b) 145
(c) 160
(d) 180

7. For a riveted or welded lacing system
(a) L/{r^c}_{\min } \le 50
(b) 0.7 x maximum slenderness ratio of compression member
(c) greater of (a) and (b)
(d) smaller of (a) and (b)

8. Minimum width of lacing bars in riveted connection for a rivet diameter of 22 mm will be
(a) 40 mm
(b) 55 mm
(c) 65 mm
(d) 80 mm

9. Minimum thickness of lacing bar if there is single lacing, is greater than or equal to
(a) l/10
(b) l/20
(c) l/40
(d) none of these
where l is length between inner end rivets.

10. The lacing of compression member should be designed to resist a transverse shear which is __ % of axial force in the member.
(a) 10
(b) 7.5
(c) 5.0
(d) 2.5

Answers

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

Saturday, September 19, 2020

Steel Structures - Compression Members

1. Factor of safety adopted by IS: 800 - 1984 while arriving at the permissible stress in axial compression is
(a) 2.00
(b) 1.00
(c) 1.67
(d) 1.50 (GATE 1997)

2. In the design of compression member, the section should be proportioned to have the ___ radius of gyration.
(a) smallest
(b) largest
(c) average
(d) none of these

3. For which of the following shapes radius of gyration is largest for a given cross sectional area?
(a) square
(b) rectangle
(c) circular
(d) triangular

4. For compression members, I sections are most suited because
(a) their radius of gyration is largest for a given cross sectional area
(b) difference between radii of gyration about two axes is smallest
(c) both (a) and (b)
(d) neither (a) nor (b)

5. In chimneys, the allowable axial compression reduces with the ratio d/t (i.e. diameter/plate thickness) and not with l/r as in columns. This is to recognize the
(a) hoop compressive strain produced by axial compression
(b) temperature gradient caused by hot gases
(c) shell buckling
(d) axial strain produced by hoop tension (IES 1999)

6. Which of the following is the most critical set of considerations in the design of rolled steel columns carrying axial loads?
(a) per cent elongation at yield and the net cross sectional area
(b) critical bending strength and axial yield strength of the material
(c) buckling strength based on the net area of the section and percent elongation at ultimate load
(d) compressive strength based on slenderness ratio and gross cross-sectional area of the member (IES 1999)

7. A single angle strut ISA 50 x 50 x 6 mm of a roof truss is 1.06 mm long. Maximum radius of gyration will be (given {r_{\min }} = 0.96 cm).
(a) 110.42
(b) 120
(c) 180
(d) 250

8. The buckling load in a steel column is
(a) related to length
(b) directly proportional to slenderness ratio
(c) inversely proportional to slenderness ratio
(d) non linearly related with slenderness ratio (IES 1992)

9. Different components of a built up compression member are connected together by
(a) lacing
(b) battening
(c) both (a) and (b)
(d) none of these

10. Lacing is generally preferred if compression member is subject to
(a) axial loads
(b) eccentric loads
(c) shear stresses
(d) tensile stresses

Answers

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