Dramix速
Dramix速 economic concrete reinforcement for safe floors on piles
Test, specify and build
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PK3 75
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Table of contents PK1
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Initially, floors were applied either plainly or reinforced with conventional reinforcing steel welded meshes. It was, however, only in the early seventies that the first experimental work was undertaken with Steel Fibre Reinforced Concrete (SFRC).
FB1e
Anne Hoekstra Technical Manager Flooring
SFRC PK3is defined as concrete, containing discontinuous steel fibres, which are homogeneously mixed into the concrete.
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Multiple research studies and tests on the behaviour of steel PK3reinforced concrete have been carried out in recent fibre years in various countries. They have greatly contributed to a better characterization and understanding of the behaviour of this material. They have also contributed to the specification of minimum performance requirements for each type of application.
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During the period 2003 – 2007, a Dutch expert commission focused on the materials, test methods, design principles and execution controls for pile supported steel fibre floors. This PK3 has resulted in the CUR 111 recommendation document.
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PK1
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PK1
Since then, SFRC has been used extensively in most of the world’s industrialized nations, for a wide variety of applications. Uses of SFRC in industrial floor applications vary from traditional saw cut floors, over jointless floors, and to most structural floor on pile application.
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FB2a
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PK3
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My aim is to familiarize the reader with the behaviour of steel fibre reinforced conrete, to draw his attention to the specific characteristics of this product, the importance of the performance described by the EN standard and propose a relevant technical solution to reach together a better quality and safety on each job site. This brochure is meant primarily for those who are active in the construction market (investors, contractors, designers) and more specially in the field of industrial floors.
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INTRODUCTION
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Introduction Application field Materials System performance, calculation of Md Calculation of Mu Punching Execution details Quality examinations Standard specification text Bibliography
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03 04 04 09 10 12 12 13 13 14
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1. APPLICATION FIELD
Depending on the design results,the recommended fibre types are:
This document discusses test methods, design and execution for a pile – suspended concrete industrial floor, reinforced with Dramix® steel fibres.
Dramix® RC-65/60-BN: Dramix® Easy Mix Dramix® Hi Perform
This guideline can only be used for: - Industrial floors and not for other applications, such as pile-suspended rafts for residential or other use. - Dramix® steel fibre reinforcement, and not for other steel fibres, synthetic fibres or traditional mesh reinforcement.
Dramix® RC-80/60-BN: Dramix® Hi Perform Specific product data sheets are available on request
Want to know more about: - Product characteristics - Approvals - Features and benefits - How to use
2. MATERIALS 2.1. Concrete: Concrete quality in accordance with EN 206, produced and delivered according to local concrete standards: - Minimum Concrete Quality: C20/25 - Maximum Concrete Quality: C30/37 The grading of aggregates will be in accordance with the applicable standards. The concrete composition must be engineered in order to obtain homogeneous distribution and good finish ability. For detailed information, consult our product data sheets and our recommendations on handling, dosing and mixing.
2.2. Steel fibres:
Download info sheets at: www.bekaert.com/building
2.3. Steel fibre reinforced concrete:
CE info sheet
The performance of a Dramix® reinforced concrete is mainly determined by following characteristics: - The performance of the fibre in the matrix (geometry, length/diameter ratio, method of anchorage, tensile strength,…) - The performance of the concrete matrix - The amount of fibres in the mix In order to define the steel fibre concrete specification, a three steps analysis must be made.
Dramix steel fibres are designed especially for the reinforcement of concrete. They are made of prime quality hard-drawn steel wire to ensure high tensile strength at extremely close tolerances. Provided with hooked ends, they deliver optimum anchorage. ®
1 2
Minimum fibre requirements are:
3
1 Fibres with CE- marking system 1, steel fibre for structural use (conform EN 14889-1-2006) For detailed info, please request our CE info sheet.
According to EN 14889, a minimum performance level must be reached. As such for every fibre type a minimum dosage is required to have CE marking system 1. Download info sheet at: www.bekaert.com/building CE info sheet
2 Fibres out of drawn wire, with a tensile strength of steel wire > 1000 MPa min. 3 Dimensional tolerances in accordance with EN 14889-1.
Minimum dosage for a needed fibre overlap. Minimum total fibre length. Dosage based on performance.
2.3.1. Minimum dosage based on minimum overlap: Minimum fibre overlap: For structurally designed applications, the average distance between steel fibres (s) should be lower than 0,4 lf in order to ensure a minimum overlap between fibres. 2 x lf s=3 πxdf 4ρf
Where :
5 Minimum fibre length : 2 times the maximum coarse aggregate size.
- lf is the length of the fibre - df is the equivalent diameter of the fibre - ρf is the fibre percentage
6 Maximum fibre length : 2/3 of the hose diameter of the pumping machine.
s should be lower than 0,4 lf to ensure a minimum overlap
7 Glued fibres for improved and risk-free pump ability and mixing.
The formula and “s” limits are taken from the thesis of D.C Mc Kee, University of Illinois, Urbana 1969: “The properties of an expansive mortar reinforced with random wire fibres.”
4 Best anchorage system : hooked ends for optimum anchorage.
4
5
2.3.3. Dosage based on performance: residual strength
Fig. 1: Minimum dosage based on minimum overlap
S
S
In order to establish the material properties, test EN 14 651 describes a notch three-point bending test which is the basis for the stress-strain diagram for steel fibre conrete.
S 2
lf
S S
S 2
Aspect ratio (lf/df)
40
45
50
55
60
65
Min. dosage when s<0,4 lf mm, kg/m3
61
48
39
32
27
23
Resulting from this test, a load displacement curve shows the different residual forces measured for predefined crack mouth openings. A
F
F
Minimum dosages of steel fibres based on different aspect ratios and steel fibre spacing
2.3.2. Minimum dosage based on minimum total fibre length:
30
Aspect ratio: I/d (length/diameter)
Minimum kg/m according to min. overlap
I
D
fibres/kg
Total fibre length
50
48 kg/m3
50
1
2.800
6.720
65
35 kg/m3
60
0,9
3.200
6.720
25
250
A
250
δII
150
150 75
30 3
δ1
75
δ
In addition to the requirement of the minimum fibre overlap, Bekaert recommends a minimum steel fibre length of 6700 meter/m³ concrete. This fibre length ensures the minimum network effect to provide a specific multi-crack process and so the redistribution of the loads through the crack-bridging steel.
150
25
500 section AA F [ kN ]
detail A
25+1
Example to reach three criteria: CE-minimum performance level, Mc Kee “2.3.1.” & minimum total fibre length “2.3.2.” The crack patterns observed on different tests explain the importance of the total fibre network.
δ FFl
1
F kN
CMOD1 = the crack mouth opening displacement at 0,5 mm CMOD2 = the crack mouth opening displacement at 1,5 mm CMOD3 = the crack mouth opening displacement at 2,5 mm CMOD4 = the crack mouth opening displacement at 3,5 mm
FR,1 F R,1
Fl = load at the first crack CMODl FR1 = load at CMOD1. FR2 = load at CMOD2. FR3 = load at CMOD3. FR4 = load at CMOD4.
FR,2 F R,2 FR,3 F R,3 FR,4 F R,4 CMOD [ mm ] CMOD mm
0,05 0,05
6
Low fibre network
High fibre network: multiple cracking
7
CMOD CMOD L L
CMOD = 0.5 CMOD = 0,5 1 1
CMOD CMOD2 2== 1.5 1,5
CMOD 2.5 CMOD33==2,5
CMOD = 3.5 CMOD 4 4 = 3,5
Based on this test, the absolute minimum residual flexural tensile strength is:
f(r1) = 4,1 N/mm² f(r4) = 3,1 N/mm²
minimum residual flexural tensile strength for a C30/37 concrete
These values are proposed for a concrete class C30/37, usually specified for a pile-supported floor. Compressive strengths with a too low or too high strength class may have undesired side effects. Please contact your local Bekaert representative in order to get the minimum residual values for other concrete classes. For the same concrete matrix, the performance level is significantly influenced by the fibre type (e.g. the anchorage type, the aspect ratio (length to diameter) and the fibre dosage. The higher the aspect ratio and fibre content, the better the performance of the SFRC.
Why yield-line theory should not be used: 1 No information is given on support reactions or deflections. 2 The adverse effects of pattern loading, such as uplift at piles, are not considered. 3 The design may be unsafe if not all the critical mechanisms have been investigated. 4 The method is only valid when slabs have adequate ductility for the assumed yield lines to develop. It is not possible to verify whether this is the case since the analysis provides no information on slab deformations. 5 Calculating the bending moments has to be done with the real pile distances. Decreasing “the design center to center distance” with the pile and/or floor thickness is not allowed.
2.4. Additional mesh or rebar:
Why use the EN 14 651 beam test method and not a round indeterminate plate test: To determine the performance of SFRC for a floor application, the beam test is much more appropriate than a round indeterminate plate test.
1 Technical Report TR63 “Guidance for the design of Steel-Fibre-Reinforced concrete” outlines that round indeterminate plate tests are not covered by standards and are not a suitable method to determine the fundamental properties of SFRC.
2 In a statically indeterminate plate test, the flexural resistance is not related to the crack width. 3 Results of round plate tests are interpreted using yield line analysis in which the flexural resistance is assumed to be constant along the yield lines. In reality, the pattern of yield lines varies very much, and so too the crack width along these yield lines. Therefore the flexural resistance derived from statically indeterminate plate tests depends heavily on assumptions made in the analysis. 4 The structural response should be predicted from rigorous material models rather than the other way around.
The yield stress of the reinforcement is 500 N/mm2. When different, the design must be adapted in line with local standards.
3. SYSTEM PERFORMANCE CALCULATION OF Md 3.1. Minimum design information: - Floor layout - Pile or pile head dimensions - Spans between piles in x and y direction - Floor loads - The edge of the floor field: line or point supported
3.2. Loads: Design is made for various load situations
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- Floor completely and fully loaded - Fields loaded - unloaded load case - Point and wheel loads The yield lines formed - as well as the total yield line length - in the system test set-up, significantly vary a lot over different test results and can therefore not be used to derive a uniform flexural resistance value.
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- Restrained shrinkage
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maximum bending moments to be calculated on top and bottom
m fftd,3 = design value of the tensile strength at CMOD = 3,5mm 0,37 * FR4 ————— γm
fftd,3 =
In view of the relatively small contribution of fftd,1, to the bending moment resistance, it is justified to use the relation shown in the next figure.
Restrained shrinkage:
In view of the relatively small contribution of f ftd,1 to the bending moment resistance, it is justified to use the relation stress-strain shown in Simplified the next figure. stress
compression
fcd
Variant 1 1 : :Nkrimp = 0,75 ε'f ε'EffE .hf.hand Variant Nkrimp = 0,75 andMM Ifloor.Κ .Κkrimp krimp f f. I.floor krimp==EE krimp Variant 2 2 : :Nkrimp = ε' ,E .hf.h Variant Nkrimp =fε' f, fE Unity check: Unity check: Mrep + krimp Mkrimp Nkrimp Mrep +M Nkrimp Variant ——————+ + ————— ————— ≤ ≤11 Variant 1 1 : :—————— Mwmax b.h.ft,rep,i Mwmax b.h.f t,rep,i
25‰
Mrep Nkrimp Mrep Nkrimp Variant –––––––––– –––––––––– ≤1 Variant 2 2 : : –––––––––– + + –––––––––– ≤1 Mwmax b.h.ft,rep,i Mwmax b.h.f t,rep,i
fftd. 3 fftd. 2
tensile
εc,1
1.75‰
strain
εc,2
3.5‰
The below diagram illustrates the theory and contains the equations based on cross-sectional equilibrium for a specifically assumed strain distribution over the height of the cross-section.
The below diagram illustrates the theory and contains the equations based on cross-sectional equilibrium for a specifically assumedCross-sectional strain distribution over the height of the cross section. equilibrium
4. CALCULATION OF Mu
ffcd
In each cross section Md ≤ Mu
εc,2 = 3,5 ‰ 7/
-
N1
εc,1 = 1,75‰
The maximum allowable bending moment in steel fibre concrete Msfrc is calculated by a cross-sectional equilibrium. The stress-strain relation conforms to EN 14651. +
Calculating of the additional reinforcement:
n this:
stress compression
fcd
1/2(h-hxu)
h
εt,2 fftd. 3 fftd. 2 fftd. 1
εc,1
1.75‰
ffcd = design value of the compressive strength. fftd,1 = design value of the tensile strength of SFRC. 10 fftd,2 = design value of the tensile strength at CMOD = 0,5mm
εc,2
3.5‰
strain
fftd,2 =
fcd = design value of the compressive strength
N1 = 0,75 hxub ffcd
fftd,1 = tensile strength design value of SFRC
T1 = Asσs = AsEsεs = AsEs (
fftd,2 =
γm
fftd,3 = tensile strength design value at CMOD = 3,5 mm fftd,3 =
0,37 * FR4 γm
εs
As
Formulae:
0,45 * FR1
+
T1
In this:
fftd,2 = tensile strength design value at CMOD = 0,5 mm
0.1‰
0,45 * FR1
Mu
d
T2,1
“The mean (uni-axial) tensile strength is used as the starting value since the redistribution capacity of steel fibre reinforced concrete industrial floors founded on piles, also regarding the minimum fibre content, is such that the use of the mean value of the uni-axial tensile strength as a basis for design is accepted, rather than the characteristic lower The maximum allowable bending moment in steel fibre concrete is calculated by a cross-sectional equilibrium. limit value.” The stress-strain relation conform EN 14651.
tensile
1/3(h-hxu)
T2,2
Consequently the CUR 111 clearly expresses:
25‰
hxu
fftd ,2
In a floor construction, yield lines must be developed and this aspect of behaviour will not occur in a notched beam, where we have only one crack. The EN 14651 test does not reflect multiple cracking. And for this reason, it is allowed to calculate with mean values.
Stress-strain diagram
15
18.hxu
Formulae:
(fftd,2 - fftd,3)
d-hxu ) 3,5.10-3 < Asfsy hxu
N1 = 0.75hxuεbffcd ft
T2,1 = b (h-hxu)(fftd,2 -
ε ft
25.10-3
(f
-f
))
25.10-3 ftd,2 ftd,3 d - hxu T1 = Asσs = AsEsεs = AsEs ( ——— ) 3.5.10-3 < Asfsy ε ft hxu T2,2 = 1 b (h-hxu) (f - f )) 2 25.10-3 ftd,2 ftd,3εft T2,1 = b(h-hxu)(fftd,2 - ——— (fftd,2 - fftd,3)) Horizontal equilibrium: ∑ H = 0 :25.10 N1 =-3T1 + T1,2 + T 2,2 1
ε
2
25.10-3
11 Bending moment equilibrium: Mftu = 18 hxu-fftd,3 N1 + T2,2 = — b(h-hxu) ———— (fftd,2 )
1 2
(h-hxu) T2,1 + 13 (h,hxu) T2,2 + (d-hxu) T1
If Md > Msvb then Mreinforcement ≥ Md- MSFRC
Horizontal equilibrium: ∑ H = 0 : N1 = T1 + T1,2 +T2,2 The amount of reinforcement is calculated in the normal way Bending moment equilibrium:
11
11 1 1 Mu = —— hxu N1 + —— (h-hxu)T2,1 + — (h-hxu) T2,2 + (d-hxu) T1 18 2 3 If Md>Msvb then
εft
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PK3
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585
A
It is necessary to limit crack widths in the punching area. In case of a too big crack width, the shear resistance capacity will decrease. It is only possible to realistically calculate crack widths in statically indeterminate structures without conventional reinforcement by carrying out a non-linear analysis, which is impractical for design. The maximum crack opening is a direct consequence of the total fibre network. It is prohibited to use fibre dosages lower than the minimum dosage based on the total fibre length. See “2.3.2. Minimum dosage based on minimum total fibre length”
6. EXECUTION DETAILS Depending on the specific project circumstances, specific execution details (joint profiles, special reinforcement,…) have to be applied. For your tailor-made job site details, please contact your local Bekaert specialist.
Benefit from our total design management: - Joint profiles - Reinforcement details - Concrete compositon Contact your local bekaert specialist or: infobuilding@bekaert.com
8. STANDARD SPECIFICATION TEXT 1
FB2a
13
B'
Fibres - Fibres to comply with European Standard EN 14 889-1. - Fibres with CE-marking system 1. Fibres out of drawn wire, with a tensile strength of steel wire > 1.000 Mpa min. Dimensional tolerances according to CE. - Minimum fibre length : 2 times the maximum coarse aggregate size. - Maximum fibre length : 2/3 of the hose diameter of the pumping machine.
3 Fibre concrete - Glued fibres for improved and risk – free pumpability and mixing. - It is prohibited to use loose steel fibres which will cause balls during mixing. Download at: www.bekaert.com/building
13
500
645
2 Performance - Minimum total wire length/m³ should be 6.700 meter in order to ensure the minimum network effect. - Minimum fibre overlap according to Mc Kee Theory. - Residual flexural tensile strength in accordance with the design, but as absolute minimum. f(r1) = 4,1 N/mm² f(r4) = 3,1 N/mm² - Concrete quality and additional reinforcement in accordance with design note.
Execution details
12
FB2b
415
FB5
305
40
- If needed: start up a quality program with beam tests, produced in accordance with the EN 490 14 651 in order to 270 290 25 control the600 performance. Our concrete585 lab is an open door for jobsite test programs. Contact your Bekaert 560 25 specialist. 2355
Punching check has to be done based on the codes. There is no agreed method for calculating the designed shear strength of fibre reinforced concrete without conventional reinforcement.
25
25
235
420
85
afm. ifv. in te betonneren box
30
330 300
Must be in line with the Bekaert design: 30 300 - The concrete thickness during casting. PK1 PK6 PK5 - PK1 The right FB3a fibre type is used. PK1 FB3b FB6 - The fibre dosage: check through several washing out tests (when an automatic dosing machine is not applied) 40 80
35
bestaande paalkop
98
20
VLOERPLAAT opleg min.15 cm op
K-101 ® wanden leveler (detail volgt) PK5that Dramix - The concrete mix needs to be designed and adapted in such a way fibres can be mixed easily and 180 a good concrete workability is obtained. Moreover, the maximum water/cement ratio is 0,5. PK7 Contact your local Bekaert specialist for optimal steel fibre concrete recepies.
55 30
283
FB1g
25
1
FB2a
430
75
375
FB1f
505
PK1 1'
85
80
0,00
PK1 2 375
Concrete cover dekking 3 cm
5
AFSTANDSHOUDERS
75
Must be in line with the Bekaert detailed drawings: - The extra reinforcement is placed. The top and bottom reinforcement need enough support to hold it in place 20 160 150 during the concrete casting process. 95 25 PK4 - The reinforcement concrete cover. FB4b FB2c PK1 - The joint profiles are positioned and oriented correctly.
FB2a
440
Concrete floor - POLIERBETON 22 cm , zie bestek PEBENOR plastic sheet - DOORZICHTIGE PE-FOLIE 0,2mm Soil - GESTABILISEERD ZAND 13cm
AANGELASTE
440
375
FB2a
440
75
PLAN
BOVENWAPENINGS - NET MET ONDER
Generals: 75 150 - Check the top level of all piles and foundations beams. These must be below the bottom of the concrete floor to allow casting. - Check the level of the subbase. PK3 must be leveled to +0 ; - 20 mm of the bottom of the concrete floor. - Check whether the plastic sheet is placed correctly, with enough overlap and fixed in such a way that the sheet will not curl up during the casting of the steel fibre concrete.
75
GECENTREERD When longitudinal reinforcement bars are provided, CUR 111 allows the contribution of concrete and steel PK1 fibres in the total shear 75stress resistance. 75 3 On the other hand, the CUR recommendation clearly describes that a fibre only floor can not be designed using the 150 fibres in the punching shear resistance.
Fig. 2: Pile head detail
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Your Bekaert local specialist can support you with a comprehensive quality control program.
For the most critical areas for punching - around columns and piles - crack openings have to be limited in order to BOVENWAPENINGS - NET have sufficient shear resistance through the concrete section. Therefore, a basic traditional upper reinforcement 8/8/150/150 MET ONDER AANGELASTE (mesh or rebar) always needs to be applied. AFSTANDSHOUDERS, PERFECT OP PAAL
PK3
7. QUALITY EXAMINATIONS
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4
3
VLOERPAAL
150
150
PK1
ASLIJN VLOERPAAL 5. PUNCHING
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375
FB2a
5
440
OPMERKING: ANALOOG DETAIL VOOR ANDERE OPLEGPUNTEN (OOK OP STEUNBLOKKEN OP PAALKOPPEN PK 3 , ENZ.)
75
ASLIJN VLOERPAAL
EA. OPLEGPUNTEN
B
9. BIBLIOGRAPHY - EN 206-1: Concrete – Part 1: Specification, performance, production and conformity. - EN 12390-3: 2002 Testing Hardened concrete – Part 3: Compressive strength of test specimens - EN 14651: 2005 Test method for metallic fibre concrete - EN 14889-1: 2006 Fibres in concrete – part 1: Steel fibres Definitions, specifications and conformity - NEN 2743: 2003: In situ floorings – execution of monolithic screeds and paving - NEN 2747: 2001 Classification and measuring of the flatness and parallelism of the surface of floorings - NEN 6700: 2005: Technical principles for building structures TGB 1990 – general principles - NEN 6702: 2002: Regulations for concrete Loadings and deformations - NEN 6720: 1995: Regulations for concrete – structural requirements and calculation methods, incl. Amendments documents - NEN 6722: 2002: Regulations for concrete – Construction - Technical report n°63: Guidance for the design of Steel-Fibre-Reinforced concrete - CUR-Recommendation 111: Steel-Fibre-Reinforced concrete industrial floors on pile foundations - design and construction
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ABOUT BEKAERT Bekaert is active worldwide in selected applications of its two core competences: advanced metal transformation and advanced materials and coatings. The combination of these competences makes Bekaert very unique. Bekaert, headquartered in Belgium, is a technological leader and serves a worldwide customer base in a variety of industry sectors. BUILDING WITH BEKAERT Bekaert products are widely used in the construction sector. Dramix® has given Bekaert a leading position in the market of steel fibre concrete reinforcement. In 1979, Bekaert introduced Dramix® steel fibres for concrete reinforcement, designed to offer an easy-to-use alternative for traditional steel mesh and bar reinforcement. Applications of Dramix® steel fibres include industrial floors, precast elements, tunneling and mining, residential applications and public works. Other Bekaert building products • Murfor® - masonry reinforcement • Stucanet® - plastering mesh • Widra® - corner beads • Mesh Track - road reinforcement
NV Bekaert SA Bekaertstraat 2 BE-8550 Zwevegem www.bekaert.com/building infobuilding@bekaert.com
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Customer service:
general form only. For ordering and design only use official specifications
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