WO2020096473A1

WO2020096473A1 - Connector for explosion protection system for constructions

Info

Publication number: WO2020096473A1
Application number: PCT/PT2019/050042
Authority: WO
Inventors: Gabriel De Jesus GOMES; Vitor Manuel Martins PEREIRA; Eduardo Nuno Brito Santos JÚLIO
Original assignee: Instituto Superior Técnico; Academia Militar
Priority date: 2018-11-07
Filing date: 2019-11-05
Publication date: 2020-05-14
Also published as: PT115138A; PT115138B

Abstract

A connector for protecting buildings against explosions, comprising: a dissipator (5) for absorbing the energy of the explosion by plastic deformation; an inner body (3) that includes a base and one or more lateral surfaces to contain the dissipator; an outer body (1) that includes a base and a lateral surface to contain and envelop the inner body; in which the inner body (3) and the outer body (1) are engaged linearly and slidingly, and locked apart from the inner body and outer body. The connector also includes a guide (2) for linearly engaging the inner body (3) in the outer body (1). The guide (2) includes a slot in the inner body (3) or in the outer body (1) and a pin (4) for sliding linearly in said slot of the outer body (1) or inner body (3) respectively. The connector also has one or more fastening orifices (7) and a cutting element (6).

Description

DESCRIPTION

CONNECTOR FOR EXPLOSION PROTECTION SYSTEM

FOR CONSTRUCTIONS

D OM I N I T CN I C O

[0001] The present disclosure, inserted in the technical field of civil engineering, refers to a system of protection of buildings, in particular buildings, against explosions that comprises a prefabricated reinforced concrete facade panel or other material with adequate capacity to deform by dissipating energy, connected to the building structure through connectors capable of absorbing energy from explosions, thus significantly reducing the actions transmitted to the structure and redistributing them at the floor level.

AN E CE D E N TE S

[0002] The analysis of several cases of buildings directly affected by explosions as well as of many studies developed on the subject allowed, among other findings, to realize that: 1) the elements of facade cladding (masonry, window frames, panels, others) present a much lower resistance than that of the supporting elements, resulting in their collapse before there are more serious consequences on the supporting structure; 2) the projection of fragments of elements from the facades into the interior of the buildings can be lethal, being an urgent problem to be controlled; 3) in a conventional explosion from the outside, the damage is primarily local (eg on a pillar) but can be translated into a global collapse (progressive collapse). [0003] For this reason, a series of protection solutions referred to in the literature are based on jacketing the elements with high performance concrete reinforced with fibers. However, these interventions are very intrusive and costly, so they are rarely applied to existing installations, in addition to not solving the problems previously described in 1) and 2). In order to reduce the weight of the protection solutions without impairing their energy absorption capacity, several researchers have focused on explosion barriers made of profiled steel panels, namely sandwich panels. The problem of fragmentation of walls (especially of unreinforced masonry) and glazed spans and the consequent possibility of injury to the occupants of the infrastructure, have been the subject of numerous studies, which are generally dedicated to: a) adding mass to the system, increasing the thickness with internal walls in masonry, concrete or metallic elements; b) addition of vertical steel elements, as a way to substantially reduce the free space for the wall system; c) use of fiber reinforced polymers (from English FRP - Fiber Reinforced Polymers), glued to the surface to better withstand the high stresses induced by the explosions. The first two have the disadvantage of involving significant disturbances to the occupants of the installation in terms of the time required for intervention and loss of interior space. The use of FRPs offers great benefits as a masonry reinforcement technique, allowing to increase the flexural strength outside the plane. Despite the increase in resistance obtained by the solutions presented above, the problem is that none of these systems truly solves the issue of vulnerability, possible local collapse and the potential global collapse of the structure.

[0004] On the other hand, the achievements presented here allow to absorb part of the energy of the explosion and to redistribute the remainder by the overall structure, at the floor level. In this way, it transforms it into an action equivalent to seismic or wind action, regulatory actions for which the structures are already dimensioned, protecting the supporting elements and ensuring structural stability. In addition, and not least, they also allow to mitigate the projection of fragments resulting from fragile elements normally contained in façades, as it functions as an encapsulation system.

[0005] These facts are presented here in order to better illustrate the technical problem solved by the present achievements.

GENERAL DESCRIPTION

[0006] The present disclosure refers to a system that dissipates energy from explosions that falls within the technical domain of Civil Engineering.

[0007] Current structures are not designed to withstand charges due to explosions, which is why the collapse of certain more vulnerable elements and / or in the vicinity of the explosion has a high probability of occurrence, with a high potential to form, following the first , progressive collapse mechanisms, which can lead to the total collapse of the structure. In contrast, the present achievements allow the absorption of most of the action generated by the explosion and the redistribution of the remaining value at the level of the structure's floors, thus requesting it as if it were a dynamic regulatory action (eg earthquake, wind), thus endowing it with the ability to resist the action of the shock wave caused by the explosion.

[0008] A connector for a building protection system against explosions is described, comprising: a heatsink to absorb the energy of the explosion by plastic deformation; an interior body comprising a base and one or more side surfaces for containing the heatsink; an outer body comprising a base and side surface for containing and enveloping the inner body; wherein the inner body and the outer body are fitted in a linearly slidable way and are blocked from separating the inner body and the outer body.

[0009] In a preferred embodiment, the connector for protecting buildings from explosions comprises a guide for linear fitting of the inner body to the outer body.

[0010] In a preferred embodiment, said guide comprises a groove in the inner body or in the outer body and a pin to slide linearly in said groove, respectively, in the outer body or in the inner body so that the inner body and the outer body fit together. linearly sliding and blocked form to separate the interior and exterior body.

[0011] In a preferred embodiment, the heatsink is tubes arranged transversely to the linearly sliding fitting movement between the inner body and the outer body.

[0012] In a preferred embodiment, said heatsink is thin-walled tubes with a circular, hexagonal or equivalent section.

[0013] In a preferred embodiment, the sections can be filled with foam, preferably metallic foam.

[0014] Said tubes may have a tubular section, open or closed, with a thin, empty wall or filled with metal foams or other material with plastic deformation capacity. Said tubes may contain additional tubes inside, with the same or different diameter, which in turn, they may contain other tubes, with the same or different diameter.

[0015] In a preferred embodiment, the heatsink is metallic, in particular aluminum alloys, mild steel (from English: mild Steel), or fiber reinforced composites (FRC).

[0016] In a preferred embodiment, the connector comprises one or more holes for fixing.

[0017] In a preferred embodiment, the connector comprises a cutting element to drive the metal structure.

[0018] Also described is a system for protecting buildings against explosions, which comprises a facade panel and a plurality of connectors in which the panel is coupled to the plurality of connectors for supporting said panel.

[0019] In a preferred embodiment, the building protection system against explosions comprises the reinforced concrete facade panel.

BRIEF DESCRIPTION OF THE FIGURES

[0020] For an easier understanding of the present disclosure, the figures are attached, which represent preferential realizations that, however, do not intend to limit the object of this disclosure.

[0021] Figure 1: represents an embodiment of an exemplary detail of the energy absorption connector in which:

(1) Represents the upper part of the metal box;

(2) Represents the guidance system;

(3) Represents the bottom of the metal box;

(4) Represents the guide screw;

(5) Represents thin-walled tubular elements;

(6) Represents the retaining pin; (7) Represents the fixing hole.

[0022] Figure 2: perspective of an embodiment of the present invention in which:

(8) Represents the connector;

(9) Represents the facade panel;

(10) Represents a pillar;

(11) Represents a slab.

[0023] Figure 3: schematic representation of realizations with possible combinations of tubes for placement in the connector housing, in which the figures in the figure correspond to the size of the tubes in mm.

[0024] Figure 4: schematic representation of realizations of types of boxes.

[0025] The following tables represent realizations with dimensions of each type of box, and realizations with the main properties of the materials used in the present invention.

[0026] Table 1: Projects with the dimensions of each type of box

[0027] Table 2: Main properties of the materials used in the present invention (according to the supplier).

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DETAILED DESCRIPTION

[0028] The use of prefabricated panels in facade coverings is not new and presents itself as a fast and efficient application solution. However, traditional panels are applied or overlaid, on the exposed faces of support elements and floors, and rigidly attached to the structure. The referred solution, when transferring all the imposed loads to the elements in contact, does not truly protect the critical elements or prevent the local collapse. The protective solutions employed more frequently are based on the addition of planar elements (dissipative cores in sandwich solutions or metallic elements) in order to mitigate the transfer of loads, but once the dissipative capacity is exceeded, the problem persists.

[0029] The present disclosure makes it possible to keep the cladding panel without direct contact with the elements to be protected, using dissipating supports at floor level, with a sufficient stroke to accommodate (by compression) the intensity of a given explosion. The advantages of the present realizations are evident, both in the protection of critical elements, and because it allows the use of the space between the cladding panel and the structure for thermal and / or acoustic insulation. As soon as the cladding panel is requested, it acts on the supports, which by compression begin to deform the material contained within. This process allows the partial or total absorption of the energy transmitted by the explosion, depending on its magnitude and the

2 connector sizing. The residual part will be transmitted to the structure at the level of the floors, thus mobilizing its capacity resistant to horizontal actions.

[0030] The connectors, according to the present realizations, are formed by a metallic box, with two parts (1,3), thin-walled tubular elements, metallic or other ductile material, in number and variable geometry (5) , placed inside said box. The shortening of the box without dimensional variation in the orthogonal directions is guaranteed by a guide system (2,4) whose linear dimension represents the available stroke for dissipation. The shortening of the connector exploits the plastic deformation capacity of the preferably tubular elements, confined by the box. The aforementioned guide system also limits the maximum widening, preventing the facade panel from falling out of the building due to the negative phase of the shock wave (suction). The connector preferably also includes a hole for placing a retaining pin (6), dimensioned to work by cutting, when a certain level of stress is exceeded. Its insertion in the connector prevents it from shortening due to actions other than explosion. Together with the guide screw (4), it simultaneously maintains the exterior alignment of the facade panels. Finally, the connector preferably has a hole for fixing it to the facade panel (7), ensuring the cohesion of the system.

[0031] Below, the results obtained with preferred realizations are described, the results of which are documented in figures 3-4 and in the tables of the present disclosure.

[0032] The quasi-static response of the different tube arrangements eligible for placement in the connector housing has been studied. Compression tests in steady state

3 quasi-static tests were carried out on an Instron 8800D universal testing machine with an adjustable hydraulic clamping system and 250 kN of load capacity. The load was applied with displacement control, and a speed of 0.4 mm / s was prescribed. Both the applied load and the relative displacement between heads were recorded using a data logger, with a data acquisition rate of 10 Hz. The specimens were tested up to a displacement level that preceded the box's closing limit, avoiding - the maximum deformable stroke of the connector is exhausted, which corresponds to an abrupt increase in the applied load - likely to damage the test instrument. In order to determine the arrangement with the best energy absorption characteristics, it was decided to test the configurations in the first line of Figure 3, selecting the most advantageous one. Once the lines evolve with the introduction of the same changes for all its elements, the next step was to analyze the column that corresponds to it and choose the element that brings together the best energy absorption characteristics.

[0033] Energy performance was assessed using indicators such as total energy absorption (TEA), specific energy absorption (SEA), average crushing force (MCF), crushing force efficiency (CFE), crushing efficiency (CE), effective work (W _ef) and energy absorbed per unit height (EHL), which are referenced in several articles published in this area. In terms of energy absorption, according to table 3, arrangement 1E presented the best behavior and, according to table 4, arrangement 1E would be the worst option. However, this was the arrangement chosen to place in the connector box evaluated in the testing phase using

4 explosives, due to its simple configuration, deformable stroke and resistant capacity under the prescribed explosive test conditions.

[0034] Table 3: Energy absorption characteristics of compression tests on quasi-static regime - ^the line I

[0035] Table 4: Energy absorption characteristics of quasi-static compression tests - column E

[0036] When submitted to the tests using explosives, whose plan and synthesis of results are shown in table 5, it was found that:

5 • The Protection System (SP) showed an excellent behavior in terms of distribution of the load from the explosions and subsequent routing to the Energy Absorption Connectors (CAE), with no localized deformation phenomenon;

• The deformation recorded in the tubular elements of the lower layers of the PPAs was very low and allows us to conclude that the use of this type of SP materializes a means of reducing the transmission of the load applied to the structure to be protected; the deformation of the PPAs also indicated the adequate stiffness ratio between the panel and the PPAs, allowing both to be deformed, absorbing the energy from the explosion;

• The obtained deformation modes were similar to those of the quasi-static compression test; thus, it is considered that the compression test meets the conditions to reproduce the effects of an explosive test on the PPAs developed in the present study;

• The reduction in the maximum arrow of the façade panel with the introduction of the PPAs was greater than 25% - it is estimated that it can reach 30% under optimal test conditions; the use of this type of CAE clearly indicates the possibility of taking better advantage of the deformation capacity of the reinforced concrete panels used, and the increase in the level of protection given to the structures; for the lower load level (NC), the SP absorbed energy mainly through the flexural deformation of the facade panel; for the upper NC (about 54% higher than the lower NC), the panel deformation increased residually compared to the reference test (10%) and the maximum displacement of the SP increased considerably (75%); the increase in maximum displacement was absorbed in its great

6 most due to the deformation of the connectors; PPAs proved to be effective in absorbing the increase in energy associated with the increase in NC. [0037] Table 5: Synthesis of test results using explosives.

7 [0038] The achievements described are combinable with each other. The present invention is not, of course, in any way restricted to the achievements described in this document and a person with average knowledge of the area will be able to foresee many possibilities for modifying it and replacing technical characteristics with equivalent ones, depending on the requirements of each situation, as defined in the appended claims. The following claims define additional realizations of the present description.

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Claims

1. Connector for building protection system against explosions characterized by comprising: a heatsink (5) to absorb the energy of the explosion by plastic deformation; an inner body (3) comprising a base and one or more side surfaces for containing the heatsink; an outer body (1) comprising a base and side surface for containing and enveloping the inner body; wherein the inner body (3) and the outer body (1) are fitted in a linearly slidable manner and are blocked from separating the inner and outer body.

2. Connector for protection of buildings against explosions according to the previous claim, characterized in that it comprises a guide (2) for linear fitting of the inner body (3) in the outer body (1).

Connector for protection of buildings against explosions according to any one of the preceding claims, characterized in that said guide (2) comprises a groove in the inner body (3) or outer body (1) and a pin (4) to slide linearly in said groove, respectively, in the outer body (1) or in the inner body (1) so that the inner body (1) and the outer body (3) fit in a linearly slidable and blocked way to separate from the inner body (3) and the outer body (1).

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Connector for protection of buildings against explosion according to any one of the preceding claims, characterized in that the heatsink (5) is a tube arranged transversely to the linearly sliding fitting movement between the inner body (3) and the outer body (D ·

Connector for protection of buildings against explosions according to any one of the preceding claims, characterized in that the heatsink (5) is thin-walled tubes with a circular cross-section.

Connector for the protection of buildings against explosion according to any one of the preceding claims, characterized in that the heatsink (5) is metallic, in particular in aluminum and steel alloys, mild steel, or fiber-reinforced composites.

Connector for the protection of buildings against explosion according to any one of the preceding claims, characterized in that the connector comprises one or more fixing holes (7).

Connector for protection of buildings against explosions according to any one of the preceding claims, characterized in that the connector comprises a cutting element (6) to drive the metal structure.

9. Explosion protection system for buildings, characterized in that it comprises a facade panel and a plurality of connectors according to any one of the preceding claims, in which the panel is coupled to the plurality of connectors for supporting said panel.

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10. Explosion protection system for buildings according to the previous claim, characterized in that the facade panel is made of reinforced concrete.

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