strategic management and rehabilitation of an aging road ... · case study: hollywell bridge...

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Strategic Management and Rehabilitation of an Aging Road Bridge Asset Portfolio

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Presenters: Tiffany Parker (City of Gold Coast)

Matt Duncanson (SMEC Australia Pty Ltd)

Presented by: Tiffany Parker (City of Gold Coast) & Matt Duncanson (SMEC Australia Pty Ltd) 2

City of Gold Coast Rehabilitation/Renewal Projects

Presented by: Tiffany Parker (City of Gold Coast) & Matt Duncanson (SMEC Australia Pty Ltd)

Presentation Outline

1. Bridge Structures Portfolio

2. Asset Portfolio Management• Asset Management Plan (AMP)

• Condition Assessments (Level 1 and Level 2)

• Development of the Bridge Renewal Program

• Project Prioritizing

3. Case Study : Hollywell Bridge

4. Level 3 Scoping

5. Inspection, Testing and Assessment

6. Repair and Rehabilitation

7. Case Study: Southport Bridge

8. Case Study: Biggera Waters Bridge

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Bridge Asset Portfolio

Bridge Type

Over Salt Water

Over Fresh Water

Over Road

Road Bridge

144 44 9

197 Road Bridge(191 concrete structures)


2%14%

69%

15%

City of Gold Coast Road Bridge Stock

Load Limited Timber Bridges

Pre 1980 (H20-S16 DesignLoad)

1980 -2006 (T44 DesignLoad)

2006 - present (SM1600Design Load)

Challenges… • Aging asset portfolio with many roads bridges exceeding 50 years old and reaching their intended service life

• Defects associated with exposure to aggressive coastal environments including tidal salt water canals and their close vicinity to the coastline.

Presented by: Tiffany Parker (City of Gold Coast) & Matt Duncanson (SMEC Australia Pty Ltd)

Context….Why?

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Transport Structures Asset Management Plan (AMP)

• Captures all structures and components in CS4

• Documents our 4 and 10 year bridge renewal plan

Condition Assessments (Level 1 and Level 2)Collect accurate condition assessment data

Level 1 inspections

• 100% structures are inspected annually and by exception!

Level 2 inspections and condition assessment

• Robust framework for Level 2 inspections setout in DTMR Structures Inspection Manual

• External services are procured by the City andhave been consistently rolled out since 2010

• Level 2 scoping: additional items


Bridge Renewal Program Development

From the Level 2 Condition Assessments…

Maintenance activities resulting from the observed defect are collated and split into two main categories.

Category 1: Operational Works program

• Routine and small maintenance activities

Category 2: Capital Renewal Program

• Planning, scoping of Level 3 investigation and options assessment

• Level 3 results will be used to determine timing, costs and rehabilitation strategy

• Rehabilitation or renewal works scheduled under a 4 year and 10 year program.



Project profiling

• Risk based prioritization approach

Score

Range

Profile

Category

Profile Category

NameDescription/Function

30-40 A High Criticality

These bridges and major culverts are the most

critical to the transport network and will be

given priority for any first response works

required during a weather event, and priority

in terms of renewal funding and upgrade

considerations.

14-29 BMedium

Criticality

These bridges and major culverts are less

critical than Group A, but will be given priority

for any first response works required during a

weather event, and priority in terms of

renewal funding and upgrade consideration,

over Group C.

8-13 C Low Criticality

These bridges and major culverts are the least

critical to the transport network and will be

considered for renewal funding and upgrade

consideration after Group A and B.

Profiling Parameters Ref Score

5 4 3 2 1

Asset Classification C BridgeMajor

Culvert

Road Hierarchy H

In

evacuatio

n routes

In any

arterial

roads

except for

ones in

Priority 5

In any

major

collector

roads

except for

ones in

Priority 5

In minor

collector

roads

except for

ones in

Priority 5

In local

urban

roads or

in rural

roads

except for

ones in

Priority 5

Traffic volume T ≥10,000

≥5,000

and

<10,000

≥1,000

and

<5,000

≥100 and

<1,000<100

Alternative Route A

Only

access for

local

residents

by any

vehicle in

any

situation

Only

access to

local

residence

for fire

engine

and

ambulanc

e, but two

accesses

for

normal

vehicles in

all

situations

Two

accesses

to local

residence

for fire

engine

and

ambulanc

e but only

one

access in

major

storm

event

Two

accesses

to local

residence

for fire

engine

and

ambulanc

e in any

situation

More

than two

accesses

for fire

engine

and

ambulanc

e in any

situation

Environmental / Exposure

< 1km from coast (Y/N) E1 Yes No

Acid Sulphate Soil Risk (Y/N) E2 Yes No

Within Tidal Water Zone

(Y/N)E3 Yes No

Material Type (Construction) P Steel

Fibre

Reinforce

d Polymer

(FRP)

Concrete Timber Other

Case Study: Hollywell BridgeDescription and Background

• Constructed circa 1980

• Three span bridge deck unit bridge withcast in-situ pier headstocks supported onprecast prestressed octagonal driven concrete piles.

• 2014 Level 2 Condition Assessment rated the bridge in CS2 (Fair).

• Level 3 recommended to investigate extent and cause of cracks and spalls


Case Study Hollywell BridgeKey Findings from Level 3 Inspection

Investigation Findings

Extensive delamination (pier headstocks and abutments)

Active corrosion

Severe cracks beneath pile marine growth

Heavy concrete carbonation and high chloride concentrations


• Poor construction quality control, variable cover

• Insufficient cover 34mm

• Chlorides reaching reinforcement steel

Case Study Hollywell BridgeHollywell Bridge Options Analysis

• Rehabilitation costs 25+ year life extension - $2.5m+

Works includes: ICCP, structural encasements, expansion joints, kerb repairs, barrier refurbishments

• Replacement structure ‘like for like’ 100 year life costs - $3.5m

• Whole of Life (WoL) assessment over 100 year service life

• Numbers speak for themselves…

• Bridge Replacement Strategy was selected offering the lowest lifecycle cost

Bridge Element Option 1 (5-10 years life extension) Option 2 (10-25 years life extension) Option 3 (25+ years life extension)

Pier piles - Structural encasement (4 piles)

- Coating (4 piles)

- Structural encasement (4 piles)

- Durability encasement (4 piles)

- Structural encasement (8 piles)

Pier headstocks and

abutments

- Concrete repairs and crack

injection

- Concrete repairs and crack injection

- Protective coating

- Concrete repairs

- Electrochemical protection (ICCP)


Case Study Hollywell BridgeLessons Learnt

• A Level 2 Assessment is a visual assessment only and further investigation may result in a change of overall condition rating

• Pile cleaning and underwater inspection is essential

• Good planning and investigation informs the capital renewal program costs and timing

• Do not assume a concrete bridge structure will reach 100 years service life


CS2 (Fair)

CS4 (very poor)

Level 3 Engineering Assessment – Client Perspective

When: Recommended in Level 2 or by

a Bridge Team Senior Engineer

Scoping:

• Quantify defects and determine deteriorationmechanisms (costs determination)

• Remaining life prediction of key structuralelements (timing determination)

• Rehabilitation options analysis and lifecycle costs (rehabilitation strategy)

• Set objectives and target the scope to achieve them

• Avoid over scoping

• Encourage innovation and new technology



Level 3 Engineering Assessment – Consultants PerspectiveInspection, Testing and Assessment

• Who should be doing inspections?

• What type of inspection techniques are needed?

• Why are nominated the inspection techniques specified?

• How is the equipment used and results interpreted?


Visual InspectionUse your eyes (or equivalent)

• Touching distance is best

• High zoom cameras/binoculars

• Drones

• Boroscopes/videoscopes

• Camera on a stick


Underwater InspectionsWhat you can’t see might change everything

• Cleaning is imperative

• ROV’s can be used (sometimes)

• AAR/DEF are main concerns


Delamination SurveysA materials engineer’s favourite tool

• Use the right hammer

• To find “drummy” concrete

• Interpretation of resonance on site


Cover Surveys and BreakoutsEasy to get wrong

• Cover meter

• Based on magnetism

• Correct bar size must be selected

• Ground penetrating radar

• Uses radio signal

• Susceptible to moisture content (dielectric)

• Both have strengths and weaknesses

• In both cases breakouts are often needed

• Ideally use both!

Source: GSSI Structure Scan Mini II manual


Neutralisation (Carbonation) DepthAlkalinity test

• Simple on site test on core samples or breakouts

• Concrete must be freshly fractured

• Magenta = good, colourless = bad

• Aggregate won’t change colour


Electrochemical TestingFor the experienced corrosion engineer

• Many types of testing

• Mostly for marine structures

• Can be time consuming

• Equipment is often expensive

• Requires training and experience


Core Sampling and TestingA justified remaining life assessment

• Make sure you get the correct core size

• Can be used for physical or chemical testing

• Don’t cut the reinforcement

• Remember to patch up!


Load Rating AssessmentCan be a deciding factor

• Requires as constructed drawings and site verification

• Theoretical “insufficient” rating can be managed with pragmatism

• Correlation with site observations

• Other management strategies can be considered


Concrete DeteriorationA brief and concise overview of a complicated topic

• Chloride induced corrosion

• Impacted by many factors

• Still a topic of on-going research and debate in industry

• Internal expansion mechanisms

• Alkali-aggregate reaction (AAR)

• Delayed ettringite formation (DEF)

• Can be damaging on its own

• Provides a pathway for contaminates

• Poor design/construction practices


Repair PrincipalsWhat are we trying to achieve?

• Repair categories (SA HB84)

• Protective coatings or moisture barrier systems.

• Patch repair systems.

• Coating of steel reinforcement.

• Cathodic protection.

• Corrosion control.

• Current guidance standard (EN1504)is now 15 years old

• Collaboration is imperative

Successful Project

Outcome

Asset Owner

ConsultingDesign

Engineer

Material Supplier

Contractor


Repair TechniquesPatching, crack injection and coating

• When is patching suitable?

• What material and methodfor crack injection?

• Is a coating needed


Repair TechniquesElectrochemical Protection

• Long term (25+ years) solution

• Impressed current, galvanic, or hybrid?

• On-going monitoring

• High capital cost, but canbe cost effective over time


Repair TechniquesPile Repairs

• Pile jacketing (non-structural)

• Pile encasement (structural)

• Consideration of formwork selection (temporary or permanent) and pour heights

• Permanent formwork material may degrade if not maintained

• Long term inspection and maintenance considerations


Repair TechniquesReplacement (not technically a repair…)

• In some cases it’s the best option

• Holding works and/or a Structure Management Plan (SMP) are often needed in the interim


Strategy SelectionThere is no silver bullet solution

• Consideration of available options (short, medium and long term)

• Understanding of full extent of repairs/upgrades needed

• Whole of life costing

• Other bridge specific considerations


Case Study – Southport BridgeBackground

• Built circa 1968

• Design and construct contract (D&C)

• Issues identified during Level 2 inspection:

• Headstock cracking

• Spalling of service supports

• Pile cleaning revealedsignificant structural defects


Case Study: Southport BridgeKey Findings from Level 3 Inspection

• Piles were found to have large vertical cracks and rust stains

• Steel-to-concrete potential testing confirm active corrosion

• Breakouts revealed full loss of prestressing strands

• Corrosion was anerobic (non-expansive)

• Cracking was initiated by DEFconfirmed by petrography

• Structural encasement wasnecessary immediately


Case Study: Southport BridgeStructural Pile Encasements

Scabbling Pre-pour Pouring


Case Study: Southport BridgeStructural Pile Encasements

Completed Product


Case Study: Southport BridgeLesson’s Learnt

• D&C contract provided an overall cost and time saving

• Budget contingency allowance was exceeded due to pile encasements

• Deterioration mechanism confirmation allowed targeting piles to be encased

• Temporary formwork allows for future inspection and maintenance

• Difficulty working in tidal environment at the site

• Robust quality assurance was specified, and enforced by the Superintendent

• Continuation of experienced project team through inception, design and construction


Case Study: Biggera Waters BridgeBackground

• Built circa 1960

• Unique pile design (mass concrete filled pipe)

• Level 2 inspection found:

• Cracking in piles

• Cracking in headstocks

• Corrosion of steelwork


Case Study: Biggera Waters BridgeKey Findings from Level 3 Inspection

• Mass concrete inside encasement was expanding

• Cracking in pipes continued to bed level (but tapered)

• Structural analysis found pipe could be removed following a set construction sequence

• Headstock cracking was concluded as a construction related defect (plastic shrinkage due to excessive cover)

• Steelwork walkway widening required repair and coating


Case Study: Biggera Waters BridgeWorks Underway

Structural Encasements Concrete Steelwork


Case Study – Biggera Waters BridgeEncasements

Completed Product


Case Study: Biggera Waters BridgeLessons Learnt

• Scope of inspections and diagnosis of the underlying cause of the pile cracking was critical

• The use of a proprietary permanent formwork system (GFRP) provide cost savings

• Concrete pressure were too high (even with bracing) which caused bursting at the vertical seam in the jacket

• Contractor improved the bracing around the vertical seam which prevented failure on subsequent pours

• Anti-washout admixture was added to the concrete mix to reduce environmental risk

• Careful selection of contractor to undertake the works


Conclusions• Learn from successes and mistakes• Review Level 2 inspection reports• Prioritizing bridge inspection and

rehabilitation is complicated• Corrosion is inevitable• Use the right people and tools

for the job• Look at the big picture when selecting

rehabilitation strategies• Don’t skimp on QA/QC

(and make sure it’s enforced)

There is no single answer to managing a deteriorated bridge

Image source: Broomfield, J.P. (2007) ‘Corrosion of Steel in Concrete 2nd Edition’


Thank you for your attention!

Special thanks to Yvonne Ulas (City of Gold Coast) and Dr. Luke Menefy (SMEC Australia Pty Ltd) for their significant contributions to the preparation of this paper.

Questions?