Note: Descriptions are shown in the official language in which they were submitted.
CA 03048763 2019-06-27
Description
Protective system for protecting buildings against aircraft crashes
The invention relates to a protective system for protecting a building against
air-
craft crashes and similar high-energy impacts of large-volume objects
according
to the preamble of Claim 1.
Such a protective system is known in the art from the patent specification DE
10
2010 037 202 B4 of HOCHTIEF Construction AG. In that specification, a protec-
tive sheath is furnished for protecting a structure from being struck by
flying ob-
jects, which is situated at a distance from the outer envelope of the
structure and
is in the form of a grid, the grid bars of the sheath consist at least
partially of
steel, the protective sheath is in the form of a self-supporting support
structure,
and the protective sheath is either not connected to the outer envelope of the
structure at all, or is not connected to it via supporting elements.
The objective of the invention is to further refine a protective system of the
above-mentioned kind, in such a way that even an impact by a heavy four-jet
air-
craft such as a Boeing 747 or Airbus A380 will not destroy the integrity of
the
protected building.
This problem is solved according to the invention by a protective system that
has
the features of Claim 1.
Accordingly, it is essential to the invention that the protective grid is
supported on
the building wall by a plurality of plastically deformable, energy-absorbing
ele-
ments -- and preferably exclusively by such elements. In addition, advanta-
geously, the grid is supported by the ground.
The invention arises from the consideration that it is desirable to support
the pro-
tective grid on the building wall in order to better distribute the impact
loads, de-
parting from the technical teaching disclosed in DE 10 2010 037 202 B4. As has
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been recognized in the context of the present invention, a portion of these
loads
may and should be absorbed by the protected building itself, to the extent
that
the building's structure is able to withstand or tolerate them without being
cata-
strophically damaged. For this purpose, the transfer of force, pressure and
defor-
mation energy into the building wall is damped by means of energy- and vibra-
tion-absorbing (damping) elements.
Advantageously, the respective energy-absorbing element comprises a steel
tube arranged between the protective grid and the building wall in such a way
that the force transmitted to the protective grid upon impact of an aircraft
acts on
the tube at least predominantly in the radial direction and squeezes the tube
to-
gether in cross-section. In contrast to ordinary shock absorbers that have a
cylin-
drical shape and are installed in such a way that when placed under load they
are resiliently compressed in the longitudinal direction, a predominantly
plastic
nonlinear deformation occurs in this case as a result of a force that acts on
tube
circumference in the radial direction. To increase energy dissipation, the
tube
may have a core or an installation made of crossed steel plates in the tube
inte-
rior.
By means of numerical simulations, it has proven possible to show that the
aforementioned energy-absorbing elements make a decisive contribution of up
to 60% of the total energy dissipation via the protective system according to
the
invention, and considerably minimize the impact-induced vibrations in the
build-
ing.
Advantageously, the protective grid comprises an inner grid plane arranged par-
allel to the building wall and formed of steel beams and an outer grid plane
ar-
ranged parallel thereto and formed of steel beams, the inner grid plane and
outer
grid plane being interconnected by steel beams.
In a preferred configuration, both the inner grid plane and the outer grid
plane
comprise a regular rectangular grid, the elementary cells of which have the
same
dimensions and are shifted from one another by half a lattice constant in at
least
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one main direction of the grid. In this case, it is preferred that the inner
grid plane
and outer grid plane are connected to each other by diagonal beams, each of
which extends from a node of one grid plane to a node of the other grid plane.
Further advantageous configurations may be found in the dependent claims and
in the following detailed description.
An exemplary embodiment of the invention is described below with reference to
the attached drawings. The drawings show a schematic, simplified representa-
tion of the following:
FIG. 1 a perspective view of a protective system installed in front of
a
building wall to protect the building from aircraft crashes,
FIG. 2 a top view of the protective system from above according to arrow I
in FIG. 1; below that, a top view from the front according to arrow II
in FIG. 1; and below that, a cross-section (side view) along line A-
A,
FIG. 3 an enlarged top view of the protective system as seen from above,
and
FIG. 4 a cross-section through a tube that serves as an energy-
absorbing
fastening between the protective system and a building wall: above,
by itself, and below, as installed in the protective system.
Parts that are identical or equivalent are given the same reference marks in
all
drawings.
The protective system 20 shown in the drawings with a protective grid 22 is
set
up in front of a building wall 24 or another section of a building envelope,
in the
manner of a protective cover, and protects it against aircraft crashes or
similar
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high-energy and large-scale impacts of rockets, components or debris as a
result
of strikes, explosions, hurricanes and the like.
The protective grid 22 is formed from interconnected, in particular welded
(steel)
beams or struts or grid bars and comprises a first grid plane that faces the
build-
ing wall, also referred to as the inner grid plane El, and a second grid plane
that
faces away from the building wall, also referred to as the outer grid plane
E2.
Each of the two grid planes El, E2 is formed by interconnected longitudinal
beams and transverse beams, which preferably span a regular surface grid. The
two grid planes El, E2 are interconnected by beams arranged between them, in
particular by diagonal beams, so that overall, a three-dimensional space grid
is
realized.
In the example shown here, it is assumed that the protected section of the
build-
ing wall 24 spans a vertical plane above the ground 26. The inner grid plane
El
is arranged parallel to the building wall 24, forming a space or gap 28 having
a
gap width (= distance) a. Likewise, the outer grid plane E2 is arranged
parallel to
the building wall 24, and thus also parallel to the inner grid plane El. The
two
grid planes El, E2 thus form spaced vertical planes with the distance b.
As already mentioned, the outer grid plane E2 is realized by a plurality of
longitu-
dinal and transverse beams that are interconnected at the intersections or
nodes
30. In this example, the beams are vertical beams 1 and horizontal beams 3.
The vertical beams 1 are arranged like columns, regularly spaced apart at
inter-
val d, and are aligned vertically, which corresponds to how they are
designated.
The horizontal beams 3 running perpendicular to the vertical beams 1 are
aligned horizontally, corresponding to how they are designated, and are ar-
ranged at regular distances h from each other, i.e. at different heights above
each other. Preferably, the horizontal beams 3 and vertical beams 1 are
prefera-
bly fixedly connected, in particular welded, at each of the intersections or
nodes
30. In this way, overall, a regular rectangular grid is created, the
elementary cell
of which has a width d and height h.
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The inner grid plane El is constructed analogously to the outer grid plane E2.
The inner grid plane thus likewise forms a regular rectangular grid of
vertical
beams 2 and horizontal beams 3', the elementary cell of which preferably has
the same width d and height h as the elementary cell of the outer grid plane
E2.
The distance between the two grid planes, i.e. the width or depth of the
protec-
tive grid 22, is designated as b.
The two grid planes El, E2 are advantageously not arranged congruently one
behind the other starting from the front in a top view, but instead are
shifted or
offset relative to each other in the horizontal direction, i.e. in the
longitudinal di-
rection of the horizontal beams 3, 3', preferably by half a grid width d/2.
The
nodes of the outer grid plane E2, when projected onto the inner grid plane El,
are thus located in the middle, between two nodes of the inner grid plane. In
the
vertical direction, in contrast, the two grid planes El, E2 are preferably not
shifted relative to each other, and thus a horizontal beam 3' of the inner
grid
plane El is associated with a respective horizontal beam 3 of the outer grid
plane E2 that is situated at the same height. This variant embodiment creates
horizontal planes between the vertical grid planes El and E2, which may be
used as floor areas. In an alternative embodiment, as shown in FIG. 1, the
grid
planes El, E2 are offset by half a storey height h/2, and in this way, the
vertical
grid area is also made more compact.
As mentioned above, the two grid planes El, E2 are interconnected by
additional
beams, which preferably are realized as diagonal beams 4, 5, and are connected
to the nodes of the grid planes El, E2, in particular by welding.
Specifically, in the exemplary embodiment of each node of the outer grid plane
E2, four diagonal beams 4, 5 are connected to each associated node of the
inner
grid plane El, except for some nodes that are arranged at the edge of the grid
surface Two of the four diagonal beams, namely those with reference sign 4,
lie
in a horizontal plane and extend to the two nearest nodes at the same height
as
the inner grid plane El. The other two of the four diagonal beams, namely
those
with reference sign 5, extend in space diagonally, i.e. obliquely downward to
the
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nodes of the inner grid plane El that are arranged directly below the aforemen-
tioned nodes (alternatively, they may also run diagonally upward, or there may
be two diagonally upward-running diagonal beams in addition to the four men-
tioned diagonal beams). As a result, the four diagonal beams 4, 5, fan out
from
the respective node of the outer grid plane E2 in a quasi star-shaped or
pyramid-
shaped manner, corresponding to the offset of the two grid planes El, E2 rela-
tive to each other, and establish the connection to the inner grid plane El.
Viewed from the nodes of the inner grid plane, the result is a mirror-image ar-
rangement. From above (FIG. 3), a triangular partitioning is observed. Less
than
four diagonal beams may emanate from the edge nodes, due to their location on
the periphery.
As is apparent from the top view of the protective grid 22 from above
according
to FIG. 3, the vertical beams 1 of the outer grid plane E2 are preferably all
ar-
ranged on the same side of the horizontal beams 3, i.e. preferably on the
inside,
namely toward the building wall 24. The same applies to the inner grid plane
El,
where the vertical beams 2 are arranged on the inside of the horizontal beams
3'.
The vertical beams 1, 2 are preferably manufactured integrally, i.e. as a
single
piece, and preferably have a double-T-shaped cross-section, or alternatively a
rectangular cross-section. The same applies to the horizontal beams 3, 3' and
the diagonal beams 4, 5.
The beams are preferably dimensioned as follows with regard to their cross-sec-
tional width B and their cross-sectional height H:
1,2 Vertical beams W/H= 500 - 1000/500 - 1000 mm
3, 3' Horizontal beams W/H= 500 - 1000/500 - 1000 mm
4 Diagonal beams (horizontal) W/H= 400 - 800/400 - 800 mm
5 Diagonal beams (diagonal) W/H= 400 - 800/400 - 800+ mm
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Preferred materials for the beams are grades of steel having high ductility
and
plastic deformability.
The structural dimensioning of the protective grid 22 is preferably as
follows:
Distance between vertical beams d = 10 - 15 m
Distance between horizontal beams h = 5 - 10 m
Width of protective grid b = 10 - 15 m
Distance from protective grid to building wall a = 0.3 ¨ 2.0 m
The overall height and width of the protective grid 22 is adapted to the dimen-
sions of the building or building section to be protected.
The protective grid 22 is preferably designed to be self-supporting and is
advan-
tageously supported on the ground 26 by means of at least some, preferably all
vertical beams 1, 2. The vertical beams 1, 2 are suitably anchored to the
ground
26 and are grounded on a foundation. The vertical beams 1, 2 may therefore
also be referred to as columns or supports.
In addition, the protective grid 22 is connected to the building wall 24 via a
plural-
ity of shock-absorbing or energy-absorbing elements 32 or dampers. These en-
ergy-absorbing elements 24 are preferably tubes 6 or hollow cylinders made of
steel, which are arranged between the protective grid 22 and the building wall
24
in such a way that upon impact of an object against the protective grid 22,
they
are compressed or squeezed and consequently plastically deformed from the
front (impact direction substantially in the direction of arrow II in FIG. 1),
perpen-
dicular to their longitudinal axis, i.e. in the radial direction 34 when
viewed in
cross-section.
In a preferred installation variant, the respective tube 6 is arranged between
the
building wall 24 and the vertical beams 2 of the inner grid plane El facing
the
building wall 24, i.e. in the intervening gap 28. The tube diameter D is
accord-
ingly at most as large as the gap width a. The longitudinal axis of the tube 6
is
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preferably arranged to be vertical, i.e. parallel to the vertical beam 2.
Preferably,
tube 6 is fixedly connected, in particular welded, to the associated vertical
beam
2 on its outer circumference, and is also leaned against the building wall 24.
In
this case, the tube 6 represents an energy-absorbing (connecting) element or a
bracket/fastening/suspension/support or bearing between the protective grid 22
and the building wall 24.
Alternatively, there may be a gap between the building wall 24 and the tube 6.
In
the latter case, it is more expedient to simply speak of an energy-absorbing
ele-
ment instead of an energy-absorbing support.
But other installation variants are also possible in which the energy-
absorbing
tube 6, for example, is attached to a horizontal beam 3' of the inner grid
plane
El. In addition, a type of series or row arrangement may be realized, with a
plu-
rality of parallel adjacent tubes arranged inside a gap 28 between the inner
grid
plane El and the building wall 24. The required tube length and arrangement de-
pends on the required energy absorption and the (expected) impact pulse.
To increase the energy absorption capacity, a plastically deformable core 36
is
advantageously arranged in the respective tube 6, which preferably consists of
cross-welded steel plates. In the cross-sectional representation shown in FIG.
4,
the core 36 forms a cross inside the circumference of the tube, and the center
of
the cross coincides with the longitudinal axis of the tube 6. The core 36 is
prefer-
ably only clamped into the tube 6 and is not attached to the inner wall of the
tube
in any other way.
Preferred dimensions for tubes 6 that are used as energy-absorbing elements
are as follows:
Tube diameter D = 300 - 1000 mm
Wall thickness t = 10 - 25+ mm
Thickness of plates in the core T = 10 - 50 mm
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The dimensions given here and further above are adapted to the requirements
for protecting a nuclear power plant building against aircraft crashes, in
particular
by four-jet passenger aircraft, and have been verified in the context of
numerical
simulations. The dimensioning varies with the requirements in individual
cases.
Preferred materials for the tubes 6 and cores 36 are grades of steel having
high
ductility and plastic deformability
Because it is anchored to the foundation, part of the energy absorbed in the
event of an impact or strike of an object on/into the protective grid 22 is
diverted
via the foot support. Another part of the energy is absorbed by the plastic
defor-
mation of the protective grid 22 itself and is distributed over a larger
impact sur-
face. In addition, a considerable part of the energy is absorbed by the energy-
ab-
sorbing elements 32 that are nonlinearly deformed when the impact occurs, and
only a small part of the energy is transferred to the building in a greatly
attenu-
ated form. This reduces the amount of energy transferred to the protected
build-
ing to an acceptable level. In this way, it is ensured that the building is
not struc-
turally overloaded and that impact-related vibrations and oscillations are
limited
to an acceptable level. Finally, the protective grid 22 splits an impacting
object
into a plurality of small debris parts, which are deflected in different
directions
and hit different parts of the building wall 24 at reduced speed.
Finally, a particular advantage of the structure is that the entire building
does not
have to be converted; instead, the protective cover may be spatially limited
to the
particularly vulnerable or sensitive sections of the building wall 24 or
building en-
velope.
In an expedient modification of the above-described structure, the protective
grid
22 may be mounted on the building wall 24 exclusively via the energy-absorbing
elements 32, without support on the ground, which is useful, for example, for
protecting ceiling sections. In this case, of course, the spatial position and
orien-
tation of the protective grid 22 must be adapted to the installation
situation. This
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means that the "vertical beams" and "horizontal beams" are then oriented
differ-
ently in space than has been described heretofore and suggested by the termi-
nology used herein.
Finally, the shape of the protective grid 22 could potentially follow the
outer con-
tour of a building, for example a circular or otherwise curved outer perimeter
of a
dome-shaped power plant building. This is expediently achieved by straight sec-
tions as described above, with bends in between.
Mentions of steel in the description above signify that the component in
question
consists at least partially of steel. This expressly includes composites of
steel
and other materials.
A particularly important field of application is the protection of power plant
build-
ings or the building envelopes of nuclear power plants or other nuclear
facilities.
Of course, many other applications are also possible for protecting industrial
plants or military objects from aircraft crashes and the like.
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List of reference signs
1 Vertical beams
2 Vertical beams
3 Horizontal beams
3' Horizontal beams
4 Diagonal beam
Diagonal beam
6 Tube
20 Protective system
22 Protective grid
24 Building wall
26 Ground
28 Gap
30 Node
32 Energy-absorbing element
34 Radial direction
36 Core
El Inner grid plane
E2 Outer grid plane
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