Calculating the volume & BBS of columns in a compound wall./ Estimating & costing of a compound wall ( part 5 ).

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Let us make a column of size 9" × 9"  as shown in the drawing.

Given data :

Column height above GL = 6 ft.+ 5"(0.416 ft.)= 6.416 ft.,  below GL = 7" (0.583ft.) 

Column size      = 9" × 9" (228.6mm × 228.6 mm )

Longitudinal bars 12mm (0.03936 ft.) - 4 nos,  cover  - 40mm. 

Lateral ties dia d1 - 6mm @ 6" (150 mm.) c/c 

From part 1, number of columns = 14 nos.

6a. The volume of the column concrete for the compound wall

  = total nos. × height × length× breadth

 = total nos.  × (height below GL + height above GL )  × length  × breadth

= 14 nos.  ×( 6.416 ft. + 0.583 ft. )  × 0.75 ft. × 0.75 ft.

= 14 nos.  × 7 ft.  × 0.75 ft  × 0.75 ft.

= 55.125 cu ft. i.e. 1.561 cum.

      6b.  BBS of a column for the compound wall.

Length of the longitudinal bar

= above GL + GL to footing top + development length ( Ld )

= 6.416 ft. + 0.583 ft. +( 50d )

( we have taken Ld as 50d, where d = bar diameter.)

= 7 ft. + (50 × 0.03936 ft.)

= 7 ft. + 1.968 ft.

= 8.968 ft.   i.e. 2.733 m.

Length of the lateral ties

= perimeter of lateral ties + total hook length - no. of bends

= 2sides × ( a - 2 × cover ) + 2 sides × ( b - 2 × cover ) +( 2nos × hook length) - (3 nos. × bend )

( Here, we have taken  hook length = 10d1 for 135°∠    & bend = 2d1 for 90°∟)

={ [ 2 × (228.6mm - 2× 40mm.) ]+[ 2 × ( 228.6 mm - 2 × 40 mm.) ] } + { 2 × 10 × 6mm }- {3 × 2 × 6mm }

={ [ 2 × 148.6 mm ] + [2 × 148.6 mm ]} + 120 mm - 36 mm.

= {297.2 mm + 297.2 mm} + 84 mm

= 678.4 mm i.e. 0.678 m.

Total number of lateral ties ( stirrups )

  ={ [length of the longitudinal bar - Ld ] ÷ stirrup spacing } + 1

Note:  Ld is deducted from the length, as no stirrups are provided over that length.

 ={[ 2733 mm - (50 × 12 mm )] ÷ 150 mm.} + 1

 = {[ 2733mm - 600mm ] ÷ 150 mm.} + 1

= {2133 mm ÷ 150 mm.} + 1

= 14.22 + 1

= 15.22 nos. 

Rounding off, the number of stirrups required = 15 nos.

Now, let us prepare BBS for a column.

sl.    bar                    dia.     no.     length    total      weight       total   

no.                        ( mm)                 (m.)     length     kg/m      weight

1.  longitudinal      12        4        2.733     10.932     0.89       9.729

2. lateral                   6        15      0.678       10.17       0.22       2.237

                                                     Total weight of bars  =  11.966 kgs.

                                                    Add 5% wastage          = 0.5983 kgs.

                                             Grand total of rebars  =  12.564 kgs.     

The total weight of  rebars for compound wall columns

 = 14 nos.× 12.564 kgs = 175.9 kgs.

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