Post Tensioned Concrete Floors Amr Abdelrahman Ain Shams

7/23/2019 Post Tensioned Concrete Floors Amr Abdelrahman Ain Shams

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1

POST-TENSIONEDCONCRETE FLOORS

Dr. Amr Abdelrahman Associate Professor, Ain Shams University, Cairo, Egypt

[email protected]

April 2006

Why post-tensioning?Structural Systems of Slabs

RC solid slabs on beams

Ribbed slabs (hollow blocks, waffle)

RC flat slabs

Hollow core precast slabs

Post-tensioning Can Provide

Faster construction

Durable structureBetter connections compared

to precast slabs

“Cheaper” alternative



2

How can we do it?normalreinforcement

tendons

middlestrip

column

stripmiddlestrip

middlestrip

middlestrip

columnstrip

middlestrip

middlestrip

columnstrip

100% banded through columnsin both directions and normal reinforcement

100% banded through columns in one directionand uniform distribution in other direction

75% concentrated in column strip and25% in middle strip in both directions

75% concentrated in column strip and 25% i nmiddle strip in one direction-other direction uniform

Post-tensioned

flat slabs

Choice of the

system:

•Aspect ratio•Constructibility issues

Analysis?

Equivalent frame method

Finite element method

SAP2000

Computer programs for prestressedconcrete members “ADAPT, Concise, ….”



3

Structural analysisEquivalent frame method

Aalami et al. 2001

Cable layout

Banded tendons Distributed tendons



4

Computer model

L

L(1-2 ) L

2 31 4 5 e5e1e3

Curve(1) Curve (2)

Curve(3)

L

Rcolumn

yi =

aix

i2 + b

ix

i+ c

i(1)

y1 = e1 ( fo r c urve 1) (2)

y3 = e3 ( fo r c urve 2) (3)

y5 = e5 ( fo r c urve 3) (4)

y2 (for curve 1) = y2 (for curve 2) (5)

y4 (for curve 2) = y4 (for curve 3) (6)

2curvefordx

dy 1curvefor

dx

dy

22

⎟ ⎠

⎞⎜⎝

⎛ =⎟

⎠

⎞⎜⎝

⎛

3curvefordx

dy 2curvefor

dx

dy

44

⎟ ⎠

⎞⎜⎝

⎛ =⎟

⎠

⎞⎜⎝

⎛

1)curve(for0dxdy =⎟

⎠ ⎞⎜

⎝ ⎛

1

3)curve(for0dx

dy=⎟

⎠

⎞⎜⎝

⎛

5

(7)

(8)

(9)

(10)

Computer model



5

SPECIMENS

Pattern No1

L y

Lx

L y

Lx

L y

Lx

L y

Lx

Pattern No2

Pattern No3 Pattern No4

The analyzed panels are

divided into three groups

according to its aspect ratio.

The applied aspect ratios in

analysis are 1.00, 1.33, and 2.00.

For plates with aspect ratio 1.33

and 2.00 “Lx” represent the

long direction and “Ly” is the

short direction.

Analysis of PT flat slabs

Test specimensPlate

Dimensions Pattern PT Force (kN)

Lx(m) Ly(m) ts(m) Px Py

1 12.50 x 12.50 12.50 12.50 0.30 1 1150 1150

2 12.50 x 12.50 12.50 12.50 0.30 2 1400 1400

3 12.50 x 12.50 12.50 12.50 0.30 3 1350 1350

4 12.50 x 12.50 12.50 12.50 0.30 4 1300 1300

5 10.0 x 10.0 10.00 10.00 0.24 1 600 600

6 10.0 x 10.0 10.00 10.00 0.24 2 950 950

7 10.0 x 10.0 10.00 10.00 0.24 3 700 700

8 10.0 x 10.0 10.00 10.00 0.24 4 700 700

9 7.50 x 7.50 7.50 7.50 0.18 1 300 300

10 7.50 x 7.50 7.50 7.50 0.18 2 350 350

11 7.50 x 7.50 7.50 7.50 0.18 3 350 350

12 7.50 x 7.50 7.50 7.50 0.18 4 350 35013 10.0 x 7.50 10.00 7.50 0.24 1 437.5 350

14 10.0 x 7.50 10.00 7.50 0.24 2 625 500

15 10.0 x 7.50 10.00 7.50 0.24 3 500 400

16 10.0 x 7.50 10.00 7.50 0.24 4 500 400

17 10.0 x 5.0 10.00 5.00 0.24 1 210 368

18 10.0 x 5.0 10.00 5.00 0.24 2 210 368

19 10.0 x 5.0 10.00 5.00 0.24 3 210 368

20 10.0 x5.00 10.00 5.00 0.24 4 210 368



6

0

50

100

150

200

250

300

350

12 . 5 x 12 . 5 10 . 0 x 10. 0 7. 50 x 7. 50

Slab dimensions

C o s t p e r m 2 ( E G P )

Pattern 1

Pattern 2

Pattern 3

Pattern 4

Effect of tendon patterns

Plates with aspect ratio “1”

Concrete 250 EGP/m3

Non PS steel 3500 EGP/ton

PS steel 16000 EGP/ton

0

50

100

150

200

250

10 . 0 x 7 . 50 10 . 0 x 5 . 00

Slab dimensions

C o s t p e r m 2 E G P

Pattern 1

Pattern 2

Pattern 3

Pattern 4

Plates with aspect ratio “1.33 and 2”

Effect of tendon patterns



7

0

50

100

150

200

250

300

56 .25 100 156 .25

PT Plate Area

C o s t p e r m 2 ( E G P )

Effect of PT plate area

0

50

100

150

200

250

300

5.0x10.0 7.50x10.0 10.0x10.0

Plates with different aspect ratios

C o

s t p e r m 2 E G P

0

50

100

150

200

250

300

7.50 x7 .50 10 .0x10 .0 12 .50 x12 .50

Plates with aspect ratio “1”

PT slabs

RC slabs

PT vs. RC slabs



8

Case study I

8 x 5. 4 = 4 3.

25 8 .5 6

115.40

5 9 . 4

0

55.67

PART 1 PART 3

PART 2

Plan of the first basement framing plan

Office Building

Smart Village

2B

1B

G

1st

2nd

3rd

roof

Elevation

E x p a n s i o n j o i n t E x p a n s i o n j o

i n t

E x p a n s i o n

j o i n t

E x p a

n s i o n j o i n t

Overview “Case study I”

Part 3

Part 1

Part 2

Autocad



9

Construction sequence “Case study I”

Form Work

Laying Ducts

Profile of Ducts

Cable layout “Case study I”

Ba nded te ndo ns

D is t r i b u ted te ndo ns



10

Concreting “Case study I”

Measurements “Case study I”

Stressing



11

Construction details “Case study I”

Jacking

end

regions not prestressed in direction parallel to tendons

tendons

free edge

Flat duct

Dead

end

Formwork removal “Case study I”



12

Grouting “Case study I”

What if it was RC ? “Case study I”



13

Does it look good? “Case study I”

Front elevation

Sideelevation

1 5 % c o s t s

a v i n g

Case study II

14.9017.0017.0011.00

59.90

1 0 . 9

1 6 . 0

1 3 . 6

4 0 . 5

Main beam

Main beam

s e c o n d a r y b e a m s

Exhibition Hall, Nasr City

opening

prestressed

non-prestressed



14

Details “Case study II”

1500

1100

Main beam

400

700

160

Secondary beam

Details “Case study II”

Frame

Bending moment

Deformed shape after stressing

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Post Tensioned Concrete Floors Amr Abdelrahman Ain Shams