tarengo bridge – inspection report - ipwea

TARENGO BRIDGE – INSPECTION REPORT

INSPECTED AND PREPARED BY

GAYAN ABEYWARDENA

XXXX Bridge Location Map

Tarengo Bridge – Inspection Report 2

Contents

1.0 Introduction…………………………………………………………………… 3

2.0 Observations…………………………………………………………………. 4

2.1 Bearing Pad………………………………………………………………….. 4

2.2 Concrete Abutments and Wing Walls……………………………………... 4

2.3 Concrete Deck……………………………………………………………….. 4

2.4 Concrete Piles/Piers, Head Stock…………………………………………. 4

2.5 Bridge Approach…………………………………………………………….. 4

2.6 Wearing Surface…………………………………………………………….. 4

3.0 Further Study of the Deck………………………………………………….. 5

3.0 Calculations………………………………………………………………….. 6

4.0 Conclusions and Recommendations……………………………………… 6

Annexure 1…………………………………………………………………… 7

Annexure 2…………………………………………………………………… 8

Annexure 3…………………………………………………………………… 19


1.0 Introduction Tarengo Bridge crosses Boorowa River on Cunningar Road approximately 6 km

south west of Boorowa, NSW. The new concrete bridge replaced a timber girder

bridge on a new upstream road alignment and was built between July 2014 and April

2015 by Murray Constructions from Deniliquin, NSW and designed by Aussie

Bridges from Bendigo, Victoria.

The bridge was designed as three spans (19.825/19.750/19.825 m) of 750 mm deep

super-t girders (4 per spans). At the abutments three driven 310UC158 steel piles

provide the foundations.

At piers 1 and 2 there are two 750 mm and 900mm diameter bored piles supporting

each reinforced concrete headstock. The bridge articulation is provided by

elastomeric bearings and the in situ cast deck is continuous for the entire length of

the bridge with no expansion joints.

There are 6 m long approach slabs at each abutment and steel traffic barrier railing

of unknown performance level.

This initial review has been well thought-out available information at present, it appears there are:

Design drawings from Aussie Bridges.

Construction records from Murray Constructions. It is decided to provide covering report with supporting evidence to the extent made possible by the current available documentation and initial site inspection. The report will also Identify:

Any further investigations or testing that may be required (eg: concrete deck cores, cover surveys, etc).

Potential repair, remediation or monitoring strategies (eg: crack repair methods, durability repairs, etc).

This report focuses the Bridge Condition Assessment Criteria attached to Annexure

1 of this report. Accordingly, the bridge was grouped for fourteen elements and

derived condition (ESCI), Material Vulnerability (Mi) and Structural Importance (Si)

for each element. Finally, Overall Structural Condition Index (OSCI) was calculated.

The calculation sheet is attached to Annexure 1 of this report

2.0 Observations

2.1 Bearing Pad

Bearing pads are in good condition as there are no deformation or visual defects seen despite the cracks in the concrete deck (Photo)


2.2 Concrete Abutments and Wing Walls

Abutments, Wing Walls, Side protections are in good working condition (Photo)

2.3 Concrete Deck

In a cursory inspection of the deck, the following deficiencies were noted

One Crack Pattern was found visible on the top side of the deck transversely closer to Pier 1. The average crack widths were in the range between 0.3mm and 0.7mm. The fore mentioned cracks were recorded having lengths up to 2.0m

Second Crack Pattern was found visible on the top side of the deck transversely closer to Pier 2. The average crack widths were in the range between 0.3mm and 0.7mm. The fore mentioned cracks were recorded having lengths up to 3.0m

The other area of the deck is in good working condition. (Photo)

2.4 Concrete Piles/Piers, Head Stock Concrete piles/piers and head stock are in a new condition (Photo)

2.5 Concrete Girders The Concrete Girders are in new Condition except handling damage in one Girder. this is recording for future use to avoid any misunderstanding of Spalling . (Photo)

2.6 Bridge Approach & Wearing Surface The Bridge Approach wearing surface is in good working condition. (Photo)


3.0 Further Study of the Deck

At this point only a preliminary analysis of the deck cracking for Tarengo Bridge has been assessed. A total of 2 crack locations were found visible on the top side of the deck transversely closer to Pier 1 and Pier 2. The average crack widths were in the range between 0.3mm and 0.7mm. The fore mentioned cracks were recorded having lengths up to 2.0m and 3.0m. High compression concrete has a higher propensity for transverse cracking. This will

lead to high maintenance costs, structural problems including accelerated corrosion of reinforcing steel, deterioration of deck concrete, and possible damage to underlying components. Transverse deck cracking can also be detrimental to the overall bridge aesthetic. Transverse deck cracking also increases carbonation and chloride penetration leading to accelerated corrosion and deterioration. Various factors may occur this type of cracking as follows:

The material properties considered included admixtures, slump, percent volume of water and cement, water content, cement content, water-cement ratio, air content, and compressive strength.

Site condition factors such as average air temperature, low air temperature, high air temperature, daily temperature range, relative humidity, average wind velocity, and evaporation.

Construction procedure factors such as placing sequence, length of placement, and curing. There were no observed relationships between length of placement or type of curing materials and cracking. No correlation between cracking and placing sequence could be determined due to lack of information.

Design factors considered such as structure type, deck type, deck thickness, top cover, transverse reinforcing bar size, transverse reinforcing bar spacing, girder end conditions, span length, bridge length, span type, and skew.

The precise reason for the cracking could be derived after doing the further study by collecting data and analyse them cautiously.

• Construction photographs. • Tender documentation. • method statement for Timber support installation and removing and • timing of Concrete deck pouring (Before or after timber support removal

Also, several exclusive tests can be carried out such as core sampling to get an idea of the depth of the crack. This is a challenging task as we need to collect more data from several parties to do the root cause analysis. The cracks occurred very less area of the deck, and no cracks/damage is visible in other components of the bridge as per the observations made except the Handling damage of one Girder (photo). Accordingly, there is no significant risk of sudden structural capacity reduction or a failure of the structure.


. But if this is exposure to weather, there is a future risk to corrode reinforcement of

the deck and reduction of Structural capacity in the future. The best option that can

be recommended at this stage is to

1. Contact the Contractor and the Consultant (QA for the Project) to get any further

details such as Construction photographs Measurements of Hoggs before and after

pouring the Deck. Method statement for Bearing Pad Timber support Installation and

removing

2. repair the crack using epoxy sealer and closely monitored the deck periodically to

observe any growth/existence of deck cracks.

4.0 Calculations

The bridge was grouped for fourteen elements and derived condition (ESCI), Material Vulnerability (Mi) and Structural Importance (Si) for each element as per the Bridge Condition Assessment Criteria (Annexure 2). Accordingly, Overall Structural Condition Index (OSCI) was calculated. The calculation sheet is attached in Annexure 1 of this report. The OCSI for the bridge is 1. Also we used the adverse case of Road factor considering Higher Mass and higher Traffic (Road factor used is R=4)

5.0 Conclusions and Recommendations

As per the assessment and calculations, the OCSI is 1. Hence there is no risk of the structural capacity. But it may have a probability to corrode the reinforcement of the deck due to water pass through the cracks. So, it has a risk of failure in the deck in the future due to corrosion of the reinforcement Accordingly, it is recommended to repair two crack locations using epoxy repair method through suitable Contractor (Refer Annexure 3) to avoid deterioration of reinforcement of the slab. These two sections specially and the entire deck should be closely monitored periodically to observe any existence/growth of further cracks to ensure the durability of the bridge. If the cracks continuing further investigation should be carried out in detail with focussing following factors.

Hydraulic effects of the river on the bridge structure.

Collision loading and the effects of collision on the superstructure.

Fatigue effects.

Substructure and soil-structure interaction for the foundations.

Longitudinal analysis of the structure, including braking, creep, shrinkage and thermal effects.

Settlement induced loading.

Bridge bearings, abutments and other elements of the bridge


Detailed design check, Detailed construction practises, method statements & procedures done during the construction and Detailed rehabilitation proposal.

Annexure 1

Calculation of Overall Structural Condition Index (OSCI) for Tarengo Bridge

Item Element Code

Element Description Total

Quantity Units

Estimated Quantity in Condition State ESCI Si Mi

ESCIxSixMi

1 2 3 4

1 BELA Bearing Pad 16 ea 16 1 3 2 6

2 CABW Concrete Abutment and Wing walls 32.95 m2 32.95 1 2 2 4

3 CDSL Concret Deck Slab 534.6 m2 517.5

17.1

1.03 3 2 6.18

4 CPHS Concrete Pier Head Stock 18.9 m2 18.9 1 4 2 8

5 CPIL Concrete Piles/Piers 149.27 m2

149.27

1 4 2 8

6 JNOS Joint No Seal 48 m 48 1 1 3 3

7 JPOS Pourable/Cork Joint Seal 415.8 m 415.8 1 1 3 3

8 MAPP Approach Carriage way 2 ea 2 1 1 3 3

9 MBAT Batter Protection 140 m2 140 1 1 3 3

10 MGCL General Cleaning 1 ea 1 1 1 3 3

11 UCSP Steel Piles 27.35 m2 37.35 1 4 1 4

12 MWWY Water way 1 ea 1 1 2 1 3 6

13 RMET Metal Railing 142.8 m 142.8 1 1 1 1

14 RPNT Railing Paint work 142.8 m 142.8 1 1 1 1

S(ESCI*Si*Mi) 59.18

CF=0.411A+0.120E+0.107R+0.362I A=1 E=1 R=4 I=2 1.68

SHI=CF*S(ESCI*Si*Mi)/n SHI=1.88*93.15/(14) 7.102

OSCI=1, when 1<SHI≤11 OSCI=2, when 11<SHI≤26 OSCI=3, when 26<SHI≤91 OSCI=4, when 91<SHI≤140 OSCI=5 When 140<SHI≤256

Annexure 2

Bridge Condition Rating Criteria

Summary and Conclusion

A methodology of an element based structural index is adopted in the condition assessment.

Overall Structural Condition Index (OSCI) is expressed as a number 1 to 5. Such as OSCI of 5

corresponds to the worst condition of a bridge and OSCI of 1 represents a new bridge. Material

vulnerability (Mi) and Structural importance (Si) are considered in the element based condition

assessment and the critical parameters that influence structural efficiency are identified as age,

environment, road type and inspection. The weight of each of those factors has been evaluated,

and the overall influence factor, which is introduced as Causal Factor (CF) is implemented as a

coefficient to the current structural condition.

Four condition states defined in the Road and Traffic Authority (RTA) for Concrete

elements

Condition

State

Description of defects

1

The element shows no deterioration. There may be discolouration,

efflorescence and/or superficial cracking but without effect on strength and/ or

serviceability.

2 Minor cracks and spalls may be present but there is no evidence of corrosion of

non-prestressed reinforcement or deterioration of the prestress system

3

Some delaminations and/or spalls may be present. No evidence of

deterioration of the prestress system. Corrosion of non-prestressed

reinforcement may be present but loss of section is minor and does not

significantly affect the strength and/or serviceability of either the element or the

bridge.

4

Delaminations, spalls and corrosion of non-prestressed reinforcement are

prevalent. There may also be exposure and deterioration of the prestress

system (manifested by loss of bond, broken strands or wire, failed anchorages,

etc). There is sufficient concern to warrant an analysis to ascertain the impact

on the strength and/or serviceability of either the element or the bridge

Sample Photos for Concrete Structure Conditions


Condition 1a

Slightly weathered, minor surface grout loss and

discolouration, still in good condition.

Condition 1b

Mild water staining inside of beams.

Condition 2a

Frequent closely spaced hairline cracks (forming a pattern) warrant Condition 2.

Condition 2b

Widely spaced fine cracking. Water staining prevalent in more sheltered areas.

Condition 3a

Single quite large spall. The spall is likely to have been caused by obstruction of movement and hence warrants Condition 3.

Condition 3b

Single medium crack <0.7 mm. Note that the crack is active and fretting.

Condition 4a

Substantial loss of section, spalling.

Condition 4b

Deck slab block cracking, cracks <0.6 mm


1. Introduction

Due to the substantial role of bridges in transportation networks and in accordance with the

limited funding for bridge management, remediation strategies have to be prioritised. A

conservative bridge assessment will result in unnecessary actions, such as costly bridge

strengthening or repairs. On the other hand, any bridge maintenance negligence and delayed

actions may lead to heavy future costs or degraded assets. The accuracy of decisions developed

by any manager or bridge engineer relies on the accuracy of the bridge condition assessment

which emanates from visual inspection. Many bridge rating systems are based on a very

subjective procedure and are associated with uncertainty and personal bias. Structural

importance and material vulnerability are the two main factors that should be considered in the

evaluation of element structural index and the causal factor as the representative of age,

environment, road class and inspection is implemented as a coefficient to the overall structural

index.

A methodology of developing an element based structural index is adopted in the condition

assessment. Overall Structural Condition Index (OSCI) is expressed as a number 1 to 5 and

OSCI of 5 corresponds to the worst condition of a bridge and OSCI of 1 represents a new bridge.

Material vulnerability (Mi) and Structural importance (Si) are considered in the element based

condition assessment and the critical parameters that influence structural efficiency are identified

as age, environment, road type and inspection. The weight of each of those factors has been

evaluated, and the overall influence factor, which is introduced as Causal Factor (CF) is

implemented as a coefficient to the current structural condition

Condition 4c

Substantial loss of reinforcement section and failure of beams. Without discolouration/staining.

Condition 4d

Severe impact damage with total destruction of the beam. Immediate action required.


2. Considering a unified bridge condition rating

Bridges are complex mixture of parallel and series systems, but almost all Bridge Management

Systems (BMS) use the evaluation of members or elements as input to calculate the overall

structural reliability.

With the purpose of being consistent with the majority of bridge inspection practices the

recommended methodology is an element level index based on four condition states defined in

the Road and Traffic Authority (RTA) in which the bridge element condition ranges from 1 to 4 in

rising order. The general description of the four condition states for reinforced concrete bridge

elements is presented in Table 1. In this system the bridge is divided into elements generally

made of a similar material (Most bridges have about ten to twelve elements and bridge sized

culverts usually have three to five elements). The inspector estimates and records the quantities

of the bridge element in each condition state independently. The total quantity must be measured

in the correct units for the elements. The units of measurement are square meters (deck, pier,

and pile), meters (joints and railings) or each (bearing pad, waterway, etc).

Table 1: Condition states for concrete bridge elements (RTA, 2007)

Condition

State

Description of defects

1

The element shows no deterioration. There may be discolouration,

efflorescence and/or superficial cracking but without effect on strength and/ or

serviceability.

2 Minor cracks and spalls may be present but there is no evidence of corrosion of

non-prestressed reinforcement or deterioration of the prestress system

3

Some delaminations and/or spalls may be present. No evidence of

deterioration of the prestress system. Corrosion of non-prestressed

reinforcement may be present but loss of section is minor and does not

significantly affect the strength and/or serviceability of either the element or the

bridge.

4

Delaminations, spalls and corrosion of non-prestressed reinforcement are

prevalent. There may also be exposure and deterioration of the prestress

system (manifested by loss of bond, broken strands or wire, failed anchorages,

etc). There is sufficient concern to warrant an analysis to ascertain the impact

on the strength and/or serviceability of either the element or the bridge


The following example shows the bridge element condition concept. The condition inspection

results of pile element with a total area of 250 m2 are presented in Table 2.

Table 2: Bridge Pile Condition Rating Results

Condition Rate Area (m2)

1 157

2 4

3 84

4 5

The overall condition of pile = [(157×1) + (4×2) + (84×3) + (5×4)] / [250×1]

=1.748

Colorado Department of Transportation suggested a frame work for condition rating of deck

cracking which is shown in Table 3.

Table 3: Conditions Rating of Deck Cracking (Colorado Department of Transportation, 1995 )

Crack Width (mm) Spacing of Cracks in Concrete Deck (m)

>3 2-3 1-2 <1

<1

1-2

2-3

>3

1 1 2 3

1 2 3 4

2 3 4 4

3 4 4 4

As a matter of fact, some elements require more attention than the others in terms of material

vulnerability and/or structural significance. For example reinforced concrete has more potential

damage than steel. A defective main beam will require more urgent attention than the bridge

drainage outlets.

One crack can be a flexural crack flagging an initial structural failure while the other may be due

to creep and shrinkage of concrete, which has limited structural importance. However the

determination of structural/ material vulnerability of various bridge elements is a difficult task.

Sometimes doing some structural analysis such as non-destructive testing program is

unavoidable. Alternatively, bridge experts and inspectors will rely on their own experience and

knowledge to determine these factors.

2.1 Material Vulnerability Factor


According to Austroads (2004) material factor is an important parameter that should be

considered in structural assessment of bridge elements. Based on vulnerability of different

material it ranges between 1 (steel) and 4 (precast concrete) (See Table 4). The greater Mi

reflects the higher material vulnerability.

Table 4: Material Vulnerability Factor Mi

Material of the element

Material Vulnerability Factor, Mi

Steel 1

Reinforced Concrete 2

Precast concrete 3

Pre stressed concrete 4

2.2 Structural Significance Factor

Generally, the prevailing condition (rating) of the particular element may cause some

inaccuracies in the overall structural assessment. For example, a minor component with worse

condition may unreasonably raise the rating value of that element under which the component is

grouped. This problem can be dealt with the introduction of element structural significance factor

which is not dependent on the prevailing condition of components as summarised in Table 5. The

higher numbers represent the superior importance.

Table 5: Structural Significance Factor Si

Element

Structural Significance Factor, Si

Barrier, Footway, Kerbs, Joints 1

Foundation, Abutment, Wingwall 2

Deck, Bearings 3

Beams, Headstocks, Piers 4

2.3 Causal Factor

Bridge elements deteriorate over an extended period of time and the rate of deterioration is a

function of various parameters. The environment the structure is located in, the length of time the

structure has been in service (Age), the function the structure is required to perform (Road Class)

and the quality of inspection and monitoring

2.3.1 Environmental Factor:


This parameter considers natural/ man caused environmental actions that cause chemical and

physical deterioration of concrete. The major concerns are freeze and thaw cycles; chloride

ingress, sulphate attack, acid attack and alkali-aggregate reaction

2.3.2 Age Factor:

As bridges are designed to withstand fatigue loading (which increases with time), age is an

important parameter involved in structural condition assessment. The life expectancy of major

concrete bridges is around 100 years.

The service life of a bridge brings to end when one of the key components fails to function as

designed. The rating of this factor is presented in Table 6. “Recently built” is allocated for the first

quarter of bridge service life, “New”, “Old” and “Very Old” are respectively assigned for the

second, third and last quarter of that.

2.3.3 Inspection Factor:

Quality and frequency of inspection play a key role in structural reliability of bridges. The

inspection data provides an inclusive information source to track the condition development

trends of bridge structures. However uncertainties and fuzziness associated to the inspection

data cause many problems in its application some of the probable errors in inspection process

are as follows

-Inadequacy of equipments

-Time constraints

-Accessibility

-Visibility

-Exaggeration of some defects (loss of steel cross section to corrosion is usually overstated)

-The inability to recognise structurally significant features, such as support condition, bridge

skew, fracture-critical members, and fatigue-sensitive details.

-Fear of traffic.

-Lack of proper inspection training

-Inappropriate forms/ check lists

-Wind, rain and snow

2.3.4 Road Type Factor:

This factor is involved based on usage and importance of the bridge to the network addressing

the road type of the bridge such as minor, Local access, Collectors, Arterials and bridge

environment such as rural or urban, and the feature crossed such as road, waterway and railway

2.3.5 Rating and priority vector of the causal factors:


All the above mentioned factors have been classified based on definitions pointed out in section

2.3.1, 2.3.2, 2.3.3 and 2.3.4 and rated from 1 to 4 as such the higher numbers are associated

with higher severity (Table 6).

Table 6: Rating of the causal factors

Rating Causal Factors

Age Road Class Environment Inspection Quality

1

2

3

4

Recently Built Minor Low Very High

New Local access Medium High

Old Collectors High Medium

Very old Arterials Very High Low

Rating Causal Factors

The importance level of the causal factors is developed as a vector of priorities which is a

normalised eigenvector and estimated by dividing each element by the sum of that column and

then computing the average of each row that shows the priority weight of the corresponding

element.

Table 8: Pair wise comparison of the causal factors and their final weights

Age Environment Road Class Inspection Weights

Age 1 3 5 1 0.411

Environment 1/3 1 1 1/3 0.120

Road Class 1/5 1 1 1/3 0.107

Inspection 1 3 3 1 0.362

The Causal Factor (CF) is calculated as follows. It ranges from 1-4:

CF= 0.411A + 0.120E+ 0.107R + 0.362I

-A is the age factor

-E is the environmental factor

-R is the road type factor


-I is the inspection factor

3.3.6. Overall Structural Condition Index (OSCI)

The Structural Health Index (SHI) integrates all of the abovementioned parameters that influence

structural efficiency and estimated as follows:

SHI= CF Σ Si x Mi x ESCIi n

-CF is the causal factor

-Si is the structural importance factor

-Mi is the material vulnerability factor

-ESCIi is the Element Structural Condition Index

-n is the number of element types

The condition of an entire structural element introduced as Overall Structural Condition Index

(OSCI) has been re-rated based on HIS and defined as:

OSCI=1, when SHI=2

OSCI=2, when 2<SHI≤16



OSCI=5 When 140<SHI≤256

The re-rated rating number for OSCI is applicable for prioritisation and also selecting the major

remedial strategies such as repair, strengthening and replacement.

Following photos included in the report

i) View from the approach at Abutment 1 end (ii) View from the approach at Abutment 2 end (iii) View of the bridge from the left hand side (iv) View of the bridge from the right hand side (v) Overall view of Abutment 1 (vi) Overall view of Abutment 2 (vii) Overall view of a typical pier (viii) Overall view of the underside of a typical span


New repairs (ix) Footpath details (x) Scour or other waterway issues (xi) Bridge and approach guardrail (typical) (xii) Substructure protection

(xiii) Expansion joint (typical) (xiv) Bearing (typical)


Annexure 3

The most commonly marketed sealers include; epoxies, reactive methyl methacrylates (MMA), methacrylates, high-molecular weight methacrylates (HMWM), and polyurethanes. All these products have distinct characteristics that make them favorable for some uses and unfavorable for others. Properties include volatility, viscosity, initial shrinkage, tensile strength, and tensile elongation. Some surveys of 40 states 60% indicated that they did not have a crack sealing program.

tarengo bridge – inspection report - ipwea

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