Dramix. Floors on piles. Introduction. General SF Theory Ground supported floors Jointless floors. Dramix. Tests Design Execution Advantages SSW

Transcription

1 Introduction Dramix General SF Theory Ground supported floors Jointless floors Floors on piles Tests Design execution advantages

2 Introduction Location : University of Braunschweig Prof. Dr. Dipl. Ing. Falkner Dipl.Ing. Ulrich Gossla Date : December -February Number of slabs tested : 3 1 slab only DRAMIX reinforcement 1 slab combined reinforcement ; DRAMIX + re-bar 1 slab combined reinforcement ; DRAMIX + prestressing

3 Concept Introduction Studying the load capacity under ultimate load Design and reinforcement rules for serviceability and ultimate state. Application field Industrial slabs on weak subbases Aim of the tests Optimization of DRAMIX reinforced suspended slabs Combination with traditional reinforcement Combination with pre-stressing

4 Test Set-up size slab : 5 x 5 m Pile distance : 2 m Slab Thickness : 140 mm 9 piles 4 pointloids in the centers

5 Test Set-up

6 Loading criteria Serviceability load = 50 kn Dynamic loading for 2 days ( cycles) Dynamic loading at + 20 % serviceability load ( cycles) Loading until rupture (Ultimate load)

7 Deformations 16 gauges to measure the deformation of the slab. 4 gauges at the edges to measure the rotation of the edges

8 Cracks Measurement of the location of the cracks Measurement of the crack propagation in function of the load Measurement of the crack widths Tests Design Execution

9 Slab 1: Composition Concrete quality : B 45 Steelfibers : DRAMIX RC-80/60-BN Dosage : 40 kg/m3 Concrete W/C ratio : 0,46 Sand 0/2 : 703 kg Aggregates 2/8 : 279 kg aggregates 8/16 : 766 kg

10 Slab 1 ; Crack pattern at top under ultimate load Slab 1 40 kg/m³ Pointload Support Go

11 Slab 1 ; Crack pattern at bottom under ultimate load Slab1 40 kg/m³ Go

12 Slab 1 : Crack pattern Initial crack width = 5/100 mm Crack width after cycles = 16/100 mm Crack Width at ultimate load = 20/100 mm

13 Slab 1 : maximum loading Theoretical serviceability load = 50 kn Measured ultimate load = 81,6 kn

14 Slab 2: Composition Concrete quality : B 35 Steelfibers : DRAMIX RC-80/60-BN Dosage : 40 kg/m3 Concrete W/C ratio : 0,53 Sand 0/2 : 681 kg Aggregates 2/8 : 280 kg aggregates 8/16 : 748 kg Steel cages : 6 x Diam. 10 mm

15 Slab 2: Composition

16 Preparation of slab2

17 Slab 2 ; Crack pattern at top under ultimate load Slab 2 40 kg/m3 DRAMIX + Steelcages Go

18 Slab 2 ; Crack pattern at bottom under ultimate load Go

19 Slab 2 : Crack pattern Initial crack width = 4/100 mm Crack width after cycles = 17/100 mm Crack Width at ultimate load = 44/100 mm More (smaller) cracks than slab 1

20 Slab 2 : maximum loading Theoretical serviceability load = 50 kn Measured ultimate load = 129,9 kn

21 Slab 3

22 Slab 3

23 Load/loadpoint (kn) Floors on piles Comparison ;load deflection curve 150 slab 1,2 and 3 Slab Slab 2 50 Slab deflection under pointload [mm] Go

24 Comparison SLAB 1 SLAB 2 Theoretical ultimate load (a) = 69,4 kn Theoretical ultimate load (b) = 72,8 kn Measured ultimate load = 81,6 kn Cracks according yield line model (b) Theoretical ultimate load (a) = 128 kn Theoretical ultimate load (b) = 137 kn Measured ultimate load = 129,9 kn Cracks according yield line model (a)

25 kn Floors on piles Real safety factor Measured value Calculated value Test Braunschw eig Measured value = measured ultimate pointload for slab 2 Calculated value = Calculated serviceability pointload according the design model

26 Load system a Go

27 Occurring stresses by a prestressed system s Go

28 Serviceability state Admissible stresses Durability Crack widths Go

29 Ultimate state Ultimate load capacity Crack widths (ULS) Go

30 Material characteristics Concrete quality min. C 30/37 30 N/mm2 on cylinders at 28 days 37 N/mm2 on cubes at 28 days Volumetric mass of the concrete 2400 kg/m3

31 Partial safety factors According to Eurocode 2 Permanent loads : 1,35 e.g. dead load of the slab Variable loads : 1,5 e.g. rack loadings Forklift trucks Uniformly distributed loads xx Boxed value ; Local codes can also be used

32 Material factors For traditional mesh reinforcement (according to Eurocode 2) 1,15 For steelfiber reinforced concrete (according the DRAMIX guidelines) 1,5 Creep factor 0,85

33 Stress-strain diagram of SF concrete

34 Design values Characteristic flexural stress of unreinforced concrete Characteristic equivalent flexural stress of DRAMIX reinforced concrete Design values of DRAMIX reinforced concrete f f ffctk, fl 0, 43 fck f ffctk fl *R 3 fctk, eq, e, fl,eq,d f fctk,eq 2 1,5 * 0,85

35 Design values SF-concrete Design values (N/mm2) DRAMIX RC-80/60-BN C 30/37 Dosage (kg/m3) Stress (N/mm2) 1,53 1,62 1,70 Design value = f fl,eq,d Minimum dosage of 35 kg/m3!!! Always the RC-80/60-BN!!!

36 Design values steel bars Steel quality BE 500 A, d , N mm

37 Design model model (a) Symmetrical yield line model Model (b) One directional yield line model

38 Inner fields Global Yield lines M f,x dp a x M s,x A sy A sx M f,y M s,y a y Reduction factor for the pilesection 3 d a Local Yield lines Stability between the steel cages. p y

39 Edge field M f,y Global yield lines A sx Optimum : a xe 2 * a xm 3 a y Local yield lines A sy M s,y M s,x M f,x a x,e

40 Corner field Check stability on global yield lines Check stability on local yield lines

41 Shear reinforcement Punching Shear Resistance v * k *( 1, 2 40 )* d Rd1 Rd 1 v 1, 6* v Rd 2 Rd1 Characteristic shear strength cd fd (RC-65/60-BN) C 25/30 0,30 0,28 0,30 0,32 0,34 C 30/37 0,34 0,31 0,34 0,36 0,38 C 35/45 0,37 0,34 0,37 0,40 0,42 C 40/50 0,41 0,39 0,42 0,45 0,48

42 Shear reinforcement Punching shear stress V Sd : Total design shear force developed :Coefficient for the effect of eccentric loading u : Perimeter of the critical section v Sd : Applied shear per unit lenght v Sd V Sd * u * Traditional flexural reinforcement must be present * Min. 50 % must be reached with DRAMIX

43 Design graphs d [cm] a s [cm/m 2 ] = a [m] m Sd [cm/m 2 ] Pile distances Load Yield moment of SF concrete Section of steel bars Slab thickness 40 = m fd [cm/m 2 ]

44 Location Ostend Reference project 1 Date of execution 20/02/98 Client Consulting engineer Flooring contractor Alheembouw

45 Design parametres Load UDL :15 kn/m2 Function of the building Pile grid : 4 x 4 m Pile sizes : 200 x 200 mm Pilecaps : None

46 Floor Specifications Slab thickness : 200 mm Size : m2 Concrete quality : C 30/37 Steelfiber : 40 kg/m3 RC-80/60-BN Joint spacing : 45 m Steelcages : 6 x diam 16

47 Piling

48 Preperation of the subbase

49 Placing of the steelcages

50 Adding of the steelfibers

51 Casting of the concrete

52 finishing of the surface

53 Location Groningen Reference project 2 Date of execution 17/02/98 Client Slagter Metalworks Contractor -Consulting engineer H. van Zijtveld (Brummen) ; Bressers (Zutphen) Flooring contractor Vloertechniek Oost (rijssen)

54 Design parametres Load UDL :20 kn/m2 Function of the building Production center Pile grid : 3,5 x 3,5 m Pile sizes : 250 x 250 mm Pilecaps : None

55 Floor specifications Slab thickness : 200 mm Size : 1000 m2 Concrete quality : C 30/37 Steelfiber : 40 kg/m3 RC-80/60-BN Joint spacing : 40x25 m Steelcages : 4 x Diam. 11,5

56 Preperation of the subbase

57 Quality of the sub-grade... Calculated settlements (*) : 150 mm in 5 years (*) : In case of a slab on grade

58 Placing of the steelcages

59 Casting and leveling

60 Quality Controls Slump - Fiber dosage - Compressive strenght...

61