Sheets used for lecture on 4th of june 2013 at TU Delft for course CIE4363 (Foundation and deep excavations)

1. Lecture CiTG
Underwater concrete floors
ir. Ruud Arkesteijn
29th of September 2015

2. Content
1st hour:
• Use and functions of UCF’s
• Distribution of forces
2nd hour:
• Design-rules (CUR77)
• Case: guidelines for preliminary design
Extra:
• Steel fibre reinforced UCF’s
• Projects
• Innovations

3. Use of UCF’s
Conditions for application in building pits:
1. sub-surface construction in ‘soft soils’…
2. below the groundwater level…
3. especially in permeable soils.
Typical Delta/Dutch conditions!

4. Bouwput en fasering

5. Bouwput en fasering

6. Bouwput en fasering

7. Bouwput en fasering

8. Bouwput en fasering

9. Bouwput en fasering

10. Bouwput en fasering

11. Bouwput en fasering

12. Bouwput en fasering

13. Functions of UCF’s
1. Water retaining layer
2. Horizontal force equilibrium (strut)
3. Vertical force equilibrium (up burst / heave)
Often a combination of the above!

14. Bouwput en fasering

15. Distribution of forces
4 mechanisms:
• Boundary-disturbance à “Randstoringseffect”
• Arching à “Boogwerking”
• Membrane-effect à “Membraanwerking”
• Re-distribution of forces à “Krachtenherverdeling”

16. Boundary-disturbance à “Randstoringseffect”

17. Arching à “Boogwerking”

18. Membrane-effect à “Membraanwerking”

19. Arching & membrane-effect

20. Re-distribution of forces à “Krachtenherverdeling”

21. Ultimate limit states
1) Bending moments (tension)
2) Bending moments in arch (compression)
3) Shear failure (near retaining wall)
4) Failure or slipping at retaining wall
5) Pull-out of retaining wall (geotechnical failure)
6) Failure of connection with tension piles (punching shear)
7) Pull-out of tension piles (structural or geotechnical failure)

22. Design rules (CUR77)
CUR77 provides
guidelines for design
of unreinforced UCF’s
with respect to:
• Schematisation
• Modelling
• Dimensioning
• Detailing
Revision in 2014!
Demand is to comply with Eurocodes (0, 2 & 7)!

23. • Longitudinal (“lange richting”):
à no boundary-disturbance
à normal forces absent
à membrane-effect is big!
• Cross-sectional (“korte richting”):
à boundary-disturbance is critical
à normal forces present (strut-function)
à limited membrane-effect
Assumption:
Schematisation #1
“lange” richting
“korte” richting
onderwaterbetonvloer
damwand
palen
Ly
Lx
Ly =< Lx
CUR77:2001+2014

24. à hgem = average height (minimum 800mm?)
à tolerances on floor thickness
à calculate stresses with:
hmin = hgem - √(tolonder
2+ tolboven
2)
Schematisation #2
Guidelines:
tolonder à 250 mm for peat/clay
à 150 mm for sand/gravel
tolboven à 75 mm for hob-dobber
à higher for slopes?

25. Modelling
à beam-model of cross-section

26. Longitudinal:
à
Serviceability Limit State (SLS)
à dry building pit
à discrete cracking (minimal compression-zone)
2
, ,
1
(without N')
8
s rep y r repq L M£× ×
Cross-sectional:
à uncracked
or with arching
or with arching + re-dristribution of forces
, ,mod , (with N')s rep el r repM M£

27. Ultimate Limit State (ULS)
à structural safety
à incl. material and load factors
Longitudinal:
à no check because of membrane-effect!
Cross sectional:
à uncracked
or with arching and infinite re-distribution of forces (local):
, ,mod , (with N' )s d el r d dM M£
2
, ,
1
8
s d s d xM q L= × ×

28. New in revised CUR77 (v2014):
1. Revised according to Eurocode 2 (NEN-EN1992)
2. No design rules for SLS in cross sectional direction
3. Optimization of arch-height (z) in ULS
4. Check on shear forces near retaining wall
5. Safety check for case of UCF slipping at retaining wall
6. Adjustments for disc-shape-connections (micro piles):
- extra safety factor kr for punching shear
- increased capacity of concrete compression strength under discs
7. Calculation of axial stiffness piles based on secant-value
à according to CUR236 : Anchor-piles
8. Calculation method for optimization with membrane force
9. Guidelines for use of 2D calculation models
Latest developments published in
Cement 2013/3 and Cement 2014/?

29. Not in CUR77…
Hydration of concrete produces heat à temp. in UCF to 30-45oC
Cooling after heating à shrinkage
Strength of concrete at 50% à sensitive for cracking
Thermal shrinkage of concrete:
à In relatively big building pits the risk of water-conducting
cracks to occur is high even before pumping out the water !

30. Verificatie en toepasbaarheid

31. Case
à Use CUR77:2001 (on Blackboard)
à Consider an unreinforced UCF (no addition of steel fibres)
Make a preliminary design for a deep building pit:
à Modelling a beam-model is not necessary…
à Do not check SLS in cross-sectional direction!
à Only check SLS longitudinal direction, punching shear, and
equilibrium in arch

32. Case: guidelines for preliminary design of UCF
1. Choose concrete strength class B25 (nowadays C20/25):
à tensional strength fb = 1,15 N/mm2
à compression strength f’b = 18,0 N/mm2
2. Determine Ly using SLS check in longitudinal direction (CUR77).
Choose Lx >= Ly
(for edge piles distance to retaining wall Lx,edge < Lx )
LxLx,edge

33. Case: guidelines for preliminary design of UCF
3. Determine effective load on piles based on:
Lx * Ly * Pwater pressure–weight of UCF (incl. load factors)
4. Check punching shear (CUR77).
Adjust hgem or Lx if needed/possible.

34. Case: guidelines for preliminary design of UCF
5. Determine normal forces in UCF (with D-Sheet Piling):
à suggested modelling:

35. Case: guidelines for preliminary design of UCF
6. Check safety in arching-mechanism (ULS cross-sectional direction)

36. Steel fibre reinforced UCF
Potsdammer Platz Berlijn
(1997)
In the Netherlands:
• Heinoseweg Zwolle
(1998)
• Betuweroute
(1999-2002)
• multiple others…
2014:
• Mauritshuis (The Hague)
• Groninger Forum

37. Staalvezelversterkt OWB
“After-crack-behaviour”
à Tensional strength ≈
à Early tensional strength
à Tensional strength after crack
à Re-distribution of forces
à Moment capacity
Effect on force distribution
tension:
bending:
à prevents big shrinkage-cracks
à limited crack-depth

38. Moment capacity for UCF with steelfibres
à example for UCF with hmin = 700 mm and N’ = 200 kN/m’
à 30 kg/m3 of steelfibres
0
100
200
300
400
0,0 2,0 4,0 6,0 8,0 10,0
momentcapaciteitMRd[kNm/m']
kromming κ [mrad] *10-6
M-N-κ diagram
SVB (UGT)
C25/30 (UGT)
fctd,pl
εUGT = 0,1%:
MRd = 380 [kNm/m']
Egescheurd = 4.664 [MPa]

39. Projects
Groninger Forum

40. Projects
Groninger Forum

41. Link to video (dutch) of the process of
pooring the UCF with steel fibres for
project Groninger Forum:
https://vimeo.com/89189883
Lecture CiTG

42. Projects
Mauritshuis (The Hague)

43. Mauritshuis (The Hague)

44. Mauritshuis

45. Link to video (dutch) with animations
made by diving company C.O.W.:
https://vimeo.com/24826624
Lecture CiTG

46. Innovations…
Traditional building method:
- Unreinforced UCF with
temporary function
- Reinforced concrete floor
has permanent function
Integrated floordesign:
- Steelfibre reinforced UCF
- For the permament
function the UCF is
collaborating with a
(traditional) reinforced
concrete floor
Permanent UCF:
- Steelfibre reinforced UCF
has a temporary and a
permament function

47. Lecture CiTG 29th of September 2015