Reg. No. :

B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2011.

Fifth Semester

Civil Engineering

CE 2306 — DESIGN OF RC ELEMENTS

(Regulation 2008)

Time : Three hours Maximum : 100 marks

(IS 456–2000 SP –16 Codes are permitted)

Answer ALL questions.

PART A — (10 × 2 = 20 marks)

1. Write any two assumptions about limit state of collapse by flexure.

2. What are the classifications available in serviceability limit state?

3. What are the rules to be followed in the design of slabs as per IS 456–2000?

4. Enumerate corner reinforcements for two-way slabs.

5. Define flexural bond.

6. What is the importance to provide laps and anchorage length?

7. Write any three assumptions made for limit state design of columns failing in pure compression.

8. What are the factors affecting behaviour of long columns?

9. Define angle of dispersion.

10. What is the formula used to find the moments on section normal to span XL and

YL in

rectangular footings?

Question Paper Code : 66283

421 4

21 4

21

66283 2

PART B — (5 × 16 = 80 marks)

11. (a) A T beam has a flange width of 1500 mm, web width of 400 mm, slab thickness of

120 mm and an effective depth of 550 mm with cover to centre of steel of 35 mm. (i)

Determine using the working stress method, the steel required to carry a moment of

375 kN-m due to characteristic loads, assume M20 concrete and mild steel rods over

20 mm as reinforcement. (ii) Also determine the steel area required by the limit state

(SP-16) method.

Or

(b) Determine the ultimate moment capacity of a doubly reinforced beam with b = 350

mm, d ′ = 60 mm, =d 550 mm. ASC = 1690 mm2,

AST = 4310 mm2, fck = 30 N/mm2 and fy = 415 N/mm2. Use working stress and

limit state methods and compare the values.

12. (a) Design a simply supported R.C.C. slab for a roof of a hall 4 m × 10 m (inside

dimensions) with 230 mm walls all round. Assume a live load of

4 kN/m2 and floor finish 1 kN/m2. Use grade 25 concrete and Fe 415 steel.

Or

(b) A series of beams placed at 2.5 m centres are supported on masonry walls and the

effective span of the beam is 5 m. The slab thickness is 100 mm and ribs below the

slab are 200 mm wide and 250 mm deep. If the slab and beams are so cast as to act

together, determine the reinforcements at midspan for the T-beam to carry an

imposed load of 5 kN/m2 of the slab. Use Fe 415 steel and M 20 concrete.

13. (a) The T-beam and slab system of a structure are made of beams spaced at 2.4 m with

clear span of 7.5 m between masonry walls of 300 mm thick. For the T beam Df =

120 mm bw = 300 mm, D = 600 mm. If

fck = 20 N/mm2 and fy = 415 N/mm2. Design the shear steel. Assume that 2 nos of

28 mm dia bars of tension steel are continued to support and live load = 8 kN/m2.

Or

(b) The T beam is shown in Fig. 1 below is subjected to the following factored loads.

Bending moment of 215 kNm. Shear of 150 kN, and torsion of 421 4

21 4

21

66283 3

105 kNm. Assuming fck = 30 N/mm2 and fy = 415 N/mm2. Design the

reinforcements according to IS 456. Cover to centre of steel is 50 mm.

Fig. 1

14. (a) Determine the longitudinal steel required for a column 400 × 600 mm carrying Pu =

1600 kN, factored M (major axis) = 120 kN-m and factored M (minor axis) = 90 kN-

m. Assume fck = 15 N/mm2 , fy = 415 N/mm

2 ,

d' = 600 mm using Bresler method.

Or

(b) An unbraced column 400 mm square is subjected in the following factored loads P =

3200 kN. At the top, Mx = 76 kN-m and My = 68 kN-m. At the bottom, Mx = 8 kN-

m and Ny = 34 kN-m, L0 = 5 m : Lx = 6.0 m at both the axes. Assuming fck = 40

N/mm2 and fy = 415 N/mm

2, design the longitudinal steel.

15. (a) Design a footing for a 500 × 350 mm column using 20 mm bars as dowels to

transmit characteristic loads of 600 kN as dead load and 400 kN as live load to a

foundation with safe bearing capacity of 120 kN/m2. Assume M 20 grade concrete

and Fe 415 steel.

700 mm

120 mm 120

800 mm

350 mm

421 4

21 4

21

66283 4

Or

(b) A solid footing has to transfer a dead load of 1000 kN and an imposed load of 400

kN from a square column 400 × 400 mm (with 16 mm dia bars). Assuming fy = 415

N/mm2 and fck = 20 N/mm2 and safe bearing capacity to be 200 kN/m2, design the

footing.

———————––––

421 4

21 4

21