A built-up laced column is subjected to the design axial concentr

SOLUTION

Concept:

As per Clause 7.6.6.1 of IS 800:2007, the lacings should be designed for a transverse shear force of 2.5% of the axial load on column.

For double lacing system on two parallel planes, force in each bar

\(\text{F}=\frac{\text{V}}{\text{N}\sin \text{ }\!\!θ\!\!\text{ }}\)

Where,

V = transverse shear force, θ = Angle of inclination of lacing with longitudinal axis of the column, and N = no of parallel planes

As per IS 800: 2007, θ is kept in between 40⁰ to 70⁰.

Calculation:

Axial Load = P

Transverse shear force, V = 2.5 % of P

V = 0.025P kN

Axial Force in each bar (F) = \(\frac{\text{V}}{\text{N}\sin \text{ }\!\!θ\!\!\text{ }}\) 

For inclination of 40° with respect to horizontal axis,

i.e θ = 90 - 40 = 50 ° 

Now,

N = 4 (2 × 2, double lacing and two parallel planes), θ = 50⁰, V = 0.025 kN

\(\text{F}=\frac{0.025}{4\times \text{sin }\!\!~\!\!\text{ }\;50}\times {{10}^{3}}\text{ }\!\!~\!\!\text{ N}= 8.158 \rm P \;N\)