Presentation outline

(1)

An

Unified

Approach

of

Non

‐

Destructive

Testing

and

Evaluation

on

Building,

Civil

Engineering

and

Underground

Utility

Structures

and

Materials

at

HKIE

(Buildings)

Division

(5

Sep

2013)

Ir.

Dr.

Wallace

W.L.

Lai

Assistant

Professor,

,

Department

p

of

Land

Who

Surveyor?

are

we?

Surveying

and

Geo

‐

informatics,

HK

PolyU

Visiting

Scientist,

Federal

Institute

of

Materials

Res.

and

Testing

(BAM),

Berlin,

Germany

HOKLAS

Technical

Assessor

y Engineer?

Scientist?

What

are

we

doing?

Surveying?

Testing?

Measurement?

Presentation

outline

• Introduction

• Ordinance

and

Code

of

Practice

• Technology:

Ground

penetrating

radar

• Technology:

Infrared

thermography

• Conclusion

C

i

t

(2)

Nondestructive

inspection

of

building,

civil

engineering

structure

and

underground

utilities

First

Q

:

People

working

on

these

structures

are

used

to

be

very

distinct

in

different

disciplines,

building

surveyors,

structural

engineers,

civil

engineers materials

engineers,

materials

engineers,

land

surveyors

(utility).

What

is

in

common?

Concl.

Milestone

of

building

diagnostic

and

(3)

Because

the

technologies

are

all

about

INSTRUMENTAL

applications

of

WAVE

and

its

properties

in

MATERIALS

So without exception amongst

nondestructive evaluation on

building, civil engineering

structures, U/G utilities, there are

common terms like:

1.Absorption (material)

Reynolds, J.M. An Introduction to Applied and Environmental Geophysics. England, John Wiley & Sons Ltd, 1997.

2.Attenuation (material) 3.Scattering (material) 4.Interface (material) 5.Frequency (instrumentation) 6.Resolution (instrumentation) 7.Dynamic range (instrumentation) 8.…..and others

How?

What

is

common?

What

happens

overseas?

Covermeter

Ultrasonic

S-wave Pile integrity test

Ground penetrating radar test on U/G utility Infrared thermography

Photo snapshots in Nondestructive Testing – Civil Engineering and surveying in Federal Institute for Materials Research and Testing (BAM), Berlin (June 2013)

(4)

• Visual

inspection:

does

not

tell

what

happens

inside,

relies

on

surface

defects

to

predict

internal

conditions

of

structures.

Why

nondestructive?

p

• Random

open

‐

up/take

core/trial

pit:

WHERE?

HOW

MANY?

REPRESENTATIVE?

• NDE

methods

are

non

‐

destructive,

effective

and

cover

a

large

area.

It

serves

as

a

screening

tool before

rational

open

‐

up/taking

core/trial

pit’s

scheme are

decided.

Visual

inspection

NDE

inspection

Presentation

outline

• Introduction

• Ordinance

and

Code

of

Practice

• Technology:

Ground

penetrating

radar

• Technology:

Infrared

thermography

• Conclusion

C

i

t

(5)

Mandatory Building

Inspection Scheme

(MBIS) which is an

Ordinance

The Buildings

(A

d

)

The Hong Kong Laboratory

Accreditation Scheme

(HOKLAS) which is a

practice

(Amendment)

Ordinance 2011

Require building owners to carry out regular building inspections and repair works in respect of their buildings

Cover private buildingsaged 30 years or above, except domestic buildings not exceeding three storeys in height

Building owners will be required to carry Building owners will be required to carry out an inspectiononce every 10 years

Areas to be inspected: common parts, external walls, certain projections and signboards of a building

Local

standards

on

concrete

and

buildings

(6)

Three

most

important

Ordinances

and

codes

of

practice on

Utility

management

in

HK

COP

M

it i

d

Structural

• COP

on

Monitoring

and

Maintenance

of

Water

Carrying

Services

Affecting

Slopes

by

ETWB

(enacted

1996,

revised

2006)

• Gas

Safety

Ordinance

CAP

51B

(1997)

Structural

Health

monitoring

Mapping

• Electricity

Supply

Lines

(Protection)

Regulation

CAP406H

(enacted

2002,

revised

2005)

Mapping

Presentation

outline

• Introduction

• Ordinance

and

Code

of

Practice

• Technology:

Ground

penetrating

radar

• Technology:

Infrared

thermography

• Conclusion

C

i

t

(7)

1. Ground

penetrating

radar

(GPR)

G

round

G

round

P

enetrating

R

adar

1. GPR is a device which emits and receives high frequency (10-3000MHz) EM wave penetrating into materials like concrete, soil, asphalt, etc.

Ground

zero

Time/

depth

2. Image reconstruction of the reflected wave amplitude by signal processing and imaging techniques. 1D waveform 2D radargram

Ground

zero

Time/

depth

(8)

2-dimensional

measurements

Data

acquisition

and

Imaging

measurements

on the surface of

elements

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Surface C-Scan

B-Scan

Imaging

A-scan: 1D stationary collection of GPR waveforms

B-Scan: 2D radargrams in x-zplane (compilation of A-scans)

C-Scan: 2D slice view in x-yplane (signal re-construction in a particular depth ‘z’)

Cube view: 3D spatial re-construction in x-y-z plane

10 100 500 1000 3000MHz

GPR centre frequency

Planetary science

Geology, geophysics,

archaeology and forensic

Snow and ice thickness

Infrastructures

(bridge, highway, tunnel, airport

runway, buried utilites)

Environmental

(9)

GPR

example

1:

slice

C

‐

scan

in

a

reinforced

concrete

wall

Salt water concrete

B-Scan Fresh water concrete Surface C-Scan Plastic pipe 1st_layer steel bar 2nd_layer steel bar Slice C-scan

Useful

GPR

parameters in

B

‐

scan

radargram

Ground surface or time zero (1) (2) (3) (4) (5) A B C D E

x

z

(3)

Information contained in GPR data

1 C t

The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. B-Scan

1. Concrete cover

2. Estimation of surface dielectric which may indicate locations with high moisture content

3. Thickness of concrete wall

4. Positions and spacing of embedded objects (steel bars, plastic pipes)

5. Amplitude of the steel bar reflections

Surface

(10)

GPR

example

2:

slice

C

‐

scan

and

radargram

B

‐

scan

of

a

reinforced

concrete

footbridge

B-Scan Surface

C-Scan

Any

possible

reasons

for

higher

intensity

in

GPR

slice

scan?

There can be several reasons, but one of those is

chloride-induced corrosion.

(11)

Concrete

floor

slab

with

embedded

corroded

steel

reinforcement

Area with corroded

steel reinforcement

Comparison

of

GPR

slice

map

(left)

and

half

‐

(12)

Accelerated

corrosion

of

steel

bar

in

concrete

1. Stationary measurement at fixed positions 2. Direct current applied

across the anode and across the anode and cathode bars 3. Specimens were

submerged into NaCl water for 7 days, de-water below the bars and surface dried for 2 days

Accelerated

corrosion

of

steel

bar

in

concrete

(cont‘d)

Specimen after corrosion

Snapshot photos on top of the

(13)

Mechanisms

between

the

interaction

of

corrosion

and

GPR

wave

are

not

yet

well

‐

understood.

Probable

mechanisms

are:

1. Positions

of

contrasting

dielectric

properties

move

upward

from

original

steel

‐

concrete

to

steel

‐

corrosion

product

‐

concrete

interface,

where

reflectors

in

shallower

depth

are

less

attenuated.

2. Generation

of

multi

‐

interfaces

(steel

‐

concrete

‐

corrosion

product

‐

air

cracks)

which

may

change

the

local

d

i i

di

ib i

d h

l b

d

Non-corroded state

conductivity

distribution

around

the

steel

bar

and

increases

the

reflectivity.

ASCE Journal of Infrastructure Systems (2013) Vol. 19(2) pp.205‐220

Corroded state

GPR

example

3:

Underground

utility’s

slice

C

‐

scan

Surface

manhole

U/G pipe at 55cm

deep

Storm drain at

89cm deep

(14)

GPR

example

4:

Ground

penetrating

radar

mapping

prior

to

excavation

in

an

archaeological

site

in

Tung

Chung

One of the GPR slices (x, y plane) at particular z – white reflections indicate

strong reflections indicative to archaeological remains

One of the GPR sections (x, z plane) at particular y – hyperbolic reflections indicate

strong reflections indicative to archaeological remains

Presentation

outline

• Introduction

• Ordinance

and

Code

of

Practice

• Technology:

Ground

penetrating

radar

• Technology:

Infrared

thermography

• Conclusion

C

i

t

(15)

Infared

thermography:

external

wall

debond

and

internal

wall‘s

water

leak

¾

The

debond,

insulated

by

air

void,

stores

heat

energy

more

rapidly

than

intact

area.

So

look

for

a

HOT

spot!!!

¾

On

the

surface

of

the

finishes,

the

sign

of

water

heats

up

slower

because

its

heat

capacity

is

4 times

than

that

of

air.

So

look

for

a

COLD

spot!!!

Qualifying

debond

and

quantifying

debond

size

Step

p

1:

adjust

j

an

‘optimum’

p

color

scale

according

to

the

principle

(1)

professional

judgment

(2)

environment

consideration

(3)

weather,

etc.

Step

2:

Highlight

the

white/yellow

area

in

iron

24.5‐27.9 degC 24.7‐38.4 degC 24.5‐26.3 degC

palette

(or

other

palette

in

different

color)

which

seems

to

represent

the

extent

of

debond

_Estimated

debond = 3.6 m2 Estimated debond = 1.2 m2 Estimated debond = ??? m2

(16)

Do it quantitatively in 7 steps?

Step

1:

ROI

extraction

1. When a debond is

id tifi d it

identified on-site, recognize the region of interest (ROI) example as follows

2 Measure the azimuth

2. Measure the azimuth angle, elevation angle and SD (or other parameters if necessary) from the camera to the debond

(17)

Step

2:

image

filter

of

exclude

tile

joints

(18)

Step

4:

Binary

transformation

(19)

Step

6:

image

resolution

(IFOV)

and

Step

7:

boundary

and

size

measurement

of

the

defect

• patch

of

defect

is

not

measurable

because

only

isolated

defect

yields

Gaussian

distribution

Limitations

(low

‐

high

‐

low

temperature)

over

both

the

defective

and

defect

‐

free

areas.

• low

thermal

contrast

between

the

defective

and

defect

‐

free

area,

that

it

is

not

adequate

to

define

a

Gaussian

distribution,

• Limitations

in

HKCI:

TM1

apply

also,

such

as

–

curved

surface

of

the

building.

–

wet building surface

×

√

–

wet

building

surface.

–

building

surface

is

obscured

by

contaminants

(bird

droppings,

mud,

oil)

–

in

rain

(20)

Presentation

outline

• Introduction

• Ordinance

and

Code

of

Practice

• Technology:

Ground

penetrating

radar

• Technology:

Infrared

thermography

• Conclusion

C

i

t

• Coming

events

Yr 30

The

concept

NDE

‐

structural

health

monitoring

(SHM)

in

building

diagnostic

and

utility

survey

0.0 0 2 Refl. to DW TTT 0.0 0.2 DW amplitude

Yr 1

Yr 5

GPR, ultrasonics, IRT and other NDEs 1.2 0.2 0.4 0.6 0.8 1.0 1.2 0.00.20.40.60.81.0 1.2 0.4 0.6 0.8 1.0 1.2 0.00.20.40.60.81.0 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.00.20.40.60.81.0 DW peak freq

Material properties by destructive tests according to rational coring

(21)

Challenges

of

NDE

survey

• Object identifications and location mapping are very mature. But

NDE interpretation on material properties is still not

straight-forward because of different sensor types, multi-dimensional

signal processing and variation of material properties. Signal

inversion in this context is still a big subject of research.

• The property it measures is not directly related to what engineers

are interested, e.g. higher ultrasonic pulse velocity (UPV) is

related to but not always implies high concrete strength.

Conclusion

• Nondestructive technologies are originated from areas like geophysics, medical imaging, aerospace engineering, remote sensing. Swopping wavelength allows survey, inspection and assessment of buildings, civil engineering structure and underground utilities.

Missile-guidance Medical

• For existing buildings, these technologies allow material/structural evaluation in large scale.

• Two relatively new NDE-CE technologies are introduced, which are ground penetrating radar, and infrared thermography. Its advantages are the ability to see through the unseen, offer very fine spatial resolution, provide traceable record and rapid data collection compared to open-up, other NDE-CE survey methods.