US20120167490A1

US20120167490A1 - Structural protection system for buildings

Info

Publication number: US20120167490A1
Application number: US13/395,185
Authority: US
Inventors: Alessandro Balducci
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-09-10
Filing date: 2010-08-31
Publication date: 2012-07-05
Also published as: US20140059951A1; ITMC20090195A1; IT1395591B1; EP2475829B1; WO2011029749A1; CN102498253B; JP2013504700A; CN102498253A; EP2475829A1

Abstract

A structural protection system of buildings is described, comprising at least one bearing structure (2) connected with at least one wall of said building (E). The bearing structure (2) is rigidly connected to the wall of the building (E) and the bearing structure (2) is a specialized structure comprising an energy dissipation device (1) adapted to dissipate the energy generated by the oscillations of the bearing structure due to earth tremor.

Description

The present patent application for industrial invention relates to a structural system for seismic protection of buildings. The structural system according to the invention is especially suitable for seismic protection of existing buildings, with special reference to buildings that play an important social role, classified as strategic buildings (hospitals, schools, barracks, etc.) and also of new buildings.
FIG. 1 illustrates a structural system for seismic protection of buildings according to the prior art.
A plurality of dissipation devices (1) are installed in building (E) to be protected, being designed to dissipate the energy generated by the oscillations of the building due to earth tremor. According to the different techniques, said dissipation devices (1) are installed inside the building (E) or outside it on the walls.
The building (E) comprises a framework of the bearing structure. By framework we mean a frame composed of multiple floors (S) and vertical elements (P), such as pillars or bearing walls, in order to generate a plurality of spaces (M).
At least one dissipation device (1) is installed in each space (M) of said framework, in bracing configuration, preferably with diagonal direction with respect to the space (M).
Each dissipation device comprises a dissipation means (1 c) disposed between two rigid rods.
A first end (1 a) of the first rod of the dissipation device is tied to a portion of angle between the lower floor (S) of the space and a first lateral wall of the building.
A second end (1 a) of the second rod of the dissipation device is tied to a portion of angle between the upper floor (S) of the space and a second intermediate wall of the building.
Therefore each dissipation device (1) works autonomously and contributes to compensate wall deformations of each space (M) of the framework.
Such a structural system is impaired by a series of drawbacks due to the fact that the dissipation devices (1) must be disposed inside the building.
JP 09 235890 (Kajima Corp.) discloses a reinforcement and vibration-damping structure for existing buildings.
The purpose of the present invention is to eliminate the drawbacks of the prior art by disclosing a structural system that is able to oppose the oscillations of buildings due to earth tremor in an efficient and efficacious way.
Another purpose of the present invention is to provide such a structural system for seismic protection of buildings that is versatile and at the same time easy to make, install and maintain.
These purposes are achieved according to the present invention with the features claimed in independent claim 1.
Advantageous embodiments are disclosed in the dependent claims.
According to the invention the building to be seismically protected is combined with a specialized structure designed to oppose seismic actions by dissipating energy.
In case of existing buildings, the specialized structures can be simply installed in external position, without having to carry out any works inside the building.
The specialized structure can consist in a tower or frame or column with suitably rigidity, connected to the building by means of rigid rods with two hinges normally disposed at each floor level.
Hereinafter, for the sake of simplicity, reference will be always made to a specialized structure that consists in a tower.
The tower is tied at the base with a spherical joint or hinge. Therefore, the tower is free to oscillate in any direction around the spherical joint, rotating and pivoting on the joint (centre of rotation).
Dissipation devices or dampers are applied around the base of the tower, which strongly oppose the rotation and oscillation of the tower, thus suffering movements and dissipating energy by means of hysteresis cycles.
To amplify displacements (travel: elongation and shortening) of the dissipation devices, suitable mechanisms that operate by means of crank gears can be provided.
The global dissipation system, which is concentrated at the base of the tower, can be of any type.
Therefore, the main function of the tower is to oppose the effects produced by earth tremor by dissipating energy in the specialized area where dissipation devices of generic type (dampers) are installed.
The re-centering (balancing) of the tower is guaranteed by the elasticity of the building structure and also by elastic elements that can be connected in parallel to the energy dissipation means.
In new buildings the tower that acts as seismic-resistant-dissipation element can be inserted inside the building (for example in the stairwell-elevator area). The structural system of the invention has several advantages compared to the known systems.
Considerable cost reduction is obtained compared to traditional systems that are made inside the buildings and require additional works in addition to structural works.
If the external seismic-resistant-dissipation structure is of spatial type (tower), it can provide additional usable volume (enlargement), no longer being an end in itself (of structural type only) and with lower incidence of the seismic adaptation cost.
Such a seismic-resistant-dissipation structure can be, for example, a vertical connection element (stairs, elevator) or emergency staircase. Reference is made to the frequent installation of steel emergency staircases outside public buildings, which can also represent a seismic protection element if designed with the structural system of the invention.
Maintenance of dissipation devices can be carried out without interrupting the use of the building during maintenance works, consequently reducing the costs caused by the temporary lack of use.
The installation of the specialized structure can be carried out without interrupting the ordinary use of the building to be protected.
Dissipation devices are concentrated in a single specialized area with limited dimensions (tower base), which is consequently easy to inspect and maintain. For very high buildings the specialized dissipation area can be also positioned at higher levels, not only at the base of the tower.
The dissipation system of the invention guarantees high efficiency, taking full advantage of the devices, and high efficacy of the seismic-resistant devices that are concentrated in a single specialized area compared to the known methods with devices disseminated on the building, the operation of which is affected by the uncertain seismic reaction of the building as a whole, especially due to the presence of non-structural elements (walls in general, etc.).
The rigidity of external seismic-resistant structures with vertical development (tower, frame, column) connected by means of rigid rods to the building is such that it regularizes the deformation (horizontal floor displacements) of the building that is subject to earth tremor, which is generally irregular.
Complete reversibility of the system is guaranteed because no alterations are made to the building, as in case of internal works.
In case of hospital or school buildings, if the structural system of the invention has been correctly studied from an architectural viewpoint, it can provide improved design and improved operation with the use of additional structures (new spaces, services, etc.). This is made possible also because of the high formal flexibility of additional structures (for example, the tower can have a square, rectangular, polygonal, circular, etc. shape, can have a constant height or can be tapered vertically).

Additional characteristics of the invention will appear evident from the detailed description below, which refers to merely illustrative, not limiting embodiments, illustrated in the enclosed drawings, wherein:

FIG. 1 is a diagrammatic cross-sectional view along a vertical plane that shows a structural system for seismic protection of buildings according to the prior art;

FIG. 2 is a diagrammatic cross-sectional view along a vertical plane that shows a first embodiment of the structural system for seismic protection of buildings according to the present invention that provides for a specialized structure with distributed energy dissipation system;

FIG. 3 is the same view as FIG. 2, except for it shows a second embodiment of the structural system of the invention with specialized structure with energy dissipation system concentrated at the base;

FIG. 4 is a plan view of the structural system of FIG. 3;

FIG. 5 is a perspective view of the structural system of FIG. 3;

FIG. 6 is the same view as FIG. 3, except for it shows a different version of the energy dissipation system of FIG. 3, which provides for a lever mechanism that multiplies the travel of the energy dissipation device;

FIG. 6A is an enlarged view of the detail contained in circle (A) of FIG. 6.

FIG. 7 is the same view as FIG. 6, except for it shows the oscillation of the structural system of FIG. 6 during earth tremor;

FIG. 7A is an enlarged view of the details contained in circles (A) and (A′) of FIG. 7;

FIGS. 8 and 9 are two side elevation views that show a different version of the structural system of the invention, wherein the specialized structure consists in a planar frame;

FIG. 10 is a plan view of the structural systems of FIGS. 8 and 9;

FIG. 11 is a cross-sectional view along a vertical plane that shows the specialized structure disposed as nucleus inside the building;

FIGS. 12 and 12A are two side elevation views that show a different version of the structural system of the invention, wherein the specialized structure consists in a column;

FIG. 13 is a plan view of the structural system of FIG. 12; and

FIG. 14 is a perspective view of the structural system of FIG. 12.

Now referring to FIG. 2 a first embodiment of the structural system for seismic protection of buildings according to the present invention is disclosed.
The building (E) to be protected comprises a plurality of levels defined by floors (S) disposed according to horizontal planes. The structural system of the invention comprises at least one bearing structure (2) rigidly connected to the building (E).
The bearing structure (2) has basically the same height as the building (E) and is rigidly connected to the building by means of a plurality of rigid rods (3). The rod (3) is provided with a first end (3 a) tied to a wall of the building (E) and a second end (3 b) tied to the bearing structure (2).
Advantageously, the bearing structure (2) is provided with a plurality of horizontal reinforcement elements (S′) disposed at the same height as the floors (S) of the building (E). Advantageously, the rigid rods (3) are disposed according to horizontal straight lines on the floors (S) of the building and the corresponding reinforcement elements (S′) of the bearing structure.
The bearing structure (2) is a specialized structure that comprises an energy dissipation system adapted to dissipate the energy of the oscillations suffered by the bearing structure (2) due to earth tremor.
It must be noted that the specialized structure (2) is rigidly connected to the building (E). Therefore the energy dissipation system of the specialized structure is able to compensate and damp also the oscillations suffered by the building (E) during the shocks.
According to the embodiment of FIG. 2, the specialized structure (2) is a tower disposed outside the building (E) and the horizontal reinforcement elements are floors (S′) of the tower disposed between a first vertical wall (2 a) facing the building (E) and a second vertical wall (2 b) opposite the first vertical wall (2 a). In this way a vertical row of parallelepiped spaces (V) is defined in the tower (2).
One dissipation device (1) is disposed in each space (V) of the tower (2), in bracing configuration, diagonally, in such a way to generate an energy dissipation system of the specialized structure (2) distributed along the entire height of the specialized structure.
The dissipation device comprises an energy dissipation means (1 c) disposed between two rigid rods. The energy dissipation means (1 c) can be, for example, a chamber with fluid. A shock-absorbing element, such as elastic means, spring means or damper can be disposed in parallel position to the energy dissipation means (1 c).
In each space (V) the dissipation device (1) comprises:

- a first end (1 a) tied to a portion of angle between the lower floor (S′) of the space (V) and the first lateral wall (2 a) of the tower, and
- a second end (1 a) tied to a portion of angle between the upper floor (S′) of the space (V) and the second lateral wall (2 a) of the tower.

In the following description identical elements or elements corresponding to elements that have already been described are indicated with the same reference numerals, omitting their detailed description.
FIGS. 3-5 describe a second embodiment of the structural system of the invention, wherein the dissipation system is concentrated at the base of the tower (2).
In such a case, the base of the tower (2) is tied to a spherical joint or hinge (4) mounted on a base (B) fixed to the ground. The vertical axis of the tower (2) passes through the centre of the spherical joint (4).
A plurality of dissipation devices (1) is disposed in peripheral position around the spherical joint (4). Each dissipation device (1) is provided with a first end (1 a) tied to the base (B) and a second end (1 b) tied at the base of the tower. Advantageously, the tower (2) has a base (20) shaped as overturned pyramid, wherein the vertex of the pyramid is tied to the spherical joint (4).
As shown in FIG. 4, to protect the rectangular building (E), two specialized structures (2) are sufficient, being disposed in the long opposite sides of the building, near the opposite angles of the building.
The connection system of the tower (2) to the building (E) comprises four rigid rods (3) in each floor, disposed in W-configuration with three connection hinges (3 a) on the building (E) and two connection hinges (3 b) on the tower.
As shown in FIG. 5, each tower (2) is damped by eight dissipation devices (1) disposed at the four angles of the tower base and along the central lines of the four sides of the tower base.
Referring to FIGS. 6, 6A, 7 and 7A, a different version of the energy dissipation system is described.
As shown in FIG. 6A, according to this version, each dissipation device (1) is connected to a lever mechanism (5) to multiply the travel of the dissipation device (1), i.e. elongation/shortening of the dissipation device (1) to compensate the oscillation of the tower (2).
The lever mechanism (5) comprises two levers (L1, L2). The first lever (L1) is pivoted in the central point (F1) to a projection (51) of a flange (50) tied to the base (B). The second lever (L2) has a first end (La) pivoted at a projection of a flange (52) tied to the base (20) of the tower and a second end (Lb) pivoted at one end of the first lever (L1).
The dissipation device (1) has a first end (1 a) pivoted at a projection of the flange (52) tied to the base (20) of the tower and a second end (1 b) pivoted at the other end of the first lever (L1).
In idle state the dissipation device (1) is basically as long as the second lever (L2) and parallel to the second lever (L2) in such a way that first lever (L1), second lever (L2), flange (52) and dissipation device (1) form an articulated quadrilateral that can oscillate around the fulcrum (F1).
Referring to FIGS. 7 and 7A, when the building (E) suffers oscillation due to earth tremor, also the tower (2) that is rigidly tied to the building (E) suffers oscillation with horizontal displacement (δ_o) of the top of the tower. Consequently, the base (20) of the tower suffers a vertical displacement (δ_v) that must be damped and compensated by the dissipation devices (1).
If Li is the length of the dissipation device in idle state and Lf is the length of the dissipation device after compression or elongation due to oscillation of the tower, the travel of the dissipation device is determined by the relationship:
δ_D =|Li−Lf|
The travel (δ_D) of the dissipation device is related to the lever mechanism (5) and vertical displacement (δ_v) of the tower base.
(b1) is the distance between the fulcrum (F1) of the first lever (L1) and the fulcrum (Lb) of the second lever (L2) with the first lever (L1).
(b2) is the distance between the fulcrum (F1) of the first lever (L1) and the fulcrum (1Lb) of the dissipation device (1) with the first lever (L1).
As shown in FIG. 7A, the travel of the dissipation device is determined by the relationship:
δ_D =|Li−Lf|=δ _V*(1+b2/b1)
If the fulcrum (F1) is in the centre of the first lever (L1), i.e. (b1=b2), the travel of the dissipation device is:
δ_D=2*δ_V
The elongation or shortening of the dissipation device (1) will be twice as the vertical displacement (δ_V) of the base (20) of the tower.
Referring to FIGS. 8, 9 and 10, a different version of the structural system of the invention is disclosed, wherein the specialized structure is a planar frame (102) composed, for example, of a reticular framework.
Also in this case, the dissipation devices (1) can be disposed at the base of the frame (102). The frame (102) is tied to the ground by means of a planar hinge (104) instead of a spherical joint.
As shown in FIG. 10, to protect a rectangular building, four frameworks (102) are necessary, being disposed in the four sides of the building.
FIGS. 3, 5, 6, 7, 8 and 9 show five-story buildings and specialized structures (2; 102) provided with energy dissipation system concentrated only at the base of the structure.
However, in case of taller buildings, each specialized structure can be made of multiple overlapped parts that are mutually tied by means of a central hinge around which the dissipation devices are disposed. The connection between the various parts of the bearing structure is exactly made as the connection of the base of the bearing structure to the ground.
Referring to FIG. 11, if a new building (E) is built, the specialized structure (202) can be the nucleus of the building, that is to say a tower inside the building that is rigidly connected to the internal walls of the building.
In such a case, the tower (202) is provided with a specialized energy dissipation system, such as the systems described in the aforementioned embodiments.
Referring to FIGS. 12 12A, 13 and 14, a different version of the structural system of the invention is described, wherein the specialized structure is a column (302).
Also in this case, the dissipation devices (1) can be disposed at the base of the column (302). The column (302) is anchored to the ground by means of a spherical joint (4).
FIG. 12 A shows an embodiment of the present invention in which the base of the column (302) is a horizontal plane under which the dissipation devices (1) and relevant multiplier lever mechanisms (5) are mounted.
As shown in FIGS. 13 and 14, to protect a rectangular building, five columns (302) are necessary, being disposed in a row on the two long sides of the building. The columns (302) are mutually connected by means of rigid rods (303).
Numerous variations and modifications can be made to the present embodiments of the invention by an expert of the field, while still falling within the scope of the invention as claimed in the enclosed claims.

Claims

1. Structural protection system of buildings comprising at least one bearing structure connected with at least one wall of said building,

wherein

said bearing structure is rigidly connected with the wall of said building, and

said bearing structure is a specialized structure comprising an energy dissipation system adapted to dissipate the energy generated by the oscillations of the bearing structure due to earth tremor,

characterized in that

the bearing structure has a base and said energy dissipation system is arranged between the ground and the base of said bearing structure, the base of the bearing structure being tied to the ground by means of at least one spherical joint or hinge;

wherein said spherical joint or hinge is arranged on the vertical axis of the bearing structure and said energy dissipation devices are arranged in peripheral position with respect to said spherical joint or hinge.

2. Structural system as claimed in claim 1, wherein said bearing structure is rigidly connected to the wall of said building by means of rigid rods having a first end connected to the wall of the building and a second end connected to said bearing structure.

3. Structural system as claimed in claim 2, wherein that said rigid rods are arranged according to horizontal planes in correspondence with the floors of the building and the bearing structure provides for reinforcement elements arranged according to horizontal planes in correspondence with the floors of said building.

4. Structural system as claimed in claim 1, wherein the energy dissipation system is composed of a plurality of energy dissipation devices comprising an energy dissipation means arranged between two rigid rods.

5. Structural system as claimed in claim 4, wherein said energy dissipation device comprises a shock-absorbing element arranged in parallel position with respect to the energy dissipation means.

6. Structural system as claimed in claim 1, wherein said energy dissipation devices have a first end tied to the ground and a second end tied to the base of said bearing structure.

7. Structural system as claimed in claim 1, wherein said energy dissipation system comprises a lever mechanism adapted to multiply the travel of said energy dissipation devices during the oscillation of the bearing structure.

8. Structural system as claimed in claim 7, wherein said lever mechanism comprises a first lever pivoted at a flange tied to the ground and a second lever having an end pivoted at the base of the bearing structure and a second end pivoted at the first lever, in which the energy dissipation device has a first end pivoted at the base of the bearing structure and a second end pivoted at the first lever.

9. Structural system as claimed in claim 1, wherein the bearing structure is a tower external to the building.

10. Structural system as claimed in claim 1, characterized in that the bearing structure is a planar frame external to the building.

11. Structural system as claimed in claim 1, wherein the bearing structure is a tower situated inside the building.

12. Structural system as claimed in claim 1, wherein the bearing structure is a column.

13. Structural system as claimed in claim 1, wherein said bearing structure is composed of multiple overlapped parts tied by a central hinge around which said energy dissipation devices are arranged.