The 2012 World Congress on

Advances in Civil, Environmental, and Materials Research (ACEM’ 12)

Seoul, Korea, August 26-30, 2012

CHALLENGES IN PROTECTIVE STRUCTURES R&D

*Theodor Krauthammer1) and Jong Yil Park2)

1)
Department of Civil Engineering, University of Florida, Florida, US
2)
Department of Safety Engineering, Seoul National University of Science and
Technology, Seoul, Korea
1)
tedk@ufl.edu

ABSTRACT

Defending society against rapidly evolving types of warfare, such as asymmetric

warfare, will remain a challenge, at least through the first half of the 21st century.
Technology will continue to play a major role in these efforts, and society must develop
appropriate innovative theoretical, numerical, and experimental approaches that will
lead to a wide range of solutions. This paper is aimed at highlighting challenges that
must be overcome to achieve the required objectives.

1. INTRODUCTION

In today’s geopolitical environment, the need to protect both military facilities and
civilian populations from attack has not diminished. Furthermore, we have noted with
great concern an increasing need to protect civilian populations against terrorism and
social/subversive unrest. Unlike the global politically and ideologically motivated
conflicts of the past, dominated by well-organized military forces, most of the armed
conflicts in the last two decades have been localized and dominated by social, religious,
economic, and/or ethnic causes. In many cases, well understood and reasonably
predictable military operations have been replaced by much less understood and less
predictable activities carried out by determined individuals or small groups that have a
wide range of backgrounds and capabilities. They are directed against well-selected
targets, and they are aimed at inflicting considerable economic damage and loss of
lives. Such activities, despite involving a few individuals or small groups, can have
devastating consequences. They can adversely affect national and international
stability, and cause worldwide serious economic, social and political damage.
Addressing this problem will require a well-planned multilayered approach that strikes a
fine balance between assuring a nation’s security and maintaining the freedoms that a
modern society enjoys. We must develop innovative theoretical, numerical and

1)
Goldsby Professor of Civil Engineering
2)
Assistant Professor
experimental approaches to protect society from a wide range of threats, and must
conduct these activities in a well-coordinated collaboration between government,
academic, and private organizations. Such technologies are the last layers of defense
between society and the threats, after all other layers of defense have failed. They are
vital for insuring the safety of people, and the preservation of valuable national assets.

2. CURRENT CAPABILITIES FOR DESIGN OF PROTECTED FACILITES

Protective design is different from typical civilian design approaches, where a code can
be followed to achieve well-defined performance and safety requirements. Although
there are several resources providing specific information on security measures,
protection levels, and structural design and analysis procedures, no single document
encompasses the full design process from start to finish. Moreover, there is little
standardization between manuals, and no hierarchy between the different resources.
Besides, most of the documents are prescriptive and not performance based. Therefore,
the designer is required to determine the requirements to ensure physical security and
safety by following the design process described in Table 1, and the specific resources
might be used to support each step with careful consideration.

For example, both the GSA guideline and the UFC manual for progressive collapse
require that a building would not fail due to the removal of a single column. However,
this does not ensure that the structure is safe from progressive collapse, since an
explosive load might damage more than a single column. Likewise, meeting the
requirements set forth by each manual may not ensure the actual physical safety of the
occupants. Too much focus is placed on individual components rather than on a holistic
perspective of the system. Another complication is that the results from each scenario
involving blast can vary so dramatically that the outcome is very difficult to predict, and
the corresponding design might not be well defined.

Also, the design needs to be worked through by a team of specialists in several areas,
and not confined to a single specialty. Finally, an important aspect to a protective
system solution is the presentation to the customer. In order to provide a successful
presentation, the team needs to do a case study on the proposed structure based on
the customer’s requirements, and present a cause-and-effect sequence that could be
addressed. A cost/benefit ratio could be outlined for the various options to enable the
rational selection of a solution with an appropriate level of protection.

Table 1. Design Process

 Design Step References
A. Define facility operational performance requirements. 1, 2, 4, 7
B. Establish quality assurance (QA) criteria for analysis, design, and 8, 12
construction work, and assign
C. Perform threat, hazard, and risk assessments, and estimate future risk. 1, 7, 13
D. Determine explosive sources, their locations, and magnitudes 1, 2, 5, 7, 11, 13
E. Estimate corresponding loading conditions. 4, 5, 11, 13
F. Establish general siting, facility layout, and design criteria. 1, 2, 3, 7, 11,
12, 13
G. Proportion members for equivalent static loads. 4, 5, 8, 9
H. Compute blast loads on facility more accurately. 4, 5, 11
I. Compute loading from fragments, crater ejecta, ground shock, etc. 5
J. Combine all dynamic loads and perform preliminary dynamic analyses. 4, 11, 5
K. Redesign facility to meet selected criteria estimated loading effects. 4, 5
L. Consider nuclear radiation, EMP, thermal effects, CB, etc., if appropriate. 10
M. Verify design by acceptable methods.
References
1. UFC 4-020-01, DoD Security Engineering Facilities Planning Manual (2009)
2. UFC 4-010-01, DoD Anti-Terrorism Standard (2007)
3. ASCE Structural Design for Physical Security (1999)
4. UFC 3-340-02, Structures to Resist the Effects of Accidental Explosions (2008)
5. TM 5-855-1, US Army Technical Manual (1986)
6. UFC 4-023-07, Design to Resist Direct Fire Weapons Effects (2008)
7. FEMA Reference Manual 426 (2003)
8. UFC 4-023-03, Design of Buildings to Resist Progressive Collapse (2009)
9. GSA Progressive Collapse Analysis and Design Guidelines (2003)
10. ASCE Manual 42 (1985)
11. ASCE Design of Blast Resistant Buildings in Petrochemical Facilities, 2nd ed. (2010)
12. ASCE Standard, Blast Protection of Buildings (2011)
13. Handbook for Blast Resistant Design of Buildings, Wiley (2010)

3. CURRENT CAPABILITIES FOR ANALYSIS

3.1 Loading Environments

Loading environments produced by conventional explosive devices include fragments

and/or debris propelled and engulfed by the blast wave. Blast parameters from bare
explosive devices cannot be used to describe the combined blast-fragment-debris
environment. A cased explosive device could cause a more severe loading
environment than anticipated from a bare explosive charge. The combination of
pressure and fragment impulse, as a function of the detonation distance from the target,
is another important issue that does not have reliable models at this time, and this topic
must be studied.

Also, the loading cannot be determined accurately for cases where explosive charges
are placed in contact with, or in close proximity to the target, and for nonstandard
explosive devices. The pressure distribution from explosive charges of shapes other
than spherical or cylindrical will be considerably different than those obtained from
cylindrical or spherical charges, and the information provided in the various design
manuals would not apply.

3.2 Structural Response and Material Behavior

Close-in HE detonations and certain nuclear loads may cause structural failures
controlled by material properties or by direct shear. At present the understanding of
these phenomena is incomplete. The same is true for possible coupled structural
responses (e.g., direct shear, flexure and in-plane forces). One must achieve a better
understanding of complicated structural dynamic behavior that would lead to improved
design methods.

Closed-form solutions for structural response are limited to simple geometries, simple
loading and support conditions, and linear materials. Obviously, one might have to
resort to explosive tests. However, there is a basic difference between many of the
explosive tests and precision tests in a laboratory. Data from typical explosive devices
may not provide accurate information for protective architecture considerations.
Consequently, it is anticipated that numerical simulations could be used more
frequently instead of some experiments. However, data from precision tests are needed
for the calibration and validation of the various computer codes. The combination of
experiments with continuum mechanics theories to clarify behavior, damage, and
transitions between response modes are also urgently needed. There is also a need to
obtain constitutive relations for various materials up to very high pressure levels, and to
define and better explain strain rate effects. So far, there is confidence in scaled tests
(structural concrete systems) as long as real materials can be used; however, it is not
clear if smaller scaled tests on typical construction materials (e.g., reinforced concrete)
can be justified. When scaled tests are to be performed, more than one scale should be
used in order to verify proper behavior, and to account for size effects. Furthermore,
there are serious questions about using scaling laws to study breaching and other
severe structural responses. Recent studies showed that size effects are coupled with
loading rate effects to significantly influence material behavior, and these findings need
to be incorporated into advanced computational tools and design recommendations.

4. POLITICAL STRATETAGE NEEDS AND POSSIBLE SOLUTIONS

In light of the known threat environments, previous recommendations must be modified

to address both the protection requirements faced by society, including land-, sea-, and
air-based systems and facilities, as well as the protection of civilian populations, as
follows:

- Expand current defense programs of both short- and long-term research on

relevant threat protection.
- Adapt existing technology developed for military use and disseminate it to
civilian design professionals through professional organizations and academic
curriculums.
 - Establish both national and multinational government-academic-industry
partnerships whose purpose is to enhance and facilitate the development and
implementation of such technologies.

Clearly, a comprehensive approach is required for developing protective technologies,

design standards for new construction, guidelines for hardening of facilities and other
structural systems. Furthermore, for the approach to be fully comprehensive, it is critical
that an effective government-academic-industry partnership is developed to provide an
institutional network to foster R&D, training, and technology transfer. Consistent with
these recommendations, an integrated and multinational systems approach should be
explored seriously. A possible approach is expected to involve a sequence of
complementary activities, from basic research through implementation. Such activities
should be conducted internationally through national centers for protective technology
research and development (NCPTR&D). These centers will direct, coordinate, and be
supported by collaborative government, academic, and industry consortia who will
perform various parts of the activities mentioned above. National academic support
consortia (NASC) should be established to engage in this critical effort through both
research and education activities. These NASCs will identify and mobilize faculty
members from universities with appropriate scientific and technical capabilities, and
lead some of the required R&D.

4. EDUCATION, TRAINING, AND TECHNOLOGY TRANSFER NEEDS

As technology is developed, it transitions to test and evaluation, which determines if the

technology is applicable for a given application. After several iterations, such
technology is transferred to operational testing for its evaluation under realistic
conditions. Upon completion of this evaluation phase, acquisition and operational
training occurs. Training for known threats relies on a predetermined course of action.
Some adversarial actions might be anticipated and counter measures could be
practiced during training. Nevertheless, in various instances, criticism was noted for not
anticipating threat evolution and not training for it. This is also a shortcoming of
conventional training for first responders; they are trained to respond to the known
conditions, and may not be able to respond adequately under different conditions. This
must be corrected by educating personnel to understand the possible threats, and the
ability of available technology to deal with them. The appropriate people should be able
to modify their actions to address such threats intelligently, and hopefully develop
preemptive measures. This structured approach does not exist yet in the general field
of protection from weapons of mass destruction (WMD). Furthermore, military solutions
are often incompatible with civilian modes of operation, and they could also be either
too rigid or too expensive to implement in nonmilitary organizations.

Leaving this process to commercial vendors could be another option, but quality
controls and costs for commercial technology are frequently controversial. Further, the
time available for the training of the appropriate persons (e.g., engineers, security
specialists, emergency and rescue operations staff, etc.) is limited, compared to that of
military personnel. Appropriate government agencies are expected to address these
issues through collaboration with industry and academic institutions, and with other
government agencies. Universities will have to be involved more than in merely basic
research. They will also have to play an integral role as think tanks, and in transferring
the developed knowledge and technology to the end-users. Within many government
agencies and their supporting industrial organizations, there is a critical need to attract
and/or develop employees with experience in protective science and technology, as the
current workforce ages and reaches retirement age. Since the mid-1980s, a gradual
decline has taken place in academic protective technology related R&D activities, along
with the involvement of academicians in these R&D efforts. As a result, very few
eminent academicians in this field are still available in the U.S. Except for the University
of Florida that has an academic program and a graduate level certificate dedicated to
protective science and technology, no comparable formal engineering training exists at
other U.S. universities. The situation is similar in most other developed countries.
Therefore, establishing government-academic-industry consortia in various countries,
with a mandate to develop new and cost-effective protective technologies, and train
current and future engineers and scientists, should be seriously considered.

The University of Florida in the USA has recognized this challenge, and has embarked
on an effort to remedy it. The Center for Infrastructure Protection and Physical Security
(CIPPS) is heavily involved in R&D on such topics, and they have established a series
of five graduate level courses that provide comprehensive training on a broad range of
related topics, as follows:

- Introduction to Protective Structures (required of all participants)

- Advanced Protective Structures
- Retrofit Methods for Protective Structures
- Applied Protective Technology
- Impact Engineering

Besides these courses, the Civil and Coastal Engineering (CCE) Department, an
academic unit of the Engineering School of Sustainable Infrastructure and Environment
(ESSIE), has related activities on protecting from natural disasters (hurricanes,
tornadoes, and earthquakes) that enables the research teams to work within a Multi-
Hazard Protection framework. Furthermore, CIPPS has established a Critical
Infrastructure Protection Certificate (CIPC) program for graduate students with interests
in the area of protecting the Nation’s critical infrastructure systems against blast, shock,
and impact incidents. This is a 9-credit program, compatible with the decision by the
College of Engineering (COE) to select the area of security and critical infrastructure
protection as one of its focus areas. This Certificate program was formulated to meet
the education needs of a diverse group of students, while working within the current
CCE curriculum to optimize the delivery of education and faculty resources.
Participants in the Critical Infrastructure Protection Certificate program can select three
courses from the five courses, but most students involved in related R&D activities take
all five courses. The Certificate is awarded to participants upon the completion of their
graduate degree studies.
5. RECOMMENDATIONS

Although current design procedures give guidelines on how to enhance the breaching
resistance of a facility, it could be impractical to protect against breaching and direct
shear effects by conventional means. Alternative construction and/or reinforcement
details should be permitted for cases in which reinforcement lacing would be required
(lacing of reinforcement is similar to textile weaving). The use of various materials and
combinations of materials (e.g., high-strength or ultra high performance concretes,
possibly in combination with conventional and/or fiber reinforcement and damage
absorption devices) should be studied, and future design guidelines should address
such options.

Also, guidelines and recommendations should be provided on how to evaluate future

capacity of previously loaded structures before and/or after renovation.

Recent studies showed that current design procedures may not be adequate for
connections or plastic hinge regions for both structural concrete and steel, and raise
questions about recommendations for both flexural and shear resistance models in
slabs. Concepts for changing the essential quantities for dynamic resistance include
mass and strength increases, modification of support conditions, span length changes ,
replacement of inadequate components, and loaded area reduction.

Additionally, retrofit effects on blast, ballistic, and forced-entry resistance should be

addressed to include analysis techniques for predicting retrofit requirements, retrofit
materials and how they should be used, forced-entry resistance retrofits, and the
corresponding anticipated costs and benefits.

Although considerable attention was given to the behavior of subsystems that are
typically found in hardened facilities subjected to nuclear effects (generators, air-,
water-, and fuel-supply equipment, communication and computer equipment, etc.),
there is no comparable source of information related to conventional weapons effects.
Nevertheless, but one may use data from related studies for such purposes. The
important findings indicate that most mechanical or electromechanical types of
equipment are sufficiently rugged to survive the anticipated in-structure shock
environments. Problems were encountered primarily with faulty wire installations or with
inadequate attachment procedures for the structure. Although shock isolation is quite
feasible, it was noticed that certain shock isolation devices may not provide the
expected protection.

When approximate, simplified methods are used, one must assume a response mode
and the corresponding response parameters. It is recommended to use such methods
together with data from computer codes that are based on current design manuals.
Current medium-structure interaction models are too simplistic, and they may not
include nonlinear effects. To accommodate a practical range of numerical capabilities,
simple, intermediate, and advanced computer codes are needed. Advanced numerical
methods require significant resources, and they should be used in the final stages of
detailed structural analyses for obtaining design guidelines, and/or in the detailed
evaluation of the anticipated structural response. Furthermore, such advanced codes
must be validated against precision test data before their application to a project to
insure their reliability. It has been shown that developing effective code validation
methodologies is very important, and that the best results are obtained when a
structure is analyzed with a range of numerical approaches. The combined effects of
material properties, loads, support conditions, and structural detailing are understood,
at least empirically, and this state of knowledge is reflected in the current design codes.

The current quasi-static design approaches for structural damage assessment are
reasonable for implementation. However, the application of traditional and simple
pressure-impulse (P-I) diagrams should be re-evaluated, and the transition between
different behavioral modes should be better defined. User-friendly and physics-based,
single-degree-of-freedom (SDOF) codes that include various structural response
capabilities should be developed and incorporated into the design process. Design
activities should be supported by review of existing data, analysis, and testing, and
design methods should be re-evaluated to include more precise criteria.

Unlike many current procedures, all designs should be based on acceptable design
criteria that include the following: construction ability, performance, maintenance, and
repair requirements for the facility under consideration. Guidelines on construction
aspects and cost control should be provided. Robustness and response levels should
be related to the facility's contents and its mission requirements (for civilian facilities,
the mission requirement parameters would be changed to address considerations of
safety). It is also desirable to introduce cost/benefit criteria for various design options.
Designers should be guided with respect to design tradeoffs, but the design process
should be well defined.

The following list of recommended long-term research activities has been developed:

- Protection methodology, threat and risk assessment, its mitigation and resource
allocation.
- Threat and loading environment definition.
- Materials’ behavior under single and combined loading environments.
- Both simple and advanced computational capabilities. ଝ
- Study the behavior and performance of building enclosures.ଝ
- Building and structural science behavior and performance.ଝ
- Facility and system behavior under combined WMD environments.ଝ
- Address multi facility conditions (e.g., installations, cities, etc.).ଝ
- Pre- and post-incident facility assessment.
- Environmental effects on all the above cases (e.g., very cold or very hot
climates).
- Technology transfer, education, and training
- Use the knowledge gained from the recommended R&D efforts to establish multi
hazard protection design approaches for facilities subjected to abnormal loading
 conditions.

These R&D activities are needed to develop much more effective solutions to problems
that can be currently addressed only with empirical and conservative approaches. The
investment in the proposed approach will enable both very meaningful technological
enhancements, and large cost savings in providing the required protection to society.
Furthermore, these cost savings are estimated to be far larger than the cost of the
recommended R&D.
ଝ

6. CONCLUSIONS

This paper was focused primarily on addressing scientific and engineering issues to
provide additional background on related capabilities in protective science and
technology, and recommendation for long-term R&D in this critical area. The
recommended activities can be conducted over the next three to five years, and they
should be supplemented with follow up R&D activities for the foreseeable future. We
must develop much more effective solutions to problems that can be currently
addressed mainly with conservative and/or empirical approaches. Also, we must
develop a competent scientific and technical human resource pool through effective
education, training, and technology transfer. The anticipated contributions will have
profound effects on critical national and international defense and security.