Correct Answer - Option 2 : 54 mm
Concept: -
As per IS 800: 2007, cl. 7.6.2.,
The minimum width of the lacing bar shall be three times the nominal diameter of the end bolt/rivet.
Calculation: -
Nominal diameter of bolt = 18mm
The minimum width of the flat required = 3 × 18 = 54 mm
Note: - Other useful Codal recommendations-
1. Thickness of the lacing bar
\(t \not < \left\{ {\begin{array}{*{20}{c}} {\frac{1}{{40}} \times effective\;length,\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\left( {For\;single\;lacing} \right)}\\ {\frac{1}{{60}} \times effective\;length,\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\left( {For\;double\;lacing} \right)\;} \end{array}} \right\}\)
2. Angle of inclination, shall not be less than 40° nor more than 70° to the axis of the built-up member.