Question

In order to account for the shear deformations and associated effects, the effective slenderness ratio of laced columns shall be taken as k times, the actual maximum slenderness ratio. The value of k specified in IS 800 is
1. 0.95
2. 0.85
3. 1.15
4. 1.1
5. 1.05

Answer 1

Correct Answer - Option 5 : 1.05

Explanation:

As per CI. 7.6.1.5 of IS 800:2007 states that the effective slenderness ratio of laced columns should be 5% more than the actual maximum slenderness ratio so that shear deformation effects are accounted for. 

Design recommendations for lacing:

• The angle of inclination of the lacing with the longitudinal axis of the column should be between 40° to 70°.
• The slenderness ratio l_e/r of the lacing bars should not exceed 145. The effective length le of the lacing bars should be taken as follows:
  • Single lacing, riveted at ends = Length between inner end riveted on lacing bar (l)
  • Double lacing, riveted at ends and at intersection = 0.7 times length between inner end rivets on lacing bars
  • Welding lacing = 0.7 times the distance between inner ends of effective lengths of welds at ends
• For local buckling criteria
  • \(\frac{L}{{{r_{\min }}}} \le 50\)
  • \(\frac{L}{{{r_{\min }}}} \le 0.7 \times {\lambda _{wholespan}}\)
• Minimum width of lacing bars in riveted construction should be as follows:

  • Nominal rivet diameter (mm)	Width of lacing bars (mm)
    22	65
    20	60
    18	55
    16	50

• In single lacing system, the thickness t of the lacing flat ≥ 1/40 of its effective length, and in double lacing system, this thickness t of the lacing flat ≥ 1/60 of its effective length.
• The lacing of compression members should be designed to resist a transverse shear, V = 2.5% of axial force in the member.