Recent Trends in Evaluation and Monitoring of Existing

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Recent Trends in Evaluation and Monitoring of Existing Concrete Structures

Technical Topic Webinar

Dr. Ana Evangelista | EIT Lecturer, Civil & Structural Engineering Course Coordinator

Presented By

Wednesday 8 September | Technical Topic Webinar

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https://vimeo.com/600624754/8393ecd921


Introduction - Presenter


Dr. Ana EvangelistaCivil Engineering Lecturer

Ana is a passionate Civil Engineer and is currently a Lecturer and Work Integrated Learning Coordinator at EIT. Her research in Australia has been focused on sustainability in construction and engineering materials and her PhD research was mostly concentrated on non-destructive tests to evaluate concrete structures.

In 1997, she started her academic career coordinating and teaching units at the School of Civil Engineering at Federal University of Rio de Janeiro (Brazil). Additionally, she managed the Construction Materials Laboratory providing external consultancy to the Construction Engineering sector.

In 2008, she joined the Environmental Engineering Program at Federal University of Rio de Janeiro (Brazil) conducting research and supervising higher degree students investigating eco-friendly engineering materials. From 2016 to 2019 she worked as a visiting research fellow in the area of recycled concrete at Western Sydney University / School of Computing, Engineering and Mathematics. Also, she worked as a casual academic teaching Engineering and Construction Management Units.


1 Welcome & Introduction

2 Structural degradation

3 NDT methods

4 Structural Health Monitoring

5 Conclusion and Q&A

Agenda


Causes of structural degradation


Structural degradation

Progressive degradation

Degradation caused by

shocks

Progressive + shock-based deterioration


Causes of structural degradation


Any change to the material orthe geometric propertiesaffecting the structuralperformance

Cracks are the most commonlyencountered manifestation thatthe structure could not resist theforces imposed on it

•Plastic shrinkage •Cracks due to improper jointing•Early thermal contraction•Cracks due to lack of isolation joint•Cracks due to freezing and thawing•Craze cracks or crazing•Settlement cracks•Corrosion of reinforcement


Structural Degradation vs Expected Service Life


✓ Improper Design of Structure✓ Poor Quality of Concrete✓ Improper concreting practice✓ Change of loading pattern or non-conventional

Loading on structure✓ Extreme weather conditions✓ Water Leakage leading to corrosion of concrete and

Reinforcement✓ Natural disasters

Source: http://www.yashkrishi.com/deterioration-of-structures

✓ Monumental Structure like temple, mosque or church to last for 500 to 1000 years.

✓ Steel Bridges, Steel Building or similar structure for about 100 to 150 years.

✓ Concrete Bridges or High-rise Building for about 100 years✓ A house or general Building for about 60 to 80 years.✓ Highways: Concrete pavements for about 30-35 years and

bituminous pavements for about 8-10 years.

The aim of structural design is to producesafe, serviceable, durable, aesthetic, economicaland sustainable structures (AS 3600)

The AS 3600 applies to plain, reinforced and prestressed concrete structures and members with a design life of 50 years ± 20%


Deterioration Modelling

The process of modelling and predicting decreased physical condition state

of infrastructures over the time is called deterioration modelling.

Age

Co

nd

itio

n/P

erfo

rman

ce

Typical asset deterioration curve with no maintenance activities

Source: EIT, MCS604, Topic 1, slide 26, 2021



Deterioration Models

Deterministic Models

Stochastic modelsArtificial Intelligent

(AI) models

• Straight-line• extrapolation• Regression models• Curve-fitting models

• Simulation• Markovian

• Artificial Neural Networks• Case-based reasoning

Source: http://osp.mans.edu.eg/elbeltagi/Infra%204-Deterioration.pdf / EIT, MCS604, Topic 1, slide32,2021



Source: EIT, MCS604, Topic 1, slide32,2021

Example of ANN BPM model proposed for bridge deterioration modelling

• Select the governing factors affecting the deterioration of a

asset class (e.g. bridges in road network)

• Collect asset condition data as well as data related to key

factor identified in first step

• Design ANN architecture to define hidden layers, neurons

in each layer, the learning rate etc.

• Train the ANN

• Test and validate the network

• Use the network for prediction


Visual inspection

Hands-on Testing

Planning and conducting in-situ inspection


Planning and conducting in-situ inspectionVisual Inspection (Concrete Construction)

• Crack width: Hairline, fine, medium, wide

• Scaling: loss of material from concrete surface

• Spalling: Detachment of concrete cover

• Extent of reinforcement corrosion

• Signs of water penetration

Sample Collection

• Cores are drilled from the structure and are tested for

compressive strength in the laboratory

• The height to diameter ratio of the core must meet the

requirements set by the standards (ASTM C42, BS EN

12504:2019)

• The strength of the core can be related to the concrete

compressive strength

Images Source: The Concrete Society


Planning and conducting in-situ inspection


Testing Methods

Destructive testing

methods

Non-destructive

testing methods


Evaluation methods


Use cover meter to measure the reinforcement

cover and location

Measure half-cell potential of reinforcement to

understand the risk of reinforcement corrosion in reinforced concrete bridges

Assessment of fatigue cracking using ultrasonic testing of

welding joints

Static and dynamic load testing

Structural health monitoring using

sensors


NDT methods – pros vs cons


Ultrasonic Pulse Velocity (ASTM C597)

Method: This technique determines the velocity of a pulse of vibrational energy through a slab. The test provides measurements regarding the concrete’s elasticity, resistance to deformation or stress, and density. This data is then correlated to the structural elements’ strength.

Pros: This is a non-destructive testing technique which can also be used to detect flaws within the concrete, such as cracks and honeycombing.

Cons: This technique is highly influenced by the presence of reinforcements, aggregates, and moisture in the concrete element. It also requires calibration with multiple samples for accurate testing.

Rebound Hammer or Schmidt Hammer (ASTM C805)

Method: A spring release mechanism is used to activate a hammer which impacts a plunger to drive into the surface of the concrete. The rebound distance from the hammer to the surface of the concrete is given a value from 10 to 100. This measurement is then correlated to the structural elements’ strength.

Pros: Relatively easy to use and can be done directly onsite.

Cons: Pre-calibration using cored samples is required for accurate measurements. Test results can be skewed by surface conditions and the presence of large aggregates or rebar below the testing location.




https://doi.org/10.1155/2013/834572




https://doi.org/10.1155/2013/834572



CRICOS Provider Number: 03567C | Higher Education Provider Number: 14008 | RTO Provider Number: 51971https://doi.org/10.1155/2013/834572




https://doi.org/10.1155/2013/834572




https://doi.org/10.1155/2013/834572


Evaluation of NDT methods


The five performance measures selectedfor categorizing and ranking the technologies:

1. Accuracy;

2. Precision (repeatability);

3. Ease of data collection, analysis, and interpretation;

4. Speed of data collection and analysis; and

5. Cost of data collection and analysis.

The evaluation of NDT technologies include four deterioration types:

1. Delamination;

2. Corrosion;

3. Cracking; and

4. Concrete deterioration.

Source: https://doi.org/10.17226/22771


Definitions of Performance Measures for Different Deterioration Types

CRICOS Provider Number: 03567C | Higher Education Provider Number: 14008 | RTO Provider Number: 51971 Source: https://doi.org/10.17226/22771

https://doi.org/10.17226/22771


Delamination


The impact echo (IE) method is a seismic or stress wave–based method used in the detection of defects in concrete, primarily delamination (Sansalone and Carino 1989)

Grades for various degrees of deck delamination (source: https://doi.org/10.17226/22771)


Corrosion …


Although steel’s natural tendency is to undergo corrosion reactions, the alkaline environment of

concrete provides steel with corrosion protection !

Source : https://www.cement.org/learn/concrete-technology/durability/corrosion-of-embedded-materials

What is the pH of hardened concrete?


Corrosion


The half-cell potential (HCP) measurement is a wellestablished and widely used electrochemical technique toevaluate active corrosion in reinforced steel and prestressedconcrete structures;

Galvanostatic pulse measurement (GPM) is an electrochemicalNDT method used for rapid assessment of rebar corrosion;


https://doi.org/10.17226/22771


Cracking


The electrical resistivity (ER) method is often used formoisture detection, which can be linked to the presence ofcracks.


https://doi.org/10.17226/22771


Concrete deterioration


Chain dragging and hammer sounding (ASTM D4580-86):

IR thermography:

✓ To detect subsurface defects - keeps track of electromagnetic wave surface radiations related to temperature variations in the infrared wavelength.

✓ Anomalies, such as voids and material changes, can be detected on the basis of variable material properties, such as density, thermal conductivity, and specific heat capacity

Principle of passive infrared thermography


https://doi.org/10.17226/22771


Concrete deterioration


Ground-penetrating radar (GPR) - electromagnetic waves tolocate objects buried inside the structure and to producecontour maps of subsurface features;

GPR - condition assessment of bridge decks and tunnel linings,pavement profiling, mine detection, archaeologicalinvestigations, geophysical investigations, borehole inspection,building inspection, and so forth…

GPR testing


https://doi.org/10.17226/22771


Statistical considerations


ASTM C823/C823M can be adapted to provide some

guidance on planning the sampling program. Sampling

situations can be assigned to two categories:

1. Where preliminary investigation and other

information indicate that conditions are similar

throughout the structure;

2. Where preliminary investigation and other

information indicate that conditions are not similar

throughout the structure, the structure is divided into

portions within which conditions are similar;

The intent is to select sampling locations in a manner that allows all locations an equal probability of being selected.

Source : ACI 228.2R-13




According to ACI 228.2R-13…. “an evaluation program that includes NDT to be

justifiable, it should satisfy as many of the following requirements as possible:

a) Approximate the price of an intrusive testing program alone for the same

area or volume tested;

b) Provide a larger amount of reliable data for the same area or volume

examined, thereby yielding more information;

c) Include areas that are difficult to examine thoroughly using more

traditional or intrusive methods;

d) Include reproducible recovered data so that future surveys of the same

structure can rely with confidence on the initial NDT data as a base

reference”




The ideal test density (data density) represents desirable spacings to achieve a statistically valid assessment of the concrete condition (ACI 228.2R-13)

All points tested on the structure can be easily identified at a later date so that tests can be repeated if necessary at the exact

test location at any time in the future.

The test results in the preliminary survey should be in such a format (graphs and numerical data) that direct comparisons

can be made between the original and subsequent test results.

The investigator should have the statistical confidence in the reproducibility of each test result.




Data on the repeatability of some in-place tests are provided in the precision

statements of the ASTM standards governing the tests (ACI 228.1R-19)

ASTM C805/C805M -Rebound number - states that the single-operator standard deviation of

the rebound hammer test is 2.5 rebound numbers, which limits the expected range of 10

readings to 12;

ASTM C597 - Ultrasonic pulse velocity - states that the repeatability of test results is within

2 % for path lengths from 0.3 to 6 m through sound concrete and for different operators

using the same instrument or one operator using different instruments


Practical considerations

Areas with difficult access …

Retaining walls, grade beams, and slabs-on-grade, where only one side of the

element is accessible

Deep foundations (piles, drilled shafts, and slurry walls), where nearly all the element

is buried

Concrete elements located in hazardous areas, such as hazardous material waste

tanks and nuclear sites


Bridge Inspections and Monitoring


To check general serviceability, users safety

Identify current maintenance needs

Identify possible defects, destresses

Get better knowledge of condition, load capacity, in-service performance

Source: http://www.wagmanengineering.com/bridge-inspection.html, MCS604, Topic 3

http://www.wagmanengineering.com/bridge-inspection.html




Source:Source: https://www.mainroads.wa.gov.au/globalassets/technical-commercial/technical-library/structures-engineering/asset-management/inspection-inventory-guidelines/detailed-visual-bridge-inspection-guidelines-for-concrete-and-steel-bridges-level-2-inspections.pdf , MCS604, Topic 3

Condition State 1 (CS1) - concrete superstructure

Mild water staining inside of beams Superficial water stains only (diaphragm)





Staining indicates hidden issues and some minor deterioration

The crack shown by the leaching might still be CS1, however, there are additional hairline cracks forming a pattern making this CS2






Several cracks greater than 0.3 mmSingle large spall, may be due to obstruction of movement





Severe impact damage with total destruction of the beam

Severe impact damage with total destruction of the beam

Fire damage as noted from the pink discolouration. Medium cracking

and tapping indicates delamination



Structural Health Monitoring


SHM aims to give, at every moment during the life of a

structure, a diagnosis of the “state” of the:

•Constituent materials

•Different parts

•Full assembly

✓ Automated monitoring system, and it is a key element of

cost-effective strategies for condition-based

maintenance.

The benefits of structural health monitoring include:




SHM in Civil EngineeringProper maintenance and management

Level of service in a safe and cost‐effective manner

Level I: Damage detection, giving a qualitative indication that damage might be present in the

structure

Level II: Damage localisation, giving information about the probable position of damage

Level III: Damage classification, giving information about the type of damage

Level IV: Damage assessment, giving an estimate of the extent of damage

Level V: Damage prognosis, giving information about the safety of the structure, e.g. estimate of

remaining useful life

Source: MCS604, Topic 2




SensorsData

acquisitionData

transmissionData

processingData

managementHealth

evaluationDecision making

The SHM involves four key elements: data acquisition, system identification, condition assessment, and decision making/maintenance




Source: MCS604, Topic 2




Source: https: //doi. org/10.1007/s11595-020-2337-y

Fibre optic pH sensor

Carbonation front of concrete determined

using phenolphthalein

Sensors




Contact sensors

AccelerometerLinear variable

differential transformer -LVDT

Strain gauge

Fiber optic sensorPiezoelectric

sensorImpedance sensor

Ultrasonic wave sensor

Wireless sensing technology

Data acquisition remains challenging due to the complexity of data transmission and

time synchronization and power consumption

Source,DOI: 10.1002/stc.2321




SmartphonesUAVs

(drones)Cameras

Robotic sensors

A schematic of various next generation sensing technology used in the SHMSource : DOI: 10.1002/stc.2321











Conclusion


✓ Several national and international codes of practice accepted and include the NDT methods;

✓ An NDT method provides indirect results which can be related to various properties of concrete structures;

✓ Combining several methods for assessing the structures is now required for better assessment;

✓ NDT engineer uses single method for evaluating a parameter, but combining more than one method has been required

Source: Evangelista, 2003.


Conclusion


DOI: 10.1002/stc.2321


Reference list


Sanjeev Kumar Verma, Sudhir Singh Bhadauria, Saleem Akhtar, "Review of Nondestructive Testing Methods for Condition

Monitoring of Concrete Structures", Journal of Construction Engineering, vol. 2013, Article

ID 834572, 11 pages, 2013. https://doi.org/10.1155/2013/834572

doi.org/10.35789/fib.BULL.0022

ASTM C823/C823M-12—Standard Practice for Examination and Sampling of Hardened Concrete in Constructions

ACI 228.2R-13—Report on Nondestructive Test Methods for Evaluation of Concrete in Structures

https://www.cement.org/learn/concrete-technology/durability/corrosion-of-embedded-materials

https://www.forconstructionpros.com/concrete/article/21072546/7-methods-for-testing-concrete-strength

Sony, S, Laventure, S, Sadhu, A. A literature review of next-generation smart sensing technology in structural health

monitoring. Struct Control Health Monit. 2019; 26:e2321. https://doi.org/10.1002/stc.2321

Evangelista AC, Shehata I. Parameters that influence the results of non-destructive test methods for concrete strength. International Symposium (NDT-CE 2003) 1 (ISBN 3-931381-49-8)

https://doi.org/10.1002/stc.2321

CRICOS Provider Number: 03567C | Higher Education Provider Number: 14008 | RTO Provider Number: 51971CRICOS Provider Number: 03567C | Higher Education Provider Number: 14008 | RTO Provider Number: 51971

This Photo by Unknown Author is licensed under CC BY-NC-ND

http://evergreenleaf.blogspot.com/2013/04/my-first-blog-award-liebster.html

https://creativecommons.org/licenses/by-nc-nd/3.0/


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Recent Trends in Evaluation and Monitoring of Existing