CN116981820A - System and method for improving earthquake-resistant and energy performance of existing buildings with reinforced concrete frame structures - Google Patents

Abstract

A system is described for improving the seismic and energy performance of existing buildings. The building has a frame structure (10) made of reinforced concrete having a plurality of perimeter columns (12) and a plurality of perimeter beams (14) intersecting each other in a perimeter node area (16), the system comprising: a reinforcing structure (24, 26) having steel reinforcing plates (24) arranged to be secured to an outer surface of the peripheral node region (16); and a reinforcement element (26) made of steel truss girder elements, the reinforcement element being arranged to be fixed to the outer surfaces of the perimeter columns (12) and the perimeter beams (14); and an external insulation and finishing system having a support frame (52, 54) carried by the reinforcing structure (24, 26) and formed of a plurality of vertical struts (52) and a plurality of horizontal profiles (54), and a plurality of insulation panels (22) mounted on the support frame.

Description

System and method for improving earthquake-resistant and energy performance of existing buildings with reinforced concrete frame structures

Technical Field

The present invention relates generally to the field of "retrofitting" of existing buildings, i.e. non-new buildings. More particularly, the present invention relates to a method aimed at combining the reduction of the risk of earthquakes with the improvement of the energy performance of existing buildings.

In particular, the present invention is directed to a building having a frame structure of reinforced concrete, which is designed without considering earthquake-proof standards or based on an earthquake-proof regulation that is not strict with the current earthquake-proof regulation, and which is constructed before the recent control regulation of building energy consumption.

Background

The type of building to which the present invention is primarily directed is a residential building having a reinforced concrete frame structure, but is not limited thereto.

This type of building is generally susceptible to both seismic effects and lack of energy control requirements for the enclosure. Accordingly, this type of building requires comprehensive upgrades in terms of shock protection and energy to improve safety and reduce maintenance costs.

Many old reinforced concrete constructions are designed as frame structures that only bear vertical loads, and thus do not take into account seismic standards, with a series of weaknesses that recur under the influence of the horizontal forces of an earthquake. These buildings are often characterized by a significant eccentricity in plan view, which determines the torsional behaviour of the building and the consequent significant increase in stresses in the event of an earthquake, in particular on the structural elements of the periphery of the building.

In general, the nodes of the frame structure (i.e., the intersection areas between the columns and beams of the frame) are fragile because they are not provided with brackets according to previous design rules and therefore are subject to brittle failure due to shear stress in the event of an earthquake. This vulnerability is particularly evident for the perimeter nodes (i.e. the nodes placed on the perimeter of the building structure), and is also particularly critical, since on the one hand they cannot benefit from the outside of the restraining effect provided by the beams, and on the other hand they are subjected to greater loads due to the torsional behaviour of the building. Furthermore, the peripheral nodes are typically the most degraded nodes due to exposure to weather factors.

In the order of vulnerability, the columns are arranged behind the nodes (in particular the surrounding nodes), since the shearing effects caused by the earthquake at the ends of the columns are generally not sufficiently counteracted by the supports, which are generally thin or at least very sparse (at least compared to the criteria of a suitable seismic design). Also in this case, the peripheral element belongs to the weakest element for the same reason as described above.

Next, in order of vulnerability, the beam is a beam whose ends are similar to posts in vulnerability to shear stress generated by an earthquake.

As a result of these crises, brittle failure of the element, the consequences of which adversely affect the functionality of the frame structure, leading to collapse. This prevents the elements of the frame structure from forming ductile failure mechanisms that would help to suppress seismic effects (so-called plastic hinges at both ends of the beam).

It is therefore desirable to provide reinforcement on the aforementioned frangible elements of the building frame structure to preclude brittle failure due to shear stress at the nodes and/or at the ends of the beams and columns, so that the behavior of the building with respect to seismic effects is significantly improved.

However, the solutions currently conceived to enhance the resistance of these old structural types to typical shear stresses in earthquakes are adversely affected by the fact that the solutions involve invasive activities inside buildings that are often occupied or in operation, and/or that the solutions are particularly expensive.

Well known examples of solutions for improving the earthquake resistance of buildings are reinforcing the structure of the building by means of a cortical coating in a high-resistance structural mortar combined with the frame ("outer protective layer") or by using a composite material consisting of strips or fabrics cured with epoxy resins (commonly abbreviated FRP, from english "Fiber Reinforced Polymers").

However, both of these solutions, even if they are operated at the periphery of the building, often result in invasive operations, as they also involve internal spaces.

In the first case, the operations of preparing the reinforced concrete surface, laying the auxiliary iron, installing the formwork and casting the mortar are costly and take time to wait for curing before removing the formwork. In addition, operational commitments of the job site for mortar mixing and strictly custom template preparation should be considered.

Even in the second case, which requires special labor, the customization of the components to be reinforced is required. In addition, such work intrudes into the interior space of the building, and involves problems associated with the use of resins having toxic components, and limitation problems in terms of durability and use temperature. The use of more technically advanced materials to reinforce critical elements of building structures, such as fibers immersed in an inorganic matrix (commonly known by the abbreviation FRCM, from english "Fiber Reinforced cemental Matrix") or high strength fiber reinforced mortars (commonly known by the abbreviation HPFRC, from english "High Performance Fiber Reinforced Concrete"), while improving some of the critical aspects of the above known solutions, does not eliminate the high cost and invasive work required to increase the shock resistance of old buildings.

On the other hand, the building standards and materials of old buildings far from the current requirements, for example in terms of heat transfer, are far from reduced energy consumption. In particular, the outer shell of a building having a frame structure of reinforced concrete is constituted by infill walls, which may be solid masonry (made of stones and/or bricks) or double-layered walls having cavities according to the age in which they are constructed. Initially, the wall cavity was empty (so the insulation was only air), whereas in decades after the 70 s and 80 s insulation materials such as vermiculite or fibre materials began to be inserted into the cavity. In any case, there are still various problems associated with many thermal bridges that are a feature of this type of building, due to the presence of elements of reinforced concrete structure in the wall, or due to the fact that in any case the cladding is almost exposed, but not deliberately exposed to give aesthetic connotation to the building, and due to the presence of protruding structural elements such as the under-floors of balconies, cornices and bay windows. These types of enclosures, even if equipped with the insulation material used at the time, do not reach the performance levels of energy control required today. Thus, measures taken to improve the energy performance of these buildings are of considerable economic and environmental interest.

Currently, the method of intervention on building shells mainly consists of applying an outer layer (so-called "cladding") and/or inserting insulation material into the wall cavity (if any).

The insertion of insulation into the wall cavity does not solve the problem of thermal bridging, except that the cavity and the minimum width achieved with the so-called "blowing" technique are required to be present, and its effectiveness is also limited by the thickness of insulation that can be obtained (equal to the width of the cavity space). Furthermore, the thermal bridge is often locally deteriorated due to the increased temperature difference between the infill wall and the structure, which results in a true condensation spot in the area of the beams and columns, especially when the blowing process is accompanied by other energy efficient measures, such as replacing the original window with a new insulating window.

Thus, a cladding material (but not exclusively blowing insulation material into the cavity) is generally the most suitable and effective method, as the type of material used and the thickness of the cladding material plate may be varied to achieve the desired energy efficiency goal. The cladding may also generally address thermal bridging due to outcrop structures. Furthermore, if this solution is implemented only on the outside of the building, it does not occupy any useful space inside the building and does not cause any inconvenience due to the internal work.

Disclosure of Invention

It is an object of the present invention to provide a system and method for improving the seismic and energy performance of existing buildings having reinforced concrete frame structures with less cumbersome and invasive interventions than the prior art.

This object is fully achieved according to a first aspect of the invention by a system having the features defined in the attached independent claim 1 and according to another aspect of the invention by a method as defined in the attached independent claim 9.

Further advantageous aspects of the system according to the invention and advantageous modes for carrying out the method according to the invention are defined in the dependent claims, the subject matter of which is intended to form part of the present description.

In summary, the invention is based on the idea of applying a reinforcing structure comprising metal wood trusses to the perimeter frame structure of a building made of reinforced concrete for the purpose of earthquake-proof protection of the building, and of applying an external insulation and finishing system integrated with the reinforcing structure for the purpose of reducing the energy consumption of the building, so that only interventions from outside the building are required.

The reinforcing structure essentially comprises the following two types of reinforcing elements:

-a first type of reinforcing element formed of sheet steel, intended to be applied on the outer surface of a node area of an existing structure of a building; and

a second type of reinforcement element, formed by steel truss girder elements, intended to be applied to the outer surface of the girders and/or columns of the existing structure of the building.

The use of such reinforcing elements makes it possible to reinforce different building structures with a limited set of standard pieces which can be manufactured industrially at low production costs and with high quality standards and which can be suitably combined to form a modular reinforcing system which is suitable for a specific application at a time, reducing the construction time and better ensuring the correct implementation of interventions.

Depending on the type of reinforcement elements, these reinforcement elements are applied to the outer surface of the node area, beam or column of the existing reinforced concrete structure of the building by means of chemical or mechanical anchor-type fixing means, i.e. by inserting the reinforcement into corresponding holes made in the concrete volume, and then fixing the reinforcement inside the holes with chemical resins and/or mechanical expansion means.

The use of chemical or mechanical anchor-type fixing members to apply the reinforcing elements to the existing reinforced concrete structure of the building allows the installation to be performed quickly without the need for special labour and without the need for preparation work on the surface of the structure or mixing or blending in the field, thus being cleaner and reducing the production of waste.

Preferably, the plates forming the aforementioned first type of reinforcement elements (hereinafter referred to as reinforcement plates) have holes suitably distributed on the surface of the plates, for example according to a symmetrical arrangement with respect to at least one axis, preferably according to a symmetrical arrangement with respect to a pair of orthogonal axes, so as to ensure a sufficient fixing of the plates to the respective node areas of the reinforced concrete structure.

Preferably, the truss girder elements forming the aforementioned second type of stiffening element comprise a first longitudinal element extending in a substantially rectilinear direction, a second longitudinal element extending in a substantially rectilinear direction parallel to the first longitudinal element, and pairs of forming bars extending along a substantially sinusoidal or substantially wave-shaped path, the pairs of forming bars being offset with respect to each other and each connected to the first and second longitudinal elements at respective opposite vertices.

The truss girder elements forming the aforementioned second type of reinforcement element may further comprise end plates on at least one of their opposite longitudinal ends, the end plates having holes for allowing the elements to be connected to the reinforced concrete structure by means of anchor-type fixing members. Preferably, the holes are arranged at a pitch corresponding to the pitch of the holes of the reinforcement plates, so as to allow the end plates of the truss girder elements to be attached to the reinforced concrete structure by means of anchor-type fixing members at the reinforcement plates, thereby creating a continuous reinforcement structure extending horizontally from the node area along one or both girders joined at the node area, and/or extending vertically along columns joined at the node area.

Furthermore, in the node area of the reinforced concrete structure to be reinforced, steel connection elements may be provided, to which opposite ends of the support element may be connected. In particular, the connecting element may be connected to the node area at the aforementioned reinforcement plate, preferably using a portion of the same anchor-type fixing member for connecting the respective reinforcement plate to the reinforced concrete structure, in such a way as to be oriented at an angle with respect to the beam and with respect to the column engaged in said node area, and thus with respect to both the horizontal and vertical directions, whether at an angle.

Preferably dissipation means of a type known per se can be associated with the support elements and are preferably positioned in alignment with these elements. In this way, the seismic damping function by means of energy dissipation is added to the reinforcing function of the reinforcing structure.

Due to the application of external insulation and finishing systems, the improvement of building shock resistance is combined with the improvement of the same building energy performance.

For this purpose, a support element for supporting the heat insulation panel is connected to the reinforcing element of the reinforcing structure. More specifically, a plurality of vertical struts, which in turn carry a plurality of horizontal profiles, act as support elements for supporting the heat insulation panels, are connected to the steel truss girder elements applied to the outer surfaces of the girders of the building existing structure, preferably by means of the same anchor fixing members for mounting the steel truss girder elements to the outer surfaces of the girders of the building existing structure.

The above-mentioned vertical struts and horizontal profiles thus form a supporting frame for the cladding sheets, which can be easily adapted to the geometry of the building facade, especially in view of the presence of openings such as windows. If access to the building structure is required, for example to check the condition of the building structure after a major earthquake, the support frame can be easily removed in whole or in part.

The vertical struts and the horizontal profiles are advantageously made of non-degradable materials, such as aluminium, PVC, etc.

Depending on the surface condition of the building facade, the external insulation and finishing system and the associated supporting frame may be mounted close to the facade or at a distance from the facade, for example a few centimetres, in order to compensate for any irregularities in the surface or to create an air space between the facade and the insulation layer, so called "ventilation facade".

The support frame for the insulation, and in particular the vertical struts of the frame, also serves as a means of preventing the exterior infill wall of the building from tilting, as it limits any movement of the masonry which tends to tilt outwards in the event of a seismic event.

In this way, the reinforcing structure and the external insulation and finishing system, and the associated supporting frame, joined to the existing structure of the building, are integrated to form a single retrofit system that can be applied to the outer shell of the existing building in order to improve their anti-seismic and energy performances.

Drawings

Further characteristics and advantages of the invention will become more apparent from the following description, given purely by way of non-limiting example with reference to the accompanying drawings, in which:

FIG. 1 is an elevation view of a portion of a reinforcing structure and supporting frame for an external insulation and finishing system, forming part of a system for improving the seismic and energy performances of a building having a frame structure of reinforced concrete;

figures 2 and 3 are respectively a front view and a cross-sectional side view of the peripheral node area of the frame structure of the building, on which steel reinforcement plates are applied as part of the reinforcement structure of figure 1;

FIG. 4 is an elevation view showing in detail the steel truss girder elements forming part of the reinforcement structure of FIG. 1;

fig. 5 is a front view of a node area to which a connecting element for connecting a support element is applied in addition to the stiffening element shown in fig. 1;

fig. 6 is an elevation view showing the beam portion of the building of fig. 1 between two columns, to which the reinforcing element of fig. 1 is applied;

figures 7 and 8 are front and side views, respectively, showing in detail the connection between the steel truss girder elements forming part of the reinforcing structure of figure 1 and the ends of two vertical struts forming part of the supporting frame of the external insulation and finishing system of figure 1;

figures 9, 10 and 11 are respectively a front view, a side view and a plan view of the connection zone between a vertical strut and a pair of horizontal profiles of the support frame of figure 1; and

figures 12 and 13 are schematic side views, in turn illustrating the installation of the insulating panels on the support frame of figure 1.

Detailed Description

Fig. 1 shows a portion of the periphery of a frame structure 10 made of reinforced concrete of an existing building to which a system for improving earthquake resistance and energy performance according to an embodiment of the present invention is applied.

For the purpose of the present invention, it is only the peripheral portion of the entire frame structure of the building that is relevant, so that the term "frame structure" used hereinafter is to be understood as referring to the peripheral portion of the entire frame structure, comprising a plurality of peripheral posts 12 and peripheral beams 14 intersecting each other in a peripheral node area 16 in a manner known per se.

On the inside of the frame structure 10 there is typically a floor 18 (as partially shown in fig. 3), the floor 18 being externally connected to the perimeter beams 14 and being internally supported by internal beams 20 (only one of which is shown in fig. 3).

The system for improving the earthquake-resistant and energy-resistant properties of a building according to the present invention basically comprises a reinforcing structure applied to the outer surface of the frame structure 10, i.e. to the outer surfaces of the perimeter columns 12, the perimeter beams 14 and the perimeter node areas 16, to enhance the earthquake resistance of the building, and an external insulation and finishing system comprising a plurality of insulation panels 22 (as shown in fig. 12 and 13), which insulation panels 22 are supported by a supporting frame attached to the above reinforcing structure.

The reinforcing structure basically includes a steel reinforcing plate 24 applied to the outer surface of the perimeter node area 16 and a reinforcing element 26 formed as a steel truss girder element, the reinforcing element 26 being applied to the outer surface of the perimeter beam 14 and preferably (as in the example of fig. 1) also to the outer surface of the perimeter column 12.

Referring to fig. 2 and 3, each reinforcement plate 24 is secured to the outer surface of the corresponding peripheral node region 16 by means of a securing member 28, the securing member 28 preferably being formed as a chemical or mechanical anchor-type securing member. An example of a fixing member 28 is shown in fig. 8, wherein the fixing member 28 is used for fixing the truss girder element 26 to the perimeter beam 14, the fixing member 28 comprising in a per se known manner steel bars 30, which steel bars 30 are intended to be inserted into corresponding holes 32 formed in the concrete volume and subsequently fixed in the holes 32 with chemical resins and/or mechanical expansion means (not shown).

The reinforcement plate 24 is preferably rectangular. Further, in the example of fig. 1 and 2, the reinforcing plate 24 is installed with its long side directed in the vertical direction, and preferably has a length greater than the thickness of the peripheral beam 14. Alternatively, the reinforcing plate 24 may be installed with its long side directed in the horizontal direction in whole or in part, and preferably has a length greater than the width of the peripheral post 12. The reinforcement plate 24 may also have a cross or T-shape to be applied not only to a portion of two perimeter columns 12, but also to a portion of one or both of the perimeter beams 14 that are joined in the perimeter node area 16 to be applied not only to a portion of the perimeter beams 14, but also to a portion of one or both of the perimeter columns 12.

To allow the insertion of the fixing members 28, the reinforcing plates 24 each have a plurality of holes suitably distributed on the surface of the plates, preferably according to a symmetrical arrangement with respect to at least one axis, in particular parallel to the axis of one of the two sides of the plates, more preferably according to a symmetrical arrangement with respect to a pair of orthogonal axes.

As described above, in addition to the reinforcing plates 24, the reinforcing structure includes reinforcing elements 26 (hereinafter, simply referred to as "reinforcing elements 26" for convenience) that make up truss girder elements, the reinforcing elements 26 being applied to the outer surfaces of the perimeter columns 12 and the perimeter beams 14 in the example of fig. 1 and connected to the reinforcing plates 24 in the perimeter node areas 16.

Referring to fig. 4, each stiffening element 26 includes a first end plate 34 having an aperture 34 a; a first longitudinal element 36 (upper longitudinal element, according to the orientation of the stiffening element 26 in fig. 4) extending in a substantially rectilinear direction (horizontal direction with respect to the view of the person viewing fig. 4); a second longitudinal element 38 (lower longitudinal element, according to the orientation of the stiffening element 26 in fig. 4) extending in a substantially rectilinear direction parallel to the first longitudinal element 36; a pair of shaped bars 40 extending along a substantially sinusoidal or more generally wave-shaped path, offset relative to each other, and each connected to the first and second longitudinal elements 36, 38 at respective opposite vertices; and a second end plate 42 having a hole 42 a.

The holes 34a in the first end plate 34 and the holes 42a in the second end plate 42 allow the reinforcement members 26 to be connected to the reinforced concrete structure by means of the same securing members 28 used to connect the reinforcement plates 24. Preferably, the holes 34a in the first end plate 34 are arranged at a mutual spacing corresponding to the hole spacing in the reinforcement plate 24, to allow the reinforcement elements 26 to be applied to the reinforced concrete structure at the reinforcement plate 24 by means of the fixing members 28 of the first end plate 34, so as to create a continuous reinforcement structure extending horizontally from the perimeter node area 16 along one or both of the perimeter beams 14 joined at said node area, and/or extending vertically along the perimeter columns 12 joined at said perimeter node area.

Preferably, the stiffening element 26 further comprises a plurality of bushings 44, the plurality of bushings 44 being arranged in the joint area between the first longitudinal element 36 and the forming bar 40 and/or in the joint area between the second longitudinal element 38 and the forming bar 40 to allow the insertion of fixation members, for example of the same type as the fixation members 28 for fixing the stiffening plate 24 and for fixing the end plates 34 and 42 of the stiffening element 26.

Fig. 5 shows the peripheral node area 16 where the stiffening plate 24 is applied. The reinforcement plate 24 is connected to the end plates 34 of the four reinforcement elements 26, two end plates for joining to the perimeter columns 12 of the perimeter node area 16, and two end plates for joining to the perimeter beams 14 of the perimeter node area 16. Furthermore, in the example of fig. 5, steel connecting elements 46 are applied to the reinforcing plates 24 for connecting opposite ends of the supporting elements 48 (only partially shown in fig. 5, where they are shown in broken lines), preferably using holes provided in the plates and the same fixing members 28 for fixing the plates to the underlying reinforced concrete structure. These connecting elements 46 are oriented at an angle with respect to the peripheral columns 12 and the peripheral beams 14, and thus with respect to the horizontal and vertical directions (in fig. 5, the angle is approximately 45 °, but the angle may be greater or less than 45 ° depending on the particular application).

Preferably, dissipating means (not shown in the figures, but in any case of a type known per se) may be associated with the support element 48 and preferably arranged in alignment with said element. Thus, the stiffening function performed by the stiffening structure described above may also be accompanied by a seismic damping function through energy dissipation.

Fig. 6 shows an elevation view of a portion of the above-described reinforcing structure applied to the perimeter beam 14 between two perimeter columns 12. In addition to the reinforcement plates 24 applied to the two peripheral node areas 16, wherein the peripheral beam 14 extends at the two peripheral node areas 16, two reinforcement elements 26 are applied along the entire length of the peripheral beam 14. For this purpose, the end plates 42 of the reinforcement elements 26 are juxtaposed to one another and are connected to one another and to the peripheral beam 14 by means of connecting plates 50.

Referring again to fig. 1, the support frame for supporting the insulation panels 22 forming the external insulation and finishing system includes a plurality of vertical struts 52 and a plurality of horizontal profiles 54.

Each vertical strut 52 is fixed at its upper and lower ends to a respective stiffening element 26, the stiffening element 26 being fixed to the respective peripheral beam 14, advantageously by means of the same fixing members 28, in the region of the bushings 44 (fig. 7 and 8). As can be seen in fig. 11, each vertical strut 52 preferably has a U-shaped cross section and is mounted with its end wall 52a parallel to the front face of the building.

Referring to fig. 9-11, each horizontal profile 54 is secured at its opposite ends to a respective vertical strut 52, for example by means of gussets 56 and bolts 58. Each horizontal profile 54 preferably has a double-T-shaped cross section, has a pair of side walls 54a and a connecting wall 54b connecting the side walls 54a to each other, and is mounted such that the side walls 54a face in the vertical direction, and thus the connecting wall faces in the horizontal direction.

The vertical struts 52 and the horizontal profiles 54 are advantageously made of a non-degradable material, such as aluminium, PVC, etc.

The spacing between the vertical struts 52 and the spacing between the horizontal profiles 54 can be easily adapted to the geometry of the building facade, especially in view of the presence of openings, such as the window F shown in fig. 1.

Finally, with reference to fig. 12 and 13, the outer side wall 54a of the horizontal profile 54, i.e. the side wall 54a facing away from the building front, is inserted into special slits 60 provided on the upper and lower sides of the insulating panel 22, so as to join the insulating panel 22 to the supporting frame and thus to the building. Fig. 12 and 13 also show how the insulation panels 22 are installed by first installing a row of panels on top of the previous row of panels, then installing the horizontal profile 54 to securely join the row of panels that was just installed, and so on.

The insulation panel 12 and the supporting frame formed by the vertical struts 52 and the horizontal profiles 54 may be mounted on a facade as shown in the example of fig. 12 and 13, or at a distance from the facade, for example a few centimetres, in order to compensate for any non-planarity of the surface, or in order to create an air space between the facade and the insulation layer.

The invention has been described so far with reference to the preferred embodiments thereof. It is to be understood that other embodiments sharing the same inventive core are contemplated, all falling within the scope of the appended claims.

Claims (12)

1. A system for improving the seismic and energy performance of an existing building having a reinforced concrete frame structure (10) with a plurality of perimeter columns (12) and a plurality of perimeter beams (14) intersecting each other in a perimeter node area (16), the system comprising:

-a reinforcing structure (24, 26) having steel reinforcing plates (24), arranged to be fixed to the outer surface of the perimeter node area (16), and reinforcing elements (26) made of steel truss girder elements, arranged to be fixed to the outer surfaces of the perimeter columns (12) and the perimeter beams (14); and

-an external insulation and finishing system having a supporting frame (52, 54) carried by the reinforcing structure (24, 26) and formed by a plurality of vertical struts (52) and a plurality of horizontal profiles (54), and a plurality of insulation panels (22) mounted on the supporting frame (52, 54).

2. System according to claim 1, wherein each of said stiffening plates (24) has holes (24 a) distributed over its entire surface, preferably according to a symmetrical arrangement about at least one axis, more preferably according to a symmetrical arrangement about a pair of orthogonal axes, to allow the insertion of anchor-type fixation members (28) for fixing the stiffening plate (24) to the respective peripheral node area (16).

3. The system according to claim 1 or 2, wherein the stiffening plate (24) has a rectangular shape and/or a cross shape and/or a T shape.

4. The system according to any one of the preceding claims, wherein each of the stiffening elements (26) comprises a first longitudinal element (36) extending in a substantially rectilinear direction, a second longitudinal element (38) extending in a substantially rectilinear direction parallel to the first longitudinal element (36), and a pair of forming bars (40) extending along a wavy path, in particular a substantially sinusoidal path, the forming bars being offset with respect to each other and each connected to the first longitudinal element (36) and the second longitudinal element (38) at respective opposite vertices.

5. The system of claim 4, wherein each of the stiffening elements (26) further comprises an end plate (34, 42) on at least one of its opposite longitudinal ends, the end plates (34, 42) having holes (34 a,42 a) for inserting anchor fixation members (28) for fixing the end plates (34, 42) to one of the peripheral columns (12) or one of the peripheral beams (14).

6. The system according to claim 4 or claim 5, wherein each of the stiffening elements (26) further comprises a plurality of bushing-like members (44), a plurality of bushing-like members (44) being arranged in the joint area between the first longitudinal element (36) and the forming bar (40) and/or in the joint area between the second longitudinal element (38) and the forming bar (40) for inserting anchor-type fixation members (28) for fixing a stiffening element (26) to one of the peripheral posts (12) or one of the peripheral beams (14).

7. The system according to any one of the preceding claims, wherein a vertical strut (52) of the support frame (52, 54) is connected to a stiffening element (26) of the stiffening structure (24, 26), and wherein a horizontal profile (54) of the support frame (52, 54) is connected to the vertical strut (52).

8. The system according to any one of the preceding claims, wherein each of the horizontal profiles (54) of the support frame (52, 54) has a lateral vertical wall (54 a), and wherein the insulating panel (22) has slits (60) on its respective upper and lower sides for inserting the lateral vertical walls (54 a) of the horizontal profiles (54).

9. Method for improving the seismic and energy performance of an existing building, the building having a reinforced concrete frame structure (10) with a plurality of perimeter columns (12) and a plurality of perimeter beams (14) intersecting each other in a perimeter node area (16), the method comprising the steps of:

a) Applying steel reinforcement plates (24) to the outer surface of the peripheral node area (16) of the frame structure (10) and applying reinforcement elements (26) making up steel truss girders to the outer surfaces of the peripheral columns (12) and peripheral beams (14) of the frame structure (10), the reinforcement plates (24) and the reinforcement elements (26) forming reinforcement structures (24, 26) arranged to enhance the shock resistance of the frame structure (10),

b) -mounting a supporting frame (52, 54) formed by a plurality of vertical struts (52) and a plurality of horizontal profiles (54) on said reinforcing structure (24, 26), and

c) A plurality of insulation panels (22) are mounted on the support frames (52, 54) to form an external insulation and finishing system.

10. Method according to claim 9, wherein the reinforcement plates (24) and the reinforcement elements (26) of the reinforcement structure (24, 26) are fixed to the outer surface of the peripheral node area (16) of the frame structure (10) and to the outer surfaces of the peripheral posts (12) and the peripheral beams (14) of the frame structure (10), respectively, by means of chemical or mechanical anchor fixing members (28).

11. The method according to claim 10, wherein the vertical struts (52) of the support frame (52, 54) are connected to the stiffening elements (26) of the stiffening structure (24, 26) by means of identical anchor-type fixing members (28) for fixing the stiffening elements (26) to the perimeter beams (24) of the frame structure (10).

12. The method according to claim 10 or claim 11, wherein the insulating panel (22) is mounted between pairs of vertically adjacent horizontal profiles (54) of the supporting frames (52, 54) and is connected to the horizontal profiles (54) by inserting side vertical walls (54 a) of the horizontal profiles (54) into slits (60) provided on the upper and lower sides of the insulating panel (22).