WO2023094947A1

WO2023094947A1 - Device for connecting construction elements

Info

Publication number: WO2023094947A1
Application number: PCT/IB2022/061066
Authority: WO
Inventors: Nicola BURATTI; Claudio MAZZOTTI; Andrea Vittorio POLLINI; Luca Pirazzini
Original assignee: Alma Mater Studiorum - Universita' Di Bologna; Sismo Solution Srl
Priority date: 2021-11-24
Filing date: 2022-11-17
Publication date: 2023-06-01
Also published as: IT202100029714A1

Abstract

A device (1) for connecting construction elements, comprising a first member (2), intended to be connected to a first construction element, and a second member (3), intended to be connected to a second construction element, so that, in use, the device (1) is interposed between said first and second construction elements so as to create a permanent connection between them; the first member (2) is configured so as to define a seat inside which the second member (3) is at least partially inserted. The device (1) also comprises at least one dissipation unit (4), interposed between said first member (2) and said second member (3), configured to absorb the energy which, due to external stress, is transmitted by said first construction element to said second construction element. The dissipation unit (4) comprises a plurality of dissipative elements (5), substantially arch-shaped, fixed to the first member and the second member.

Description

“DEVICE FOR CONNECTING CONSTRUCTION ELEMENTS”.

TECHNICAL FIELD OF THE INVENTION

The present invention concerns a device for connecting construction elements.

More in detail, the present invention concerns a device for connecting construction elements with energy dissipation capacity and consequent reduction of stress on the structural elements.

DESCRIPTION OF THE PRIOR ART

Seismic events of considerable intensity often highlight the high vulnerability of many existing buildings, e.g. prefabricated structures not built in accordance with anti-seismic regulations.

One of the measures currently implemented to limit the potential damage caused by intense external stress applied to structures, including, but not limited to, seismic events, is the use of dissipative connecting devices, interposed between structural elements (e.g. pillars, beams, etc.), which have the function of internally absorbing the energy generated by the aforementioned stress, limiting transfer of such stress to the structural elements; this transfer would lead to structural part damage and/or to the occurrence of potentially dangerous situations for people and/or things.

There are various types of energy dissipation, damping and absorbing devices on the market, e.g. hysteretic, metallic, impeded instability, fluid-viscous devices and others.

Each of these has advantages and disadvantages, depending on the intended scope of application.

With particular reference to devices of the mechanical type (also called hysteretic devices), a known type generally comprises a first member and a second member, which can be connected to respective portions of two distinct structural elements, e.g. with screw-type connections.

The aforesaid first member and second member are, in turn, mutually connected via at least one mechanical fuse, i.e. a metal element which, when placed between the aforesaid members and subjected to a given amount of stress, deforms plastically, thus absorbing a given amount of energy and thus preventing it from being transmitted through the connection between structural elements.

In a specific type of device, the metal connecting elements between the first member and the second member, made of steel, are basically crescent-shaped or arc-shaped; they are able to effectively dissipate a given amount of energy, thanks precisely to steel yielding achieved when the stress intensity exceeds certain values. Such devices of the known type, however, have some drawbacks deriving mainly from the way in which the one or more dissipative metal elements, intended to undergo yielding when external stress is applied, are connected to the aforesaid first member and second member.

More particularly, in devices of the known type, the aforementioned connection between the dissipative elements and the two members is not able to ensure that the relative displacement, which occurs due to the effect of stress, between the first member and the second member, takes place in a controlled way.

In other words, when external stress is applied, there is a risk for the two members to move one with respect to the other in an unpredictable way, and there is no guarantee that the desired energy absorption effect is not also associated, which is in fact highly probable, with displacements, or deformations of the construction or building, of an unknown entity and therefore potentially risky.

It should also be added that devices of the known type are constructively rather complex, and their installation and removal, in and from structures, are often labour-intensive and difficult.

OBJECTS OF THE INVENTION

The technical aim of the present invention is to improve the state of the art in the field of dissipative type devices between connecting construction elements.

Within such technical aim, an object of the present invention is to provide a device for connecting construction elements which is improved from the point of view of the relative displacement which occurs, between members that constitute it, due to external stress.

Another object of the present invention is to provide a device for connecting construction elements wherein the relative displacement between the members that compose it, due to the effect of external stress, occurs in a controlled and predictable manner.

Another object of the present invention is to develop a device for connecting construction elements which allows for improvement of the seismic behaviour of buildings, structures, and the like, in which it is installed.

Another object of the present invention is to make available a device for connecting construction elements which can be installed and replaced easily in the event of damage.

A further object of the present invention is to provide a device for connecting construction elements constructively simple and cost efficient.

This aim and these objects are achieved by the device for connecting construction elements according to the attached claim 1.

The device comprises a first member, intended to be connected to a first construction element, and a second member, intended to be connected to a second construction element, so that, in use, the device is interposed between the first construction element and the second construction element so as to create a permanent connection between them.

The device includes at least one dissipation unit, interposed between said first member and said second member, configured to absorb the energy which, due to external stress, is transmitted by the first construction element to the second construction element, and vice versa.

The first member is configured so as to define a seat inside which the second member is inserted, at least partially; additionally, the first member and second member are mutually movable along a direction of relative displacement.

According to one aspect of the invention, said dissipation unit comprises a plurality of dissipative elements, substantially arc-shaped, fixed to the first member and to the second member in a mirror-like manner with respect to the second member.

More in detail, in a preferred embodiment of the invention, the aforementioned dissipation unit comprises four dissipative elements fixed, to the first member and to the second member, with their respective hollow parts opposed two by two, on one side and the other with respect to the second member.

In this way, the four dissipative elements define and implement two sorts of tubular bodies, interposed between the first member and the second member.

According to another aspect of the invention, the device comprises guide and limit means of the relative displacement between the first member and the second member, configured to limit the extent of the possible relative displacement between the first member and the second member, and furthermore, to define and impose a forced direction of such relative displacement.

More in detail, the guide and limit means comprise at least one slot, made in the second member, and at least one pin, integral with the first member, slidingly engaged inside said at least one slot.

Thanks to this feature, which works synergistically with the particular arrangement of the dissipative elements, the deformation of the dissipative elements takes place in a very controlled way (in particular, according to mutually sliding planes), which is therefore much more predictable than in known solutions, so as to increase the safety guarantees provided by the device.

These advantageous effects are also obtained with a constructively simple and cost- efficient solution.

Dependent claims refer to preferred and advantageous embodiments of the invention.

BRIEF DESCRIPTION OF DRAWINGS.

The features of the invention will be better understood by anyone skilled in the art from the following description and accompanying drawings, provided by way of non-limiting example, wherein:

Figure 1 is an axonometric view of the device for connecting construction elements according to the present invention; figures 2, 3, 4 are more axonometric views, from different angles, of the same connecting device; figure 5 is a side, partly sectioned, view of the connecting device; figure 6 is a front view of the connecting device; figure 7 is a top view of the connecting device; figures 8, 9, 10 are respective side views of the connecting device, wherein the first member and the second member are in different relative positions with respect to each other; figure 11 is a force-displacement graph which illustrates the hysteretic behaviour, observed experimentally, of the connecting device according to the invention.

EMBODIMENTS OF THE INVENTION

With reference to the attached figure 1, a device for connecting construction elements according to the present invention is globally indicated by 1.

The device 1 comprises a first member 2.

The first member 2 is intended to be connected to a first construction element (e.g. a construction element of a building, a structure, or the like).

The device 1 further comprises a second member 3.

The second member 3 is intended to be connected to a second construction element (e.g. a construction element of a building, a structure, or the like).

In use, therefore, the device 1 is interposed between the first construction element and the second construction element, creating a permanent connection between them, removable, however, if needed, e.g. for maintenance requirements.

The first member 2 and the second member 3 are preferably, but not exclusively, made of steel.

The device 1 furthermore comprises at least one dissipation unit, globally indicated by 4.

The first member 2 is connected to the second member 3 by means of the aforementioned dissipation unit 4; in other words, the dissipation unit 4 is interposed between the first member 2 and the second member 3.

As will become clearer hereinafter, according to the invention the dissipation unit 4 is configured to absorb the energy which, due to external stress (e.g. an earthquake of a certain magnitude, a strong gust of wind, an explosion, or others), is transmitted from the first construction element to the second construction element, or vice versa, in relation to their specific location/function within the construction or structure.

In more detail, the absorption of energy by the aforementioned dissipation unit 4 allows the transmission of stress to be limited (in a substantial way) from the first to the second construction element (or vice versa), thus preventing these elements - or possibly others connected to them - from suffering damages, which could jeopardize the safety of people or things, e.g. inside a building.

In a preferred embodiment of the invention, corresponding to that illustrated in the attached figures, the dissipation unit 4 comprises a plurality of dissipative elements 5.

The aforementioned dissipative elements 5 connect the first member 2 to the second member 3, and are arranged, inside the device 1, in the manner explained below.

The first member 2 is configured in such a way as to define a seat within which the second member 3 is, at least partially, inserted.

Furthermore, the first member 2 and the second member 3 are mutually movable along a relative displacement direction A.

In more detail, the first member 2 comprises a fork-like body 6, or a substantially fork-like one.

Furthermore, the first member 2 comprises a first connecting portion 7, to which the fork-like body 6 is rigidly fixed.

The first connecting portion 7 is intended to be connected to a specially provided part of the first construction element.

The fork-like body 6 comprises, in turn, a first prong 8 and a second prong 9.

The first prong 8 and the second prong 9 are arranged opposite each other, and have a symmetrical/mirror-like shape (with respect to an ideal plane of symmetry passing through the first connecting portion 7.)

The first prong 8 and the second prong 9 are preferably flat, or substantially flat, and also plane-parallel. The first prong 8 and the second prong 9 define, between them, a seat of suitable width.

For example, the fork-like body 6 can consist of a single plate, or sheet, substantially folded into a "U" shape, so as to define the aforementioned first prong 8 and second prong 9.

Furthermore, the fork-like body 6 comprises an intermediate portion 10 (flat or substantially flat), which connects the first prong 8 to the second prong 9.

The first connecting portion 7 comprises a base 11, suitable for connection with the fork-like body 6 (in particular with its intermediate portion 10.)

The connection between the fork-like body 6 and the first connecting portion 7 can be achieved, for example, via screw means 12.

These screw means 12 can comprise a threaded stem 13, integral with the base 11 of the first connecting portion 7, inserted in a specially provided hole in the intermediate portion 10.

Furthermore, the aforesaid screw means 12 can comprise a locking nut 14, screw- tightened on the aforesaid threaded stem 13 (with the possible interposition of a washer 15).

The first connecting portion 7 can comprise, for example, a first through hole 16, for the insertion e.g. of a screw suitable for connection to the first construction element (or the insertion of other suitable connecting members.)

The second member 3 is housed inside the fork-like body 6, i.e. in the seat comprised between the first prong 8 and the second prong 9 of the fork-like body 6. The second member 3 has a flat, or substantially flat, shape.

The second member 3 can comprise (or consist of) a rectangular, or substantially rectangular, plate.

From the dimensions point of view, the second member 3 can have, for example, a length substantially equal to that of the prongs 8, 9 of the first member 2, and a width equal to, or smaller than, that of the prongs 8, 9.

The second member 3 comprises a second connecting portion 17.

The second connecting portion 17 is intended to be connected to a specially provided part of the second construction element.

Preferably, the second connecting portion 17 is provided at one end of the second member 3, and can comprise, for example, a second through hole 18, for inserting a screw, or other suitable connecting members.

According to one aspect of the invention, each one of the dissipative elements 5 of the device 1 is substantially arc-shaped (or substantially crescent-, or "C"-, shaped.) Each one of the dissipative elements 5 is made of steel.

In more detail, each dissipative element 5 comprises (or is constituted by) a respective steel sheet folded into an arc (or substantially crescent-, or "C"-, shaped.)

Each dissipative element 5 comprises two parallel legs connected by a curved portion; according to an aspect of the invention, the ratio of the thickness of the sheet to its curvature radius is less than 0.25/0.3.

This ensures that the behaviour, under stress, of each dissipative element 5 is of the elastic-perfectly plastic type.

According to another aspect of the invention, the length of the parallel legs of each of the dissipative elements 5 is at least equal to the possible relative displacement between the first member 2 and the second member 3 along the relative displacement direction A: this characteristic also guarantees that the behaviour, under stress, of each dissipative element 5 is of the elastic-perfectly plastic type.

In a preferred embodiment of the invention, shown in the figures, the device 1 comprises four dissipative elements 5 of the type described.

The dissipative elements 5 are fixed both to the first member 2 and to the second member 3.

In particular - with reference to figure 5 - the dissipative elements 5 are fixed to the first member 2 and to the second member 3 in a mirror-like way, in pairs opposed two by two, with respect to the second member 3.

In more detail (see in particular figure 5), the dissipative elements 5 are fixed, to the first member 2 and to the second member 3, in a mirror-like way, in pairs opposed two by two with respect to a plane, passing through the second member 3, and which contains the aforementioned relative displacement direction A.

In other words (again with reference to the side view of figure 5) the four dissipative elements 5 are fixed, with their respective hollow parts opposite each other, on one side and on the other with respect to the second member 3.

Each dissipative element 5 therefore has one leg fixed to the first member 2, and the other leg fixed to the second member 3.

In this way, the four dissipative elements 5 define and implement two sorts of tubular bodies, interposed between the first member 2 and the second member 3, and mutually connecting them.

The dissipative elements 5 are also arranged according to a symmetrical configuration with respect to a plane perpendicular to said relative displacement direction A.

This ensures that the behaviour, under stress, of each dissipative element 5 is of the elastic-perfectly plastic type, and characterized by a symmetrical hysteretic cycle, with equal force in traction and compression.

The four dissipative elements 5 are fixed to the first member 2 and to the second member 3 - respectively, via first screws 19.

Preferably, each dissipative element 5 is fixed to the first member 2 and to the second member 3 -respectively, by means of six first screws 19 (three of which for connection to the first member 2, and three for connection to the second member 3).

The first screws 19 are aligned in threes along respective directions perpendicular to the largest dimension of the prongs 8, 9 of the first member 2 and of the second member 3 (and therefore, perpendicular to the relative displacement direction A). According to another aspect of the invention, the device 1 comprises guide and limit means 20 of the relative displacement between the first member 2 and the second member 3.

The aforesaid guide and limit means 20 are configured to limit the extent of the possible relative displacement between the first member 2 and the second member 3, and furthermore, to define and impose a forced direction for this relative displacement.

They therefore have the function of ensuring that the deformation of the dissipative elements 5 occurs in a fully controlled manner.

In more detail, the guide and limit means 20 comprise at least one slot 21, 22 made in the second member 3.

Furthermore, the aforesaid guide and limit means 20 comprise at least one pin 23, 24, integral with the first member 2, slidably engaged inside the aforesaid at least one slot 21, 22.

The sliding of the at least one pin 23, 24 inside the at least one slot 21, 22 limits the extent of the relative displacement between the first member 2 and the second member 3, along the direction A, so that it does not exceed a pre-set maximum value; the latter depends, in particular, on the type of application in which the device 1 is installed according to the invention.

In a preferred embodiment of the invention, which corresponds to that illustrated in the attached figures, the guiding and limiting means 20 comprise, more particularly, a first slot 21 and a second slot 22, obtained in the second member 3.

In particular, the first slot 21 and the second slot 22 are positioned so that their respective longitudinal axes coincide.

The first slot 21 and the second slot 22 are made, in the second member 3, on opposite sides with respect to its (substantially central) area intended for connection to the dissipative elements 5.

Furthermore, in this preferred embodiment, the guide and limit means 20 comprise a first pin 23 and a second pin 24, both integral with the first member 2; in particular, the first pin 23 and the second pin 24 are integral with the first prong 8 and with the second prong 9 of the fork-like body 6 of the first member 2.

The first pin 23 and the second pin 24 are fixed to the first member 2 and to the second member 3 - respectively, via the second screws 25.

The first pin 23 and the second pin 24 are fixed to the first member 2, on opposite sides with respect to its (substantially central) area intended for connection to the dissipative elements 5. For example, the second screws 25 are engaged in respective through holes provided in the first prong 8 and second prong 9, and the respective shanks are engaged in respective threaded holes made on the heads of both shaft ends of the first pin 23 and of the second pin 24 (figure 5).

Alternatively, a first pin 23 and a second pin 24 could be used consisting of stud screws, locked at the ends by respective nuts, which abut on the outer surfaces of the first prong 8 and the second prong 9.

According to another aspect of the invention, and again for the purpose of limiting and defining the direction and extent of the relative displacement between the first member 2 and the second member 3, the guide and limit means 20 comprise pairs of first bushings 26 and second bushings 27, inserted along the first pin 23 and the second pin 24 - respectively, on opposite sides with respect to the second member 3.

The first bushings 26 and the second bushings 27 therefore abut both against the inner surfaces of the prongs 8,9 of the first member 2 and against the surfaces of the second member 3.

Thanks to this measure, any movements between the first member 2 and the second member 3 in a direction perpendicular (or having a perpendicular component) to the relative displacement direction A are prevented, as they are unwanted, and could generate harmful effects for the device 1 and for the structure or construction in which it is installed.

The way of using the device 1 is, in the light of what has been described, entirely intuitive.

As mentioned, the first connecting portion 7 and the second connecting portion 17 are fixed to respective parts of a first and a second element of a construction, or of a structure, so that the device 1 is interposed between them.

Figure 9 shows the device 1 in a non-deformed configuration (or in any case, one in which it is not subjected to external stress exceeding a given extent).

Under the effect of external stress of a given extent, on the other hand, the device 1 behaves as illustrated in figures 8 and 10, i.e. the first member 2 and the second member 3 are displaced with respect to each other, and this displacement is possible only along the direction of displacement A, causing deformation of the dissipative elements 5.

Figures 8 and 10 in particular show the two opposed travel limit configurations.

In these figures deformations are clearly evident that are undergone by the dissipative elements 5, the respective legs of which move according to parallel planes which mutually slide (i.e. the planes of the surfaces of the prongs 8, 9 of the first member 2 and the surfaces of the second member 3).

When the external stress exceeds a certain amount, the yielding of the material of the dissipative elements 5 (which, thanks to the characteristics of the device 1, takes place with an elastic-perfectly plastic behaviour) allows the external stress energy to be absorbed, whose transmission between construction elements is thus considerably limited.

Furthermore, the guide and limit means 20 limit the extent of this displacement, which, in its maximum permissible value, is substantially defined by the longitudinal dimension of the first slot 21 and of the second slot 22 of the second member 3, within which the first pin 23 and the second pin 24 of the first member 2 - respectively, are free to slide.

The invention, thus conceived, enables to obtain important technical advantages.

In the first place, the particular arrangement (symmetrical with respect to the second member 3) of the dissipative elements 5 and the configuration of the guide and limit means 20 operate synergistically so that the relative displacement between the first member 2 and the second member 3 occurs in a very controlled and predictable way, according to a single predetermined displacement direction, and also with limited extent displacement.

Therefore, between the two members 2, 3, no uncontrolled displacements or deformations will occur which could cause risky situations for the construction. Furthermore, the shaping and arrangement of the dissipative elements allow to obtain, under the effect of external stress, a yielding of the dissipative elements 5 characterized by wide, symmetrical and stable hysteretic cycles both in terms of stiffness and in terms of resistance (figure 11).

Furthermore, the guide and limit means 20, in the event of yielding of the dissipative elements 5, ensure that the first member 2 and the second member 3 remain constrained to each other. Moreover, the guide and limit means 20 are sized according to the elements connected to the first member 2 and to the second member 3, and according to the application.

The constructive solution adopted for the device according to the invention is simple and cost-efficient, and all the components are connected by screw-type members; there are no welds.

Thanks to this constructive simplicity, also the installation and/or removal of the device 1, for maintenance/replacement purposes, are particularly quick and easy. It has thus been seen how the invention achieves the intended purposes.

The present invention has been described according to preferred embodiments, but equivalent variants can still be conceived without departing from the scope of protection of the attached claims.

Claims

1. A device (1) for connecting construction elements, comprising a first member (2), intended to be connected to a first construction element, a second member (3), intended to be connected to a second construction element, so that, in use, the device (1) is interposed between said first and second construction elements so as to create a permanent connection between them, at least one dissipation unit (4), interposed between said first member (2) and said second member (3), configured to absorb the energy which, due to external stress, is transmitted by said first construction element to said second construction element, or vice versa, said first member (2) being configured so as to define a seat inside which said second member (3) is inserted, at least partially, said first member (2) and second member (3) being mutually movable along a relative displacement direction (A), said dissipation unit (4) comprising a plurality of dissipative elements (5), substantially arch-shaped, fixed to said first member (2) and second member (3) in a mirror-like way with respect to said second member (3), wherein said first member (2) and second member (3) are mutually movable along a relative displacement direction (A), and wherein said dissipative elements (5) are fixed to said first member (2) and second member (3) in a mirror-like manner with respect to a plane passing through said second member (3) and containing said relative displacement direction (A), said device further comprising guide and limit means (20) of the relative displacement between said first member (2) and second member (3), configured to limit the extent of said relative displacement between said first member (2) and second member (3), and also to define, in a compulsory manner, said relative displacement direction (A) between said first member (2) and second member (3), characterised in that said guide and limit means (20) comprise at least one slot (21, 22), made in said second member (3), and at least one pin (23, 24), integral with said first member (2), slidingly engaged inside said at least one slot (21, 22).

2. A device (1) according to claim 1, wherein said dissipation unit (4) comprises four dissipative elements (5) fixed to said first member (2) and second member (3), with the respective hollow parts opposed two by two, on one side and the other with respect to said second member (3).

3. A device (1) according to claim 2, wherein said four dissipative elements (5) define and implement two kinds of tubular bodies, interposed between said first member (2) and second member (3).

4. A device according to claim 2 or 3, wherein said dissipative elements (5) are arranged according to a symmetrical configuration with respect to a plane perpendicular to said relative displacement direction (A).

5. A device (1) according to one of the preceding claims, wherein said first member (2) comprises a fork-like, or substantially fork-like, body (6) and a first connecting portion (7), to which said fork-like body (6) is rigidly fixed, said first connecting portion (7) being intended to be connected to a specially prepared part of said first construction element, said fork-like body (6) comprising a first prong (8) and a second prong (9) opposed to each other, and of mirror-like shaping.

6. A device (1) according to claim 5, wherein said second member (3) is housed in the seat comprised between said first prong (8) and said second prong (9) of said fork-like body (6), said second member (3) comprising a second connecting portion (17) intended to be connected to a specially prepared part of said second construction element.

7. A device (1) according to claim 1, wherein said guide and limit means (20) comprise a first slot (21) and a second slot (22), made in said second member (3) on opposite sides with respect to the provided area for connection to said dissipative elements (5), the longitudinal axes of said first slot (21) and second slot (22) being coincident.

8. A device (1) according to claim 7, wherein said guide and limit means (20) comprise a first pin (23) and a second pin (24), both integral with said first member (2), fixed to said first member (2) on opposite sides with respect to the area provided for connection to said dissipative elements (5). 16

9. A device (1) according to claim 8, wherein said guide and limit means (20) comprise pairs of first bushings (26) and second bushings (27), inserted along said first pin (23) and second pin (24), respectively, on opposite sides with respect to said second member (3), so as to prevent possible displacements between said first member (23) and second member (24) according to a direction perpendicular to said relative displacement direction (A).

10. A device (1) according to one of the preceding claims, wherein each of said dissipative elements (5) comprises two parallel legs connected by a curved portion, and wherein the ratio between the thickness of the sheet and its curvature radius is less than 0.25/0.3.

11. A device (1) according to the preceding claim, wherein the length of the parallel legs of each of said dissipative elements (5) is at least equal to the possible relative displacement between said first member (2) and second member (3).