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Building Blast Analysiswind engineering & architectural aerodynamics
London | Hong Kong | Kuala Lumpur | Abu Dhabi | Dubai | Shanghai | Houston
dynamic loading produced by the detonation of high-explosive materials is, unfortunately, an increasingly important load case that designers of important structures need to consider for the safety of the people interacting with the structure and integrity of the structure itself.
Tel: +44 20 8614 4400 Fax: +44 20 8943 3224 Email: enquiries@bmtfm.com Website: www.bmtfm.com
in recent years, considerable attention has been given
to explosive loads on landmark structures as a result
of both accidental and intentional events. at the same
time, building designers the world over have been
increasingly pushing the boundaries on design with ever
more demanding architectural and structural forms and
utilizing advanced structural materials and methods.
understanding how these designs and materials are able
to withstand blast loads and maintain structural integrity
is now no longer possible with semi-empirical methods
without making highly conservative assumptions that drive
up asset cost and compromise design.
the balance of compromising design for the safety of the
structure is heavily influenced by the acceptable level of
risk. a risk-based approach to design for blast loading
should be taken where accurate methods are employed to
assess the consequence of an event, and combined with
the likelihood of an event occurring.
Bmt have taken their extensive experience in risk-based
explosion load analysis from the oil and gas industry
and coupled it with class-leading software for non-linear
dynamic structural finite element analysis (Fea), and
unparalleled knowledge of structural environmental
loadings to provide the construction industry a complete
package for blast load design. the approach that Bmt
provide through all stages of design ensures that the risk
posed to building occupants and structural integrity from
terrorist and other explosions is significantly reduced. the identification of key threats is the first stage of any blast
study for a new development. explosion threat scenarios
are typically specified in terms of an explosive charge weight
at a standoff distance from the target structure. Bmt works
closely with security consultants and governmental bodies
to determine the likelihood of a given scenario occurring.
Key services
• identification and assessment of likely threat scenarios
• Blast load Prediction
• non-linear dynamic structural analysis to assess resistance to blast loading
• analysis of blast resistant façade and glazing systems
• advice on blast resistant design and development of mitigation measures
• risk-based assessments
• determination of protection levels
• Building evacuation analysis
Key BeneFits
• risk-based assessment of security related threats
• cost effective structural and façade designs that balance an acceptable level of risk
• interactive solution development
• iterative design optimisation
• visualisations of the blast waves, cladding and structural response to aid design development
Blast loads
threat assessment
Overpressure resulting from a small device (~20kg TNT equivalent) detonated in a built-up urban area. Reflection of the blast wave-front is
shown, resulting in successive cycles of overpressure.
the quantification of blast loads on structures from
explosion events requires the accurate modelling of
peak overpressures and the associated impulse from
the expanding gases of detonation as well as taking into
account the geometric effects of blast wave reflection
and diffraction. the recent developments in the fields
of computational Fluid dynamics (cFd) and non-linear
Finite element analysis (Fea) have meant there have been
significant advances in the prediction of blast loads that
were not possible up until recently. accurate explosion
loads and structural responses can now be modelled using
software that couples these technologies for complex
designs and for a range of threat scenarios.
Bmt use advanced three-dimensional cFd software to
calculate the evolution and movement of the blast pressure
wave through the air and its interaction with surrounding
structures. the end result is an accurate blast pressure
distribution across the structure that is then coupled to the
dynamic structural response model.
Protection of a structure’s occupants by the façade
system is the first line of defence against blast. however,
for extreme events or events where terrorists target weak
points in a structure’s design, the integrity of the structure
is vitally important. Bmt can carry out detailed blast
analysis to ensure that the structure is robust enough
to maintain integrity for an acceptable blast risk event
through the development of alternate load paths. the
analysis of structural elements to resist blast loading
requires a dynamic analysis with non-linear ductile
response where ultimate limit state assessments are
carried out. where complete structural failure is predicted,
Bmt can work with the building designer to develop
alternative load paths and mitigation strategies.
design of structural elements
design of Protected sPaces
design advice & mitigation measures
in some buildings, it is necessary to design protected
spaces that are hardened to resist the effects of external
explosions and protect the occupants inside or a critical
piece of equipment. in the event of a bomb threat,
sometimes it is safer for the building occupants to seek
internal shelter or to evacuate through subterranean exits
due to the high risk of injury from falling glass and other
debris that occurs over a wide area.
Bomb shelter areas (Bsas) are ideally located in
basements using reinforced concrete and away from
areas exposed to high blast and direct fragment hazards.
to ensure that the Bsa does not become a hazard itself to
evacuees, it is vitally important to determine the protection
offered for a range of threats. in other words, its limiting
blast capacity must be quantified.
Bmt are able to determine the limiting capacity of a
Bsa from a blast by modelling the structural integrity of
the building and shelter for a range of blast threats. the
analysis of the modelling results can be used to determine
the optimum location of the Bsa and identify ways for
strengthening the shelter.
in the early stages of a structure’s design, Bmt can
provide advice on good design practice for blast
resistance and mitigation measures to reduce the risk
of damage from bomb blasts. often this requires an
assessment of the buildings external form to identify
areas of re-entrant corners, cantilevered upper floors/set-
backs of the lower floors, recesses, internal courtyards
and arcades which will exacerbate the effects of an
external bomb blast. Bmt then work with the building
designers to reduce these problem areas and introduce
mitigation schemes such as convexly curved or faceted
facades and barrier schemes around the building’s
perimeter.
the proliferation of fully glazed facades in new building
designs means that the importance of glazing system
design to resist blast loading is more important than ever.
the fragmentation and subsequent projection of glass
fragments from bomb blasts is frequently the highest
threat to human life. ordinary annealed or toughened
glass forms elongated shards and small fragments when
subjected to blast loads of sufficient strength that will
travel at high speed and cause severe or lethal injuries
to personnel and extensive damage to fixtures, fittings
and equipment. appropriately supported laminated glass
panels have far superior blast resistance properties that
allow them to absorb energy with little or no fragmentation.
the key to optimum protection from laminated glazing
systems is the laminate composition and the support
system. Bmt’s advanced non-linear Fea tools are capable
of modelling the failure mechanism of glazing laminates
and the supporting system to identify areas of design that
can be optimised for maximum protection. the levels of
protection can then be categorised using standards such
as gsa –ts01, astm F 1642-04, and iso 16933.
design of glazing systems
Fully-coupled blast simulations showing the initial failure of a double
glazed facade element and glass fragmentation after complete failure
Adapted from the US General Services Administration (GSA) standard testing criteria for blast resistant glazing.
Pressure waves travel through the structure during a blast
faster than the wave-front travels through air, resulting in
structural stresses in advance of the main blast impact.
Tel: +44 20 8614 4400 Fax: +44 20 8943 3224 Email: enquiries@bmtfm.com Website: www.bmtfm.com
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