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DIGITAL IMAGE CORRELATION FOR
CONSTRUCTION
Evan Guilfoyle

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INTRODUCTION
Digital Image Correlation (DIC) is a full-field
image analysis method which employs high
resolution digital cameras to track displacement
occurring on the surface of an object. It has
gained recognition for the potential that it
possesses for a number of industries, not least
among them the construction industry. This white
paper focuses on potential applications for the
construction industry drawing on examples of
previous testing applications and highlighting the
advantages DIC offers over conventional
structural and materials testing methods.
The non-contacting 3D measurement system can
be used to create full-field strain and
displacement maps which can then be converted
into video footage for further examination. With
current developments in optical measurement
systems and computer analysis techniques, the
use of DIC, in conjunction with traditional
measurement techniques, is set to increase
greatly over the coming years.
Traditionally, in order to examine strain and
displacement, strain gauges and Linear Variable
Differential Transducers (LVDTs) are placed on
the surface of a specimen at the points of
interest. However, if a large or complex specimen
needs to be analyzed, accurate placement of the
devices can be problematic. Traditional point-
based testing methods only receive input from a
limited amount of data points. The ability to
forego strain gauges and LVDTs offers a distinct
advantage to the DIC user and allows full-field 3D
analysis to be carried out on objects.
WHAT CAN DIC BE USED FOR?
The applications of DIC are vast; it can be applied
to all areas of construction, from individual
building materials through to large-scale
structures. The DIC technique calculates surface
deformations and can be utilized to enhance
traditional testing methods, as well as providing
more detailed results. As a compact and portable
system, DIC can be conducted both on-site and
in the laboratory.
COMPRESSION TESTING
MASONRY WALLS
The measurement of surface displacements,
deformations and crack widths, as well as the
accurate mapping of surface cracks, is vital in
order to understand the load-resistance
mechanisms and failure modes of concrete and
masonry structures.
During laboratory tests, these parameters are
usually measured by stationary sensors such as
strain gauges, crack opening gauges and linear
displacement potentiometers which do not
necessarily give a full understanding of what
failure mechanism is occurring. In order to
understand the material properties, the load path
and load transfer through contacting surfaces
needs to be analyzed. Using DIC, the failure
mechanisms can be recorded and analyzed until
a full understanding is achieved.
New building materials, such as blocks and
bonding agents are continuously being
developed and the properties of these materials
require testing. Full scale masonry walls
subjected to single or multidirectional forces can
be evaluated using the DIC measurement
technique in order to quantify their new
mechanical properties.
Figure 1. A concrete block under load testing
Figure 1 shows a concrete block being tested
under load using DIC; the colored map shows the
calculated stress distribution. The technology
highlights crack propagation that cannot be
detected by the human eye.

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WIND LOAD TESTING
ROOFING MATERIALS
Modern roofing materials used in the
construction of flat roofs, portable cabins or
industrial buildings are highly susceptible to
damage and distortion from exposure to high
winds and adverse weather conditions during
their lifetime. Designing and testing materials to
be resistant to multidirectional wind speeds can
be a complex and time consuming process. In
order for new roofing materials to pass rigorous
certification processes, the failure mechanisms
associated with the materials design need to be
fully understood.
The complex uplift forces generated by wind
loads can be hard to measure accurately.
Conventional measuring methods use point wise
sensors to measure uplift deformations. This
method is limited to the number of sensors used
and can be susceptible to large or inaccurate
readings.
The 3D displacement maps generated by DIC
analysis can be used to describe the progressive
change of the deformed shape of any roofing
material at increasing wind speeds. The system
facilitates a better understanding of how failure
mechanisms under wind load progress. Full-field
3D measurements enable the analysis of any
point across the material, providing a much more
detailed explanation of the failure mechanisms
occurring under wind loads compared to point
sensors.
LARGE STRUCTURAL TESTING
In addition to laboratory testing, the DIC system
can be used on-site to analyze large existing
structures or structures that cannot be
transported easily. By adjusting the camera
settings, structures of various sizes and shapes
can be analyzed in detail. The main advantage of
using DIC to examine large structures is the
increased number of data points collected. The
full-field maps produced by DIC allow the system
to analyze any point within the camera’s field of
view. The system eliminates the need for strain
gauges and provides highly accurate and precise
calculations.
BRIDGE ANALYSES
Evaluating the structural performance of existing
bridges is an important task carried out by
engineers across the world. The evaluation tests
include monitoring deflection, strain, natural
frequency and dynamic responses when loading
occurs across the structure. To measure these
parameters, several different types of measuring
sensors need to be attached to the bridge; this
can be a difficult and time consuming process.
With the majority of the sensors located in hard
to reach places, the test set-up time requires
considerable planning, and can still result in loss
of data due to poor connections.
By carrying out consecutive tests at various
points, deflection distribution across the entire
bridge can be analyzed and presented.
Malesa1
discusses a test in which a locomotive
train was passed back and forth on a bridge
structure at various speeds whilst the DIC system
measured the entire bridge system.
One set of cameras were used to examine bridge
deflection while localized cameras were used to
examine rivet joints and welds within the
structure. The test was carried out to validate the
structural stability of the bridge and to compare
the DIC results to a finite element model of the
bridge.
DIC’s ability to measure displacement
distributions across a bridge can be extremely
useful, especially in the evaluation of old bridge
structures which have been subject to increased
traffic flow in recent years. The non-contacting
test could provide a solution to evaluating the
structural performance of bridges without having
to close down or divert traffic paths during set-
up, testing and evaluation.
This powerful non-contacting technique can also
be used to monitor other large civil engineering
structures such as load bearing walls, roofing
structures and large piping systems.

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CONCRETE
CONCRETE FLOORS
The structural properties of concrete as a
building material can vary depending on its
composition and application. To fully understand
new concrete compositions, various load tests
need to be carried out.
Static and dynamic load testing of concrete slabs
is carried out to examine crack initiation and
propagation, and loading capabilities. New
material combinations and setting times can be
tested to optimize the production or construction
of concrete floors.
DIC provides a more detailed analysis of concrete
floor structures compared to point sensor
methods. The system can be used to analyze new
reinforcing methods and materials, comparing
them in much more detail than previously
possible. Conventional steel reinforcements along
with reinforcing materials such as steel fibers can
also be tested with the DIC system to examine
the improved ductility, fracture toughness and
durability of the concrete slabs.
In figure 2 (below), the DIC system was used on a
scale PC beam to analyze crack initiation with
increased loading.
Figure 2. Progression of a strain cycle through
loading of a scale reinforced concrete beam
PRESTRESSED CONCRETE BEAMS
Prestressed Concrete (PC) beams vary in size,
shape and composition, and can be designed for
different applications dependent upon the type
of structure being built. The challenge faced by
engineers is not only to design the beam but to
ensure that it is structurally stable and able to
withstand the loads applied. Large-scale
mechanical tests such as point bend tests are
carried out on PC beams to simulate real-life
failure conditions. The DIC system is extremely
versatile and can be used to analyze various
aspects of structural behavior of PC beams,
including the load path in complex structural
geometries, the effect of boundary conditions
and load transfer through contact surfaces.
The optical system highlights points of interest
such as locations where high strain is occurring
which may not be visible to the naked eye. Using
the DIC technique, it is possible to produce a full-
field strain map and measure any displacement.
By applying a sophisticated speckle pattern
across the specimen, DIC can produce accurate
measurements that can be used to identify the
mode and location of failure.
RENDER TESTING
The durability of mortars and other render
materials is highly dependent on cracking at the
surface of the material as well as the substrate to
which it adheres to. Crack evolution caused by
dry shrinking can be extremely hard to accurately
measure with traditional methods such as shrink
ring tests, yet close monitoring is important in
order to improve the understanding of new
material combinations.
External conditions such as temperature,
humidity, wind, rain, etc. all affect the properties
of various rendering materials. Using the DIC
system, surface parameters of different material
mixes can be analyzed before, during and after
their exposure to different boundary conditions.
Debonding between the mortar layer and the
substrate material can be analyzed by calculating
the out-of-plane displacement that occurs. DIC
can also be used to complement other render
tests such as the pull out test. As well as giving
the mechanical force required to pull off the
render, the technique is used to analyze the
strains occurring in the surface. This may be

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useful before and after temperature controlled
cyclic tests to compare the change in surface
failure modes.
STRUCTURAL STEEL TESTING
JOINT PLATES
The use of DIC for full-scale in-situ testing of civil
engineering structures as a method of monitoring
the structure’s stability is being increasingly
adopted. By carrying out DIC full-field strain
mapping, data can be acquired for various types
of structural connections; such mapping offers
advantages over traditional point measurement
methods. In order to gain a full understanding of
what is happening in a joining section, DIC can be
used to focus on specific points of interest.
Large-scale testing of bolted plate connections
for steel structures can be quite complex due to
the various interactions between the different
strut connections. The strategic placement of the
strain gauges is often difficult due to the small
surface area. The use of DIC allows the
examination of the entire connecting plate along
with all other points of interest e.g. the
connecting bolts and other truss members.
DIC color maps allow stress concentrations to be
monitored around the bolts as the load is applied.
This method can be very useful in identifying the
locations of maximum stress, as well as the effect
of elastic and plastic deformation during a test
cycle.
PRESSURIZED VESSELS
The DIC technique has proven to be useful for
measuring elastic and plastic surface strains and
thus can be used for examining surface
deformation in all types of enclosed systems such
as fluid flow in pipelines and pressurized tanks. Its
main advantages include: ease of specimen
preparation, robust methods for different and
harsh test conditions, and full field capacity.
DIC can be used to validate FEA models for
design purposes and to examine vessels or
pipelines which have suffered metal losses due to
corrosion or erosion damage. It also accurately
measures and records surface deformation.
The DIC method is very versatile, allowing all
types of materials to be tested. It can also be
applied to a variety of internal and external
pressurized tests to examine the deformation
occurring in the material.
3DSTRAIN
Lucideon has launched a dedicated service
developed around DIC technology which
incorporates the company’s testing and analysis
capabilities and its materials expertise.
3DStrain provides construction companies with
all of the data that DIC can generate alongside
services that ensure the data is analyzed and
interpreted to find meaningful results and
solutions. The technology itself can be used for
large or small scale products, materials and
structures, and can be used on-site or in the field
where required.
CONCLUSION
A huge advantage of the DIC technique is its
portability. The camera system can be set up on-
site and in remote locations, and still produces
accurate results. The visual outputs from the
system allow users to carry out post-test analysis
of the failure mechanisms that occurred during
testing.
The use of Digital Image Correlation provides far
more detailed results than traditional methods
used for the analysis of construction materials
and structures. The applications of DIC are vast
and can be applied to all areas of construction,
from individual building materials through to
large-scale structures. With current advances in
optical measurement systems, the use of DIC as a
standard method of measurement looks certain
to increase in the near future.
REFERENCES
1. “Monitoring of civil engineering structures
using Digital Image Correlation technique”.
M. Malesa

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ABOUT LUCIDEON
Lucideon is a leading international provider of
materials development, testing and assurance.
The company aims to improve the competitive
advantage and profitability of its clients by
providing them with the expertise, accurate
results and objective, innovative thinking that
they need to optimize their materials, products,
processes, systems and businesses.
ABOUT THE AUTHOR
EVAN GUILFOYLE – MECHANICAL
AND MATERIALS ENGINEER
Evan is a Mechanical Engineer with a first class
honours Bachelor Degree in Mechanical and
Materials Engineering. Evan has extensive
experience in the construction industry as well as
mechanical testing and Anatomical Wear Testing.
Through its offices and laboratories in the UK, US
and the Far East, Lucideon provides materials
and assurance expertise to clients in a wide range
of sectors, including healthcare, construction,
ceramics and power generation.