How is the brickwork wall length obtained?

Centre-line: 2[(3.00+0.23)+(2.00+0.23)] = 10.92 m

2[(3.00+0.46)+(2.00+0.46)] = 11.84 m

How is steel weight found when 1% steel is assumed?

1% of the RCC volume x 7850 kg/m3

1% of the brickwork volume x 7850

What is done with the 0.60 x 0.60 manhole in the cover slab?

Its volume is deducted from the slab concrete

It is deducted from the floor slab

2082 Baisakh · 3×3 marks

Underground RCC tank: brick, PCC, steel (1% steel)

Short answer

On assumed dimensions, brickwork by centre-line method: 3.767 m³. PCC for floor and top slab (deducting manhole) is 2.255 m³. Steel at 1% of RCC volume weighs177.0 kg.

Prepare detailed estimate for the following items of works for an underground RCC water tank given in Figure 1. i) Brickwork ii) PCC for RCC works iii) Steel reinforcement in RCC works (assume 1% steel) [Figure 1 not included in the scanned paper]

Figure 1 is not available, so the working is shown on assumed dimensions; the method is the same for any drawing.

Assumed dimensions

Clear internal size $3.00 \times 2.00$ m, clear depth $1.50$ m.
Brick walls $0.23$ m thick in 1:4 mortar, $1.50$ m high, resting on a $0.15$ m RCC floor.
RCC floor $0.15$ m thick and top cover slab $0.12$ m thick, both of outer size $(3.00 + 0.46) \times (2.00 + 0.46) = 3.46 \times 2.46$ m; a $0.60 \times 0.60$ m manhole opening in the cover.
Steel $1\%$ of the volume of RCC; density $7850$ kg/m³.

i) Brickwork (centre-line method)

Centre-line length $= 2\,[(3.00 + 0.23) + (2.00 + 0.23)] = 10.92$ m

$V = 10.92 \times 0.23 \times 1.50 = 3.767$ m³

ii) PCC (concrete) for the RCC works

Member	Working	Volume (m³)
Floor slab	$3.46 \times 2.46 \times 0.15$	1.277
Top slab	$3.46 \times 2.46 \times 0.12$	1.021
Deduct manhole	$0.60 \times 0.60 \times 0.12$	−0.043
Total		2.255

iii) Steel reinforcement

$W = 1\% \times 2.255 \times 7850 = 177.0$ kg

Answer (for the assumed figure): brickwork = 3.767 m³; concrete in RCC = 2.255 m³; steel = 177.0 kg.

✓ Answer checked by Claude Opus 5.5 (high effort)

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Underground RCC tank: brick, PCC, steel (1% steel)

Assumed dimensions

i) Brickwork (centre-line method)

ii) PCC (concrete) for the RCC works

iii) Steel reinforcement

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