to the HOT
Architectural Surety No 3 !
EARTHQUAKE / TERRORIST BLASTPROTECTIVE
STRUCTURAL CIRCUIT BREAKER
| The main lesson
learned by structural engineers from the latest terrorist bombings of
buildings (ASCE 1999)
is a need to assure structures ability to sustain significant local damage
standing. To achieve this goal, it is not necessary
to make significant sacrifice as to local damages provided
the concept of the Blast
Protective Structural System (
BPSS) is employed (Shustov
Despite some advantages of the building elevation configuration (
Topic 5 ),
it can neither eliminate nor mitigate a potentially
destructive dynamic input.
For this reason, the structural
circuit breaker shown on the left should be
included in the optimal design. Therefore, an
architecturally secure building
the following combination of innovative approaches: elevation
shock and terrorist blast
The superstructure of this building
is shaped in accordance with he elevation configuration technique in
order to suppress resonant amplifications of the
occupying the first story and basement, is meant to mitigate horizontal
of earthquake input or a terrorist blast.
It consists of two major components: a row of impact
bents , aligned
with the building perimeter, and shock evaders,
positioned on each footing of the inner area.
The shock evader (on the left) partially
interrupts and decreases the
seismic waves penetrating into the superstructure
from a fresh concept of an automatic passive control that
progressive frequency separation plus an ultimately
, the shock evader is a much
more effective device than
other known types of base isolators. The shock
evader includes a
and a pedestal plate . The slip-joint
consists of a housing,
attached to the superstructure, with a consumable-while-sliding
cylinder resting on the pedestal plate positioned
on a footing.
| In order to facilitate
a sliding, the cylinder is made of material with an adequate vertical
capacity and horizontal (shear) resistance but
with a low friction coefficient and ability to wear away easily
at the contact with the pedestal plate.
Since it is unlikely that a structure will experience more than some
hundred strong pulses during its lifetime, the
abrasion of the cylinder will not cause any structural damage.
| It is widely believed
that a building subject to an explosive blast loading has a chance to remain
only if it possesses an extraordinary resistive
capacity. This belief rests on the assumption that the specific
impulse or the time integral of pressure, which
is the dominant characteristic of the external blast load, is
fully beyond our control. Fortunately, the
last statement is only half-true. We actually cannot control a
magnitude of a load itself but we can influence
timing of its application to structural elements as well
as the pattern of interaction
of those elements, and this may make a difference.
This concept was used
in the BPSS presented as the
impact protective bent in the top figure above.
When a blast impulse has developed, the vertical
wall panel does not transfer its load share to the building
frame immediately. Instead, it smoothly
transforms its kinetic energy of translation into potential energy
of elevation. Therefore, the horizontal
component of the panel's induced pressure on the frame remains
relatively small. The main advantages of
It is simple and able to perform satisfactorily
under severe conditions of spatial distortions.
It can be operational in both
external and internal explosions.
It will restore its initial, pre-explosion
position after several excursions.
| In contrast with
the basic mode of BPSS described
above, the model building under the current project
can go even farther. The impact
protective substructure (the top figure above) combines
with shock evaders,
which create a new level of blast protection. Thus, in case of a
powerful but a rather
distant blast, the building will have the ability
to recall by means of sliding on its shock evading devices,
thus providing an additional blast impact mitigation.
page was last updated on 04/19/00
V., 1994, “Adaptive Systems: A New Application”, Proc. 1st
World Conf. on Struct. Control,
3: FP-32-FP-41, Pasadena, CA.
1996, “Blast Protective Structural System”, Proc. 4th Int’l Conf. SUSI-96,
T., Marchand, K.A., Mlakar,
P.F. (Task Committee), 1999, "Structural
Design for Physical Security: State of the
Practice", ASCE, Reston, VA.