What length of decking is used in the quantities?

6.00 + 2 x 0.45 = 6.90 m (clear span plus bearing at both ends)

How is the volume of the three ribs found?

3 x 0.35 x 0.75 x 6.90 = 5.434 m3

How is total reinforcement obtained?

Percentage of steel x concrete volume x 7850 for each member group: ribs/fillets 2.5%, slab/kerbs 1%, posts 1%, totalling 2,060.7 kg

17.402 x 2.5% x 7850 for all members

17.402 x 1% x 7850 for all members

Sum of concrete volumes in tonnes

2080 Baisakh · 4+3 marks

T-beam decking: PCC for RCC and steel

Short answer

Concrete for RCC members (PCC) = 17.402 m³. Reinforcement: ribs+fillets 1157.8 kg, slab+kerbs 877.5 kg, posts 25.4 kg; total 2060.7 kg.

From the given figure of RCC T-beam decking of one span of 6 m, of which the section is given, calculate the following items of works: a) PCC for RCC work b) Reinforcement quantities for all RCC members. [Figure: RCC T-beam decking cross-section. Overall width 7.7 m, 7 m roadway, 20×20 cm kerb on each side, 10 cm wearing coat of C.C., 20 cm slab, three ribs each 35 cm wide with 225 cm clear between ribs, rib depth below slab 75 cm (107.5 cm projections at the edges), 15×15 cm fillets, 15×15 cm RCC railing posts 120 cm high at 136 cm c/c, 40 mm dia G.I. pipe 4 nos., railing height 120 cm.]

Assumptions from the figure

Length of decking $= 6.00 + 2 \times 0.45 = 6.90$ m (clear span plus bearing at both ends).
Overhang of slab beyond outer ribs $= (7.70 - 3 \times 0.35 - 2 \times 2.25)/2 = 1.075$ m (matches the 107.5 cm in the figure).
Fillets are taken as triangles of 15 × 15 cm at both sides of each rib (6 in total). The railing posts are at 1.36 m c/c: with 6.90 m length this gives 6 posts per side, 12 in all.
The 20 cm slab is taken from the figure; the kerb is 20 × 20 cm above the slab, and the wearing coat (10 cm) is laid between the kerbs over the 7.0 m roadway.
Percentage of steel is not stated; the usual values for T-beam decking are taken: beams 2.5%, slab and kerbs 1%, posts 1%. Density of steel 7850 kg/m³.

(a) Concrete for the RCC work (1:2:4)

Member	Working	Volume (m³)
Slab	$7.70 \times 6.90 \times 0.20$	10.626
Ribs (3)	$3 \times 0.35 \times 0.75 \times 6.90$	5.434
Fillets (6, 15 × 15 cm triangular)	$6 \times \tfrac12 \times 0.15 \times 0.15 \times 6.90$	0.466
Kerbs (2)	$2 \times 0.20 \times 0.20 \times 6.90$	0.552
Railing posts (12 nos, 15 × 15 × 120 cm)	$12 \times 0.15 \times 0.15 \times 1.20$	0.324
Total RCC (1:2:4)		17.402

(b) Reinforcement

Member	Concrete (m³)	% steel	Steel (kg)
Ribs and fillets	5.899	2.5	1,157.8
Slab and kerbs	11.178	1.0	877.5
Posts	0.324	1.0	25.4
Total			2,060.7

Answer: concrete in RCC members = 17.402 m³; reinforcement = 2,060.7 kg (2.061 tonne).

✓ Answer checked by Claude Opus 5.5 (high effort)

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T-beam decking: PCC for RCC and steel

Assumptions from the figure

(a) Concrete for the RCC work (1:2:4)

(b) Reinforcement

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