Correct Answer - Option 4 : assures unified behaviour
The lacing bars and battens plate sin built up compression members are not designed as load carrying elements. Their function is primarily to hold the main component members of the built up column in their relative position and equalize the stress distribution in them.
Rules Specified in IS 800:2007 about lacing system:
1. Minimum width of lacing bar = 3 times the diameter of bolt.
2. Minimum thickness is 1/40th of the effective length for single lacing and 1/60th for double lacing.
3. The SR for lacing bar shall not exceed 145.
4. The lacing should be designed to resist a transverse shear of 2.5 % of axial load in column.
5. The effective slenderness ratio of the laced built up column shall be taken as 1.05 times maximum slenderness ratio of the column to account for the shear deformations.