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Transcript of Rcs1-chapter4-durability
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Marwan SADEK 1
Reinforced Concrete
Structures 1 - Eurocodes
RCS 1
Professor Marwan SADEKhttps://www.researchgate.net/profile/Marwan_Sadek
https://fr.slideshare.net/marwansadek00
Email : [email protected]
If you detect any mistakes, please let me know at : [email protected]
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Marwan SADEK 2
PLAN – RCS1
M. SADEK
Ch 1 : Generalities – Reinforced concrete in practice
Ch 2 : Evolution of the standards – Limit states
Ch 3 : Mechanical Characteristics of materials – Constitutive relations
Ch 4 : Durability and Cover
Ch 5 : Beam under simple bending – Ultimate limit state ULS
Ch 6 : Beam under simple bending – serviceability limit state SLS
Ch 7 : Section subjected to pure tension
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Marwan SADEK 3
Selected ReferencesFrench BAEL Code (91, 99)
Règles BAEL 91 modifiées 99, Règles techniques de conception et de calcul des ouvrages et constructions en béton armé, Eyrolles, 2000. J. Perchat (2000), Maîtrise du BAEL 91 et des DTU associés, Eyrolles, 2000. J.P. Mougin (2000), BAEL 91 modifié 99 et DTU associés, Eyrolles, 2000.….
EUROCODES H. Thonier (2013), Le projet de béton armé, 7ème édition, SEBTP, 2013. Jean-Armand Calgaro, Paolo Formichi ( 2013) Calcul des actions sur lesbâtiments selon l'Eurocode 1 , Le moniteur, 2013. J. M. Paillé (2009), Calcul des structures en béton, Eyrolles- AFNOR, 2009. Jean Perchat (2013), Traité de béton armé Selon l'Eurocode 2, Le moniteur,2013 (2ème édition) Manual for the design of concrete building structures to Eurocode 2, TheInstitution of Structural Engineers, BCA, 2006. A. J. Bond (2006), How to Design Concrete Structures using Eurocode 2, Theconcrete centre, BCA, 2006.https://usingeurocodes.com/
M. SADEK
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Marwan SADEK 4
In addition to Eurocodes, the references that are mainly used to prepare this course material are : Thonier 2013
Perchat 2013
Paillé 2009
Some figures and formulas are taken from
Cours de S. Multon - BETON ARME Eurocode 2 (available on internet)
Cours béton armé de Christian Albouy
M. SADEK
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Marwan SADEK 5
Chapter IV
Durability and Cover
M. SADEK
1. Exposure Classes
2. Structural Classes
3. Cover
4. Detailing of Members / Reinforcement
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Marwan SADEK 6
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
Introduction : Optimization of durability
The cover is the distance between the surface of thereinforcement closest to the nearest concrete surface.It should be sufficient in order to guarantee :
the protection of the steel against corrosion;
the safe transmission of bond forces;
an adequate fire resistance.
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Marwan SADEK 7
The cover of steel and the characteristics of the surrounding
concrete are principal parameters that permit to control the
longevity of the structures.
Introduction : Optimization of durability
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 8
Exposure CLASSES
18 classes - EC2
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 9
Exposure classes related to environmental conditions in accordance with EN 206-1
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 10
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 11
DIFFERENCE between the classifications of NF EN 206-1 & EC 2 (PAILLÉ 2009)
We should make the distinction between the classification relative to the concrete
(NFEN206-1) and that relative to the steel cover (EC2) function of the exposure condition.
The criterion is not always the same.
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 12
DIFFERENCE between the classifications of NF EN 206-1 & EC 2 (PAILLÉ 2009)
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 13
Indicative strength classes for durability
(NF EN 206-1)
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 14
Design working life
Design workinglife category
Indicative design
working life (years)
F NA Examples
1 10 10 Temporary structures
2 10-25 25Replaceable structural parts, e.g. gantry girders,bearings
3 15-30 25Agriculture and similar structures
4 50 50 BUILDING STRUCTURES AND OTHER COMMON STRUCTURES
5 100 100 Monumental building structures, bridges and other civil engineering structures
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 15
Structural classes (6 Classes S1S6)
Classe S4 : The recommended Structural Class (design
working life of 50 years) is S4, for buildings and common civil
engineering structures
The bridges are classified in the the class S6 (4+2), for a design
working life of 100 years (Increase class by +2)
The class may be reduced function of design working
life, the strength class, and the binder type
(Table 4.3.NF, NA)
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 16
Criterion Exposure Class
XO XC1 XC2, XC3 XC4 XD1 / XS1 / XA1
XD2 / XS2 / XA3
XD3 / XS3 / XA3
Design working life
100 years, Increase class by 2
25 years and less, Reduce class by 1
Strength Class
C 30/37 C 30/37 C 30/37 C 35/45 C 40/50 C 40/50 C 45/55
If the strength is greater, Reduce class by 1
C 50/60 C 50/60 C 55/67 C 60/75 C 60/75 C 60/75 C 70/85
If the strength is greater, Reduce class by 2
Binder type
- C 35/45 C35/45 C 40/50 - - -
-
Concrete with CEM Iwith fly ashes
- - -Reduce class by 1
CompactCover
Reduce class by 1
Obtaining compactness in the cover zone concerns for example :
Steel form work, precast elements ..
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 17
Nominal cover cnom
cnom : nominal cover
cmin : minimum cover
cdev : allowance in design for deviation (Recommended value FNA = 10 mm)
(Recommended value FNA = 0)
Note : the Calculation should be conducted for longitudinal and transverse steel
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 18
Nominal cover cnom
cmin,b : minimum cover due to bond requirement
(if dg>32)
1 bar
Bundle of nb barres
cmin,b =
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 19
Nominal cover cnom
cmin,dur : minimum cover due to environmental conditions
requirements with regard to durability for reinforcement steel in accordance
with EN 10080 (Table 4.4 N - NF EN 1992-1-1)
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 20
Nominal cover cnom
Raft foundation
The cover of a reinforced concrete raft cast directly against soil, the cover should be at least 75 mm (65 mm FNA).
This value could be reduced to 40 mm (30 mm ANF) concrete cast against
prepared ground (including blinding)
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 21
Some detailing requirements
(Constructional details)
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 22
Overlapping and anchorage of reinforcement (SBA2)
Transverse Steel
Bad practice very common in lebanon !!
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 23
Minimum permissible mandrel diameter for bent bars avoid damage
to reinforcement
Other criterion : Avoid concrete damage (SBA2),
For this second condition we can reach quickly a value > 10 ( The obtained value with EC2 are higher than those obtained with the previous French code BAEL)
x 2mnomc
mandrin de cintrage
mdiamètre:
t
sdbt
5y
point de départ de l'ancrage
45°
nomct t
2/c tnom
For civil engineering constructions and in case of a good bond condition,
when the tensile force (at the origin of the bar bent) is lower than 75% of the
maximum design force (bt0.75fyd), the mandrel diameter could be taken
m=10 .
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 24
Horizontal and Vertical spacing between bars (EC2, 8.2)(the concrete can be placed and compacted satisfactorily for the development of
adequate bond)
(dg=2.5 cm in general)
The bars should be placed symmetrically
to avoid any additional excentricity
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 25
Reinforcing bars are in tension and therefore should never be bent around an
inside corner beams. They can pull straight !!
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 26
Expansion joint
o Lmax = 25 à 30 m for Lebanon
o Top of the foundation
Construction joint
o in case of high differential settlement
Lmax
Lmax
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 27
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 28
EXAMPLE Developed length for stirrups:
o m=5 (6 16)
o with straight length : max(10 ; 70 mm) (90°)
Carefull : When using other value of m, we obtain different values of developed length
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 29
Bundle of bars
the bars should be of the same characteristics (type and grade).
Bars of different sizes may be bundled provided that the ratio of diameters
does not exceed 1,7.
Where two touching bars are positioned one above the other, and where
the bond conditions are good, such bars need not be treated as a bundle
[EC2 - 8.9.1(4)]
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 30
Bundle of bars
In design, the bundle is replaced by a notional bar having the same
sectional area and the same centre of gravity as the bundle.
o nb ≤ 4 for vertical bars in compression and for bars in a
lapped joint
o nb ≤ 3 for all other cases. (tension)
1.Exposure Classes 2. Structural Classes 3. Cover 4. Detailing for members
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Marwan SADEK 31
Determination of cover for longitudinal and transverse steel
Steel ratio including longitudinal and transversal steel (column , beam section)
Exercises