02 Constructions service life and its prediction - ULisboa · PDF fileby NP EN 13670-1); • A vast data compilation about the environmental conditions in the vicinity of the structure

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Authors: Prof. Jorge de Brito, Prof. João Ramôa Correia

Coordination: Prof. F.A. Branco, Prof. Jorge de Brito, Prof. Pedro Vaz Paulo e Prof. João Ramôa Correia

Translation: Prof. Jorge de Brito

CONSTRUCTIONS

SERVICE LIFE

AND ITS

PREDICTION

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1. INTRODUCTION AND BASIC CONCEPTS

2. QUALITY DEGRADATION

3. MINIMUM QUALITY LEVEL IN REINFORCEDCONCRETE

4. WAYS TO APPROACH THE PROBLEM

5. SERVICE LIFE PREDICTION ASSOCIATEDTO REINFORCEMENT CORROSION

6. PRACTICAL EXAMPLE

TABLE OF CONTENTS

CONSTRUCTIONS SERVICE LIFE AND ITS PREDICTION

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7. THE JAPANESE CODE OF SERVICE LIFEPREDICTION OF BUILDINGS

8. THE NEW PORTUGUESE BUILDINGSGENERAL CODE (RGE)

9. CONCLUSION

10. REFERENCES

TABLE OF CONTENTS


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1. INTRODUCTION

AND BASIC

CONCEPTS


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g1. INTRODUCTION AND BASIC

CONCEPTS

• Evolution of the construction materials over time andempirical durability notions (timber, stone, iron and steel, reinforced concrete, fibre reinforced polymers - FRP)

Reality did not confirm the research made…

• Structural design with great evolution in the last century (theoretical level, computers)

• Durability analysis (scientific vs. empirical) is much more recent (only ~ 30 years) → Service life prediction

Bauschinger Memorandum (1887): “The steel rebars embedded in concrete remain completely unchanged and oxide-free for a long period of time.”


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• Service life of a construction (or a construction element):“the period of time after it is placed in service during whichall the properties exceed the minimum acceptable values,assuming there is a routine maintenance”, ASTM(insufficiently clear concept to obtain a scientific estimate…)

- New constructions - the user assumes that the servicelife will equal at least his/hers own life (which does not always happen…), and in general is not worried about the problem

- Old constructions - the question “how long will it last?”is asked more frequently (the answer is generally vague…)

• Its definition: a technical or an economic problem?


1. INTRODUCTION AND BASIC

CONCEPTS

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CONCEPTS

Decisions about the life of a construction

• Curve 1 - demolish the construction (life time T1)

• Curve 2 - leave the construction as it is (life time T2, even though the end of its use occurs only at T'2 > T2)

• Curve 3 - rehabilitate or repair/strengthen the construction (lifetime T3 > T2 and end of its use at T'3 > T3)

Technical or economic problem?Initial quality level

Minimum quality level

Failure

Time

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• The definition of the end of the service life of a construction is very often more an economic problem than a technical one

• A construction reaches the end of its service life when the investment needed to demolish it and build a replacement one is available and the operation as a whole is lucrative

The decision on the end of the construction's servi ce life is basically economic , and the technical part is limited to

(1) quantification of the degradation rate and the (2)definition of the minimum quality level

NOTE: Sometimes, the previous conditions do not exist(“degraded neighbourhoods”) ⇒⇒⇒⇒ the definition of the service life istechnical (curve 2!)



CONCEPTS

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NOTE: In some cases the decision on the end of the service life may even be political, taking into account the architectural and historical value of a construction

D. Maria Pia Bridge($$ maintenance ↑ ; Functional value ↓ ; Historical or heritage value ↑)



CONCEPTS

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2. QUALITY

DEGRADATION


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g2. QUALITY DEGRADATION

a) Safety and serviceability conditions

Aspects related with failure, cracking, deformation (safety levels defined in the codes)

They are conditioned by the evolution of the actions and materials

b) Habitability/functionality conditions

They are conditioned by the users’ needs, geometry and space use

Evolution difficult to estimate(in buildings and bridges), sinceIt frequently depends on humandecisions…

Quality of a construction defined by:(concept used in the definition of the service life )


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g2. QUALITY DEGRADATION

a) Changes in the constructions (e.g. changes concerning the initial permanent or variable loads);

b) Evolution of the code actions (e.g. increase of the actions associated with traffic in a bridge or the space use in a building or differences in the quantification of seismic actions).

Evolution of the actions

Evolution of the safety due only to the actions


* Real (gradual) increase of traffic in a bridge

*


Initial safety level

Minimum (code) safety

level

Failure

Time

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Evolution of the safety due only to the materials degradation (e.g. valid for concrete)

• Degradation of the structural materials over time - more complex problem: natural ageing, environmental aggressiveness, deficient design/construction, adequacy of use in service (difficult to predict)

• Non-structural materials: safety → performanceExample: Render

Evolution of the materials





level

Failure

Time


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Global evolution of safety

Evolution of the structural safety

• Superimposition of the effects of the actions and materials

• Initial confidence degree exceeds the code safety level (real values of the actions and materials properties below and over, respectively, the corresponding characteristics values; structural redundancy)

End of the expected

service life

In practice, there are many construction

kept in service below the MSL





level

Failure

Time


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• Associated to the restriction to the evolution of the users needs due to the fixed geometry of the construction

Examples: (i) Bridges with insufficient width for the traffic; (ii)Car parks with limited area; (iii) Buildings too small or insufficient for new needs; (iv) Football stadiums

• Generally, there are three options:

a) Demolish the construction and build a new one adapted to the new conditions (end of the life);

b) Abandon (partially) the construction, eventually reinstating its initial functionality conditions(rehabilitation);

c) Adjust the construction to the new conditions(strengthening).

Evolution of the functionality conditions



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3. MINIMUM QUALITY

LEVEL IN

REINFORCED

CONCRETE


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g3. MINIMUM QUALITY LEVEL IN

REINFORCED CONCRETE

Effects of steel corrosion

3.1 Some basic concepts

• Steel corrodes in contact with some degradation factors (O2, H2O, CO2, Cl-, etc.)

• Corrosion ⇒ loss of cross-section (strength ↓) + expansion(cracking, adherence loss, spalling)


concrete

SpallingCracking

cracking

due to tensile stresses in the concrete cover

the concretecover is “pushed” out

Steel with active corrosion

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Corrosion rate over time

T0 → the degradation factor starts acting

T1-T0 → initiation period (up to steel depassivation)

T2-T1 → propagation period (active corrosion)

steel depassivation

Initiation Propagation

What is the minimum

quality level?


3. MINIMUM QUALITY LEVEL IN

REINFORCED CONCRETE

Corrosion rate

limit state

Time

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1. Corrosion initiation

Repair of the structural element and steel passivation when active corrosion is detected (adequate for prestressed steel)

2. Cracking initiation or limitation

Repair (injections, impregnations) for corrosion-related cracking (adequate for carbonation-related corrosion with no ↑ cross-section loss or adherence loss ; - adequate for chlorides-related corrosion:advanced corrosion/ ↑ cross-section loss without cracking)

3. Limitation of steel cross-section loss

Repair with removal of the corroded reinforcement and replacement by new rebars (inadequate for carbonation-related corrosion: ↓ cross-section loss with ↑ adherence loss)

3.2 Definition of the “steel corrosion limit state”



REINFORCED CONCRETE

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4. Concrete cover spalling initiation (or loss of adherencebetween the reinforcement and the concrete cover)

Overly permissive limit state (since no measure is taken until very severe damage occurs)

(even though it is frequent to see constructions in service with a significant percentage of structural elements with this type of damage)…

5. Other limit states

For example, aspects aesthetical aspects (in specific cases)

The definition of the minimum quality level in reinforced concrete is a very complex problem !



REINFORCED CONCRETE

3.2 Definition of the “steel corrosion limit state”

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Where to place the “steel corrosion limit state”?



REINFORCED CONCRETE

Quality level

Time

Failure

Spalling

Start of the service life

Depassivation

Cracking

Aesthetical limits

Fixed ratio of cross-

section loss

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Evolution of the structural safety level over time when conditioned by steel corrosion

the “limit state” defined for the Vasco

da Gama Bridge

the “limit state” defined in E465

(cracking with no cross-section loss)



REINFORCED CONCRETE

Time

Failure

Spalling

Cracking

Fixed ratio of cross-

section loss

Start of the service life

DepassivationStructural safety level

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3.3 Practical difficulties in the implementation of acorrosion limit state (regulations)

• It is necessary to know the materials used in the structures with much further detail than what happens now (type/cement composition, w/c ratio, content of aggressive substances in the components; partly solved by NP EN 206-1);

• Casting and curing of concrete more standardized than they are now;

• Increased control of the size of the structural elements and reinforcement (and their cover) and lower tolerances (partly solvedby NP EN 13670-1);

• A vast data compilation about the environmental conditions in the vicinity of the structure is necessary (T, RH, rain → macroclimatic mapping for corrosion; indirectly NP EN 206-1);



REINFORCED CONCRETE

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g • Microclimate around the structural elements (measured in mm or cm) has much more influence on the definition of the corrosion process that the macroclimate around the structure (e.g. local humidity/lack of watertightness; de-icing salts; wind exposure)

• Degradation mechanisms (depassivation by carbonation, chloride ions diffusion and corrosion) are not yet completely known and, apparently, depend on many parameters;

• What is the number and location of the sections analysed? (in current structural design (t=0) this question is easier to answer…)



REINFORCED CONCRETE


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Opposing faces of a column (José Saramago Secondary School, Mafra)CONSTRUCTIONS SERVICE LIFE AND ITS PREDICTION


REINFORCED CONCRETE


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4. WAYS TO

APPROACH THE

PROBLEM


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g4. WAYS TO APPROACH THE

PROBLEM

Ways to approach the problem of the prediction of t he service life of constructions

- The experimental method, i.e. using deterioration tests, which canbe accelerated or not (e.g. accelerated carbonation tests);

- The analytical method, i.e. using mathematical models, whichallow simulating the effects of the aggressive agents over time,using three methods to determine quantitative values of theservice life:

• Purely statistical (analysis of numerous samples);• Deterministic (discreet value of the service life, based ondegradation models as a function of the average/characteristicbehaviour);

• Probabilistic (an extension of the previous one, using probability analyses and considering uncertainties of the most importantfactors).


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g4. WAYS TO APPROACH THE

PROBLEM

Relations D(t) between deterioration and time (very often they are not linear, are not accurately known or depend on many secondary factors)

• to - the degradation factor starts acting;

• t1 - t0 - initiation period, i.e. period before deterioration starts (e.g. in reinforcement corrosion it corresponds to the destruction of the passivating layer around the rebars);

• t2 - t1 - propagation period, i.e. time during which the deterioration occurs.

Deterioration models

Deterioration model: mathematical representation of the degradation rate over time


Degradation rate

Time

Limit state defined

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5. SERVICE LIFE

PREDICTION

ASSOCIATED TO

REINFORCEMENT

CORROSION


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5. SERVICE LIFE PREDICTION ASSOCIA-

TED TO REINFORCEMENT CORROSION

Carbonation progress for concrete with Portland cement and various w/c ratios

and exposure conditions

Carbonation: (1)

where:

• t is time

• a and b (carbonation coefficient) are constants that depend on the exposure of the element to the environment and the concrete quality

tbax ×+=

Initiation stageDepassivation is essentially associated with two mechanisms:

• Carbonation progress

• Chlorides penetration

NOTE: For a given cover, the initiation period can be estimated.

Cover = 20 mm

Exposed to rainProtected from rain


Time (years)C

arbo

natio

n de

pth

(mm

)

w/c

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Chlorides penetration (Fick’s diffusion law):

(2)

where:

• C (x, t) is the chloride ions content inside concrete, at thedepth x after time t

• C1 is the chloride ions content on the element’s surface (as a percentage of the weight of cement)

• Deff is the effective diffusion coefficient of Cl- ions in concrete

• “erf” is the error function

• m is an empirical constant (m = 0.4)

C(x, t) = C1

1 - erf

x

2 Deff1 - m t (1-m)

Initiation stage

NOTE: For a given cover, the initiation period can be estimated, taking into account the critical value of the chloride ions content (0.4% of the cement mass); Deff and C1 measured experimentally.




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Cl- content profile over time in a single dimension

• C = content at any depth over time;• Co = initial content;• C1 = content on the surface;• l = diffusion length (usually the element’s thickness except when it is very thick);• t = time;NOTE: The figures next to the curves represent the relation Deff t / l2 where Deff

(effective diffusion coefficient of chloride ions in concrete) is given in the next table.

t ↓↓

t ↑↑

surface

Initiation stage

(l-x)/l




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Estimates of the effective diffusion coefficient in concrete

Initiation stage

NOTE: Deff must be obtained from in situ or laboratory tests




Water/cement ratio

toto to

to

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Initiation period as a function of the chloride ions diffusivity and their critical value

Influence on the initiation period of the following factors: diffusivity, Cl- ions content on the surface (and next to the reinforcement), cover




Initiation stage

Influence of the diffusivity

Time (years)

Influence of the contents on thesurface and next to the

reinforcement

Content on the surface

Influence ofthe size

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Corrosion progress rates (µm/year) in ordinary reinforcement for various concretes, water/cement ratios and average relative humidity levels

Propagation stage

w/c=0.40

w/c=0.40

w/c=0.40

w/c=0.40

Portland cementw/c = 0.70Carbonated reinforcement

Cement with additionsw/c = 0.70Carbonated reinforcement

Portland cementw/c = 0.705% CaCl2

Cement with additionsw/c = 0.705% CaCl2

Corrosion progress rate - difficult to predict because it depends on several factors:• w/c ratio• Additions• RH• Carbonation• De-icing salts




Cor

rosi

on ra

te in

the

anod

ic r

egio

n (µ

m/y

ear)

Cor

rosi

on ra

te in

the

anod

ic r

egio

n (µ

m/y

ear)

Cor

rosi

on ra

te in

the

anod

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egio

n (µ

m/y

ear)

Cor

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te in

the

anod

ic r

egio

n (µ

m/y

ear)

Relative humidity (%) Relative humidity (%)

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Corrosion progress rates (mA/m2) in ordinary reinforcement embedded inMortars as a function of the environment

Propagation stage

(de-icing salts)




decontaminated

carbonated

containing

partially immersed

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Average values of the corrosion rate ( Tuutti, T=10 ºC )

- concrete indoors or constantly immersed in water → 0

- concrete outdoors (corrosion conditioned by carbonation) → 50 µm / year

- concrete outdoors (corrosion conditioned by chloride ions) → 200 µm / year

Maximum values

- maximum values: 5 to 10 times the average values.

Galvanic current measured as a function of the temperature




Galvanic current

Temperature

CoolingControl after the test

Carbonated concrete

CoverRH

w

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(3)

where:

• Dt is the diameter of the ordinary reinforcement rebars after time t, due to corrosion

• Di is the initial diameter

• Ic is the corrosion rate (1×10-1 to 1×10-2 mA/cm2, great range →

difficult to make estimates with in situ measurements…)

Evolution of the diameter of the rebars after initi ation

cit ItDD ××−= 023.0




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Reinforcement endurance after corrosion starts (Tuutti ’s recommendation)

• Prestressing steel → 0

• Ordinary steel:

- corrosion conditioned by carbonation → 15 to 20 years

- corrosion conditioned by chloride ions → 5 to 10 years




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6. PRACTICAL

EXAMPLE


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g6. PRACTICAL EXAMPLE

Scheme of a reinforced concrete slab to be executed in a building’s envelope

Options to be analysed:

1. 15 mm cover without waterproofing;

2. 30 mm cover without waterproofing;

3. 15 mm cover with waterproofing and maintenance every 20 years;

4. 15 mm cover with waterproofing and maintenance every 10 years.

Study that associates durability (service life pred iction) to an economic analysis (Siemes)


blast furnace slag cementlength

lengthcoverlength

w/c ratioblast furnace slag cement

slags

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L =

c - ∆

Rk

2.7

46 w - 17.6

2 +

0.08 dφ v

c +

c - ∆ 180 f

o

T T

o ln f

o

1 - ee

T T

o ln f

o

• First part - carbonation process for unprotected concrete• Second part - time before corrosion is visible• Third part - extra service life due to the waterproofing

Unit costs estimate (currency unit* per square mete r)

Degradation model(determination of the service life L, conditioned by carbonation )

* Dutch guilders



COSTOPERATIONNew slabs (d = thickness)Change of the cover to d = 150 mmRepair by guniteRepair with synthetic mortarWaterproofing on new concreteWaterproofing on old concreteMaintenance of the waterproofingRepair of the waterproofing

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Estimate of the variables related with carbonation

(probabilistic analytical method)

Probabilistic distribution of the variables involved in the model



deterministic

deterministic

deterministic

year

yearsyears

15 mm nominal cover30 mm nominal coverdifference between the maximum and average carbonation depthtype of cement parameterclimate parameterwater/cement ratiorebars diametercorrosion ratewaterproofing thickness

waterproofing deterioration coefficientdurability parametermaintenance period

DESCRIPTION PROBABILISTIC DISTRIBUTION

AVERAGE VALUE

VARIATION COEFFICIENT

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Distribution of the estimated service life for alte rnatives 1 and 2

Distribution of the estimated service lives (in yea rs)

µ µ µ µ = 34 years

µ µ µ µ = 123 years



DESIGN ALTERNATIVE

AVERAGE SERVICE LIFE

STANDARD DEVIATION

PROBABILITY THAT THE SERVICE LIFE IS < 60 YEARS

Time (years)

cover

cover

prob

abili

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dens

ity

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Relative percentage contributions to the results



DESIGN ALTERNATIVEDESCRIPTION

coverdifference between the maximum and average carbonation depthtype of cement parameterclimate parameterwater/cement ratiorebars diametercorrosion ratewaterproofing thicknesswaterproofing deteriorationcoefficientdurability parametermaintenance period

Total

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Expected discounted costs (currency unit, Dutch gui lders)

NOTES:

• Discounted cost:

• Life Cycle Cost analysis:

(LCC)

nat

F

)1(P

+=

P - present value

F - future value (year n)

ta - discount rate

∑= +

=n

1in

a

i

)t1(

CLCC



DESIGN ALTERNATIVEPARTIAL COSTS

extra coverwaterproofingwaterproofing maintenanceexpected repairTotal cost (average value)

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Comparative table of the two methods

Comparison with the Tuutti method (deterministic):

• Concrete protected from the rain (lower face)

• Water/cement ratio = 0.55

• Cover: 15 or 30 mm

• Corrosion conditioned by carbonation

• Average temperature = 10 ºC



DESIGN ALTERNATIVE

METHODINITIATION

TIME[YEARS]

REINFORCEMENT CORROSION TIME

[YEARS]

ESTIMATED SERVICE LIFE

[YEARS]

Values obtained from the first part of the equation for the average values of all variables

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g 7. THE JAPANESE

CODE OF SERVICE

LIFE PREDICTION OF

BUILDINGS


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7. THE JAPANESE CODE OF SERVICE

LIFE PREDICTION OF BUILDINGS

Guide for service life planning of buildings

Objectives:

• Control the quality of new buildings

• Adapt the design, construction and maintenance to the objectives planned in terms of durability


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Construction

Maintenance

Contract




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• Planned service life (as long as possible): “period of time, since the end of the building’s construction until the building as a whole or its elements, components or equipment reach given limit states related with the physical deterioration, the performance degradation or the economic or functional obsolescence”

• Limit state - need of a renovation, reconstruction, repair or replacement/large-scale demolition

• Service life classes (3, 6 10, 15, 25, 40, 60, 100, 150 years): classes are recommended for the building as a whole and for its elements, components and equipment




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120




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g (and material)




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NOTE: The recommended classes take into account the need to guarantee flexibility for replacement




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• Service life = lowest of the values that correspond to (i) physical degradation (characteristics inherent to the behaviour of the materials over time, factors related with environmental deterioration, acceptable deterioration level at the end of the service life, intensity of the factors of environmental degradation, level of yearly deterioration) and to (ii)functional obsolescence (less data referred);

• Examples of the service life prediction method are presented for:

- Timber buildings;- Reinforced concrete buildings;- Steel structure buildings protected with paint;- Waterproofing layers (exposed asphaltic systems);- External cementitious coatings in reinforced concrete buildings;- External ceramic coatings in reinforced concrete buildings;- Interior piping.

Principles to predict the service life




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Example of the method to estimate the service life of reinforced concrete structural elements of buildings

• Service life = instant when it is expectable considerable corrosionin most of the reinforcement of the element and when effective recovery of its bearing capacity is unlikely resorting only to maintenance and small repair




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Factors that influence the corrosion of the reinfor cement of concrete elements




Factors Relevant conditionsCharacteristics related withthe behaviour over time

Materials behaviour Type and quality of the cement,aggregates, mixing water, admixtures,additions and reinforcement rebars,strength class and composition of theconcrete

Design quality Coating thickness, type of surfacecoating, type of reinforcement rebars,waterproofing systems and their details

Construction quality Casting control and inspection methodson site

Maintenance quality Maintenance methodsFactors related with thedeterioration

Geographical location andenvironmental conditions

Ambient temperature, relative humidity,precipitation, contents of CO2, SO2 andmarine salts in the air, exposure to seawaves

Building location Use of the building and spaces, type ofelement and its location

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Estimated service life of structural elements Y given by

Y = Ys x A x B x C x D x E x F x G x H

where:• Ys - reference service life of reinforced concrete structural elements (60 years)• A depends on the type of concrete• B depends on the type of cement• C depends on the water/cement ratio• D depends on the cover of the rebars• E depends on the type of coating material • F depends on the quality control during construction• G depends on the maintenance level• H depends on the building’s location and the associated environment

FACTOR METHOD (empirical formulae)




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cement




FACTOR METHOD (empirical formulae)

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8. THE NEW

PORTUGUESE

BUILDINGS GENERAL

CODE (RGE)


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Clause 1 - Scope of application

1. The general buildings regime, from now on designated RGE, applies to the execution of new buildings, to intervention works in existing buildings and to demolitions.

2. Intervention works in listed buildings or located in areas classified as historicalare not included, as long as the safety and health demands established in this regime and in applicable specific regulation are safeguarded

3. Buildings that, due to its intended use, are subjected to their own technical specifications must comply with this regime in the aspects not covered by those specifications.

4. It is the competence of the central and local authorities, as the licencing entities, to ensure the compliance with this regime.

5. The compliance with the provisions of this regime is the responsibility of technicians dully habilitated and enrolled in professional associations, namely architects, landscape architects, engineers, technical and urban engineers, within the performance of the functions they are legally habilitated for and according to the definition of the corresponding professional deeds.

6. The municipalities may prepare municipal regulations intended at the proper use of this regime.

7. When situations not covered by this regime occur, the European regulations, the international or other countries’ regulations and specialized technical advice or specifications must be adopted in this order, as long as these situations are subjected to previous analysis and approval by the licencing entity.

8. THE NEW PORTUGUESE

BUILDINGS GENERAL CODE (RGE)

RGE (new RGEU, still not in force)


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Clause 2 - Interventions in buildings

1. The interventions in existing buildings are classed in the following categories: Level I: Q ≤ 5% Level II: 5% < Q ≤ 25% Level III: 25% < Q ≤ 50% Level IV: Q > 50%

2. Concerning what is stated in number 1, Q is the percentage of the cost Ci, of the intervention relative to the cost Cn, of the construction of a new building, in the same place, of identical constructive and functional characteristics, with a gross area identical to that of the original building, determined based on prices per square meter of the construction gross area defined in a law to be published annually by the responsible Minister, i.e.:

Q = Ci / Cn * 100



RGE (new RGEU)


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Clause 1 19 - Service life of a building

1. The service life of a building, from now on also designated by VUE, corresponds to the period during which the respective structure does not show degradation of the materials, as a result of the conditions, which lead to the reduction of the initial structural safety, namely in the critical sections of the main structural elements.

2. During the service life of a building, inspection, maintenance and repair activities must be performed, namely concerning the various building components that have lower durability than the service life.

3. The service life of each building component must be defined by the respective manufacturer based on the degradation observed during use.

4. The VUE must be defined by the owner and when that is not done it is considered by default the value of 50 years.

5. The adoption of a VUE lower than 50 years must only be accepted in special cases and be requested of the licencing entity based on proper justification.

6. In an intervention of level IV, the VUE after the intervention must be defined by the owner, considering in the analysis of the durability of the elements reused the degradation that they present at the rehabilitation time.



RGE (new RGEU)


CHAPTER VII DURABILITY AND MAINTENANCE

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Clause 1 20 - Design with durability

1. The design with durability of new buildings and of level IV interventions, for the target service life, demands that the following aspects are taken into account in the execution design: a) Design of the structure for the building’s service life; b) A design that minimizes the degradation effects of the aggressive agents,

namely the environmental ones; c) Specification of flexible designs that allow the easy replacement of the

components with durability lower than the VUE; d) Specification of access conditions that allow performing periodic

inspections of the most degradable components, as well as proceeding with maintenance and cleaning operations needed to guarantee their durability.

2. A VUE of 50 years for the buildings’ structure must be guaranteed by specifying design and construction demands defined in applicable specific regulation.

3. In the absence of applicable regulation, the degradation observed during usemust be considered in the analysis of the service life of the materials of the buildings’ structures.

4. The adoption of a VUE for the structure higher than 50 years must lead to an analysis of the structure using degradation models of the constituent materials and a follow-up of the structure’s behaviour over time.



RGE (new RGEU)

Next class


CHAPTER VII DURABILITY AND MAINTENANCE

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9. CONCLUSION


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• The service life of constructions depends on their various lifestages, with special emphasis on design and construction

• The service life prediction of constructions (with or withoutreinforced concrete structure) is, in principle, possible; it isnecessary to increase the knowledge on degradation modelsand the influence of the factors called secondary on thesemodels, to collect more data that allows statistical analyses,etc.

• The prediction must be dynamic in the sense that its resultscan and must be corrected from time to time to take intoaccount the data collected in the meantime

• The service life prediction of constructions still hasfundamentally a qualitative and comparative nature; absolutevalues will tend to come later on


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10. REFERENCES


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[1] ASTM E632-81, “Standard Practice for Developing Accelerated Tests to a Prediction of the Service Life of Building Components and Materials”, American Society for Testing and Materials, Philadelphia, 1981

[2] Tuutti, K., “Corrosion of Steel in Concrete”, Swedish Cement and Concrete Research Institute, Stockholm, 1982

[3] CEB Bulletin n.º 166, “Guide to Durable Concrete Structures”, Comité Européen du Béton, General Task Group n.º 20, Copenhagen, 1985

[4] Fernando A. Branco e Jorge de Brito, “A Vida Útil das Estruturas de Betão -Considerações Sobre a Sua Caracterização”, Revista Portuguesa de Engenharia de Estruturas, n.º 30, Lisboa, 1990

[5] Jorge de Brito, “Patologia de Estruturas de Betão - Degradação, Avaliação e Previsão da Vida Útil”, Dissertação de Mestrado em Engenharia de Estruturas, Lisboa, 1987

[6] K. F. Müller, “The Possibility of Evolving a Theory for Predicting the Service Life of Reinforced Concrete Structures”, Matériaux et Constructions, V. 18, n.º 108, Paris, 1985

[7] C. L. Page, “Barriers to the Prediction of Service Life of Metallic Materials”, Problems in Service Life Prediction of Building and Construction Materials, Martinus Nijhoff Publishers, NATO ASI Series, Boston, 1985


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[8] G. Fagerlund, “Essential Data for Service Life Prediction”, Problems in Service Life Prediction of Building and Construction Materials, Martinus Nijhoff Publishers, NATO ASI Series, Boston, 1985

[9] A. Siemes et al., “Stochastic Modelling of Building Materials Performance in Durability”, Problems in Service Life Prediction of Building and Construction Materials, Martinus Nijhoff Publishers, NATO ASI Series, Boston, 1985

[10] A. Vrouwenvelder et al., “Duurzaamheid van Gabouwen”, Rapport TNO-IBBC B-83-521/62.3.1916, 1983

[11] Jorge de Brito, “Noções Básicas sobre Previsão da Vida Útil de Estruturas de Betão Armado e Pré-Esforçado”, Curso de Patologia, Reabilitação e Manutenção de Estruturas e Edifícios (F.S.E.), Lisboa, 1987

[12] “Final Technical Report”, Programa BREU-0186-C - Assessment of Performance and Optimal Strategies for Inspection and Maintenance of Concrete Structures Using Reliability Based Expert Systems, Copenhagen, 1993

[13] “(The English Edition of) Principal Guide for Service Life Planning of Buildings”, Architectural Institute of Japan, Tokyo, 1993


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Work supported by the Programa Operacional Sociedade da Informação - POSI

Documents

02 Constructions service life and its prediction - ULisboa · PDF fileby NP EN 13670-1); • A vast data compilation about the environmental conditions in the vicinity of the structure