Anti-explosion protection system for damping barriers

Abstract

The present invention relates to an anti-explosion protection system based on containment barriers, which allows energy to be absorbed using a damping system formed by two walls that are connected by means of oscillators. According to the invention, the front wall (1) is supported by a system of bearings or a sliding surface (4) allowing the front wall to move relative to the second wall (2). The front wall receives the pressure wave and, owing to the movement of the mass of said front wall (1), a reduced pressure is transmitted to the rear wall (2), which is protected by the system. In said barrier, a large part of the energy from the explosion is transformed into the kinetic energy of an oscillating mass.

Description

ANTI-EXPLOSION PROTECTION SYSTEM FOR DAMPING BARRIERS RELATED APPLICATION The present application is the Canadian National Phase Entry of International Patent Application SN: PCT / ES2018 / 070267, entitled "ANTI-EXPLOSION" PROTECTION SYSTEM FOR DAMPING BARRIERS", filed March 28, 2018, which claims benefit of priority to Spanish Patent Application serial number: P201730533, filed March 31, 2017. FIELD OF INVENTION The present disclosure relates to a system of blast loading protection by means of containment barriers. More particularly, the presently disclosed system allows energy to be absorbed by means of a damping system comprising two walls connected by oscillators, where a first wall receives the pressure wave and transmits a reduced pressure to the second wall by way of the movement of the mass of the first wall. BACKGROUND OF THE INVENTION Safety barriers are a possible alternative to the provision of an adequate safety distance and are a clear solution when there is not enough space available (a situation that occurs systematically within large transportation centers). Moreover, if the barriers are properly implemented, they can ensure a high level of safety. Barriers are mainly used to attenuate the pressure wave and stop high-velocity fragments that form as a consequence of an explosion and that which can come into contact with elements of the receiving system, for example elements which may require protection, such as people, equipment or secondary explosives. However, due to their configuration, protective barriers are often only useful if they are located at a short distance from the explosion; generally, not more than ten times the height of the barrier. Whereas for longer distances, protective barriers generally do not give rise to adequate attenuation. Barriers can have several forms: they can be covered or not, they can be cantilever walls or structures in the form of cubes in which one or more sides (and / or the roof) can be open or closed to prevent the entrance to the protected elements. Additionally, protective barriers may also be subdivided into continuous and porous barriers. For example, to mitigate the danger of coal dust explosions, coal deposits were kept damp. This procedure was substituted after the First World War by the mineral powder procedure, which, at first, was prescribed for coal veins with high volatility coals and then for all veins. These mineral powder barriers are intended to resist and limit the effects of explosions, which is also the object of the so-called water barriers that were introduced after the Second World War. In both mineral powder barriers and water trough barriers, a support frame is attached to the mine gallery shoring, on which the actual mineral powder barriers or individual water troughs are then placed. The explosion wave that strikes the barrier installation destroys the barrier, so that the applied mineral powder or water is distributed across the gallery and extinguishes the flame that follows the pressure wave. The state-of-the-art rigid retaining devices consist of so-called splice consoles (housing elements) which are mounted on part of the shoring with hook screws. On the splice consoles, crossbeams are fixed in the longitudinal direction to the gallery axis. In the blocking systems of the crossbeams, beams are inserted and run transversally to the axis of the gallery and are kept together by means of blocking systems. The beams mounted in this way are then used to install or suspend water troughs. Explosion barriers of this type of construction are costly as a result of the large number of them which must be installed in an underground mine. The aim is, therefore, to provide an explosion barrier, having a less expensive construction type. Other known protective structures such as bomb shelters consist of steel- reinforced concrete structures, usually mounted at ground level or below the ground, with special reinforced concrete walls having a large thickness. However, the disadvantage of conventional bomb shelters is that, because they are located at or below ground level, they are particularly susceptible to chemical attack, as the chemicals used normally used have a higher density than air and, therefore, accumulate in low locations near ground level. This problem was faced by the Israeli authorities during the Gulf War from 1990 to 1991, when it was necessary to warn the civilian population about how they could best shelter themselves in the event of a missile attack as the missiles were suspected of carrying chemical warheads. It would, therefore, be desirable to construct the upper parts of buildings, e.g. apartments and offices, in such a way that they would be explosion-resistant. However, this is not practical, as reinforced concrete walls built to the thickness normally required would be excessively expensive. Also known, are composite structures that include a grouping of hollow blocks with a plurality of intercommunicated holes filled with a mass of reinforced concrete. This type of construction using slag or concrete blocks are described in U.S. Patent No. 1,884,319 by Smith and No. 2,994.162 by Frantz. Smith describes the use of his structure to provide insulation against "heat, cold and humidity". Frantz states that his construction is simply easier to assemble than other block wall constructions. U.S. Patent No. 4,577,447 by Doran reveals a construction similar to those of the above patents but uses expanded polystyrene blocks. The Spanish patent application P9402107 reveals a hollow block formed by a mixture of mineralized wood shavings and concrete with a density not exceeding, approximately, 1 t per cubic meter, for the construction of a wall of blocks and reinforced concrete to absorb the energy of an explosion. Within the hollow blocks, there are openings in orthogonal directions which allow the reinforced concrete to be placed therethrough. Because the hollow block is load-bearing, it cooperates with the reinforced concrete to resist explosion forces. Also disclosed is a procedure for building an explosion-resistant wall which includes the following steps: the grouping of a plurality of the hollow blocks described above to form a wall. The blocks have in their interior vertical and horizontal holes, and it is possible to place the blocks one on top of another and one alongside another so that the vertical and horizontal holes of the adjacent blocks are aligned. An integral grid of concrete and reinforcing steel is formed in the interconnected vertical and horizontal holes, obtaining a composite wall construction with the hollow blocks and reinforced concrete, thus forming the grouping of a plurality of hollow blocks and forming an integral grid which gives the composite wall construction the ability to substantially retain its structural integrity in the presence of explosion forces of sufficient magnitude to destroy a wall of blocks and reinforced concrete that does not use such hollow blocks. Document EP 0009654 A1 describes an explosion-proof barrier in which two parallel walls are involved. Briefly, a chamber is defined between the two parallel walls, with a series of angular folds that act as shock-absorbing elements on the front wall, which can be displaced by the deformation of these elements, thus absorbing the energy received from the impact by plastic deformation. These types of structures are generally single-use, since once the internal structure has been deformed, the barrier does not return to its initial position, becoming useless or materially weakened against another subsequent impact. A similar situation occurs in the case of the invention patent WO 9830772, relating to a construction panel in which two external and extreme walls are defined between which an internal nucleus is established based on a honeycomb of cells. The structure disclosed therein is susceptible to deformation in the event of an explosion to absorb its energy. As noted above, these types of structures are generally single-use in nature, since once the internal structure has been deformed, the panel becomes unusable or materially weakened for resisting another impact. Document WO 2009085966 A1 also describes a structure designed to absorb the energy produced in explosions and similar, in which this structure is designed to work through flexure of vertical elements within the structure of the wall, not providing means of cushioning against impacts perpendicular to the wall, so its application is significantly different from the objective of this invention. U.S. Patent 6298607 describes a ventilated membrane to mitigate the effects of explosions, involving a highly complex structure, in which multiple inflatable and deformable chambers are defined, designed to cushion the effects of a possible explosion. As noted above, the structure involves a large number of flexible elements and intercommunicating chambers which must be watertight for proper operation, ultimately making the installation complex and consequently expensive. U.S. Patent US 3500773 describes a system for protection against the impact of projectiles involving a frontal and metallic wall designed to receive the impact in question. The wall is divided into sectors which are joined to a posterior wall that forms part of the structure to be protected, and where the union between both walls is made by means of elastic elements, such as springs. The elements limit the magnitude or distance which the metallic wall is able to be displaced with respect to the posterior wall. These elements that limit the distance or margin of displacement of the metal wall are embodied in metal profiles that occupy a considerable volume within the chamber that is defined between the anterior metal wall and the posterior wall, such that the aforementioned barrier that constitutes this structure is designed to behave in two well-differentiated operational phases. In an initial phase, the protection system has a merely elastic character, in which the metal plates participating in it move along complementary profiles against the elastic media until they come into contact with the profiles that function as stops associated with the concrete back wall. Thus, in this first phase, there is a small displacement of the metal plate that is subjected to a small impact, being able to return to its initial position by the elastic effect of the recovery media contained inside it. However, when it comes to more powerful impacts, the system behaves in a plastic way, that is to say, that the elements functioning as stops, arranged in the space defined between both walls, are deformed and flattened to allow the metal plates to move a greater distance, in such a way that, as in the other patents mentioned above, the structure is irreversibly damaged after the explosion. Consequently, this system presents a problem in which the following aspects should be highlighted: - Since it requires elements to function as stops between both walls , as well as to define a space or range of displacement with respect to this stop, the wall must have a large volume. - Its plastic behaviour in the event of powerful explosions makes it single-use. - The front wall, based on metal plates, is made of multiple independent plates, which complicates assembly. Finally, U.S. Patent 4718356 can be mentioned, in which a system is disclosed to protect a wall against damage caused by explosions, in which the wall itself can be displaced by the expansion wave of the explosion through guides perpendicular to it with a means of braking that opposes this displacement. Although this solution is effective against expansive waves, it does not plan for the impact of shrapnel or other objects which could damage the wall. At the same time, once the impact has been absorbed, the wall will be blocked and displaced with respect to its initial position, which would require a complex and consequently costly "re-assembly" process, if possible, such that the wall could withstand a new impact should it occur. The present disclosure is directed a barrier system against explosions based on elastic damping, in which much of the energy of the explosion is transformed into the kinetic energy of an oscillating mass, so that the system is not single-use, as described above, and can withstand multiple impacts without affecting its internal structure. The proposed system proves to be very effective and is formed from elements that are easy to manufacture and install. It is of a type that enables adequate integration into architecture and can be combined with windows that allow visualization of the damping system. A clear application of this can be the protection of control rooms. SUMMARY The following presents a simplified summary of the general inventive concept(s) described herein to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is not intended to restrict key or critical elements of embodiments of the disclosure or to delineate their scope beyond that which is explicitly or implicitly described by the following description and claims. A need exists for blast loading protection system for damping barriers that overcome some of the drawbacks of known techniques, or at least, provides a useful alternative thereto. In one aspect, there is provided a damping barrier system for blast load protection which, comprises a moveable first wall for receiving a pressure wave where the moveable first wall is supported on a surface which permits reversible movement of the moveable first wall responsive to the pressure wave relative to a second wall. The movable first wall and the second wall being operatively coupled by way of one or more intervening elastic dampers. In one aspect, there is provided a damping barrier system for blast load protection, which comprises a moveable first wall and a static second wall where the movable first wall is provided for receiving a pressure wave. The moveable first wall is supported on a surface which permits reversible movement of the moveable first wall responsive to the pressure wave relative to the static second wall. The movable first wall and the static second wall are operatively coupled by way of one or more intervening elastic dampers which remain with the elastic range throughout movement. In some embodiments, the moveable first is formed from a metal. In some embodiments, the elastic dampers allow oscillatory motion. In some embodiments, elastic dampers have at least one degree of freedom. In some embodiments, the elastic dampers are springs. In some embodiments, the springs are metallic. In some embodiments, the is an interface between the surface on which the movable first wall is supported allows the movable first wall to slide. In some embodiments, the surface on which the movable first wall is supported is one or more rails. In some embodiments, the movable first wall and the surface is intervened by one or more rollers. In some embodiments, the movable first wall and the surface is intervened by one or more roller bearings. In some embodiments, the second wall is part of a structure to be protected. In another aspect, there is provided a system for blast load protection using a damping barrier which comprises a moveable frontal wall for receiving a pressure wave where the frontal wall being supported on a sliding surface, or roller bearings and / or rails. The frontal wall is connected to a rear wall where the rear wall forms part of a structure to be protected. There is also provided a plurality of elastic dampers which connect the frontal wall to the rear wall. In one aspect, there is provided a system for blast load protection using a damping barrier which comprises a movable moveable frontal wall for receiving a pressure wave where the movable frontal wall is supported on a sliding surface, or roller bearings and / or rails. The movable frontal wall is operatively coupled to a static rear wall where the static rear wall forms part of a structure to be protected. There is also provided a plurality of elastic dampers which provide the operative coupling of the movable frontal wall to the static rear wall. In some embodiments, the frontal wall is metallic. In some embodiments, the elastic dampers are oscillators. In some embodiments, the oscillators have a (one) degree of freedom. In some embodiments, the dampers are springs. In some embodiments, the springs are metallic. Other aspects, features and / or advantages will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawing. DESCRIPTION OF THE FIGURE To complement the description and in order to give a better understanding of the characteristics of the invention, in accordance with a preferred example of its practical embodiment, a figure which forms an integral part of the description and represents for the purposes of illustration is provided and without limitation the following: Figure 1. is perspective view of the system representing the arrangement of the walls and oscillators with respect to the sliding surface. DESCRIPTION OF THE INVENTION With reference to Figure 1, the system has two walls joined together by a plurality of oscillators having a degree of freedom <semantics>(mi,ki,ci)<annotation encoding="application / x-tex">(m_i, k_i, c_i)< / annotation>< / semantics>. The front wall has a certain mass (the greater the mass, the better), for which it is conceived as a metallic element, to receive the pressure wave of an explosion and transmit it to the reaction wall, which would be made of concrete, with a reduced pressure thanks to the setting in motion of the mass of the front wall The front wall, which receives the shock wave, is supported by a system of wheels or bearings or rails, or supported on a sliding surface so that it can move independently of the rear wall. Therefore, the system is based on dissipating part of the energy generated by the explosion through setting in motion an initially static mass (the front wall). The rear wall can be part of the barrier system or directly part of the structure to be protected. The front wall can be made of steel which provides both high mass and adequate strength. The mass can be increased by adding metal boxes to the front wall to add soil, for example. The system can be integrated into the architecture in multiple ways that can include all types of metal surface treatments. Likewise, the system can be enhanced from an architectural point of view, leaving the oscillators visible, either from a side or through "windows" in the metal panel. A system of this type can be effective for protecting a control room, for example, at a reasonable cost. PREFERRED EMBODIMENT OF THE INVENTION The system of the present invention comprises a barrier formed by a frontal wall 1 preferably metallic, which receives the pressure wave at the time of the explosion, where the said frontal wall 1can be considered as a metallic element of a certain mass. The front wall 1, made of metal, is supported by a sliding surface 4 that enables its displacement and where this front wall 1 is in contact with a rear wall 2 preferably of concrete by means of a plurality of oscillators 3, of a single degree of freedom, which can be springs or similar. The barrier system works in such a way that at the time of the explosion, the front wall 1 receives a pressure wave that is transmitted to the rear wall 2 by means of the plurality of oscillators 3 interspersed between both walls due to the movement of the front wall 1, resulting in a reduced pressure on the rear wall 2, since only a part of the energy of the explosion is transformed into energy of deformation of the springs, the rest of the energy being dissipated in providing movement to the front wall. The sliding surface 4 can be replaced by a system of roller bearings or a system of sliding rails. To analyze the response of the oscillator system, the explosion can be treated as an impulse on the outer wall, i.e. the frontal wall 1 of metal. If the duration of the law of triangular pressures is short with respect to the period of the oscillators 3, as is the case, the impulse is equivalent to imposing an initial velocity on the plurality of oscillators 3 of a value equal to the value of the impulse divided by the mass. Under these conditions, assuming, in a simplified way and as an initial approximation, that the shock absorbers move synchronously, the equation of motion of the wall as a whole can be written as indicated in the following equation [Image disponible dans le document PDF, Image available in the PDF document] Where: ξ is the damping index; i is the impulse to the wall due to the explosion; <semantics>pr<annotation encoding="application / x-tex">p_r< / annotation>< / semantics> is the reflected pressure due to the explosion that is imposed on the barrier; <semantics>trf<annotation encoding="application / x-tex">t_{rf}< / annotation>< / semantics> is the duration of the equivalent triangular wave; <semantics>Awall<annotation encoding="application / x-tex">A_{wall}< / annotation>< / semantics> is the area of the wall affected by the pressure of the explosion; <semantics>ωn<annotation encoding="application / x-tex">\omega_n< / annotation>< / semantics> is the natural frequency of the system of 1gdl; <semantics>ωd<annotation encoding="application / x-tex">\omega_d< / annotation>< / semantics> is the natural damped frequency of the system of 1gdl; and <semantics>mi<annotation encoding="application / x-tex">m_i< / annotation>< / semantics> mass of each of the harmonic oscillators <semantics>M=∑mi<annotation encoding="application / x-tex">M = \sum m_i< / annotation>< / semantics>. The system can be appreciated in a simpler way by means of a numerical example. Example 1 Assuming a detonation, an explosive equivalent to 20 kg TNT located 3.00 meters from the wall, the reflected pressure, <semantics>pr<annotation encoding="application / x-tex">p_r< / annotation>< / semantics>, would be 3952 kPa, and the duration of the equivalent triangular law of pressures, <semantics>trf<annotation encoding="application / x-tex">t_{rf}< / annotation>< / semantics> would be 0.68 ms. Admitting that there are 4 steel springs per square metre of wall, that the springs have an average diameter of 25 cm(<semantics>D<annotation encoding="application / x-tex">D< / annotation>< / semantics>), 20 mm bar diameter, <semantics>d<annotation encoding="application / x-tex">d< / annotation>< / semantics>, and 9 coils(<semantics>N<annotation encoding="application / x-tex">N< / annotation>< / semantics>), the stiffness of the 4 springs would be: [Image disponible dans le document PDF, Image available in the PDF document] Regarding the mass of the system, it would be necessary to have the mass of the panel (MP) plus the mass of the 4 springs, so that per square meter, if it is assumed that the front panel is a steel plate of 40 mm thickness, the mass would be: [Image disponible dans le document PDF, Image available in the PDF document] Therefore, the angular frequency of the system and the damped angular frequency (assuming damping, consistent with a metallic structure of 1%) would be: [Image disponible dans le document PDF, Image available in the PDF document] [Image disponible dans le document PDF, Image available in the PDF document] By applying the expression of <semantics>x(t)<annotation encoding="application / x-tex">x(t)< / annotation>< / semantics>, the displacement due to the explosion and the corresponding reaction in the concrete wall can be determined. [Image disponible dans le document PDF, Image available in the PDF document] [Image disponible dans le document PDF, Image available in the PDF document] [Image disponible dans le document PDF, Image available in the PDF document] It is observed that a high load is obtained, but is compatible with the size of a conventional wall. For a wall height of 3.00 m, and assuming that the wall is simply supported and that the depth of the wall is 25 cm (a minimum value), the required reinforcement would correspond to a minimum amount, as can be seen in the following equation and it would not be necessary to have shear reinforcement: [Image disponible dans le document PDF, Image available in the PDF document] In order to evaluate what would be the difference compared to the unprotected wall, in the same case, one would have: [Image disponible dans le document PDF, Image available in the PDF document] [Image disponible dans le document PDF, Image available in the PDF document] [Image disponible dans le document PDF, Image available in the PDF document] [Image disponible dans le document PDF, Image available in the PDF document] The above expressions are obtained by means of an equivalent static analysis, simulating the wall, which is treated as a doubly embedded beam, as a system of one degree of freedom. It is observed that, without the protective barrier, the load acting on the wall is 40 times greater than for the scenario studied. It therefore follows that the proposed system is highly effective. In order to be able to support this level of load with a conventional solution, it would be necessary to have a wall of great thickness with buttresses, etc., giving rise to a very significant occupation of space. The system is, therefore, a barrier having reversible dampening means, in which much of the energy of the explosion is transformed into the kinetic energy of an oscillating mass. From the example given above, it can be deduced that damping barriers are an effective and promising alternative, which are also made up of elements that are easy to manufacture and install. It is of a type that enables adequate integration into architecture and can be combined with windows that allow visualization of the damping system. A clear application of this can be the protection of control rooms. Information as herein shown and described in detail is fully capable of attaining the above-described object of the present disclosure, the presently preferred embodiment of the present disclosure, and is, thus, representative of the subject matter which is broadly contemplated by the present disclosure. The scope of the present disclosure fully encompasses other embodiments which may become apparent to those skilled in the art, and is to be limited, accordingly, by nothing other than the appended claims, wherein any reference to an element being made in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural and functional equivalents to the elements of the above-described preferred embodiment and additional embodiments as regarded by those of ordinary skill in the art are hereby expressly incorporated by reference and are intended to be encompassed by the present claims. Moreover, no requirement exists for a system or method to address each and every problem sought to be resolved by the present disclosure, for such to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. However, that various changes and modifications in form, material, work-piece, and fabrication material detail may be made, without departing from the spirit and scope of the present disclosure, as set forth in the appended claims, as may be apparent to those of ordinary skill in the art, are also encompassed by the disclosure.

Claims

1. A damping barrier system for blast load protection, comprising: a moveable first wall and a static second wall; the movable first wall for receiving a pressure wave, the moveable first wall being supported on a surface which permits reversible movement of the moveable first wall responsive to the pressure wave relative to the static second wall; the movable first wall and the static second wall being operatively coupled by way of one or more intervening elastic dampers which remain with the elastic range throughout movement.

2. The damping barrier system of claim 1, wherein the moveable first wall is formed from a metal.

3. The damping barrier system of either one of claim 1 or claim 2, wherein the elastic dampers allow oscillatory motion.

4. The damping barrier system of claim 3, wherein the elastic dampers have at least one degree of freedom.

5. The damping barrier system of any one of claims 1 to 4, wherein the elastic dampers are springs.

6. The damping barrier system of claim 5, wherein the springs are metallic.

7. The damping barrier system of any one of claims 1 to 6, wherein an interface between the surface on which the movable first wall is supported allows the movable first wall to slide.

8. The damping barrier system of any one of claims 1 to 6, wherein the surface on which the movable first wall is supported is one or more rails.

9. The damping barrier system of any one of claims 1 to 6, wherein the movable first wall and the surface is intervened by one or more rollers.

10. The damping barrier system of any one of claims 1 to 6, wherein the movable first wall and the surface is intervened by one or more roller bearings.

11. The damping barrier system of any one of claims 1 to 10, wherein the second wall is part of a structure to be protected.

12. A system for blast load protection using a damping barrier, comprising: a movable moveable frontal wall for receiving a pressure wave, the movable frontal wall being supported on: a sliding surface, or roller bearings and / or rails; and the movable frontal wall is operatively coupled to a static rear wall, the static rear wall forming part of a structure to be protected; and a plurality of elastic dampers providing said operative coupling of the movable frontal wall to the static rear wall.

13. The system of claim 12, wherein the frontal wall is metallic.

14. The system of either one of claim 12 or claim 13, wherein the elastic dampers are oscillators.

15. The system of claim 14, wherein the oscillators have a (one) degree of freedom.

16. The system of any one of claims 12 to 15, wherein the dampers are springs.

17. The system of claim 16, wherein the springs are metallic.