EP4717854A2

EP4717854A2 - Removable anti-seismic bracing system applicable to existing buildings with improved fire resistance and related kit for its construction

Info

Publication number: EP4717854A2
Application number: EP26154357.3A
Authority: EP
Inventors: Vanessa RACCONCI; Alessia RAMBUSCHI
Original assignee: Universita' Iuav Di Venezia
Current assignee: Universita' Iuav Di Venezia
Priority date: 2022-01-21
Filing date: 2023-01-18
Publication date: 2026-04-01
Also published as: EP4717855A2; EP4717853A2; WO2023139624A1; EP4466427A1; IT202200000977A1; EP4466427B1; EP4466427C0

Abstract

The invention relates to a modular anti-seismic bracing system for a building equipped with horizontal structural elements (20), comprising
two pillars (2)
a Saint Andrew's cross (3) that can be fixed between the two pillars (2)
two upper clasping elements (10) that can be fixed to the upper ends of the pillars (2)
wherein the upper clasping elements (10) comprise tie-wrapping means for tying said structural elements (20) so that said structural elements (20) are not modified by the application or removal of the module (1).

Description

The present invention relates to a reversible anti-seismic bracing system, applicable to existing buildings with a frame structure, which makes it possible to prevent their static equilibrium from being affected. In detail, such removable system is suitable for making existing buildings, for example historical buildings, safe and minimises the intervention on the structure of the building itself, reducing the time for its realisation and facilitating the maintenance and/or replacement of those components which could be deteriorated.

Field of the invention

In particular, it is a system that makes an existing building safe, leaving most of its surfaces visible, without affecting the static equilibrium of the building itself.
In the following, the description will be directed to an anti-seismic kit applicable to a historic building of particular architectural value, but it is quite clear how it should not be considered limited to this specific use. In fact, it is clear that the applications of such system are various, and also include industrial and civil buildings not belonging to the historical heritage, but equipped with a frame structure and in any case requiring an anti-seismic improvement intervention that avoids stopping the use of the building itself.

Prior Art

Currently known anti-seismic bracing systems comprise a reinforcing structure aimed to stiffen the structure, capable of absorbing vibrations or transmitting them to the ground without creating damages to the building to which they are applied; such structure clasps to the load-bearing parts of the building, in an invasive way and with the result of affecting the resistance of the building itself from a static point of view.
Furthermore, in the case of external structures, these require a fire protection that protects them over time from any flames; this protection usually consists of a concrete or masonry coating, and therefore of a wall, which substantially hides from the observer's view not only the structure, but also the building to which it is applied. The consequence of this coating is the loss of the architectural and historical value of the building, as it is no longer enjoyable, nor appreciable from an aesthetic point of view.
Again, the known anti-seismic systems require an irreversible installation, which requires to organise long-term demolition sites which damage or in any case modify the existing one.

Aim of the invention

The main objective of the present invention is to provide a system for realising an anti-seismic bracing which makes it possible to overcome the aforementioned drawbacks and which in particular makes it possible to enhance the existing building, leaving it completely visible and making the intervention of seismic improvement or retrofitting, a light and elegant system.
In detail, the objective of the invention is to realise a kit for securing a building quickly and effectively.
Another objective of the present invention is to avoid as much as possible modifying the load-bearing structure of the building.
Therefore, advantageously, the anti-seismic action of the bracing that can be achieved using the kit of the invention becomes active exclusively during the seismic shocks of the earthquake and prevents major damage to the architectural structure to be protected.
Instead, in the absence of shocks, the system remains mobile (not rigid) following the movements of the structure thanks to the cushioning of the shock transmitters placed at the base, without affecting the load-bearing structure of the building and therefore both the static equilibrium and the fibres of the load-bearing beams remain unchanged.
In essence, the obtained alteration of the existing building is the insertion of the obtained anti-seismic system, which is fixed, even if advantageously removable, without causing damage to the building and whose components can be separated and potentially reusable.
In other words, the anti-seismic system of the invention is reversible, recyclable and does not damage the existing one. Furthermore, it is advantageous because it does not require to organise long-term demolition sites: its elements are assembled together on site by welding of steel tubular elements.
In particular, the basic module of the bracing of the invention consists of two shock transmitters at the base, of two tubular elements which by tie-wrapping clasp to the existing beams, of a Saint Andrew's cross lowered relative to the tubular elements and of a box-like system of protection in fireproof glass. Advantageously, each element works to ensure an optimal resistance in the event of an earthquake.
In this context, Saint Andrew's cross means a transverse cross, such as the one required for railway signs by the Vienna convention on road signs, i.e. with angles between arms other than 90°. In detail, such transverse cross has a larger footprint along the direction parallel to the ground, resulting instead shorter in the direction perpendicular to the ground.
At the base of the bracing system of the invention, the shock transmitters, sized according to the magnitude of the seismic zone, make it possible the stiffening of the system only in the event of an earthquake, while in a normal situation the system remains mobile, to adapt to the movements of the building structure in non-seismic field. Advantageously this characteristic does not affect the static equilibrium of the existing structure, does not involve variations in the fibres of the load-bearing beams and the consequent deterioration of the structure subject to intervention.
Therefore, in the event of an earthquake, the shock transmitters respond positively to the vibrations of the ground, so that the shocks are already largely sorted out at the base of the structure.
As for the shock transmitters, the hollow steel tubular elements acting as pillars were sized according to the seismic zone with a safety factor of 1.5 and depending on the seismic risk of the area. The thickness of the tubular element is sized according to the resistance required by the magnitude of the area where the building to be secured is located.
In detail, the tubular shape of the pillars is preferable to other shapes, as the circular section assumes an unchanged behaviour regardless of the direction of the thrusts it may receive.
Furthermore, in the case of use of tubular pillars, due to their geometry it is preferable to provide welding as a fastening system, instead of bolting for example, to connect each component of the bracing system.
In any case, the Saint Andrew's cross remains visible, standing out from other bracing systems which are often covered by layers of concrete.
This choice involves the issue of compliance with fire regulations, which can be solved, for example, by inserting a glass box-like structure to protect the Saint Andrew's cross and guarantee the time required to evacuate the building. An alternative is the application of a fire-retardant paint to the bracing elements.
However, the REI class of the fireproof glass is higher than the fire-retardant paints currently on the market, consequently enabling a longer life of the system.
The connection between the lowered Saint Andrew's cross and the pillar on which the tie-wrapping solution is installed is subject to momentum and has been calculated to determine the thickness of the steel tubular elements to resist the thrusts during the earthquake.

Object of the invention

Therefore, it is an object of the invention a kit for realising an anti-seismic bracing module for a building equipped with horizontal structural elements, comprising two pillars, a Saint Andrew's cross which can be fixed between the two pillars, two upper clasping elements which can be fastened to the upper ends of the pillars. According to the invention, the upper clasping elements comprise tie-wrapping means for tying the structural elements so that the structural elements themselves are not modified by the application or removal of the module.
This makes the obtainable bracing totally reversible and removable, without causing any damage to the existing structure.
Furthermore, according to the invention, a box-like element in fireproof glass is included, which can be fixed to the Saint Andrew's cross, so as to increase the resistance time of the structure in the event of a fire and facilitate its evacuation safely.
In case of damage to the load-bearing structure of the building during the fire, the bracing system would support it, increasing its resistance time.
Preferably, according to the invention, the box-like element in fireproof glass may be surrounded by steel profiles, so as to further reinforce the fire protection of the anti-seismic bracing and, potentially, the overall structural integrity of the box-like element itself.
Again, according to the invention the box-like element in fireproof glass may comprise an opening system in the steel profiles, to carry out the maintenance of the system. Said opening system, in fact, facilitates access to the internal components of the anti-seismic bracing module for inspections, repairs or replacements, ensuring the longevity and efficiency of the system over time.
The invention also concerns an anti-seismic modular bracing system comprising one or more modules realised using the kit described above.
In particular, it is possible to provide for a repetition of one or more modules in height, to be clasped through said upper clasping elements to the horizontal structural elements of each floor of the building.
In more detail, two systems orthogonal to each other must be installed on the floor to ensure a bracing of the building and therefore a resistance in the event of an earthquake.
In essence, advantageously, the system of the invention:

does not modify the static equilibrium of the structure,
becomes active only in the event of an earthquake,
does not affect the load-bearing structure of the building,
does not affect the architecture as the old bracing systems do,
is suitable to any building with horizontal load-bearing beams,
makes the building anti-seismic, and
helps to support the load-bearing structure in the event of a fire.

Brief description of the drawings

The present invention will now be described, by way of non-limiting example, according to some of its preferred embodiments, in particular with the objective of recovering a historic building. These measures can be adapted according to the needs of each building. The description will be made with the help of the attached figures, wherein:

Figure 1 is a front view of a module of an anti-seismic system which can be realised using the kit of the invention;
Figure 2 is a side view of the module of Figure 1;
Figure 3 is an enlarged detail of Figure 2;
Figure 4 is an enlarged detail of Figure 1;
Figure 5 is a first perspective view of the module of Figure 1, applied to two beams of a building;
Figure 6 is a second perspective view of the module of Figure 5;
Figure 7 is a first perspective view of the enlarged detail of Figure 3;
Figure 8 is a second perspective view of the enlarged detail of Figure 3;
Figure 9 is a third perspective view of the enlarged detail of Figure 3.

Detailed description

In the various figures, similar parts will be indicated by the same reference numbers.
With reference to Figures 1-2 and 5-6, a module 1 of a modular anti-seismic system is represented, comprising two pillars 2, a St Andrew's cross 3 having a height H lower than the height L of the pillars 2, two anti-seismic support elements 4, for resting on the ground, two horizontal tubular elements 5 placed at the base and at the top of the Saint Andrew's cross 3 and two upper clasping elements 10, for clasping to the horizontal structural elements of the building to be seismically improved.
The horizontal elements 5 makes it possible to have a greater resistance to thrusts.
In particular, as mentioned above, images 5 and 6 and the corresponding enlargements 7, 8 and 9 refer to the application of the modular anti-seismic system to a building equipped with exposed beams, but it is clear that the anti-seismic system in question can be easily adapted also to a building whose beams are hidden by a lower protection layer, by making a few small holes.
For example, in the case of load-bearing beams embedded inside the floor, it will be necessary to make four holes of about 2 cm each in the non-load-bearing part of the floor, to make it possible the tie-wrapping of the load-bearing beam.
In fact, in more detail, Figure 3 shows the bolting system with the trapezoidal elements that make it possible the orthogonal bolting of the inclined screws. The upper clasping elements 10 comprise a first plate 11, connecting to the top of the respective pillar 2, provided with a first area A of contact with the beam 20 of the building, a second plate 12, provided with a second area B of contact with the beam 20, larger than the first contact area A, and transverse elements 13 connecting the first plate 11 to the second plate 12.
Preferably, the first plate 11 and the second plate 12 have a rectangular base, in order to be able to tie the beam better. In detail, they can have their centres of gravity aligned with the axis according to which the respective pillar 2 develops. Furthermore, it is advisable that the plates 11 and 12 are oriented so as to have the corresponding edges parallel to each other.
Equally preferably, the transverse elements 13 connect the plates 11 and 12 by joining the respective corresponding corners present on each plate, so to be oriented along the edges of a truncated pyramid having the first plate 11 as the smaller base and the second plate 12 as the larger base.
In a preferred variant of the invention, such transverse elements 13 each comprise a worm screw 14 and two bolts 15 to be screwed to their ends, once the worm screw 14 has passed through each of the holes drilled at the corner 16 of the respective plate 11, 12 to be connected. In detail, in correspondence with each corner 17 of the first plate 11 and with each corner 16 of the second plate 12, there may be holes with an axis transversal to the main plane of the respective plate 11 or 12, and inclined thereto by the same inclination that the transverse element 13 would have to connect the corner 16 to the corner 17.
In this case, it is possible to arrange also a seat 18 in each hole, in order to arrange a base perpendicular to such inclination, which acts as a stop for the bolt 15 to tighten the transverse element 14 more effectively and secure it to the beam 20 to be tied by means of the upper clasping element 10.
Therefore, the obtained structure has a Saint Andrew's cross 3, lowered relative to the building to be protected and reinforced by two horizontal elements 5, which form a rectangle with two pillars 2; such pillars 2 protrude from the Saint Andrew's cross 3 and the horizontal elements 5, upwards until they clasp the beams and downwards to the ground.
In this embodiment shown in the attached figures, the aforementioned elements constituting the module of the structure are made of stainless steel, whose thickness is sized according to the load placed at the top and to the resistance necessary to support the thrusts of the earthquake on the structure, since the pillars 2 protruding from the Saint Andrew's cross 3 are subjected to a cantilever-type bending behaviour.
According to a preferred variant of the invention, the rectangular part of the bracing is covered by a box-like element 6 (Figures 5 and 6) in fireproof glass, possibly surrounded by steel profiles, so as to both protect the metal structure from fire and show its composition: the glass transparency in fact makes it possible to see the architectural structure as well as the constituent parts of the anti-seismic module 1, leaving the upper part of the pillars 2 uncovered and the anti-seismic elements 4 placed under the flooring.
The latter include "Shock transmitter" systems. Advantageously, in this way the anti-seismic elements 4 at the base are blocked and allow the bracing structure 1 to become active exclusively during the seismic vibration, so as not to modify the structural nature of the fibres of the beams 20 in static field; otherwise, in fact, the structural nature of the beams 20 would be altered by a fixed bracing which is stressed also in compression.
A further preferred variant of the invention provides for the upper clasping elements 10 to be permanently fixed, for example welded to a spacing element 30, in particular a cylindrical element, for example made of steel. For example, such spacing element 30 may simply be a continuation portion of the pillar 2, uninterrupted up to the upper clasping elements and then to the lower plate 11; this structural continuity makes it possible to not create momentums during the forces of the earthquake.
Of course, it is possible for such spacing element 30 to have any polygonal section, without significantly affecting the spacing function itself.
Below the spacing element 30 there is a protection element 31 having the shape of an inverted truncated pyramid, to get closer to the shape of the plate 11, protecting the welding of the clasping between the tubular pillar 2 and the plate 11, however leaving a gap, preferably of a few centimetres. This is useful for having the physical space to make it possible the proper bolting of the screws of the lower part.
Above the spacing element 30, there is the first plate 11, preferably made of steel and equally preferably about 5 centimetres thick, to avoid bending problems. The spacing given by the steel tube 30 advantageously makes it possible the bolting of the tie rods 13 in an easy way.
The tie rods 13 join the first plate 11, which is under the beam 20, to the second plate 12, which is above the beam itself 20. The second plate 12 has a larger area so as to make it possible the insertion of the aforementioned tie rods 13 (e.g. worm screws 14), positioned along each corner 16, 17 of the plates 11, 12 in a configuration of sides of an inverted isosceles trapezium, so as to be inclined by at least 10° outwards and therefore advantageously resist the seismic thrusts in both directions.
On the surfaces A and B of the first and second plates 11,12 facing the beams 20, neoprene bearings 32 are applied, preferably about 3 cm thick, to avoid any rubbing between the different materials and to cushion the movements of the structure. Such slabs 32, in addition to avoiding a direct contact between the metal plates of the anti-seismic system and the beams of the existing building, also follow the volumetric variations of the material due to thermal variations.
In other words, the slabs 32 have the function of separating the different materials from each other (the load-bearing beams of the existing building from the new system), but above all of acting as a bearing to make it possible the movements of the structure in static field and the thermal expansion of the materials, thanks to the elasticity of the elastomeric material used as a slab.
In fact, the use of these slabs mainly helps to follow the natural movements of the building in static field and ensure that the anti-seismic bracing system of the invention does not affect the static nature of the existing one and the nature of any fibres of the beams, for example the fibres of wooden beams.
The choice of slabs fell on elastomer materials because of their excellent characteristics of resistance and elasticity, which include materials from the most to the least efficient.
Contact areas A and B each have a neoprene slab 32, for example, of a few centimetres, to:

avoid a direct contact between the steel plates and the load-bearing beams of the existing building,
ensure that the system adapts to the movements of the structure in static field,
not damage the beams of the structure,
follow the thermal expansion of the materials,
not affect the static equilibrium of the existing building and therefore
not change the fibres of the beams.

To fix the tie rods 13, through-holed three-dimensional metal connection elements 19 have been conceived, with a trapezoidal section along a plane parallel to the axis of the hole, so as to modify the angle of the central hole for the tie rod 13 to go through, so that it is inclined to the vertical by at least 10° outwards; in fact, the connection elements 19, bolted to the plates, will have a central axis C corresponding to the inclination of the tie rods, such as to ensure that the eyelet and the bolt are perfectly orthogonal to the tie rod.
The clasping to the existing beams takes place using the upper clasping system 10 described above, in detail a truncated pyramid tie-wrapping system, which advantageously is connected to the existing load-bearing structure without drilling holes and ensuring a response resistant to the horizontal displacements of the ground in any direction due to a seismic event.
What has been described is possible by means of worm screws 13 which connect the smaller plate to the larger plate by bolting. The smaller plate 11 is connected to the tubular pillar 2 by means of a truncated cone or pyramid 31 in steel which is for example welded, in turn, around the top of the pillar 2. The worm screws 14 placed in a truncated pyramid configuration rest on pyramidal or trapezoidal adapters 19 and are bolted to the larger plate 12.
The plates 11,12 have a dividing neoprene slab 32 (Figures 3, 8) to prevent the steel from directly touching the existing truss.
In the case of existing load-bearing beams hidden in the floors, the tie-wrapping solution may be applied by drilling four holes with a diameter of about two centimetres.
To guarantee the anti-seismic response, two bracing modules orthogonal to each other, which are resistant to horizontal displacements in both directions, must be inserted, placed in two different points of the building and repeated on each floor.
Moreover, the proposed system is advantageously adaptable to any size both in height and in width, since it can be adjusted through calculations, while keeping the ratios for the sizing of the tie-wrapping unchanged.
Compared to other seismic improvement or retrofit solutions, costs are lower because no demolition is necessary for the insertion of the system and the welding of the prefabricated pieces on site makes it possible a fast installation.
Operationally, once an existing building to be seismically protected has been identified, the operator sizes thickness, height and width of the pillars 2 according to the building requirements and so that, once they are assembled to the seismic support elements 4 and to the upper clasping elements 10, the latter may be coupled to the horizontal load-bearing elements of the building itself, keeping the pillars 2 fixed to the ground through the seismic elements 4, and are oriented in a vertical position.
Similarly, the Saint Andrew's cross 3 is sized so that the pillars 2, assembled at its ends, may be positioned in correspondence with the beams of the building.
Subsequently, the operator assembles, preferably by welding, the pillars 2 to the St Andrew's cross 3, so that the pillars 2 themselves protrude from the St Andrew's cross 3 on the upper part.
Likewise, the operator assembles the horizontal elements 5 at the ends of the Saint Andrew's cross 3, also in this case preferably by welding.
At the upper end of each of the pillars 2 it is possible to place the protection element 31, which preferably has a truncated cone or inverted pyramid shape.
In this case, it is possible to interpose, between the protection element 31 and the first plate 11, a spacing element 30, which then allows the tie rods 13 to be bolted to the aforementioned first plate 11.
In any case, it is possible to proceed with the positioning of the pyramidal or trapezoidal connection elements 19 in the seats 18 of the plate 11 corresponding to its corners 16. Subsequently, by arranging similar connection elements 19 in similar seats 18 of the larger plate 12, the operator places the larger plate 12 on the beam 20 and carries out the tie-wrapping by means of worm screws 13 bolted to the connection elements 19 to connect the smaller plate 11 to the larger plate 12.
The pillars 2 can be fixed to the ground using the shock transmitters 4 suitably chosen on the basis of the required resistance.
On a system, the use of at least two of them is preferred, one at the base of each pillar by clasping the base of the pillar to the upper plate of the Shock Transmitter (by bolting or better still by welding), to more effectively follow the movements of the existing building in static field, promptly adapting to the movements of the structure, and to have a greater resistance to the seismic waves and therefore a better response in seismic emergencies.
In fact, since each shock transmitter responds autonomously for each single pillar, an optimal dissipation of the oscillations is guaranteed, since these are placed at the ends of the structure and clasped to the main part.
At this point, in the case that the pillars 2, the Saint Andrew's cross 3 and the horizontal elements 5 are not provided with fireproof paint sufficient to protect the obtained structure 1 in case of fire, it is possible to assemble a fireproof glass box-like structure 6 to the module 1, which in any case allows the anti-seismic bracing system of the invention and the building floor to be seen from the outside.
In this case, it is possible to provide for an opening system in the metal profiles of the fireproof glass box-shaped element 6, to carry out the maintenance of the system.
In the case of a building having several floors, it is possible to provide for the assembly of one or more modules, similar to the one described above, on the upper surface of the second plate 12, so that the sequence of the Saint Andrew's cross, pillars and tie-wrapping elements is repeated, until reaching the highest floor of the building.
The invention so conceived and herein illustrated is susceptible of numerous modifications and variations, all falling within the scope of the inventive concept.
Furthermore, all the details may be replaced by other technically equivalent elements.
Finally, the components used, as long as they are compatible with the specific use, as well as with the size, may be any according to the requirements and the state of the art.
Where the characteristics and techniques mentioned in any claim are followed by reference marks, such reference marks have been included for the sole purpose of increasing the intelligibility of the claims and, consequently, such reference marks do not limit the interpretation of each element identified by way of example by such reference marks.

Claims

A kit for realising a module (1) of an anti-seismic bracing for a building equipped with horizontal structural elements (20), comprising
two pillars (2)

a Saint Andrew's cross (3) that can be fixed between the two pillars (2)

two upper clasping elements (10) that can be fixed to the upper ends of the pillars (2)

wherein the upper clasping elements (10) comprise tie-wrapping means for tying said structural elements (20) so that said structural elements (20) are not modified by the application or removal of the module (1),
characterised in including a box-like element (6) in fireproof glass that can be fixed to the base of the module (1).
The kit for realising a module (1) of an anti-seismic bracing for a building equipped with horizontal structural elements (20), according claim 1, characterised in that the box-like element (6) in fireproof glass is surrounded by steel profiles.
The kit for realising a module (1) of an anti-seismic bracing for a building equipped with horizontal structural elements (20), according claim 2, characterised in that the box-like element (6) in fireproof glass comprises an opening system in the steel profiles, to carry out the maintenance of the system.
A modular anti-seismic bracing comprising one or more modules (1) realised using the kit according to one of the claims 1-3.
The modular anti-seismic bracing according to claim 4, characterised in that it provides for a repetition of one or more modules in height, to be clasped by means of said upper clasping elements (10) to the horizontal structural elements (20) of each floor of the building.