Challenges in managing structural asset portfolios in the Middle East

1 Concrete Maintenance Workshop - Faiz M Khan

Challenges in managing ageing structural asset portfolios

Faiz M Khan

CH2M HILL28th November 2013

28 November 2013

2 Concrete Maintenance Workshop – Faiz M Khan

Safety Moment

• Assess your journey

• Prepare

• Check

• Slow down

• Use headlights

• Wait it out

• Do not use cruise control

• Track the car ahead of you

• Stay toward the middle lanes

• Avoid lane changes

• Give trucks and buses extra distance

• Stay out of moving water

28 November 2013


Challenges….

• Original challenges and transformation of the industry

• Where do we stand today – technology available

• The next challenge – how do we maintain structural assets?

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Transformation of the concrete industry in region

• Original challenge:

• Highly aggressive regional climatic conditions

• Poor quality materials

• Growing infrastructure investment

• Lack of experienced local contractors

• Outcome:

• Regional concrete construction sector has transformed over 30-40 years

• From: fraught with problems

• To: capable of achieving high performance and long-life durability

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Contrasts with other regions• Climatic effects

• High temperature

• typ. ~15-20°C > London

• typ. design over 100-year life 5 - 55°C shade

• Very high sunshine levels

• Low precipitation (about 10% of London)

• Natural environmental effects

• High salinity in the sea

• High salinity in the ground

• Man-made environmental effects

• Higher salinity in industrial plants

Mean monthly high temperature (C)

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A World ocean salinity chart o oo

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A World ocean temperature chart

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Physical effects of climate

• High temperatures and low precipitation:

• High evaporation rates

• Hot dry materials

• Coastal strip:

• High water table

• Highly saline ground water

• Extreme drying and salinity:

• Potential for lower as-built quality …

• … and faster deterioration in-service

J F M A M J J A S O N D0

2

4

6

8

10

Dai

ly e

vapo

ratio

n/ra

infa

ll - m

m

Gulf location

Typical daily evaporation

Typical daily rainfall

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Physiological effects of climate

• Construction quality = materials quality + workmanship

• Humans are vulnerable to:

• temperature

• humidity / evaporation

• solar radiation

• Summer months are extreme for human physiology

• Demanding to expect good quality from a workforce that is toiling in ‘uncomfortable’ conditions, even with the amended summer timings

Great discomfort - Danger of heatstroke

Distinct stress

Everyone feels discomfort

Over 50% uncomfortable

Some people uncomfortable

No discomfort

Air temperature - C15 20 25 30 35 4540 50

RH 100%80%

60%40%

20%

0%

o

Ref G MacMillan, MoW, Bahrain

28 November 2013


Implications for lifecycle asset management

• Extreme climate, and potential poor quality, lead to faster deterioration

• “Imported” codes and guides often come from temperate regions

• High vulnerability requires measures beyond most codes:

1. Design-out vulnerability, where possible

2. Materials selection based on durability modelling in design

3. Robust construction specification and management

4. Whole life-cycle view

• Growing recognition of importance of asset management

Extreme Environment

Poor as-built Quality

Special Measures

CODES

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Concrete durability technologies

• Technologies and experience for achieving long-term durability have now been available for some time.

• Materials and processes for improving concrete durability are available in cements, admixtures, steel and electrochemistry.

• Codified approaches have been developed which address durability as a design procedure including service life prediction models .

28 November 2013


Durability-based design

• At the 3rd Bahrain Conference on Deterioration and Repair of Concrete in the Arabian Gulf, in 1989 (~25 years ago), the closing panel discussion concluded: “the technology all exists for long-term (100-year) durable reinforced concrete construction in the Gulf, the issue is implementation”.

'Special' structures“Structures with extended design lives, i.e. greater than 30 years, and structures in extreme exposures

require special consideration and may need some form of enhanced protection.”

“A durability study should be undertaken by designers leading to a project specific

durability plan”

28 November 2013


Durability by “designing-out” vulnerability

• Piled foundation vulnerable to deterioration caused saline ground-water

• Evaporation-driven mechanism designed-out by waterproofing

• Highly-vulnerable berth design based on network of deck beams supported on piles

• Splash-zone vulnerability designed-out by switching to non-reinforced mass concrete blocks

Ref: Guide to the design of concrete structures in the Arabian Peninsula

Splash

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“Designing-for” durability

1. Determine• Required life of facility

• Exposure conditions

• Deterioration mechanisms

2. Identify options and their performance

3. Deterioration models

4. Reliability analysis

2.05m1.68m MHHW

0.35m MLLW

Submerged zone

Tidal zone

Splash zone

Atmospheric zone

Exposure zones

Effect of Cement Replacement on Time to Cracking

0 20 40 60 80

100 120

0 10 20 30 40 50 60 70 80 Cover Depth mm

Tim

e (y

ears

)

opc 7% microsilica 30% pfa 60% ggbfs

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 20 40 60 80 100 120 140 160 180 200 220Time (Years)

Failu

re P

roba

bilit

y (P

f)

BS 8500-1 Specification: Nominal cover 50mm

Hunterston Design: Nominal cover 80mm

20% failure probability at 100 years

Serviceability Limit State reached at 62 years

Serviceability Limit State reached at 170 years

Failure probability v/s time

28 November 2013


chloride, %vs. depth, mm

Principles of durability modelling• Surface chloride

• Diffusion co-efficient

• Ageing factor

• Temperature

• Chloride threshold

• Background chloride

Allowable crack-width

Maximum cover

Target service life

Concrete constraints(e.g. available sources,

structural design)

Requirements for additional protection

Options and costs of additional protection

Durability model

Cover tolerance

Concrete optionsMinimum cover

Nominal minimum cover

Casting method

Possible solutions ? N

Y

28 November 2013


Cement Admixture Rebar Surface Electrochem

PC Plasticisers Carbon Steel Rebar

Extended Curing

Chloride Monitoring

Micro-silica

Self-compacting

agents

Non-reinforced

Design

Controlled Permeability Formwork

Corrosion Monitoring

PFA Water-proofers Stainless Steel Rebar

Penetrating Sealers

Provision for future CP

GGBFS Corrosion Inhibitors

Non-metallic Rebar

Surface Coatings

CathodicPrevention

Durability “Menu” of possible materials choices

Controlling penetration

Controlling corrosion

Legend :

28 November 2013


40km sea-crossing structure with long design life: durability in design• “Materials selection for main structural elements shall be based upon

a Durability Strategy Study to demonstrate that proposed materials are suitable for 120 years service life, without major repair or replacement, and only normal maintenance.”

• “Accessible components exposed to significant wear or deterioration shall be designed for demonstrated cost-optimal service life and replacement, as defined in the Operation and Maintenance Manual. (e.g. roadway pavement, bearings, lighting, ...).”

construction methods

protection options

exposures

Project Name:

Strength grade 25 MPa Diffusion coefficient estimated Est by w/cConcrete density 2350 kg/m3 Diff Coeff (at 20°C) 1.18E-12 m2/sTotal cementitious content 350 kg/m3 Age of measured value (yrs)Binder type (pc, ggbs, pfa, sf ) PC Age Dependant Diffusion YPercentage Binder 0 % wt of binder Switch off age dependency at given date YWater/binder (w/b) 0.50 Turn off age dependancy at (yrs) 20Background Chlorides 0.20 % wt of binder

Dca at 35 days 2.10E-11 35

Reinforcement Type Carbon Steel Dca at 20 years 2.91E-12

Bar diameter 10 mm Dca at 20 years 2.91E-12 m2/sAge Factor 0.37

Ambient Temperature 35 oCTemperature affected Dca Y Surface chloride level 0.60 % cementTemperature affected threshold Y Adjusted surface chloride level 0.60 % cementSurface Chloride Level (% wt cem) 0.6Exposure Condition 3. Cyclic wet/dry Temp & Binder adj threshold (Ct) 0.10 % cement

Carbonation factor considered? Y

Relative Humidity (%) 70

Coating used? No Minimum Chloride Time to Cover Depth threshold > initiation

(mm) 0.1 % by mass cement plus crackingControlled permeability formwork? NSilane Impregnation N 15 1Integral Waterproofer N

56

Estimated Values (Temp adjusted)Reinforcement Details

Exposure Details

Time to Serviceability Limit State (Years) (Deterministic)

Modelling for Chloride Ingress into ConcreteTime to corrosion initiation and cracking

Analysis Type: DETERMINISTIC

Concrete Details Diffusion Coefficient Details

Additional Protective Measures

28 November 2013

Presenter

Presentation Notes

the graph shows various projections of %initiation vs time, from probabilistic version of Corrpred, used as a choice of performance criteria for durability planning.


Port berths with severe early-age cracking : neglecting durability in design

• Gravity quay wall constructed from large pre-cast non-reinforced concrete blocks

• Concrete displaying severe cracking 2-3 years from construction, confirmed due to Delayed Ettringite Formation (DEF)

• Future damage development modelled

• Potential impact on structural behaviour leadsto loss of stability by overturning or bearing failure

• Key remedial considerations include:

• Maintaining structural stability

• Existing alignment of cranes and berths

• Confidence in existing facilities during reconstruction

28 November 2013


The next challenge ?

• Effective life-cycle management of critical concrete structures, needs understanding of the wider implications of technical decisions.

• The next infrastructure challenge is likely to be effective management of substantial ageing asset portfolios, now 15, 25 or even 35 years old.

• Techniques are needed for understanding how condition assessment and deterioration prediction inform life-cycle cost and overall business impact, as a basis for prioritisation, including

• portfolio-level views,

• remedial-policy comparison,

• and operational decision optimisation.

28 November 2013


Service Life

Evolution of reinforced concrete corrosion

CO2, Cl¯Cor

rosi

on o

f Ste

el R

einf

orce

men

t

TimeInitiation Phase

Maximum Permissible Corrosion

Propagation Phase

Service Life

Presenter

Presentation Notes

This slide presents a graphical representation of the evolution of corrosion in reinforced concrete and the service life time or time before reparation


Service Life

Effect of Maintenance/Rehabilitation on Service Life

Det

erio

ratio

n of

Stru

ctur

es


Maximum Permissible Deterioration

Propagation Phase

No visible damage Visible damage

Proactive

Reactive


Service Life

De Sitter’s Law of Five

Det

erio

ratio

n of

Stru

ctur

es


Maximum Permissible Deterioration

Propagation Phase

$25

$1$5

Equ

ival

ent C

ost f

or P

rolo

ngin

g S

ervi

ce L

ife

$ 125

No visible damage Visible damage


Cooling-water basin with premature reinforcement corrosion: expensive repair at early age• Cooling water basin in a cooling-tower at major petrochemical plant.

• Basin constructed of pre-cast slabs with liner, elevated on beam and column support structure. 32m x 220m in plan.

• Severe reinforcement corrosion due to leakage onto support structure.

• Cathodic protection chosen for :

• Minimised break-out to beams/columns = speed

• Embedment in replacement slab = longevity

• Remedial programme included constructingdivider wall to avoid loss of availability

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Regional infrastructure timeline

1970s 1980s 1990s 2000s 2010s 2020searly

constructionearly

remedialsboom

5 15 25 35 45potential

ages (years) of infrastructure in the region

5 15 25 355 15 25

5 15

recent downturn ??

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How do you spend your maintenance budget?

November 2013


Understanding risk-exposure

• Hazard : operational impact of infrastructure

• Likelihood (L)• Increases with time for deteriorating assets

• Linkage to business cycle

• Consequences (C) • Direct cost (often premium cost e.g. out of hours)

• Indirect cost (management)

• Penalty costs (e.g. highway possession)

• Cost of lost availability (e.g. lost production)

• Safety

• Monetised costs of accidents

• Consequential costs of accidents

• Environmental

• Reputational

Asset Name MSCP 1

Purpose Short stay multi-storey car park (public)Age Commissioned 1967 (Extended 1976)

How to Use:Likelihood Ranking: 1=Improbable (<10%); 2=Unlikely(10-30%); 3=Less Than Likely(30-50%); 4=More Than Likely(50-80%); 5=Probable(>80%) fill in yellow to describe

fill in brown to describe URGENTConsequence Ranking: 1=Minor; 2=Moderate; 3=Significant; 4=Substantial; 5=Grave fill in blue to describe progressionConsequence Category: pick from matrix for (5x likelihoods) and (max consequence)Safety 1=Minor injuries, 2=Major injuries, 3=Single fatality, 4=Multiple fatalities (eg up to 100), 5=Multiple fatalities(eg over 100)Security 1=Minor breach of regulations, 2=Reportable breach of regulations, 3=Prosecution, 4=Short airport closure, 5=Long airport closureEnvironment 1=Short term local damage, 2=Short term regional damage, 3=Long term local damage, 4=Long term widespread damage, 5=Widespread permanent damageFinancial (based on EBIT) 1=<£1m, 2=>£1-25m<, 3=>£25-50m<, 4=>£50-100m<, 5=>£100mReputation & Legal 1=Improvement notice, minor local reputation damage, 2= Prohibition notice, major local reputation damage, 3= Prosecution with fine, national adverse media coverage, 4= Directors charged

with corporate killings, fraud, etc. International adverse media coverage, short term, 5= Directors convicted of corporate killing, fraud, etc. International adverse media coverage - >1year.Control Rating:

1. Excessive Controls exceed the level required to manage the risk 2. Optimal Controls are reasonably practicable, comprehensive and commensurate with the risk. All controls are evidenced as working as intended3. Adequate Some shortfall in level of controls but these do not materially affect the level of residual risk 4. Inadequate Weaknesses and inefficiency in controls do not treat the risk as intended. Remedial action required

< 6 m

ths

>6 / <

12 m

ths

> 1 yr

/ < 3

yrs

Maxim

um

1

Widespread distress or deformation of MSCP structure potentially leading to collapse (structural failure).

Deterioration of waterproofing/floor coatings and structural concrete topping resulting in reduced capacity and increased risk of corrosion. Joint leaks and blocked drainage allowing water ingress and accelerated corrosion.

1 1 1 1 2 4 1 2 4 4 4

Meetings of 3 & 14/12/10, and site visits 14 & 17/12/10. Jacobs Report No. J24172A8/508/061/01.1 & J24172ME/506/001.1.

Repair structural topping and floor coatings to prevent water ingress. Repair/replace joints to prevent leaks and reduce risk of corrosion.

3Car park closure and major structural propping. Road closures in the vicinity of Terminal 1.

A A A A A

2

Localised distress or deformation of multi storey car park structure (reduced load capacity).

Deterioration of waterproofing/floor coatings and structural concrete topping resulting in reduced capacity and increased risk of corrosion. Joint leaks and blocked drainage allowing water ingress and accelerated corrosion. Overloading from temporary office building (NW of building). water ingress and corrosion to cantilever sections.

1 1 2 3 4 3 1 2 2 3 3


Repair structural topping and floor coatings to prevent water ingress. Repair/replace joints to prevent leaks and reduce risk of corrosion.

3 Car park closure and major structural propping. G G A A R

3

Members of the public injured by concrete spalling (particularly adjacent to joints)


2 2 3 4 5 3 1 2 2 3 3


Repair/replace joints to prevent leaks and reduce risk of corrosion. Repair/replace defective waterproofing.

3 Localised car park closure and structural propping. A A A R R

4Spalling concrete damages EDF electrical equipment in basement.


2 2 3 4 5 2 1 2 2 3 4Jacobs Report No. J24172A8/508/061/01.1 & J24172ME/506/001.1.

Repair/replace joints to prevent leaks and reduce risk of corrosion. Repair/replace defective waterproofing. NOTE: Access to the basements was not available as part of Jacobs inspections. Comments are precautionary.

3 Electric failure resulting short term airport closure. A A R R R

5 Public injury due to trip hazards

Isolated areas of debonded decorative surfacing. Deterioration of structural concrete topping particularly adjacent to joints.

3 3 4 5 5 1 1 1 1 1 1


Carry out concrete repairs to structural topping to remove trips. Replace joints and maintain drainage to minimise water ingress and risk of corrosion.

3 Localised closure of affected areas. G G A A R

6 Collisions between vehicles and pedestrians

Isolated areas of worn and/or debonded decorative surfacing. Deterioration of structural concrete topping particularly adjacent to joints.Ponding water resulting in ice. Poor lighting/dark atmosphere.

2 2 2 2 2 3 1 1 1 3 3


Carry out concrete repairs to structural topping to remove trips. Replace joints and maintain drainage to minimise water ingress and risk of corrosion. Repair/replace defective waterproofing.

3 Localised closure of affected areas. A A A A A

7 Failure of canopies at Level 6

Water ingress resulting in internal corrosion of steel tubes. Possibility of overstressing during high winds.

2 2 3 4 4 3 1 2 1 3 3Site visits 14 & 17/12/10. Jacobs Report No. J24172A8/508/061/01.1 & J24172ME/506/001.1.

Carry out structural inspection to assess extend of internal corrosion. Where necessary strengthen or grout tubes as approriate.

3 Localised closure of affected areas. G G A R R

Finan

cial

Repu

tation

Safet

y

> 8 yr

s

Evidence (i.e. source reference)

Risk Assessment vs time, using RAG

matrix

< 6 m

ths

>6 / <

12 m

ths

> 3 yr

s / <

8 yrs

> 1 yr

/ < 3

yrs

Contr

ol Ra

ting

Actions / Controls at 0-6 months

(i.e. what should be done urgently, if anything)

Actions / Controls at maximum likelihood

(i.e. what would have to be done to prevent the worst form of this

UNMITIGATED hazard)Haza

rd re

f

Secu

rity

Envir

onme

nt

> 3 yr

s / <

8 yrs

Hazard (i.e. what could

happen if no action/control taken)

Root Cause (i.e. why it would

happen)

> 8 yr

s

likelihood vs time consequence

5A R R R R

4A A R R R

3G A A R R

2G G A A R

1G G G A R

1 2 3 4 5

Likeli

hood

Consequence

Likelihood Consequence

28 November 2013

Presenter

Presentation Notes

Each row is an asset and a risk (= a “hazard”), for which we assess likelihood and consequence to determine relative risk (R A G). The innovation it to time-link the likelihood. The lower graph: monetising the risks allows the risk to be built up vs time for each of the various listed consequences. The resultant “Risk-Cost” increases towards a renewal as the failure likelihood is rising.


Optimising timing based on risk

• Lost revenue from lost availability

• Direct and management cost of interventions

• Reputation damage• Accidents • Environmental damageMaintenance cycle (years)

Tota

l cos

t (A

ED/y

ear)

Optimised timing

Cost/year of maintenance(reduces as becomes less frequent)

Total risk cost /year (increases as hazard becomes more likely)

$RISK

CONDITION

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Budget-setting down to a risk-level

• Priority order based on task risk cost

• Budget = cumulative task cost

Result =

1.funding down to a risk level

2.visible impact of budget setting

Maintenance tasks

Task risk cost

Cumulrisk cost

Task cost

Cumul task cost

task 2000 2000 1000 1000

task 1800 3800 500 1500

task 1500 5300 800 2300

task 1300 6600 3000 5300

task 1000 7600 800 6100

task 950 8550 300 6400

task 750 9300 1400 7800

task 300 9600 700 8500

task 200 9800 450 8950

task 100 9900 300 9250$ risk

risk level at available budget

Value = ${risk mitigated} / ${cost}

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Life-cycle cost assessment

1. Portfolio cost of ownership

2. Maintenance policy-testing

3. Operational decision-making

• BS ISO 15686 – Service Life Planning

• Built up from components to the whole.

• Performance of components under expected conditions

• Likely failure modes

• Causes of loss of serviceability

• Risk of premature failure

• Effects on service life.

£0

£50,000,000

£100,000,000

£150,000,000

£200,000,000

£250,000,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

WLC elements v/s time

28 November 2013

Presenter

Presentation Notes

Upper standard graph explaining the WLC terms – renewal cost, routine maintenance, mid life overhaul, routine maintenance costs increase toward end of life, increasing failure risk and declining condition Lower typical example plot of WLC elements vs time


1: Overall portfolio level cost of ownership

• Consistent treatment of multiple asset types

• Overall cost of ownership:

• Asset “creation” costs

• Corrective maintenance at transfer

• Major interventions

• O&M

• Benefits:

• Informs expenditure requirements

• Service charge tariffs

• Asset values and depreciation

WLC elements v/s time

NAV forecast

28 November 2013

Presenter

Presentation Notes

upper actual plot of WLC elements vs time from Palm Jum (suggest don’t tell them the project name), early tall bars = construction, later peaks = larger renewals middle same modelling tool, this time showing asset values; a rise = investment, downward slope = depreciation lower same modelling tool, data capture screen, asset hierarchy on left, data captured in centre, data source records on right


2: Maintenance policy testing for lowest WLC

• Population condition and intervention modelling.

• Benefits:

• Compare management policies, e.g.

• Periodic major repairs

• Little and often

• Justify budget submissions

Year 1 : No Spend Year 5 : AED 30M/yr Year 5 : No Spend Year 5 AED 70M/yr

0%

10%

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100%

1 6

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96 Year

Lik

eli

ho

od

of

Co

nd

itio

n S

tate

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% Component Condition in Poor % Component Condition in Marginal % Component Condition in Good% Comparator in Poor % Comparator in Good

£0k

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0 20 40 60 80 100Year

Cum

ulat

ive N

PV

£k

£200k

£400k

£600k

£800k

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£1,200k

Nom

inal

Expe

nditu

re p

.a.

Cash Flow Baseline Comparator

Expenditure & NPV over life

Effe

ct o

f inv

estm

ent

prof

ile o

n co

nditi

on

28 November 2013

Presenter

Presentation Notes

red amber green graph shows effect of an investment profile on condition split; in the main example (coloured blocks) spending hard in the first 8 years yields a big improvement in condition so %-green grows a lot, then steady spend holds condition. In the (hard to see) lines example, there is only steady spend, and the condition improvement is obtained more slowly. The upper graph is from the same model, showing the ££ investments, both individual and cumulative. bottom row similar concept from a roads what-if modelling package, where condition in colours changes according to condition data at the start, and then the spend rates being analysed.


3: Operational decision-making

• Industry R&D project to produce:

• Process & methods guidance

• Decision-support tools

• Case studies & templates

• Tool-kit for optimising:

• managing aging degrading assets,

• obsolescence, renewals and refurbishments,

• inspection & maintenance timings.

• Benefits:

• All pilot studies revealed >£700k/year potential improvements; one up to €25M

• Generic approach is effective, and uses existing tacit knowledge to help technical people make robust, transparent & auditable WLCC decisions and business cases

e.g. Moving from 12 to 24 mths inspection interval saved £37,000/mth (= £438,000/yr).

cost of delaycost of caution

28 November 2013

Presenter

Presentation Notes

a Salvo/APT example - - horizontal axis is length of intervention cycle/interval, not simple time. Effect is that average direct costs fall as the interval grows and interventions get further apart in time; similarly the risk-costs rise (yellow) and the combination (black) indicates the optimum point for intervention. Blue arrow shows the cost of delays. A similar blue arrow, if placed to the left of the optimum, would show the cost of caution.


Putting it all together for the challenges ahead…

• Plan for durability

• Use condition assessment and deterioration prediction tools

• Understand your risk-exposure

• Set maintenance budgets to the appropriate risk level

• Optimize timing of maintenance intervention

• Use whole life cycle cost assessment

• Overall portfolio cost of ownership

• Test maintenance policies for lowest WLCC

• Optimize operational decision making

28 November 2013

32 Concrete Maintenance Workshop - Faiz M Khan

Thank you

Faiz M Khan

[email protected]

+971-50-9295278

P.O.Box 360, Dubai, UAE

1 October 2012

mailto:[email protected]

Engineering

Challenges in managing structural asset portfolios in the Middle East