CA3048763A1

CA3048763A1 - Protective system for protecting buildings against aircraft crashes

Info

Publication number: CA3048763A1
Application number: CA3048763A
Authority: CA
Inventors: Adam Fila; Viktor Vlaski
Original assignee: Framatome GmbH
Current assignee: Framatome GmbH
Priority date: 2017-02-07
Filing date: 2018-02-06
Publication date: 2018-08-16
Also published as: JP2020506312A; DE102017201915A1; EP3510217A1; US20190271170A1; WO2018146104A1; RU2019115830A; EP3510217B1

Abstract

The invention relates to a protection system (20) for protecting a building from airplanes crashing into them and similar high-energy impacts, having a three-dimensional protective grid (22) mounted in front of a building wall (24) at a distance thereto, and which comprises supports (1 - 5) which are interconnected. The aim of the invention is to improve said type of protection system such that even impacts of heavy four-engine aircraft, for example a Boeing 747 or airbus A380, does not destroy the integrity of the building protected by that system. This is achieved such that the protective grid (22) is supported on the building wall (24) by a plurality of plastically deformable, energy absorbing elements (32).

Description

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

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 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

2 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

3 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.

4 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

5 I

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

6 I

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 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

7 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

8 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

9 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.

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

Claims

1. Protective system (20) for protecting a building from aircraft crashes and similar high-energy impacts, having a three-dimensional protective grid (22) con-structed in front of a building wall (24) at a distance therefrom and comprising in-terconnected beams (1 to 5), characterized in that the protective grid (22) is supported on the building wall (24) via a plurality of plas-tically deformable, energy-absorbing elements (32), wherein each energy-absorb-ing element (32) comprises a steel tube (6) arranged between the protective grid (22) and the building wall (24) in such a way that the force transmitted to the pro-tective grid (22) when an aircraft strike occurs acts on the tube (6) at least predom-inantly in the radial direction (34) and squeezes it together in cross-section.

2. Protective system (20) according to Claim 1, wherein the protective grid (22) is supported on the building wall (24) exclusively by means of the energy-ab-sorbing elements (32).

3. Protective system (20) according to Claim 1 or 2, wherein the diameter (D) of the tube (6) is in the range between 0.3 and 1.0 m, and the thickness (t) of the tube wall is in the range between 10 and 50 mm.

4. Protective system (20) according to Claim 3, wherein the tube (6) has a core (36) made of crossed steel plates in the tube interior.

5. Protective system (20) according to one of the foregoing Claims, wherein the protective grid (22) comprises an inner grid plane (E1) arranged parallel to the building wall (24) and formed from steel beams (2, 3'), and an outer grid plane (E2) arranged parallel thereto and formed from steel beams (1, 3), and wherein the in-ner grid plane (E1) and outer grid plane (E2) are interconnected by steel beams (4, 5).

6. Protective system (20) according to Claim 5, wherein the distance (b) be-tween the two grid planes (E1 , E2) is in the range between 10 and 15 m.

7. Protective system (20) according to Claim 5 or 6, wherein both the inner grid plane (E1) and the outer grid plane (E2) comprise a regular rectangular grid, the elementary cells of which have the same dimensions (d, h) and are displaced relative to one another by half a lattice constant (d/2) in at least one direction.

8. Protective system (20) according to Claim 7, wherein the width (d) of the el-ementary cell is in the range between 10 and 15 m, and the height (h) of the ele-mentary cell is in the range between 5 and 10 m.

9. Protective system (20) according to Claim 7 or 8, wherein the inner grid plane (E1) and outer grid plane (E2) are interconnected by diagonal beams (4, 5) that respectively extend from a node (30) of one grid plane (E1) to a node (30) of the other grid plane (E2).

10. Protective system (20) according to one of the foregoing Claims, wherein the protective grid (22) is supported on the ground (26) by means of a plurality of beams (1, 2).

11. Protective system (20) according to one of the foregoing Claims, wherein the beams (1 to 5) of the protective grid (22) have a double-T or rectangular cross-section, the dimensions of which are in the range between 400 and 1000 mm.

12. Protective system (20) according to one of the foregoing Claims, wherein the distance (a) between the protective grid (22) and the building wall (24) is in the range between 0.3 and 2.0 m.