Publications by Atkinson-Noland & Associates
Citto, C., Geister, A., & Harvey, D.,
Feasibility of Integral Water Repellent Admixtures in Low
Pressure Compatible Injected Fill Grouts, Proceedings
of the 12th International Conference on Structural Repairs and
Maintenance of Heritage Architecture, Chianciano Terme, Italy,
September 2011.
For almost two decades, compatible injected fill (CIF) grouts
have been used in the restoration and repair of historic
masonry structures. CIF materials are installed using a
low-pressure injection process and often serve the dual
purposes of structural strengthening and enhancement of
moisture resistance. In the past, improved weather resistance
was primarily the result of the CIF material filling voids
in collar, head, and bed joints through which moisture could
penetrate. However, the CIF materials were not specifically
formulated for moisture resistance. The weather resistance of
CIF installations could be significantly improved by increasing
the water repellency of the CIF material. However, if this
innovation comes at the expense of significant changes to
other material properties, it may not be a viable approach.
This paper presents the ability of injected CIF material to
improve the moisture resistance of masonry walls through a
series of water penetration test results, and also describes
a comparative study of CIF material properties in formulations
with and without integral water repellent (IWR) admixture.
Material properties relevant to typical CIF installations were
evaluated using standard laboratory test procedures. Samples
were tested for plastic properties, compressive strength,
flexural bond strength, shear bond strength, vapor permeability,
and water repellency. Tested samples used the same proprietary
blend of cementitious materials, aggregate, and admixtures. The
effects of IWR on material properties are discussed as well as
overall feasibility of IWR admixtures in CIF materials.
Show Abstract
Citto, C., Wo, S., Willam, K., & Schuller, M. (2011),
In-Place Evaluation of Masonry Shear Behavior Using Digital
Image Analysis, ACI Materials Journal, V. 108, No. 4,
p. 413-422.
One of the critical aspects of masonry failure is the shear
capacity of the composite brick-mortar assemblage. In the
last four decades, an increasing effort has been devoted to
study the shear behavior of masonry structures. Different
test approaches have been used to determine the shear strength
of masonry, including laboratory tests and in-place measurements.
In this paper, a close view of the test method used for the
in-place measurement of masonry shear strength is taken, using
an innovative approach based on image correlation techniques.
A series of in-place shear tests were conducted at one of the
masonry infilled reinforced concrete (RC) frames tested at the
University of Colorado Boulder, Boulder, CO, within the framework
of a comprehensive NSF-NEESR-SG project at the University of
California San Diego, San Diego, CA. Initial cohesion and
friction angles were determined for the infill wall, and the
lack of uniformity along the shear failure planes was investigated
with the aid of finite elements and digital image correlations.
Show Abstract
Citto, C., Wo, S., & Willam, K.,
Image Correlation Diagnostics of Masonry Assemblies,
Proceedings of the 11th North American Masonry Conference,
University of Minnesota, June 2011.
The performance evaluation of masonry has been at the
core of a large number of studies in the past decades
as masonry structures, existing world-wide, can provide
a significant contribution to the shear resistance of
existing buildings subjected to lateral loads. Prediction
of masonry behavior is a major challenge as the composite
interaction of brick-mortar assemblies leads to complex
failure mechanisms. Furthermore, successful evaluation
of masonry structures based on numerical models depends
on the accuracy of information provided by material tests.
The laboratory identification of mechanical properties
in support of an ongoing test program on masonry infill
walls at the University of Colorado at Boulder provided
the opportunity to closely investigate the failure processes
in compression and shear of composite brick-mortar assemblies.
Prism tests with horizontal mortar joints were carried out
to examine the axial performance of brick-mortar assemblies
and the importance of mismatch among the elastic and
inelastic properties of brick units and bounding mortar
layers. In situ shear experiments on single bricks in the
existing masonry infill wall were conducted under different
preload conditions to determine the masonry shear capacity.
An innovative approach based on digital image correlation
technique was extensively used throughout the experimental
work to provide additional insight into the prism failure
during progressive axial loading and slip mechanisms during
shear loading.
Show Abstract
Tanner, J., Schuller, M., Thomson, M., & Wo, S.,
Validation of a Newly Developed Standard for Evaluating
Mortar for the Repair of Historic Masonry (ASTM C1713-10),
Proceedings of the 11th North American Masonry Conference,
University of Minnesota, June 2011.
A series of mortar tests was conducted to evaluate three
mortars following the requirements of the newly developed
ASTM C 1713, Standard Specification for Mortars for the Repair
of Historic Masonry. This specification, published in 2010,
serves as a performance specification for historic mortars
and is a departure from ASTM C 270, Standard Specification
for Mortar for Unit Masonry, in that the curing regime for
high lime mortars is 120 days in chambers with controlled
levels of relative humidity, and the level of CO2 is monitored
to ensure sufficient carbonation. One cement-lime and two
pozzolanic hydraulic lime mortar binders were prepared with
a ratio of 1 part binder to 3 parts masonry sand. Tests of
plastic properties included initial flow, air content, and
water retention. Hardened mortar tests included total porosity,
absorption rate, compressive strength, flexural bond strength,
and water vapor transmission. In addition to reporting on
material properties, recommendations for improving the
Standard and related research are suggested.
Show Abstract
Woodham, D., & Geister, A.,
Water Vapor Transmission Rates In Common Masonry Construction,
Proceedings of the 11th North American Masonry Conference,
University of Minnesota, June 2011.
Water Vapor Transmission (WVT) compatibility is an important
consideration when selecting replacement or repair materials
for use in masonry structures, particularly in historic masonry
construction. Inappropriate materials added to masonry assemblages
can prevent or inhibit water vapor from exiting walls and can
create moisture, salt or freeze-thaw damage to the masonry.
Testing the water vapor transmission of masonry materials is
typically done using the wet cup method described in ASTM E96,
Standard Test Methods for Water Vapor Transmission of Materials.
This paper presents the results of numerous WVT tests using this
method, conducted on materials including historic brick, modern
brick, mortars, injection grouts, and several types of stone.
The typical precision of the ASTM E 96 method will be discussed
as well as the variable results form multiple coupons obtained
from the same sample. The determined WVT values will be compared
to those reported by others and will be of use as reference values
for likely conditions in existing construction and determining the
suitability of replacement masonry materials.
Show Abstract
Citto, C., Aschermann, S., & Woodham, D.,
Improved Load Rating Procedures for Masonry Arch Bridges,
Proceedings of the 8th International Masonry Conference, Dresden, Germany,
July 2010.
Historic masonry arch bridges were not designed to carry
modern truck and rail loads. However, due to their inherent
strength and durability, many masonry arch bridges remain
in daily service. The logical question is: “Do these
bridges have an adequate factor of safety for modern
loads?” Semi-empirical rating methods can be overly
conservative and lead to unwarranted load postings. A
more refined approach, based on Finite Element Method
(FEM) or Discrete Element Analysis (DEA), can provide
improved understanding of the actual behavior of arch
bridges and possibly predict their complex failure
mechanism. However, this requires that the assumptions
on material properties, soil properties, soil-structure
interaction and other parameters are realistic. To
improve the accuracy of computer models of masonry arch
bridges, nondestructive evaluation (NDE) techniques can
be employed to provide additional information. Impulse
radar can be used to provide additional geometric data
such as the depth and configuration of the fill over the
arch barrel, the thickness of the arch barrel and the
location of utilities or voids in the fill. Further
verification of the model can be accomplished by a simple
load test on the bridge, which measures the bridge’s
response to a known load.
Show Abstract
Willam, K., Blackard, B., & Citto, C.,
Failure Studies on Masonry Infill Walls: Experimental and
Computational Observations, Proceedings of EURO-C 2010,
Computational Modeling of Concrete Structures, Rohrmoos/Schladming,
Austria, March 2010.
At the core of model-base simulation is the upscaling
of the constitutive properties from ‘proper’ material
tests to the structural level of observation. This issue
raises fundamental questions when ‘softening’ is
introduced to model the degradation of stiffness and
strength of material properties. The paper addresses
softening from the perspective of snap-back instabilities
which lead to control problems of the localized energy
release in numerical solutions and experimental investigations.
Show Abstract
Wo, S., & Schuller, M.,
Estimating Compressive Strength of Historic Unreinforced
Masonry Using Flatjack Deformability Tests, 12th
International Structural Faults & Repair Conference,
Edinburgh, Scotland, June 2008.
When rehabilitating a historic unreinforced masonry
building, properties such as compressive strength,
stiffness, and shear strength may be required for
structural analysis and stabilization design. In situ
nondestructive testing methods such as flatjack deformability
tests are often used to measure masonry compression response
in lieu of destructive sample removal for laboratory testing.
In some situations it is not desirable or even not possible
to load the masonry to its full compressive strength. In
these circumstances an estimate of masonry ultimate strength
can be made based on the initial elastic modulus or the shape
of the stress-strain curve. A database has been compiled to
include in situ and laboratory flatjack deformability test
results carried out by Atkinson-Noland & Associates over
the last twenty years. Other information contained in
published literature is added to the database, and a
statistical analysis has been conducted to determine the
relationship between compression modulus and compressive
strength for historic masonry. From the literature review
and database analysis, recommendations are made on how to
use data from in situ deformability tests to estimate masonry
compressive strength.
Show Abstract
Schuller, M., Lockrem, A., & Locke, R.,
Modifying Building Response Using Energy Absorbing Diaphragm to
Wall Connectors, Seminar on Structural Analysis of Historic
Construction, Padua, Italy, November 2004.
A system that uses energy absorbing connectors placed
between a building's walls and its floor and roof
diaphragms is described. A research program, under the
direction of the authors, is underway to determine
behavioral characteristics of the connection system and how
the system modifies building response during a typical
seismic event. The concept uses a unique patented
double-cone connector through which vertical post-tensioned
rods pass. The connectors allow the floor and roof
diaphragms to displace slightly with respect to the walls
during earthquake excitation. Seismic energy is transmitted
by the relative motion in the conical connectors into the
vertical post-tensioned rods. The combination of the
vertical motion of the wall mass and the elongation of the
tensioned rods redirects a portion of the seismic energy
and thereby reduces the building's lateral seismic demand.
Show Abstract
Schuller, M.,
Nondestructive Testing
and Damage Assessment of Masonry Structures,
Invited paper for the Journal of Progress in Structural Engineering
and Materials, Vol. 5, No. 4, John Wiley & Sons, 2003.
Recent advances in nondestructive testing technology have
led to mainstream use of several methods for evaluating
masonry construction. Nondestructive approaches such as
rebound hardness, stress wave transmission, impact-echo,
surface penetrating radar, tomographic imaging, and
infrared thermography are useful for qualitative condition
surveys as well as identification of internal features such
as voids or areas of distress. In situ test methods are
also available for determination of engineering
properties. Flatjack methods are used to measure the state
of compressive stress and compression response, masonry bed
joint shear stress may be evaluated by an in situ shear
test, and mortar unit bond strength is tested by an
adaptation of the bond wrench approach. Standardization
methods exist for many of the evaluation approaches and
related efforts are ongoing within ASTM and RILEM.
Show Abstract
Schuller, M., & Woodham, D.,
Development
of a Flexible Flatjack for Quantitative Evaluation of Masonry,
Proceedings of the 9th North American Masonry Conference, Clemson
University, June 2003.
The flatjack method has been used for more than 20 years in
U.S. masonry testing. Two standard test methods, C 1196 and
C 1997 which use metal flatjacks, are incorporated within
the ASTM International Standards. Although conventional
flatjacks have been proven to be accurate and durable
instruments, a more resilient flatjack is desirable when
testing historic masonry and masonry constructed with
irregular-shaped units. Metal flatjacks are often difficult
to remove from masonry walls if significant distortion of
the envelope occurs under pressure. A flexible flatjack has
been developed which has a more uniform stress distribution
over the surface of the jack and maintains a calibrated
pressure output over a larger range of displacement. The
flexible flatjack requires less energy to deform the jack
into indentations within the brick ("frogs") and soft
mortar joints, and the flexible flatjack returns to its
deflated dimensions upon removal of the hydraulic pressure.
In addition, the flexible flatjack can incorporate internal
displacement gauges which allow the determination of
masonry deformability properties for inner wythes of
masonry walls.
Show Abstract
Schuller, M., Ruth, W., & Waite, J.,
Use of Nondestructive Methods to Determine Historic Masonry
Construction Means and Techniques at Latrobe's Baltimore
Cathedral, Proceedings of the 9th North American
Masonry Conference, Clemson University, June 2003.
Restoration of a historic nineteenth century dome designed
by the Unites States' first professional architect, who
also was responsible for the construction of the United
States Capitol, requires extensive research. To identify
and assist in the preservation of historic fabric, a
symphony of cutting-edge technologies, historical insights,
and practical masonry knowledge are utilized to "virtually
rebuild" a nineteenth century icon. Combinations of
nondestructive tools assist the historical architect in
determining how the cathedral and dome were constructed,
and the level of sophistication in comparison with other
early nineteenth century American buildings.
Significantly, the investigation has immediate impact on
conservation of other structures dating from the same time
period.
Show Abstract
Woodham, D., & Conyers, L.,
Evaluation
of Inaccessible Elements of a Cathedral using Ground Penetrating
Radar, Proceedings of the 12th International Brick and
Block Masonry Conference, Madrid, Spain, June, 2000.
The Basilica of Baltimore, Maryland is the first Catholic
cathedral to be established in the United States. As part
of a masonry testing and monitoring program, the
configuration and condition of critical structural elements
were evaluated in 1999. Ground penetrating radar (GPR) was
used to determine the subgrade configuration of the clay
masonry piers in the cathedral's undercroft. In addition,
GPR was used to investigate the structure underneath the
portico on the west side of the Basilica. The results from
GPR were inconclusive regarding the geometry of the base of
the masonry piers. However, the technique identified two
previously unknown barrel arches under the portico that
were later confirmed by excavation.
Show Abstract
