IT201800004026A1 - LICORD DEVICE FOR CONSOLIDATION AND SEISMIC PROTECTION OF MASONRY BUILDINGS - Google Patents

Description

TITLE

LICORD DEVICE FOR CONSOLIDATION AND SEISMIC PROTECTION OF

MASONRY BUILDINGS

TECHNICAL FIELD

The present invention refers to the technical sector of the adaptation and improvement of structural or non-structural elements in existing buildings, when stressed by seismic events.

STATE OF THE ART

The current design criteria in areas with a high seismic risk try to limit the damage to structures under light or moderate earthquakes, while they admit the presence of damage even in life-saving conditions, in the case of major earthquakes.

In the latter eventuality, the need to abandon the building is determined, to allow it to be repaired and made safe again, almost always with high costs and long times.

Recently, in the field of research, another line of thought is spreading, known under the name of DAD (Damage Avoidance Design), which provides for a low degree of damage by virtue of controlled dynamic motions that reduce the intensity of seismic stresses.

This design technique is based on admitting and limiting rocking motions to avoid generalized damage to large parts of both new and existing buildings.

The out-of-plane movement mechanisms of masonry or prefabricated facades are particularly dangerous from the point of view of seismic safety.

If the connections between the walls or vertical elements are not appropriate, the building does not behave in the manner of a box, but out-of-plane motions are activated, well known to structural designers.

These out-of-plane motions are characterized by a much lower inertia than in-plane motions, and are associated with kinematic chains that can cause overturning if not effectively counteracted.

The consequences, as well as being serious for the integrity of the building itself, constitute a high potential danger to human life, and can damage adjacent buildings.

The traditional construction technique is based on the general presence of chains or tie rods, generally inserted at the height of the floors or roofs, to contain the out-of-plane mechanisms.

This expedient, also advocated by the regulations in force, exposes the chains or tie rods to the loss of effectiveness if the rocking action impressed by the seismic event produces on them increases in stresses that exceed their capacity for elastic deformation. , to get to permanent deformations and, in extreme cases, to overcome the yield strength, with the tearing of the chain.

Furthermore, even if it does not reach yield or break, the elongation of the chains or tie rods produces instability due to peak load in the return phase of the macroelement.

Non-structural elements must also be considered, such as objects of artistic and historical value, similar to rigid bodies that rock and need to be placed in safety in the presence of seismic actions.

The nature of the out-of-plane motion is complex and only an analytical / numerical approach, able to model the rocking phenomenon, can grasp it: in fact it can exhibit rebound phenomena due to the non-linearity of the boundary conditions of the rocking element, causing peaks of tension incompatible with the material, as well as overturning. In any case, as widely demonstrated in the scientific literature on the subject, the boundary conditions of rocking blocks, such as transverse walls or chains, crucially influence the dynamic response.

The complexity of the phenomena, the number of variables involved, and all the specificities of each individual event also make it difficult to establish adequate regulatory indications.

SUMMARY OF THE INVENTION

The purpose of the present invention is therefore to propose a device for the consolidation and seismic protection of masonry buildings that overcomes the limits of traditional techniques as regards the response to seismic events, with particular regard to the out-of-plane motions induced in the external walls of buildings.

Another purpose of the invention is to provide a device that allows to drastically reduce the uncertainties related to the evaluation of the behavior in the return phase of the wall, limiting the possibility that the chain or tie rod undergoes instability or plastic deformations due to the stresses of compression or traction.

Another object of the invention is to reduce the risk of tearing the chain or tie rod due to excessive deformability caused by the rocking motion.

A further object of the invention is to provide a device which offers at the same time superior functional characteristics with respect to the prior art in the event of seismic events, but does not activate for low intensity earthquakes, allowing the chain or tie to behave in a manner that is traditional, working in its own elastic range.

Yet another purpose of the invention is to propose a device that is simple to manufacture, install and subject to maintenance, control and replacement, in various types of buildings with methods similar to those envisaged in traditional construction techniques.

These and other purposes are fully achieved by a device for the consolidation and seismic protection of masonry buildings, of the type comprising a chain or metal tie rod suitable to be anchored at its ends, in a substantially horizontal configuration, to two walls or structural elements of said buildings, so as to interconnect them and prevent their mutual distancing in the face of seismic events, with said device comprising:

- an anchoring member of the chain or tie rod, associated with at least one end of the latter and spaced from one of said structural elements of the building;

- a reinforcing organ, having the shape of a plate, stably anchored to the same structural element of the building, so as to be parallel to the aforementioned anchoring organ, facing the latter and spaced by a predetermined height;

- collapsible coupling means, interposed between said anchoring member and said reinforcing member;

- constraint means with calibrated resistance, provided in said collapsible coupling means to lock them so as to stabilize the distance between said anchoring member and said reinforcing member, and in such a way that axial sliding of the aforesaid members is prevented coupling means collapsible up to a certain stress value, or to allow it beyond this value;

- elastic members, acting in an axial direction to the aforementioned chain or tie rod, to bias said anchoring member and reinforcing member in mutual displacement, according to a predetermined direction;

- viscous fluid energy dissipating members acting in the axial direction of said chain or tie rod, between said anchoring member and reinforcing member;

the aforementioned device being provided to define a rigid body for connection between said chain or tie rod and said structural element in the absence of axial stresses and up to a predetermined intensity thereof, beyond which, as a consequence of the failure of the aforementioned resistance constraint means calibrated and of the axial excursion of the aforesaid collapsible coupling means, an axial movement is allowed between said anchoring member and reinforcing member, opposed and taken up by said elastic members and progressively attenuated by the aforementioned viscous fluid energy dissipating members.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics of the invention will become evident from the following description of a preferred embodiment of the device for the consolidation and seismic protection of masonry buildings, of which the subject is concerned, in accordance with what is proposed in the claims and with the aid of the attached tables drawing, in which:

Fig. 1 illustrates, in schematic sectional side view, a first embodiment of the device, in inoperative condition;

- Fig. 2 shows, in front view, an anchoring member of the device of Fig. 1;

- Fig. 3 shows a view similar to Fig. 1, in which the device is in operating condition;

Fig. 4 is a schematic sectional side view of a second embodiment of the device, in an inoperative condition;

- Fig. 5 is a front view of an anchoring member of the device of Fig. 4.

DESCRIPTION OF THE PREFERRED MANUFACTURING FORMS

In the figures listed above, reference 1 indicates the device object of the present invention, as a whole.

Device 1 is designed to be installed in masonry buildings (not shown) for consolidation and seismic protection purposes.

Obviously, one or more of these devices 1 may be present in the same building, suitably located in the masonry walls.

The device 1, in a per se known manner, comprises a metal chain or tie rod 2 suitable for being anchored at its ends, in a substantially horizontal configuration, to two walls or structural elements 3 (of which only one is partially illustrated) of said buildings, in order to interconnect them and prevent their mutual distancing in the face of seismic events.

In a first construction variant, as per Figures 1 to 3, in the device 1 an anchoring member 4 of the chain or tie rod 2 is provided, associated with at least one end 2E of the latter and spaced apart from one of said elements structural 3 of the building.

The anchoring member 4 is advantageously shaped like a plate, extending transversely to said chain or tie rod 2, to which it is made integral, in a substantially central position, for example by means of screw members 2F.

The anchoring member 4, in the preferred embodiment of the figures, is arranged outside one of said structural elements 3, to which a reinforcing member 5, having the shape of a plate, is stably anchored, so as to turn parallel to the same anchoring member 4, with respect to which it is spaced by a predetermined height.

The reinforcing member 5 has, in the plane of contact with said structural element 3, a sufficiently extended surface to obtain, on the latter, a load distribution such as not to exceed a certain specific pressure, and is equipped with shaped appendages 51 (also known as anchors) intended to penetrate into the thickness of said structural element 3 and to be blocked to the latter, for example with concrete or epoxy resins.

The reinforcing member 5 is affected, in a substantially central position, by a through hole 50, for the free transit of said chain or tie rod 2 towards the interior of the aforementioned building, through a coaxial hole 30 made for this purpose in the element structural 3.

Preferably, especially in the case that the connecting element between the walls consists of a tie rod, the through hole 50 is equipped with a gasket bush in anti-friction material (not shown in detail).

Between the anchoring member 4 and the reinforcing member 5 are interposed collapsible coupling means 6, arranged substantially coaxial to said chain or tie rod 2, and comprise two telescopic tubular sleeves 61, 62, mutually engaged and sliding, the first of which sleeve 61 is associated with the aforementioned anchoring member 4 while the second 62 is associated with the reinforcing member 5.

The telescopic tubular sleeves 61, 62 preferably have a circular section, and are interposed with a bearing 60 of material with a low coefficient of friction, so as to facilitate their mutual axial sliding, if allowed, as better specified below.

Between the first and the second tubular sleeve 61, 62, in fact, constraint means with calibrated resistance 7 are provided, suitable for locking the same sleeves 61, 62 in a predetermined extraction position.

The provided constraint means with calibrated resistance 7 are for example constituted by at least two radial pins 70, each of which simultaneously engages a pair of radial holes 61A, 62A, respectively made in said tubular sleeves 61, 62 and which are coaxial in the position of predetermined extension of the latter, so as to define and stabilize said distance between the anchoring member 4 and the reinforcing member 5.

The radial pins 70 therefore block the axial sliding of the sleeves 61, 62 and, up to a certain stress value, the device 1 is a rigid body for which the structural element 3 and the chain or tie rod 2 are in fact rigidly connected ( Fig. 1). In this way, for minor earthquakes, the retaining system of the wall is the chain or tie rod 2 which responds to the external stress with its own elasticity.

If the thickness of the structural element 3 allows it, the aforementioned reinforcement member 5 is recessed by means of a masonry, so that the protrusion of the device 1 outside the building is limited.

Consequently, at least a portion of the second sleeve 62 is likewise recessed.

In the device 1 there are also provided elastic members 8, acting in an axial direction to the chain or tie rod 2, to solicit in mutual displacement, according to a predetermined direction, said anchoring member 4 and reinforcing member 5, between which dissipating elements are interposed. viscous fluid energy 9, also acting in the axial direction to the chain or tie rod 2.

In the constructive solution of Figures 1 to 3, said elastic members 8 are constituted by at least one helical compression spring, while the energy dissipating members 9 are constituted by a known type shock absorber, preferably with double effect;

The elastic members 8 and the energy dissipating members 9 are arranged coaxial to the aforementioned chain or tie rod 2, inside the aforementioned telescopic tubular sleeves 61, 62; for this purpose, the energy dissipating members 9 advantageously constitute an axial portion of the chain or tie rod 2.

As already mentioned, the device 1 behaves like a rigid body in the absence of axial stresses and up to a predetermined intensity thereof, or in the presence of minor earthquakes.

Beyond a certain intensity of the seismic tremors, the aforementioned radial pins 70 collapse, due to shear stress due, in this case, to the contraction of the collapsible coupling means 6 imposed by the traction exerted by the structural elements 3 on the chain or tie rod 2 (Fig. 3).

At this point, the sleeves 61, 62 are allowed reciprocal axial excursions, both in extension and in contraction, which correspond, respectively, to distances and approaches between said anchoring member 4 and reinforcing member 5, to support earth tremors.

The contraction excursions of the sleeves 61, 62 are contrasted, controlled and damped by said elastic members 8, while the energy dissipating members 9 progressively dampen the oscillations in both directions, until they are zeroed.

The contraction excursions of the sleeves 61, 62 are opposed by said elastic members 8, while the energy dissipating members 9 progressively dampen the oscillations in both directions, until they are zeroed.

The axial excursion allowed to the two tubular sleeves 61, 62, is limited to a predetermined value by end-of-stroke stops defined, in contraction, by the heads of the same sleeves 61, 62 which, in pack, intercept the reinforcing member 5 and the anchoring member 4, while in extension by mechanical stops provided for this purpose in the sleeves 61, 62 and not shown.

By way of indication, some possible sizing values of the components described above of the device 1 are reported, which are considered correct on the basis of both calculations and experimental analyzes.

The radial pins 70 are designed to yield with a shear breaking force of approximately 20% of the yield strength of the chain or tie rod 2.

Beyond this value, the yielding of the radial pins 70 allows the sleeves 61, 62 the reciprocal axial excursions, both in extension and in contraction, as described above.

Thanks to the high damping values (at least 20-40% of the critical value), due to the combined action of the elastic elements 8 and the energy dissipating elements 9, the rocking is strongly attenuated, so as to exclude the onset of oscillating motions.

The elastic members 8 have an elastic modulus such that their stiffness is equal to about 1 / 20-1 / 50 of the extensional stiffness of the chain or tie rod 2, so that for medium-sized earthquakes they work safeguarding the chain or tie rod from elongation beyond the relative yield point, thus allowing the wall to return to its previous position. Basically, the reduced stiffness of the elastic members 8 allows the chain or tie rod 2 not to undergo appreciable increases in tension and to remain in elastic conditions during the steps of retraction of the wall from its position.

In a second constructive variant of the device 1, illustrated in Figs. 4 and 5, the aforementioned collapsible coupling means 6 consist of a plurality of operating groups, for example three 6A, 6B, 6C.

Each of said operating groups 6A, 6B, 6C comprises, similarly to what has already been described with reference to said first construction variant, two telescopic tubular elements 61, 62, preferably with circular section and mutually engaged, of which the first is associated with the aforementioned control member anchor 4 and the second to the aforementioned reinforcement member 5.

Each of the operating groups 6A, 6B, 6C therefore provides respective constraint means with calibrated resistance 7, consisting of at least two radial pins 70, inserted in corresponding holes 61A, 62A provided in the respective tubular sleeves 61, 62 in predetermined positions, for uniquely define the aforementioned distance between the anchoring member 4 and the aforementioned reinforcing member 5.

The radial pins 70 of each operating group 6A, 6B, 6C normally have the same shear resistance characteristics, so that their breaking occurs at the same time as that of the others, however it is not excluded to slightly differentiate this resistance, for obtain a more gradual response of the device 1 with respect to seismic stresses.

Preferably, each operating group 6A, 6B, 6C is equipped with its own elastic members 8 and energy dissipating members 9, coaxial to the respective telescopic tubular sleeves 61, 62 and within the same.

While in the first variant embodiment described the collapsible coupling means 6, the elastic members 8 and the energy dissipating members 9 are coaxial to the chain or tie rod 2, in the second embodiment the operating groups 6A, 6B, 6C as described above are mutually parallel and symmetrically arranged with respect to the longitudinal axis of said chain or tie rod 2, in this case angularly equidistant at 120 ° from each other. All the remaining construction features of the second construction variant are substantially similar to those of the first variant, apart from some dimensional dimensions, which are not significant as regards the invention, therefore the description is omitted for the sake of brevity.

The operation also almost completely reflects the previous description, except for the parameters of response to shocks which depend on the dimensions established for the elastic members 8 and for the energy dissipating members 9, as well as on the number of the same which are simultaneously stressed.

From what has been described above, the peculiar and advantageous characteristics of the device object of the invention emerge clearly which, starting from an absolutely traditional technique such as the interconnection of the walls of masonry buildings by means of chains or tie rods, for the purpose of consolidation and seismic protection, it exceeds its congenital limits as regards the response to seismic events, considerably increasing its performance, in particular to contain the out-of-plane motions induced in the aforementioned walls.

It is necessary to highlight how the original conformation of the device allows to differentiate its behavior based on the extent of the seismic event in progress; as already mentioned in the description, in fact, it defines a rigid body for connection between the chain or tie rod and the walls, as in the known art, in the absence of shocks and up to a predetermined intensity of the same, beyond which an axial movement is allowed amortized, thanks to the elastic elements and the energy dissipating elements, limiting the possibility that the chain or tie rod undergoes plastic deformations due to traction stresses.

In this way, the uncertainties related to the evaluation of the behavior in the return phase of the wall are drastically reduced.

An important advantageous aspect of the device is that of reducing the risk of tearing the chain or tie rod due to excessive deformation caused by the out-of-plane rocking motion during the earthquake; in the return phase of the wall (during the earthquake), moreover, the possibility that the same chain or tie rod can become unstable due to peak load is limited.

It should be emphasized that the described advantageous characteristics allow the device to be easily manufactured and installed in various types of buildings, in a manner very similar to those envisaged in the prior art.

However, it is understood that what has been described above has an exemplary and non-limiting value, therefore any detailed variations that may be necessary for technical and / or functional reasons, are considered from now on to fall within the same protective scope defined by the claims reported below.

Claims (10)

CLAIMS 1. Device (1) for the consolidation and seismic protection of masonry buildings, of the type comprising a metal chain or tie rod (2) suitable to be anchored at its ends, in a substantially horizontal configuration, to two walls or structural elements (3) of said buildings, so as to interconnect them and prevent their mutual spacing in the face of seismic events, said device (1) being characterized in that it comprises: - an anchoring member (4) of the chain or tie rod (2), associated with at least one end of the latter and spaced from one of said structural elements (3) of the building; - a reinforcing member (5), having the shape of a plate, stably anchored to the same structural element (3) of the building, so as to be parallel to the aforementioned anchoring member (4), facing the latter and spaced apart a fixed quota; - collapsible coupling means (6), interposed between said anchoring member (4) and said reinforcing member (5); - constraint means (7) with calibrated resistance, provided in said collapsible coupling means (6) to lock them so as to stabilize the distance between said anchoring member (4) and said reinforcing member (5) , and in such a way that the axial sliding of the aforesaid collapsible coupling means (6) is prevented up to a certain stress value, or to allow it beyond this value; - elastic members (8), acting in an axial direction to the aforementioned chain or tie rod (2), to solicit said anchoring member (4) and reinforcing member (5) in mutual displacement, according to a predetermined direction; - viscous fluid energy dissipating members (9) acting in the axial direction of the aforementioned chain or tie rod (2), between said anchoring member (4) and reinforcing member (5); the aforementioned device (1) being provided to define a rigid body for connection between said chain or tie rod (2) and said structural element (3) in the absence of axial stresses and up to a predetermined intensity thereof, beyond which, consequently of the yielding of the aforementioned constraint means (7) with calibrated resistance and of the axial excursion of the aforementioned collapsible coupling means (6), an axial movement is allowed between said anchoring member (4) and reinforcing member (6), opposed and taken up by said elastic members (8) and progressively attenuated by the aforementioned viscous fluid energy dissipating members (9). 2. Device (1) according to claim 1, characterized by the fact that: said anchoring member (4) of the chain or tie rod (2) is shaped like a plate, extending transversely to said chain or tie rod (2), and is arranged externally with respect to one of said structural elements (3) of the building; said elastic members (8) are of the compression type; said reinforcement member (5) is affected, in a substantially central position, by a through hole (50) for the free transit of said chain or tie rod (2) towards the interior of the aforementioned building. 3. Device (1) according to claim 1 or 2, characterized in that said collapsible coupling means (6) are substantially coaxial to said chain or tie rod (2) and comprise two telescopic tubular sleeves (61, 62), mutually engaged, of which the first (61) is associated to the aforementioned anchoring member (4) and the second (62) to the aforementioned reinforcing member (5), in that said constraint means (7) with calibrated resistance consist of at least two radial pins (70), inserted in corresponding holes (61A, 62A) provided in said tubular sleeves (61, 62) in predetermined positions, to define the aforementioned distance between said anchoring member (4) and said reinforcing member (5), and by the fact that said elastic members (8) and viscous fluid energy dissipating members (9) are arranged coaxial to the aforesaid chain or tie rod (2), inside the aforementioned telescopic tubular sleeves (61, 62). 4. Device (1) according to claim 1 or 2, characterized in that said collapsible coupling means (6) consist of a plurality of operating groups (6A, 6B, 6C), mutually parallel, arranged symmetrically with respect to the longitudinal axis of said chain or tie rod (2 ), with each of said operating groups (6A, 6B, 6C) comprising two telescopic tubular elements (61, 62), mutually engaged, of which the first associated with the aforementioned anchoring member (4) and the second with the aforementioned reinforcing member (5), by the fact that said constraint means with calibrated resistance (7) consist of at least two radial pins (70) for each of the aforementioned operating groups (6A, 6B, 6C), inserted in corresponding holes provided in the respective tubular sleeves (61, 62) in predetermined positions, to uniquely define the aforementioned distance between said anchoring member (4) and the aforementioned reinforcing member (5), and by providing a number of said elastic members (8) and energy dissipating organs (9 ) corresponding to that of the aforementioned operating groups (6A, 6B, 6C), with the elastic members (8) and energy dissipating members (9) of each pair coaxial to the respective telescopic tubular sleeves (61, 62), inside the same. 5. Device (1) according to claim 3 or 4, characterized in that said two telescopic tubular sleeves (61, 62), provided in the aforementioned collapsible coupling means (6), are mutually engaged sliding with the interposition of a bearing of low coefficient of friction material. 6. Device (1) according to claim 3, characterized in that the aforementioned viscous fluid energy dissipating members (9) constitute an axial portion of said chain or tie rod (2). 7. Device (1) according to any one of the preceding claims, characterized in that the aforementioned reinforcing member (5) is equipped with shaped appendages (51) intended to penetrate into the thickness of said structural element (3) of the building and to be locked to the latter, by the fact that the same reinforcing member (5) is recessed in the thickness of the aforementioned structural element (3), so that a predetermined portion of the aforementioned collapsible coupling means (6) is also recessed, and by the fact that the same reinforcing member (5) has, in the plane of contact with said structural element (3) of the building, a surface suitably extended to obtain a load distribution such that the specific pressure on the same structural element (3 ) is lower than a predetermined value. 8. Device (1) according to any one of the preceding claims, characterized in that the axial excursion allowed to said two telescopic tubular sleeves (61, 62), in the aforementioned axial excursion of the aforementioned collapsible coupling means (6), is limited at a predetermined value by end-of-stroke stops. Device (1) according to any one of the preceding claims, characterized in that said two telescopic tubular sleeves (61, 62), provided in the aforementioned collapsible coupling means (6), have a circular section. 10. Device (1) according to claim 2, characterized by the fact that said elastic compression members (8) are of the helical type, and by the fact that they are preloaded according to predetermined parameters in static conditions, before the aforementioned failure of the aforementioned constraint means with calibrated resistance (7) and of the contraction of said collapsible coupling means (6).