WO2010018269A1

WO2010018269A1 - Seismic energy dissipater for a primary resistant structure of a construction

Info

Publication number: WO2010018269A1
Application number: PCT/ES2009/000419
Authority: WO
Inventors: Amadeo Benavent Climent
Original assignee: Universidad De Granada
Priority date: 2008-08-07
Filing date: 2009-07-28
Publication date: 2010-02-18
Also published as: CR20110125A; ES2357591A1; ES2357591B2

Abstract

The invention relates to a seismic energy dissipater for the primary resistant structure of a construction, which can be installed in a structure as a traditional diagonal bar. In response to axial loading, the invention dissipates energy in a stable manner without buckling. The dissipater is formed by two or more telescopically arranged tubes connected at multiple connection points by means of welds or screws. Two rows of perforations are provided in the areas close to the connection points on the walls of the tubes, the number, shape and separating distance thereof determining the volume of plastic-coated steel and the axial stiffness and resistance of the dissipater. In addition, a larger perforation is provided at either end of the aforementioned two rows of perforations. The end of each tube is joined to the primary structure using plates. Optionally, springs can be provided inside the tubes.

Description

SEISMIC ENERGY SINK FOR A PRIMARY RESISTANT STRUCTURE OF A CONSTRUCTION

FIELD OF THE INVENTION

The present invention falls within the field of home design and construction, non-residential building and civil engineering works, and has its maximum application in building structures (residential or not). The invention is part of the "energy dissipation" devices that are installed in the structures to protect them against earthquakes. These types of devices are included in the so-called "passive control systems".

BACKGROUND OF THE INVENTION

Earthquakes can introduce a large amount of energy (seismic energy input) into buildings, which if they are not able to absorb or dissipate, will cause them to collapse (collapse). In traditional solutions of seismic-resistant structures, this seismic energy input is dissipated by means of plastic deformations in the primary resistant elements of the construction (mainly beams and pillars), which implies causing significant structural damage. These traditional solutions have the sole objective of preventing the structure from falling apart during the earthquake so that its inhabitants have time to escape, but they assume that after the earthquake the building may be so damaged that it is necessary to demolish it.

In recent decades, innovative solutions have been developed generally called "passive control systems" that consist of installing special devices called "energy dissipators" in the structure that are responsible for dissipating practically all the energy introduced by the earthquake. In this way, the damages can be concentrated in specific points of the construction (in the heatsinks themselves) and avoid damaging the primary resistant elements of the construction (mainly the pillars and beams that must bear the gravitational loads). The heatsinks function as "seismic fuses" that can easily be replaced by new ones after the earthquake. In this electric simile, the pillars and beams of the structure would constitute the "cables" of the installation, and the Earthquake an electrical overload in the circuit.

Passive control systems are increasingly popular, and constitute a solution that allows the construction to be adjusted to the modern seismic regulations of many countries that have adopted the paradigm called "performance based design". The benefits-based project seeks not only to prevent the loss of human life in the face of a severe earthquake, but also to control (minimize or avoid) damage to the primary resistant elements of the construction.

Energy dissipators are of several types: hysteretic, viscous or viscoelastic. The invention object of this patent is of the first type. Hysterical energy dissipators consist of a metallic element that deforms inelastically under different types of load. In recent years, several energy-dissipating elements of the hysteretic type have been developed: X-shaped or triangular steel plates that deform to bending, perforated steel sheets that are deformed to shear, circular section bars subjected to bending or torsion , steel bars that deform in the axial direction etc.

In all cases, to install the energy dissipation element in the building it is necessary to use an auxiliary secondary structure that joins the energy dissipation element to the beams, pillars or beam-pillar nodes of the main structure of the construction. In the case of X-shaped or triangular steel sheets, perforated steel sheets, or bending or torsion bars, this auxiliary secondary structure normally consists of reinforced concrete or steel walls (see for example the patent Japanese 7-158315A), or also in metallic triangulations. Sometimes perforated steel plates are installed directly on the beam-pillar node (see for example Japanese patent 2000204788) and the auxiliary secondary structure is reduced to plates welded to the energy dissipating element. In the case of bars subjected to axial deformations, the auxiliary secondary structure must ensure that the bar can freely deform without compression buckling. For it

The bar that constitutes the energy dissipating element is embedded in concrete walls or in steel tubes filled with concrete that are installed in the primary structure of the construction as conventional diagonal bars (see for example Japanese patent 6-57820A). This solution is known as "bars with restricted buckling"("buckling restrained brace" or "unbonded brace"). The existing solutions cited present several problems. First, the auxiliary secondary structures of the concrete wall type increase the structure's own weight (and with it the inertia forces generated by the earthquake), reduce the diafanity of the spaces, hinder or not allow the opening of gaps and significantly restrict The flexibility in the design of the building. These problems, a little less pronounced, also occur when the secondary auxiliary structure consists of metallic triangulations instead of steel or concrete walls. The alternative of installing dissipating elements based on perforated steel sheets directly at the nodes significantly complicates their construction. Second, the cost of auxiliary secondary structures or complex solutions for the nodes is usually greater than the cost of the energy dissipating element itself, and this makes the entire passive control system more expensive. Third, the joints (normally screwed or welded) between the energy dissipating elements (plates or bars) and the auxiliary secondary structure must be very careful so that they do not affect the properties of the material to be deformed plastically; The execution of these unions also increases the cost of the complete passive control system. In the case, of the steel bars subjected to axial deformations ("bars with restricted buckling"), it is necessary to coat the energy dissipating element with a material that prevents adhesion with the concrete, and then embed it inside a steel tube concrete filling, which makes the solution more expensive and also does not allow visually inspect the energy dissipating element after the earthquake.

These problems are minimized or disappear with the new heatsink object of this patent. First, in comparison with the dissipating elements of the X-shaped or triangular steel sheet type, perforated sheet steel or bending or torsion bars, the invention object of this patent does not require any auxiliary secondary structure because the walls of the Steel tubes that join the main structure of the building constitute the material or energy dissipating element that plasticizes. This reduces costs and extra weights in construction. The new invention can be installed in the main structure of the building as a conventional diagonal bar and therefore has less impact on the diafanity of the spaces and can be incorporated more flexibly in the design of the building. In addition, it does not require any type of union between the energy dissipating element that plasticizes and the steel tube that joins it to the primary structure of the building, since both parts are integrated. All this greatly simplifies the design of the heatsink and significantly reduces the costs of Manufacturing and installation

Unlike the "bars with restricted buckling" that are also installed in the main structure of the building as conventional diagonal bars, the new heatsink object of this patent does not need any coating or outer tube of steel filled with concrete to avoid the buckling of the element that plasticizes; The telescopic arrangement of the two tubes and the perforations in the walls thereof make the diagonal bar plasticize before panning. Another important advantage of the new heatsink with respect to "bars with restricted buckling" is that in the first part the parts that deform plastically (the walls of the tube) are visible and are therefore easy to inspect since they are not covered by concrete and outer steel tubes as with "bars with restricted buckling". In short, the new heatsink object of this patent is much simpler than existing solutions and allows to reduce costs substantially.

DESCRIPTION OF THE INVENTION

The invention relates to a seismic energy dissipator for a primary resistant structure of a construction, that is, the set of beams, columns, slabs or bases that are part of the structure of the construction. Said energy dissipator is applicable in those situations in which the primary resistant structure is subjected to loads due to oscillations or vibrations, due to earthquakes when oscillations and vibrations are high, or may also be due to wind or other agents that may cause oscillations in smaller buildings than those created by earthquakes, said loads being supported, due to their intermittent, sporadic or occasional character, due to elements other than the resistant structure of the construction.

In accordance with the invention, said hysterical seismic energy dissipator, comprises at least two tubes arranged telescopically and connected to each other at least one point of attachment. In at least one wall of at least one of the tubes there will be at least one perforation made around a junction point. In the case of more than one perforation, each of them would be located around a different point of attachment. The function of said perforations is to allow the tubes a capacity to plasticize, absorbing an energy, deforming around the Ia drilling. In this way the energy is absorbed by the energy sinks and not by the resistant structure. In case these heatsinks become unusable, they may be replaced by new heatsinks. The control of the dissipated energy is exerted by modifying the number of perforations in the surface of the tube wall, as well as the perforated area. The perforated area also has an impact on the threshold of effort required for the heatsink to start dissipating energy, not being effective for stress values below that threshold. Finally, the energy dissipator has closure plates that cover or close the ends of the tubes and connection plates that connect the tubes with the primary resistant structure. The heatsinks made as described allow plasticizing specific and predetermined areas of the walls of the tubes when they are subjected to axial loads in the direction of the tube guideline. In the same way, by means of a simple configuration and of easy execution, an structural element can be installed in a construction such as a simple conventional diagonal bar, but with the advantage that it is able to dissipate energy in a stable way, without buckling, by means of plastic deformations.

The connection between the different tubes that form the energy dissipator can be carried out by welding, so that there will be no possible relative movement between the different tubes that form the dissipator. Alternatively, the union can be carried out by means of screws. Said screws may be smaller than the housing defined by the attachment points. Therefore, there will be some clearance between the screw and the point of attachment, the larger the smaller the screw or the larger the housing at the point of attachment. In this way it is possible that small oscillations do not have to be absorbed by the energy dissipator, absorbing only those efforts that cause a relative movement between the tubes greater than the clearance mentioned above.

The tubes inside may be empty. In this sense, the thickness of the tube wall is also a parameter that influences the energy that the heatsink can absorb, since, the thicker the tube wall, the more energy the dissipation of the invention can dissipate.

Inside the tubes, or only one of them, at least one elastic element may be placed, such as a spring, spring, or elastomeric material, anchored at a first end to the resistant structure and by a second end to a fixed point inside the tube. In this way two effects are achieved, on the one hand the heatsink would always be in a centered position and, more importantly, an elastic behavior in collaboration with the previous one would be added to the purely hysterical behavior of the invention. In this way, for example, the failure of the hysteretic heatsinks could be compensated and react to any oscillation, regardless of the threshold defined by the perforations performed.

DESCRIPTION OF THE FIGURES

Figure 1.- Shows the basic version of the heatsink of the invention. Figure 2.- Shows a cross section of the basic version of the heatsink of the invention. Said section is made by a plane perpendicular to the axis of the tube, said plane containing one of the perforations that lies between two points of attachment.

Figure 3.- Shows a longitudinal section of the basic version of the heatsink of the invention, made by a wall of the tube that does not contain perforations. Figure 4.- Shows a detailed view of the perforations and junction points of the heatsink of the invention in which the union is carried out by means of screws.

Figure 5.- Shows a cross section of the heatsink of Figure 4, made by a plane perpendicular to the axis of the tube, said plane containing one of the perforations that is between two junction points.

Figure 6.- Shows a longitudinal section of the heatsink of Figure 4. The section has been made by one of the walls of the tube that do not have perforations.

Figure 7.- Shows a longitudinal section of the embodiment of the heatsink comprising springs inside the tubes. The section has been made by a tube walls that have no perforations. Figure 8.- Shows a first mode of placement of the heatsink of the invention within a porticoed structure. The heatsink is aligned with the axis that defines the centers of two diametrically opposed beam-pillar knots in the rectangle that form the adjacent beams and pillars.

Figure 9.- Shows a second mode of placement of the heatsink of the invention within a porticoed structure. The heatsink is aligned with an axis that joins the center of one of the beam-pillar nodes with an intermediate point of the beam. Figure 10.- Shows a third way of placing the heatsink of the invention in a triangulated structure or in latticework. The heatsink of the invention introduced by replacing one or more elements of the triangulated or lattice structure.

PREFERRED EMBODIMENT OF THE INVENTION

The object of this invention is a new energy sink of simple, cheap and easy to inspect hysteretic type, which can be installed in the primary structure of a construction such as a conventional diagonal bar subjected to axial solicitations, and which is capable of dissipating energy stably and without buckling. The new heatsink, see Figure 1, is formed by two tubular profiles, made for example in steel, hereinafter they will be called tubes, of square section, although no other type of section such as circular is excluded, for example, arranged in a way telescopic, that is an inner tube (1) inside an outer tube (2). The connection between both tubes (1, 2) is made at several points of connection (3) by welding. In the walls of the tubes (1, 2) and specifically in areas close to the junction points (3), two preferably parallel rows of perforations (4) are made, one on each side of the line that joins the centers of the junction points (5). The number, the geometry and the separation between these perforations is variable and with these three parameters the volume of steel to be plasticized is controlled, as well as the axial strength and rigidity of the heatsink. At both ends of the two preferably parallel rows of perforations (4) a larger perforation (6) is performed. The end of each tube (1, 2) joins the primary structure of the construction as if it were a conventional diagonal bar, preferably by connecting plates (7). The ends of the tubes are terminated with a closure plate (8) preferably welded. Figures 2 and 3 show a cross section and a longitudinal section of the heatsink, respectively.

The heatsink of the invention operates under axial tensile / compression loads in the direction of the tube axis (1, 2). When the new heatsink is subjected to said axial loads and a tube (1, 2) tries to slide with respect to the other, the steel of the tube wall (1, 2) located between the perforations deforms plastically and thereby dissipates energy.

The above description constitutes an embodiment of the new heatsink, whose Hysteretic behavior is of the elastoplastic type. This embodiment can have the following variants, and all of them form part of the invention: the section of the tube can also be rectangular, circular, rhomboidal, etc .; the number of telescopically arranged tubes can be greater than two; The position of the perforations along the tubes can be centered, at the ends or in one or more areas along the axis of the tubes; the number of faces of the perforated tubes can be one, several or all; the number of tubes that are drilled can be one, several or all; The material of the tubes can be steel, aluminum, special alloys, plastics etc.

In addition to these variants, the invention includes different embodiments of the new heatsink consisting of introducing one or both of the following modifications:

A) The second embodiment is illustrated in Figures 4, 5 and 6 showing an elevation, a cross section and a longitudinal section of the central part of the heatsink, respectively. This second embodiment is based on replacing the welds at the junction points (3) with screws (9), and leaving a controlled clearance between the diameter of the screw and that of the hole (10) made in the center of the joint point (5). ). With this it is achieved that the heatsink does not work, that is, that the walls of the tubes (1, 2) do not deform, when the relative axial displacement between the ends of the tubes is less than the clearance. This feature may be desirable when it is intended to avoid fatigue problems under low amplitude cyclic loads caused, for example, by wind or vibrations, for which the collaboration of the heatsink may not be desirable.

B) The third embodiment is illustrated in Figure 7 which represents a longitudinal section of the heatsink. This modification consists of incorporating into the tubes (1, 2) two springs (11, 12) joined by one or more central bars (13) and an edge plate (14), which allow adding to the hysterical law of the heatsink a Purely elastic component, and give it recentration properties. The springs (11, 12) and the central bars (13) can be replaced by an elastomeric or viscoelastic material that fulfills a similar function.

Once the energy dissipator of the invention has been described, three possible alternatives for placing said energy dissipator in resistant structures are described below. Figure 8 shows a first mode of placement of the heatsink (15) of the invention, installed within a porticoed structure (16) that can be metal, reinforced concrete, wood etc. The porch consists of beams (17), columns (18) and beam-column knots (19). The heatsink is arranged aligned with the axis defined by the centers of two diametrically opposed beam-column knots (19) in the rectangle that form the beams (17) and adjacent columns (18). The heatsink comprises the tubes (1, 2), with perforations on their faces (22) and arranged telescopically, which are connected at the first and second points of attachment to the structure (23, 24) by means of welds or screws. The connections of the free end of the outer tube (2) at the first point of attachment to the structure (23), or of the free end of the inner tube (1) with the second point of attachment to the structure (24) can be real joints made with pins, or simple standard structural connections made with welded or bolted plates.

Figure 9 shows a second mode of placement of the heatsink object of this patent, installed inside a porticoed structure (16) that can be metallic, reinforced concrete, wood etc. The main difference with the embodiment of Figure 8 is that the heatsink is aligned with an axis that joins the center of one of the beam-column nodes (19) with an intermediate point of the beam (17). The configuration of Figure 9 allows to leave an open space in the opening that may be desirable to arrange doors or windows in it.

Figure 10 shows a third mode of placement of the heatsink object of the invention, installed in a triangulated or lattice structure that can be metal, reinforced concrete, wood etc. The latticework is generally formed by horizontal (27) or inclined cords, uprights (28) and diagonal bars (29). The new heatsink can be introduced by replacing one or more cords (30), uprights (31) or diagonal bars (32). With this it is possible to significantly increase the energy dissipation capacity of a structural type - the triangulated or lattice structures - which, when constructed with conventional bars, have a very low plastic deformation capacity, being limited by the buckling of the compression bars. .

The new heatsink can also be installed in the resistant structure, forming part of diada ("toggle brace") or "scissor" (scissors jack system) systems.

Claims

1. Seismic energy heatsink for a primary resistant structure of a construction, characterized in that it comprises: a) at least two tubes telescopically arranged and connected to each other at least one junction point, b) at least one hole in the at least one wall of at least one tube; at least one perforation is made around a junction point, c) closing plates that cover the ends of the pipes and connecting plates that connect the tubes with the primary resistant structure.

2. Energy dissipator according to claim 1, characterized in that the connection of the tubes is carried out by welding.

3. Energy dissipator according to claim 1, characterized in that the connection of the tubes is made by screws leaving a gap between the screw and the point of attachment.

4. Energy sink according to any of claims 1-3, characterized in that the inside of the tubes is empty.

5. Energy dissipator according to any one of claims 1-4, characterized in that the at least one tube comprises at least one elastic element connected by a first end attached to the resistant structure and a second end to a fixed point inside said tube.

6. Energy dissipator according to any of claims 1-4, characterized in that the at least one of the tubes comprises in its interior at least one elastic element joined by a first end connected to the resistant structure and by a second end to a fixed point inside said tubes.