Example # 2

الرحمن الله بسمالرحيم

Design of Concrete Structure II

University of Palestine

Instructor:

Eng. Mazen Alshorafa

Design the two way solid slab shown in Figure. The covering materials weigh 2.3 KN/m2 and the live load is 3.2 KN/m2. Also, Calculate the factored load acting on beam 1 due to slab.Use fc’ = 25 MPa, fy = 420 MPa. All beams are 250mm wide

Example # Example # 22

3m 5m 5m

4m

4m

4m

C16

C15

C14

C13

C12

C11

C10

C9

C8 C7 C6 C5

C4 C3 C2 C1

Beam

1

Page 0Instructor:

Eng. Mazen Alshorafa

الرحمن الله بسمالرحيم

Design of Concrete Structure II

University of Palestine

SolutionSolution1- Evaluate slab thickness: Ln,max = 5.0 – 0.25 = 4.75 m = 4750 mm

The largest slab thickness is given by

Use a slab thickness of 140 mm =14 cm

2- Determine the total factored load per unit area of slab: wu = 1.2[0.14(25)+2.3] + 1.6(3.2) = 12.1 KN/m2

wu = 12.1 KN/m2 =1.21 t/m2

mm

fylh n

5.14236

)1500/4208.0(475036

)1500/8.0(max

Page 1Instructor:

Eng. Mazen Alshorafa

الرحمن الله بسمالرحيم

Design of Concrete Structure II

University of Palestine

3- Evaluate load distribution in both directions:

3m 5m 5m

4m

4m

4m

C16 C15 C14 C13

C12 C11 C10 C9

C8 C7 C6 C5

C4 C3 C2 C1

S1

S5

S4

S3

S6

S7

S8

S2

Based on Egyptian code load coefficients:

For panel S1,S2 and S8:

For panel S3 and S6:

For panel S4:

23.0475.0

,25.1)87.0(0.4

)87.0(0.5'

and

r

190.0517.0

,33.1)87.0(0.3

)87.0(0.4'

and

r

23.0475.0

,25.1)76.0(0.4

)76.0(0.5'

and

r

Page 2Instructor:

Eng. Mazen Alshorafa

Design of Concrete Structure II

University of Palestine

3- Evaluate load distribution in both directions:

For panel S5:

For panel S7:

For all panels,For a strip 1m wide,

ws = α wu

wl = β wu

295396.0

,092.1)87.0(0.3

)76.0(0.5'

and

r

174.0565.0

,43.1)76.0(0.4

)87.0(0.5'

and

r

3m 5m 5m

4m

4m

4m

C16 C15 C14 C13

C12 C11 C10 C9

C8 C7 C6 C5

C4 C3 C2 C1

S1

S5

S4

S3

S6

S7

S8

S2

Page 3Instructor:

Eng. Mazen Alshorafa

Design of Concrete Structure II

University of Palestine

Loads in both directions:

3m 5m 5m

4m

4m

4m

C16 C15 C14 C13

C12 C11 C10 C9

C8 C7 C6 C5

C4 C3 C2 C1

5.75 KN/m2

2.78 KN/m2

5.75 KN/m2

2.78 KN/m2

5.75 KN/m2

2.78 KN/m2

4.79 KN/m2

3.57 KN/m2

6.84 KN/m2

2.10 KN/m2

5.75 KN/m2

2.78 KN/m2

2.30 KN/m2

6.25 KN/m2

2.30 KN/m2

6.25 KN/m2

Page 4Instructor:

Eng. Mazen Alshorafa

Design of Concrete Structure II

University of Palestine

4- Select Representative 1m wide design strips to span in short and long direction.

3m 5m 5m

4m

4m

4m

C16 C15 C14 C13

C12 C11 C10 C9

C8 C7 C6 C5

C4 C3 C2 C1

Strip #1

Str

ip #

4 Strip #2

Strip #3Str

ip #

5

Strip #6

Page 5Instructor:

Eng. Mazen Alshorafa

Design of Concrete Structure II

University of Palestine

5- Design each stripFor Example, take Strip # 1

5 m 5 m

2.78 KN/m

S.F.D

B.M.D

5.2 KN8.7 KN

8.7 KN 5.2 KN

8.7 KN.m

4.9 KN.m4.9 KN.m

Average effective depth (davg)

davg =140-20-12 = 108 mmAssuming that dstirrup = Φ 8 && dbar = Φ12

A - Check slab thickness for shear

KOKNN

dbfc

V wc

....5.6767500

10810006

25*75.0

6

'

Page 6Instructor:

Eng. Mazen Alshorafa

Design of Concrete Structure II

University of Palestine

Design of Strip # 1(Contd.)

5 m 5 m

2.78 KN/m

5.2 KN8.7 KN

8.7 KN 5.2 KN

8.7 KN.m

4.9 KN.m4.9 KN.m

B- Design of reinforcement

mmUsemmAsAs

mKNMFor

mmUsemmAsAs

mmAs

mmAs

dbfc

M

fy

fc

req

u

req

req

w

u

300@10.252

.9.4

300@10.252

252140*1000*0018.0

.218108*1000*002.0

0020.0

)108)(1000)(25()9.0(85.0

)7.8()10(211

420

25*85.0

'85.0

)10(211

'85.0

2min

2min

2min

2

2

6

2

6

Φ 10 @ 300 mm

Φ 10 @ 300 mm Φ 10 @ 300 mm

Page 7Instructor:

Eng. Mazen Alshorafa

Design of Concrete Structure II

University of Palestine

Check slab thickness for beam shear for each strips and determine the required amount of reinforcement for each strips then prepare neat design drawings showing slab thickness and providing reinforcement.

140

mm

Sec. A-A

3m 5m 5m

4m

4m

4m

C16 C15 C14 C13

C12 C11 C10 C9

C8 C7 C6 C5

C4 C3 C2 C1

Φ 10 @ 300 Φ 10 @ 300

Φ 10 @ 300

Φ 10 @ 300 Φ 10 @ 300

Φ 10 @ 300

Φ 10 @ 300

Φ 10 @ 300

Φ 10 @ 300 Φ 10 @ 300

Φ 10 @ 300

Φ 10 @ 300

Φ 10 @ 300

Page 8Instructor:

Eng. Mazen Alshorafa

Design of Concrete Structure II

University of Palestine

3m 5m 5m

4m

4m

4m

C16 C15 C14 C13

C12 C11 C10 C9

C8 C7 C6 C5

C4 C3 C2 C1

140

mm

Sec. A-A

Φ 10 @

300 Φ

10 @ 300 Φ

10 @ 300

Φ 10 @

300 Φ

10 @ 300

Φ 10 @

300 Φ

10 @ 300 Φ

10 @ 300

Φ 10 @

300 Φ

10 @ 300

Φ 10 @

300 Φ 10 @

300 Φ

10 @ 300

Page 9Instructor:

Eng. Mazen Alshorafa

Design of Concrete Structure II

University of Palestine