Pre stressed concrete and post tensioning technology

1. UTRACON STRUCTURAL SYSTEMS PVT LTD
ISO 9001 : 2008
POST TENSIONING SLABS CONSTRUCTION SEQUENCE
VIT UNIVERSITY - AMARAVATHI

2. 11 October 2017 2
PT Flat slab : Shuttering Plan drawing

3. 11 October 2017 3
Bottom shuttering in progress.

4. 11 October 2017 4
Completion of Bottom shuttering.

5. 11 October 2017 5
PT Flat slab : Reinforcement drawing

6. 11 October 2017 6
Tying of Bottom Nominal reinforcements

7. 11 October 2017 7
Completion of Bottom Nominal reinforcements

8. 11 October 2017 8
Drawings For Tendon Layout indicating Pour strips and stressing
ends

9. 11 October 2017 9
GI Ducts Laying in Progress

10. 11 October 2017 10
Fixing of ducts at end stressing anchorages.

11. 11 October 2017 11
Stressing end Anchorages fixed at Edge RCC Beams .

12. 11 October 2017 12
De coiling of HT strands
HT strands are cut to
required length

13. 11 October 2017 13
Inserting of HT strands into GI Ducts .

14. 11 October 2017 14
Shop drawings showing Tendon Layout Profile

15. 11 October 2017 15
Fixing of bar chairs to form tendon profile.

16. 11 October 2017 16
Stressing end anchorage, grout vents on completion of laying

17. 11 October 2017 17
Bursting links at Stressing anchorages

18. 11 October 2017 18
Fixing of Dead ends and Fixing of grout vent.

19. 11 October 2017 19
Laying of Tendons on completion

20. 11 October 2017 20
Pour strip provided for construction feasibility

21. 11 October 2017 21
Side Shuttering
Strands
Block Out
Castings
G.I.Duct
Grout Hose
Grout Vent
Working Platform
PT Materials

22. 11 October 2017 22
Aerial view of Tendons Laying before concreting

23. 11 October 2017 23
PT Flat slab after completion of Tendon laying ,before concreting

24. 11 October 2017 24
Concreting In Progress

25. 11 October 2017 25
Block outs/Recess Formers
at Stressing anchorages
Fixing of anchor Blocks and
wedges .

26. 11 October 2017 26
25 % of initial stressing to remove slag.

27. 11 October 2017 27
Stressing Of Slab Tendons.
Paint Mark shows
Elongation

28. 11 October 2017 28
Paint Mark
shows
Elongation

29. 11 October 2017 29
Anchorages seen after stressing in edge beams

30. 11 October 2017 30
Excess strand has been cut after stressing

31. 11 October 2017 31
Patching of stressing Pockets

32. 11 October 2017 32
Adding cement in to the mixing tank

33. 11 October 2017 33
Mixing of Cementicious Grout

34. 11 October 2017 34
Tying the hose at other end
after witnessing good grout
mix and exists of air bubbles
if.
Closing of Grout hose end .

35. Primary Objective Secondary Objective
QA / QC Recommendations
Registering of Drawing
PT Laying
Profiles
Stressing
Grouting
Check the
shuttering
Check the bottom
rebar orientation

36. Registration of Drawing
Latest incoming drawing register should be maintained at site
office with the details of
1. Drawing number
2. Revision
3. Date of receipt
4. Date of approval by consultant.
Based on this register Project Manager has to arrange the drawing
for site execution.

37. PT - Laying
 Drawings to be thoroughly studied by Utracon team at site.
Clarifications are to be brought to the Utracon design team through project manager at site
Approved drawing / corresponding Engineering instructions are to be made available before
commencing the work at site.
 Tendon spacing should be followed as per tendon layout drawing.
 Duct joints are to be sealed well to avoid any ingress of concrete.

38.  Based on tendon layout drg, the live and dead ends are to be fixed. If any
difficulties/deviations /obstructions ,it is to be brought to the notice of concerned Design
Engineer.
Ensure that the protruding strand length is sufficient for stressing ( min 350 – 400 mm)
Based on Tendon layout no. of strands to be
threaded into ducts.
Fix the grout vents.

39.  Profiles need to be checked by PT team and finally verified /approved by PMC team.
 PT Engineer should make sure that while checking the profiles, all the tendon support bars &
chairs are placed at specified intervals as per the drawings.
The tolerances of vertical profiles is ± 5mm for high and low points.
 The tolerances for horizontal profiles are ± 150 mm.
Any openings / fixing of rebars ,etc. are to be provided ,the importance should be given to the
Profiles

40. Stressing
 Before stressing PT Engineer has to check with the cube result with the main contractor
 whether the slab has achieved the minimum cube strength as specified in design/drg.
 Once concreting is completed ,the platform are to be arranged for
carrying out the stressing with the help of Main contractor.
Remove the block outs and clean the castings to fix the anchor blocks
for stressing activity
 The theoretical elongation calculations must be approved by the consultant before stressing.
 Fix the wedge plate and wedges.
 25% of the stressing force shall be applied to the tendon to remove the slack in the strands.
 spray mark should be made to strands.

41. Once the cube test result is made available by main contractor,
stressing can be started to initial stressing of 25% ,to remove slacks
 Marking is to be done in strands before carrying out the 75% stressing
and elongation is to be measured This will reflect the strand’s
elongation form 25 % to 100% force.
 Elongation shall be checked with measured reading in random after 24 hrs of final
stressing to confirm that there is no slippage of strands
The recess pockets left for the stressing shall be patched with cement mortar.
Stressing

42. Grouting
1. After consultant /PMC has approved the stressing result ,grouting can be started.
2. Before grouting the ducts shall be thoroughly cleaned by compressed air.
3. Grout mix shall be prepared in W/C ratio of 0.45 with workability additive of 0.2% of weight
of cement.
4. Inject grout from the tendons inlet hose and lock the
outlet hose
Lock the outlet hose when the pressure of 3 bars is achieved.
6

43. Do Before Concreting
1. After the Bottom mat completed. We start our work
2. We lay the tendon both horizontal and vertical then fix our castings.
3. After laying of tendons both directions and making the profiles then start the
tieing of top reinforcement
4. Side shuttering can made after fixing of our casting & backing.
5. Proper VIBRATIONS required at the time of concrete (At least at the place of
live ends & Dead ends).
Do after concreting
1. Curing properly then only we can achieve the concrete strength.
2. Side shuttering should be removed next day of the concrete.
3. If any honeycomb found immediately batch up with fosroc or rich mix depends
upon honeycomb at site condition.
Don’t Do
1. Don’t walk onto tendon Profile.
2. Don’t dump materials like Rebar’s, Shuttering materials onto tendon
3. Don’t disturb tendon profile.
4. After concrete anybody should not cut the grout hose at any reason.
5. At the time of stressing anybody should not stand behind the stressing jack.
6. Don’t remove shuttering before getting approval from engineer.
DO’s and DONT’s

44. Don'ts
1. Don’t place the strand on the ground. It has to be placed above the ground with wooden
packers to avoid contamination.
2. Don’t start tendon laying without checking the slab bottom reinforcement orientation and
cover.

45. 3. If you found any defect on the bulb of the strands, should be replaced with the new bulb.
4. Don’t allow the peoples to stepping on ducts.
6. Don’t commence the stressing without confirmation from main contractor on the required
cube result.
7. Don’t stand in front of the jack and look behind the jack while stressing in progress.
8. Don’t allow grouting without cleaning the ducts by using compressed air.
9. Don’t allow to do grounding if water cement ratio is more than 0.45
10. Ducts to be grouted using max pressure of 0.5 N/mm2 and not lower than 0.2N/mm2
11. Pressure should be duly controlled so as not to cause segregation of grout. Required
pressure to be maintained shall be 3 to 5 bars

47. LAYING CHECKLIST

48. STRESSING – CHECKLIST

49. GROUTING – CHECKLIST

51. Sample Elongation Calculation
1 st basement flr
D = (PL /AE)
Where P = (Po + PI) / 2
Po = Force @ Stressing end
75% UTS
0.75 X 183.7 = 138 KN
PI = Force @ Far end
E = Modulus of Elasticity = 1 9 5 KN/MM2
A = Area of Stand
PI = Po x e-(µα + kL)
Where µ = Co efficient of friction = 0 .2
K = Wobble Factor = 0 .0 0 1 7
L= Length of Tendon
α = Angular Deviation
α =
D = (PL /AE)
where P = (Po+ PI) /2
Theroritical Elongation = D
Sample Elongation Calculation:
+ +
Horizontal Distance Between HP2-LP2
4 (HP1-LP1) 4 (HP2-LP2)
Horizontal Distance Between HP1-LP1

52. 10/11/2017
Sample Elongation Calculation
Example : Calculation of 1st basement flr
( Refer Attached Drawing)
Tendon No : T1 2 1
Length of Tendon = 1 3 .6 8 m
α = 4 (190-115) 4 (190-35) 4 (115-35)
3200 5500 4975
α = 0.27 Radian
Po= 138 KN
PI = Po x e
-(µα+ kL)
= 138 x e
-(0.2x0.271 + 0.0017x13.68)
PI = 1 2 7 .7 1 KN
D = (PL )
AE
P0+ PI X L
d1 = 2
138+ 127.71 x 13.68
= 2
100x195
Theritical Elongation = 9 3 .2 mm
+ +
AE

53. Jacking force
UTS= 183.7 KN
Stress=Load/Area
Apply=75%
NO OF STRAND 75% 76% 80% 75% 76% 80% Jack loss =2%
Anchorage Loss = 3%
= (183.7*0.75*1.05*1000)/3325
= 43.51 Mpa
JACK LOSS
ANCHORAGE LOSS
STRESSING PRESSURE OF ALL HIS JACK MODELS
All Pressure indicated above is in Mpa
For conversion to Bar = Mpa X 10
UTS=Ultimate tensile strength
3% 3%
46.41
PISTON AREA 3709MM2 3325MM2
2% 2%
1
39 39.52 41.6 43.51 44.09
STRAND TYPE: 0.5"(12.7MM)
TYPES OF JACK
IHS IHS
CH 258 DA CH 258 DA
UTS UTS

54. Jacking force
UTS= 260.7 KN
Stress=Load/Area
Apply=75%
NO OF STRAND 75% 76% 80% 75% 76% 80% Jack loss =2%
Anchorage Loss = 3%
= (260.7*0.75*1.05*1000)/3325
= 61.74 Mpa
JACK LOSS
ANCHORAGE LOSS
STRESSING PRESSURE OF ALL HIS JACK MODELS
All Pressure indicated above is in Mpa
For conversion to Bar = Mpa X 10
UTS=Ultimate tensile strength
STRAND TYPE: 0.6"(15.2MM)
3% 3%
2% 2%
UTS
TYPES OF JACK
1
PISTON AREA 3709MM2 3325MM2
55.35 56.09 59.04 61.74 62.57 65.86
CH 258 DA
IHS
UTS
IHS
CH 258 DA