189

Steps Taken in Building and Insurance Industries for
Extreme Wind Related Disasters
Timothy A. REINHOLD
Institute for Business & Home Safety
4775 E. Fowler Avenue, Tampa, Florida, USAe-mail: treinhold@ibhs.org

Abstract
Worldwide property losses due to extreme wind events are escalating. While a large portion of the increases in loss can be attributed to population growth and concentration of property value in vulnerable
areas, global climate change could exacerbate losses in vulnerable areas and make buildings and infrastructure in relatively safe areas more vulnerable. Advances in forecasting and warning systems can provide residents with time to seek shelter from natural perils; in some cases (e.g., hurricanes), advanced warning canenable property owners to take steps to reduce losses. However, last–minute property protection measures
are usually limited to activating pre-established systems. The best overall building protection systemremains passive strength and mitigation measures that are built into a structure.
This paper explores steps taken by the building and insurance industries that clearly indicate that losses
can be reduced and risks managed in ways that provides greater individual and community security and economic stability. It is also clear that efforts to reduce or reverse the rapid escalation of property losses as theresult of natural perils face significant technical, systemic and public policy challenges. This paper identifies
weaknesses in current extreme wind loss reduction efforts and offers suggestions for enhancing these efforts.
It also identifies steps that are being taken by the building and insurance industries that will mitigate futuredamage to existing buildings and structures and help society adapt to existing risks and changes in risk due
global climate change.
Key words: adaptation, building codes, building performance, global climate change, hurricane damage,
mitigation,

1. Introduction
Loss summaries produced by the Munich Re
NatCatService (Munich Re, 2009) indicate that losses
caused by extreme wind-related disasters worldwide are
increasing dramatically (Fig. 1). While most of theincreases in losses can likely be attributed at this point
in time to increased population density and greater
concentrations of property value in vulnerable areas,
global climate change could exacerbate these increases
in losses. Perhaps the clearest example of global climatechange effects to date is the increase in so-called“mega-fires” that occur under extreme fire conditions,affect large areas, and exceed the ability of firefighters
to contain them using conventional fire control techniques. These fires usually continue uncontrolled until
there is a break in the weather, or a break in the available fuel. As average temperatures have increased anddroughts have become more severe, wind-driven wildfires are affecting larger areas and proving to beuncontainable until the winds die down. Mega-fires
Global Environmental Research
13/2009: 189-196
printed in Japan

have occurred on several continents, with the first one ofmodern times being the Great Dragon Fire of 1987 in
China (Brookings Institution, 2005).
Regardless of whether the frequency and severity of
extreme wind events remains constant or increases due
to global climate change, there is a clear need to reduce
the rate of increase in losses and, hopefully, reverse thistrend. This will require a change in the design and construction of buildings in many parts of the world, and aneffort to reduce the vulnerability of the trillions of dollars worth of existing buildings located in vulnerable
areas around the globe. The approach to reducing future
losses can be expressed as a merging of mitigation andadaptation strategies. Mitigation is needed because
actions must be taken if there is any hope for reducing
loss frequency and severity when it comes to damage ofexisting buildings and structures, as well as new structures being built in the same manner. Adaptation isneeded because the constant increase in losses is notsustainable. Furthermore, every building that is damaged or destroyed uses up valuable natural resources and©2009 AIRIES190

T. A. REINHOLD

Fig. 1 Trends in overall and insured weather catastrophe losses 1950-2008.

increases the global carbon footprint through both waste
output and the use of new materials. Adaptation also
involves improving current mitigation measures to makethem more cost effective, more attractive to building
owners who must be motivated to spend money toreduce the vulnerability of their buildings, and better
suited to meet changes in risk that may occur as a resultof global climate change. Ultimately, in order for
development to be truly sustainable, it must not simply
focus on “first” costs – it must consider the full life
cycle of a building, with proper accounting for all risks
associated with its location.
Beyond these steps that are aimed at improving theresiliency of families, businesses and communities in
the face of extreme wind events, it is clear that there is a
growing interest in mitigating the effects of global
climate change as well. There has been a significant
increase in interest in the “green” movement as it
applies to buildings through U.S Green Building
Council’s LEED program and other initiatives. There
has also been substantial growth in “green”-related
insurance products. The second annual Ceres study of
insurer response to climate change (Ceres, 2009) documents 643 specific activities from 246 different insurers
located in 29 countries during 2008, a 50% increase
from a similar survey conducted in 2007. The largest
increase in activities involved creation of innovative
insurance products, and the second largest increase wasin leadership activities where companies sought toreduce their own carbon footprints.

2. Building Codes: Improvement, Adoption,
and Enforcement
While building codes can be traced (in one form or
another) back across many centuries, the treatment ofwind loads and wind effects on buildings has been avery recent advance. Recognition of the important effectatmospheric turbulence plays in defining wind loads onbuildings is a 19th century discovery that played a keyrole in the emergence of boundary layer wind tunnels as
the tool of choice for determining wind loads onhigh-rise buildings and long-span bridges. The modification of these tools and their application to the study ofwind loads on low-rise buildings is an even more recent
advance. In fact, most modern building codes thatprovide reasonable estimates of localized wind loads forthe design of components and cladding elements of
low-rise buildings have been developed in the last quarter of the 19th century, and are still being improved asmodeling and instrumentation advances are made.
The definition of wind loads on components andcladding elements in U.S. building codes and standards
that delineate areas of high localized negative pressuresnear corners, edges and ridges of roofs have changed
significantly since the 1980s. The changes have been
greatest for low-rise buildings, including homes andsmall businesses that frequently suffer the greatest damage in hurricanes and other extreme wind events. Alongwith these improvements in codes and standards, there
has been a growing emphasis on engineering-based
design for homes and small businesses in areas subjected to the most common extreme wind events. In the
U.S., this is the coastal area subjected to hurricane riskthat includes the Gulf Coast and the Atlantic Coast fromthe tip of Florida to Maine.
Unfortunately, adoption and enforcement of theseengineering-based requirements has been spotty at best,
and many areas have still not adopted them. An early
adopter of engineering-based requirements for designand construction of residential buildings was the State of
Florida. Miami-Dade and Broward Counties quickly
moved to adopt the American Society of Civil Engineers
Standard 7 (ASCE 7-88) wind load requirements in theSteps Taken in Building and Insurance Industries for Extreme Wind Related Disasters

aftermath of Hurricane Andrew, which struck the area in1992. The remaining coastal areas of Florida moved toadopt the engineering based high-wind requirements of
the Standard Building Code (SBC) in 1995 (SSTD
10-93). The first real test of these improved building
codes came in 2004 when Hurricane Charley struck thesouthwestern part of Florida, making landfall in the
Punta Gorda and Port Charlotte areas. The highest windspeeds in Hurricane Charley were about 15% above thedesign wind speeds for the area.
An analysis of claim frequencies as a function ofyear built for 5,604 properties insured by one company
in the Punta Gorda and Port Charlotte area where theage of the home was known is shown in Fig. 2. There
are at least two ways to interpret the trends in this data.
One way is indicated by the two red lines. In thisapproach, the data suggests that there was a substantial
drop in the claims rate for houses built after 1996 andthat the claims rate for homes built in 1997 through2002 remained relatively constant. A second way tointerpret the trends in the data is indicated by the yellow
dashed line. The trend shown by the yellow dashed line
suggests that the claims rate decreases almost linearlywith age. It is likely that the reductions in claims rate
results from a combination of code changes and age
effects.
If the trends shown by the red lines are used as thebasis for analyzing the losses, the following statistics areproduced. The claims rate for homes built prior to 1996
was 41 claims per 100 policies, and this dropped to 17
claims per 100 policies for homes built between 1996
and 2004. Similarly, the claim amount per square meterof home area dipped from $258 per square meter forhomes with a claim that were built before 1996 to $150
per square meter for homes with a claim built between
1996 and 2004. Continuing this type of analysis andlogic, the data shown in Fig. 2 also suggests that it took
about a year after the new codes were adopted before
claim frequency was substantially impacted and settled
at the lower level. Some of this delay could be due to a191

rush to get permits before the new code went into effect;but, it is more likely that it took a year or so before thebuilding officials and builders became comfortable with
the new requirements and contractors actually did agood job of following the new code requirements.
Continuing to use building code changes as a basis
for interpreting reductions in losses, the data shown in
Fig. 2 suggests that adoption of the new statewide 2001
Florida Building Code in 2002 led to further reductions
in losses. Beyond the changes in the code that added
requirements for installing high-wind rated roof covers,a significant emphasis was placed on education andtraining of all builders in the State of Florida. However,there were so few properties in the data set for theseyears that there is less confidence in the statistical
validity of the numbers for the last year or two.
In contrast to the analysis based on the red lines, theyellow dashed line suggests that age is a dominant factor in the vulnerability of the homes to hurricane damage. It is interesting to note that a similarly sloped line
(but shifted to higher claims frequency numbers) could
be applied to the claim frequency data between the mid
1970’s and the mid 1980’s. Those homes would havebeen 20 to 30 years old at the time Hurricane Charley
struck and many of the homes with shingle roofs of thatage would have been reroofed within the past 10 years.
The loss data from Hurricane Charley suggests thatbuilding codes, the improvements in products and theageing of products and systems all play a role in reducing losses. The relative importance of the different
factors in reducing claims rates and losses remains animportant research subject and one that can be extremely important for those assessing risks and modeling the performance of portfolios of buildings. Most
models predict substantial reductions in losses forhomes designed and built under modern engineering
based building codes that are properly enforced. If theyellow line in Fig. 2 were to continue to slide to theright as the building stock built under new codes ages,
the models will need to undergo substantial changes.

Fig. 2 Claims rate for properties impacted by Hurricane Charlie (2004) from one insurance
carrier in the Punta Gorda and Port Charlotte area.

192

T. A. REINHOLD

3. Well-Connected Wind ResistantComponents and Products
One benefit of having strong building codes andenforcement is that manufacturers and distributors areforced to provide products that at least meet these code
requirements. Figure 3 shows the trend in garage door
replacements in Hurricane Charley as a function of yearof home construction. The change in building codes that
occurred in 1995, when the high wind provisions of the
SBC were adopted, was accompanied by a greater scrutiny of design pressures for garage doors. It is clear thatthe replacement rate of garage doors plummeted forhomes built in 1995 and later years. It is likely thatmuch of this drop was due to the fact that rated products
were available and were being installed on homes.
Figure 4 shows results of an analysis of re-roofing
permits for shingle roofs in the Punta Gorda and PortCharlotte area following Hurricane Charley. The age ofthe home is used as a proxy for the age of the roof, so
data is only shown for homes that are new enough tostill have their original roof. This chart shows that inareas where the 3-second gust wind speeds were estimated to be less than about 100 miles per hour (45 m/s),
re-roofing was relatively infrequent if the home was lessthan 10 years old, but jumped to about a 20% re-roofing
rate if the shingles were more than 10 years old. However, as the wind speeds increased towards 140 mph(63 m/s) 3-second gusts, the frequency of re-roofing
became much higher and the effect of age became muchless pronounced, except for roofs that were less than few
years old.
A detailed analysis of damage to shingles on about
1,000 hip roof houses that experienced Hurricane Ike

suggests that age and product ratings can have a significant effect on roof cover performance. These homes
were subjected to 3-second gust winds between 80 mph(36 m/s) and 90 mph (40 m/s). These wind speeds areabout 20% below the design wind speeds for the area.
Figure 5 shows the results of the roof damage analysis.
Very little damage was observed for homes with roofs
that were less than about five years old. However, there
was a sharp increase in roof cover damage rates forroofs older than five years, and the damage rateincreases significantly with age beyond that point.
The building code for this area was changed to theInternational Residential Code in 2004. The IRC includes requirements for wind-rated roof covers. While
the reduction in damage to the newer roofs is significant,it is not clear how much of the reduction may be due toage of the roof cover, since shingles are definitely subject to aging effects, and how much is due to the use of
better products. Also, it is important to note that thewinds at this location were well below the design windspeeds for the area. On the Bolivar Peninsula, where the
3-second gust wind speeds were on the order of
115 mph, high-rated shingles that were less than two
years old were heavily damaged. Consequently,
concerns persist that current standard test methods are
not a good predictor of actual roofing performance inextreme wind events.
It is clear that good, durable products are needed,
and that their assessment must be based on test standards that adequately reflect real world conditions in
extreme wind storms. In order to prevent building
components and materials from ending up in landfills
when extreme wind events occur, they must be bothstrong and durable.

Fig. 3 Garage door replacement permit totals as a percent of properties in Charlotte County by year of construction.

Steps Taken in Building and Insurance Industries for Extreme Wind Related Disasters

193

Occurrence Rate of Roof Cover Damage

Fig. 4 Frequency of roof cover replacements for 3-Tab shingle roofs as a function of age and 3-second gust windspeed in miles per hour – Hurricane Charlie in Punta Gorda and Port Charlotte area.

Age - Year of Construction
Fig. 5 Roof cover damage rates (Bayton TX Community, Hurricane IKE).

4. Education, Training and Motivation
While strong building codes, good enforcement andappropriate products are all important to producing
buildings that will withstand extreme wind events, theunderstanding and commitment of the builders, contractors and sub-contractors is also critical. Products must
be installed and connected properly in order to perform
as expected. In the United States, several states that haveadopted new building codes have taken that opportunity
to require training and education for designers, building

officials, builders and contractors. Some states are
requiring continuing education as one of the requirements for license renewal.
The “green” building movement is gaining momentum and attracting a great deal of attention worldwide.
Significant debates rage over the definitions of “building green” and the a-la-carte methods for obtaining
green designations used by both LEED and the U.S.
National Association of Home Builders/International
Code Council to designate buildings. These methods can
produce designated buildings that are not as energy effi-

194

T. A. REINHOLD

cient as owners might expect, nor as durable as theyshould be. Yet, with many estimates indicating thatbuildings consume about 40% of energy and resources
worldwide (Straube, 2006; 2009), there are many reasons
to promote energy efficient strong durable buildings thatmaximize the intelligent use of renewable resources.
Other efforts have been aimed at creating demand forstronger buildings that are more likely to resist extreme
wind events. In the early 2000s, the Institute for Business and Home Safety (IBHS) created a code plus program for residential construction called Fortified . . . forsafer living®. The code-plus elements for high windareas mean that design loads are increased, and a number of loss mitigation measures that had proven to bebeneficial have been added to the design and construction requirements. The designation process requires
additional building inspections to assure that the key
mitigation measures are properly installed. Both stateadministered and privately run insurers in several states
now offer premium discounts for buildings receiving theFortified . . . for safer living® designation. There isincreasing awareness and recognition of the fact that thebuilding code should be treated as a minimum and that
there can be cost effective measures that go beyond thecode requirements and produce even more resilient
buildings.
Efforts to educate the public about the benefits ofhazard resistant buildings and to motivate them to ask
for hazard reduction features are taking a number offorms. First, there are messages being disseminated describing and warnings pegged to disruptions of lives andbusinesses due to damage from extreme wind-related
events can be substantial, regardless of financial support
that may be available for repair and rebuilding. Second,
there are a variety of efforts to create incentives forbuilding hazard-resistant homes and businesses. Beyond
incentives provided by insurers noted above, there havebeen efforts to get incentives from realtors, bankers andgovernment agencies. The intent is to get each group torecognize the benefits of disaster resistant buildings and,to the extent possible, monetize that value so there are
greater incentives for owners to build stronger and more
resilient structures.
Greater demand for buildings that are resistant to extreme winds should make it easier for realtors to sell
homes quickly and at a higher price. At a minimum,
realtors should recognize that if the buildings survive
and are habitable/functional after a storm, they will havemore properties available to sell, and it is more likelythat a community will remain an attractive place to live.
Bankers should recognize that with less damage anddisruption after an event, building owners are more
likely to keep up mortgage or lease payments. This
lower risk could then translate into slightly lower interest rates or fees. In addition, when buildings suffer lessdamage, the demands on government agencies to help
communities recover after an event are reduced. Communities could eliminate or reduce taxes related to thecost of strengthening or retrofitting buildings, and could

give priority to applications that include hazard resistantelements.

5. Pricing Risk: The Role of the Insurance
Industry
It is a primary role of the insurance industry is toassess risks and spread the risk of loss, so that companies will be in a position to provide policyholders withfunds to recover when an extreme wind event occursthat damages the property. The large dollar losses from
Hurricane Hugo in 1989 provided a warning that theconcentration of high-value at-risk properties along thecoast could result in an unacceptable, extreme level ofloss when a hurricane struck. At that point, there had
been significant work on catastrophe models for assessing seismic risks, but relatively little work on developing catastrophe models for assessing risks associatedwith hurricanes or other types of extreme wind events.
The huge losses from Hurricane Andrew that pushed a
few insurance carriers into insolvency and the realization that the losses could have been much greater if thestorm had struck 30 km to 50 km further north createdgreater demand for better catastrophe modeling of hurricane risks and for insurance companies to use them intheir planning and underwriting.
The fact that the insurance industry was able toweather the 2004 and 2005 hurricane seasons, where
losses dwarfed those of Hurricane Andrew and one infive Florida homeowners submitted a claim, testifies tothe success of changes initiated during the intervening
12 years. Risk models moved from deterministic/
empirical models, where total losses were estimatedbased on the maximum wind speed and the property
value in a 100,000 square mile area centered on thestorm’s landfall, to probabilistic models where Monte
Carlo simulation techniques are used to subject portfolios of properties to thousands of years of storms. The
models are continually being improved by including
such things as more realistic descriptions of wind fields,
more finely tuned, complex building characteristics forvulnerability analysis, multiple strike probabilities, andmore data about increases in rebuilding costs (e.g., torepresent demand surge) that occur when a major event
hits a heavily populated area. Nevertheless, models haveto rely on test data for building components and connections coupled with damage data collected from postevent studies and closed claim files to develop
vulnerability curves for various failure modes. Systems
effects and the correlations between vulnerabilities thatare represented by similar damage levels being createdby failures of different components remains a criticalneed. As modeling has become more sophisticated, there
are now opportunities for the insurance industry to capture additional information about buildings, which canprovide a better overall picture of their risks.
Nevertheless, risk continues to evolve, and somevariance in both frequency and severity of events no
doubt will be tied to climate change. With this will comeSteps Taken in Building and Insurance Industries for Extreme Wind Related Disasters

the need to bring analytical capabilities to the point
where regional changes in climate related risk can beunderstood. Other transformation of risk will come fromsteps being taken to reduce the carbon footprints ofhomes and businesses. As more and more “green” features are incorporated into buildings, the insurance
industry must be able to properly quantify specific risks
associated with new materials and systems – some ofwhich add significant costs to buildings, and/or complex
control systems that can malfunction. Clearly the Ceres
report indicates that the insurance industry is stepping
up to the challenge and responding with many new
products and services.

6. Mitigation and Adaptation
Many existing buildings will suffer significant damage if they are exposed to extreme wind events thatapproach or exceed typical design values for their location. Furthermore, trillions of dollars worth of property
is directly at risk in areas subjected to extreme wind
related events across the globe. If the current trend ofincreasing losses is to be halted, much less reversed, theexisting building stock needs to be strengthened andmade less vulnerable to both wind loads and wind effects, such as wind-driven water and wind-driven
embers.
The starting point is an inspection of the building toassess its vulnerabilities. Once that has been accomplished, a mitigation plan can be developed that allows
the owner to begin selected retrofits, usually accompanying routine maintenance or re-modeling efforts as away to make the retrofits more cost effective. A key element in the assessment process is a systems-based
approach to mitigation efforts. In other words, ana-la-cart method to mitigation modeled after the popular“green” building approaches probably makes little sensewhen the goal is mitigation against damage from an
extreme wind-related event. In the development of agreen building, each element or choice that lessens the
carbon footprint adds to the overall reduction – i.e., theelements are additive. Wind hazard reduction, by contrast, follows more of a synergistic “chain” analogy,
where the weakest link is the first to go, and can undermine the entire protection system. Other links in the
chain may be almost as weak as the worst one, so there
is no real substantial reduction in risk of loss unless anduntil all relatively weak links in the building system areaddressed.
FM Global has been successful in its approach torisk management for large commercial properties inlarge part because it conducts detailed inspections ofevery property and requires property owners to undertake prescribed mitigation activities to reduce risks as apre-condition of insurance.
In 2010, IBHS is launching an inspection–driven,system-based approach to hurricane mitigation for existing residential buildings. This tiered designation program focuses on mitigation against the types of damage

195(weakest links) that show up most frequently, and thenleads the homeowner to address the next-weakest links
as the designation levels increase. The first level
concentrates on strengthening the roof and minimizing
the chances that wind and water can enter the building
through that surface or the roof ventilation system. The
next level addresses the rest of the building envelope
and includes a few key structural retrofits that can beaccomplished at a reasonable cost but target the mostvulnerable elements, e.g., gable ends and porch anchorage.
The insurance industry is also making a large investment in a new wind, water, fire and hail research facility
being built by IBHS. This research facility will be capable of engulfing a full-scale two-story building in simulated wind fields with a variety of flow and gustcharacteristics with maximum gust speeds of 60 m/s.
The first few years of research primarily will focus onroof and roof cover issues. The facility will be useful fordeveloping vulnerability curves, correlations between
failure modes and damage, and the development ofeffective remedial measures and mitigation strategies.

7. Conclusions and Recommendations
Some industry experts see the rapid growth of interest in “green” building as a sign that society is ready for
and, in fact, looking for a change in the way that buildings are built. As such, it represents an opportunity tocreate energy efficient, strong, durable buildings that
optimize the use of resources. Unfortunately, durability
is frequently treated as an afterthought, and many areasthat would benefit from engineering-based design ofbuildings have not adopted the building codes thatwould help ensure strong safe construction. This isparticularly troubling, given the level of population andproperty value concentration in vulnerable areas. The
solution lies in active mitigation against risks posed byextreme wind-related hazards, and identifying andpromoting best practices for adaptation, so that existingrisks, as well as any new risks arising from global climate change, can be reduced.

Acknowledgment
This paper reflects observations and insights provided by a number of experts in wind engineering,building science, insurance and re-insurance. The author
would like to acknowledge the contributions of presenters at the 2009 IBHS Annual Conference, which had as
its theme “Going Green and Building Strong” – with thegoal of crystallizing a framework for presenting a broad
view of these complex and inter-related issues. The
presentations of speakers at the conference can be accesses through the IBHS web site www.disastersafety.
org.

196

T. A. REINHOLD

References
American Society of Civil Engineers (1990) ASCE 7 Standard:
Minimum Design Loads for Buildings and Structures, Washington, DC
Brookings Institution (2005) The Mega-Fire Phenomenon:
Toward a More Effective Management Model, Washington, DC
Ceres (2009) From Risk to Opportunity: Insurer Response to
Climate Change 2008. Mills, E. (ed.), http://www.ceres.org/
Page.aspx?pid=592
Munich Re (2009) http://www.munichre.com/app_pages/www/@res/pdf/ts/geo_risks/natcatservice/long-term_statistics_since_
1950/MRNatCatSERVICE_1950-2008_Great_weather_catastro
phes_Losses_en.pdf
Standard Building Code Congress International (1993) SSTD
10-93 Guidelines for Hurricane Resistant Construction,
Birmingham, AL.
Straube, J. (2006) Green building and sustainability. Building
Science Digest 005, http://www.Buildingscience.com
Straube, J. (2009) Green Building and Insurance Risks,
http://www.disastersafety.org/resource/resmgr/con_2009/ibhs20
09_john_straube.pdf

Timothy A. REINHOLD
Born in the Democratic Republic ofCongo on 27 March 1951, Timothy
Reinhold graduated from Virginia Tech,
BS in 1973, MS in 1975 and Ph.D. in1978 majoring in Engineering Mechanics.
He was a National Research Council
Postdoctoral Research Associate and latera Research Structural Engineer at the US
National Bureau of Standards, 19771983. He was a Senior Engineer at Rowan Williams Davies and Irwin,
1983-1985, a Principal Engineer with Applied Research Associates,
1985-1990, and Chief Engineer for Aerodynamics at the Danish Maritime
Institute, 1990-1992. He was an Assistant Professor, 1992-1995, Associate
Professor, 1995-2003 and Full Professor, 2003-2004 all at Clemson
University. He joined the Institute for Business & Home Safety in 2004 as
Director of Engineering and Vice President and was promoted to SeniorVice President of Research and Chief Engineer in 2008. Dr. Reinhold has
conduced research on wind effects and structural resistance for most of his
professional career. In addition to directing numerous studies to determine
wind loads for tall buildings and specialty structures, he has been heavily
involved in research relating to the performance of housing and low
buildings in hurricanes and other severe wind events. His research
includes post event assessments, model and full-scale laboratory studies,and in situ field structural testing. Tim Reinhold serves on the American
Society of Civil Engineers ASCE 7 Committee and the ASCE 7 Wind
Loads subcommittee. He is a past member of the Board of Directors for
the American Association for Wind Engineering. He has authored or
co-authored numerous journal papers, chapters of books and conference
publications.

(Received 15 December 2009, Accepted 25 December 2009)