EP2683889B1

EP2683889B1 - Pillar for building constructions

Info

Publication number: EP2683889B1
Application number: EP12713289.2A
Authority: EP
Inventors: Franco Daniele; Gian Michele CALVI
Original assignee: Tecnostrutture Srl
Current assignee: Tecnostrutture Srl
Priority date: 2011-03-08
Filing date: 2012-03-08
Publication date: 2016-08-10
Anticipated expiration: 2032-03-08
Also published as: WO2013050812A1; EP2683889A1; ITUD20110030A1

Description

FIELD OF THE INVENTION

The present invention concerns a pillar made of steel and concrete which can be applied to bearing structures of single story or multistory buildings and which can be used in zones with an earthquake risk.

BACKGROUND OF THE INVENTION

Problems concerning pillars are known in seismic zones, where the pillars are subjected to lateral forces which affect the joints and from there the pillars themselves.
Here and hereafter in the description and claims, by joints we mean the zones of interconnection between the pillars and the bearing beams of the floors.
These lateral forces, given the current constructive solutions, generate stresses which damage the joints between beams and pillars or create a bending in the pillar which causes it to collapse.
From the patents US-A-3.350.821 , US-A-5.660.007 and FR-A-2.747.418 it is known to combine energy dissipators with concrete pillars, in order to absorb and dissipate seismic energy. Nevertheless, the systems described in the three above-cited documents do not completely solve the problem connected to the joints in the structures.
Purpose of the present invention is to increase the deformation capacity of the critical zone of the pillars without substantial increase in stresses and therefore preventing the collapse and breakages or damages which can cause the structure to be unfit for use.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.
In accordance with the above purpose, a pillar for buildings comprises a metal reinforcement with a substantially vertical development and hence longitudinal to the pillar embedded in a cast of concrete.
According to a variant, as well as the metal reinforcement the pillar can be provided with an external circling ring, or jacket, while the section can be various.
According to one feature of the present invention, in a position close to a joint, or in an intermediate position along the pillar itself, the pillar comprises at least a separator element of the plate type which extends substantially ever the entire cross section of the pillar. The separator element is passed through by the reinforcement with the function of dissipating energy and/or by first energy dissipating elements, also made of metal, distinct and autonomous with respect to other parts of the reinforcement and of the pillar. The at least one separator element has a deformability which is greater than that of the concrete so as to be able to deform in the event of stresses due to an earthquake.
According to the invention, the function of dissipator element can be carried out by the first dissipator elements and/or by second dissipator elements which are the rods of the reinforcement.
In any case, each energy dissipator element has a coefficient of elasticity greater than that of the cast of concrete.
The dissipator elements are firmly anchored, by means of anchoring means, to the cast of concrete on opposite sides with respect to the separator element. The anchoring means can comprise at least one support element which, as understood here, can be a bearing plate, also solid to the part of the cast of concrete adjacent to the separator element, or the cast of concrete itself in which the reinforcement is drowned, or a foundation or other solid element suitable to adequately support the pillar and to constitute a stable anchorage for the reinforcement rods and/or for the dissipator elements other than the reinforcement.
It comes within the spirit of the present invention to provide that the separator element is at least partly elastic, for example of a material similar or comparable or equal to the material commercially known such as neoprene, even if the use of other materials having similar deformability to that of neoprene is not excluded.
In other forms of embodiment the separator element is any material or device able to achieve a structural type discontinuity along the extension of the pillar.
According to the invention, during a seismic event, because of the effect of lateral forces, a fissure with a triangular section or similar is created between the upper part and the supporting base of the separator element, which puts the dissipator elements in traction and generates a dissipation of the seismic energy.
The calculation of the dissipator elements in the dissipation zone can provide a sizing suitable to the allowed lengthening, possibly extending the non-adherent zone between dissipator elements and concrete, or increasing the thickness of the separator element, or providing to insert elements to coat the dissipator elements to make them at least partly non-adherent to the concrete.
If the energy absorbed is such as to maintain the traction and/or the compression of the dissipator elements within the elastic field of the steel, the structure is not damaged.
The separator element has a thickness adequate for the design specifications and to the load it has to bear, as well as to the type of constituent material.
Purely as an example, for a pillar of about 20 cm x 20 cm, 4 to 5 meters high, the thickness of the separator element can be comprised between 0.8 mm and 5.0 mm, advantageously between 1.0 mm and 1.5 mm.
For a pillar of 50 cm x 50 cm, about 3 meters high, the thickness of the separator element will be comprised between 10 mm and 50 mm, advantageously between 25 mm and 35 mm.
The thickness of the separator element, according to the invention, can vary from 0.8 mm to 150 mm and more.
It is obvious that these values can vary in relation to particular seismicity of the site where the pillar is applied, or depending on the level of seismicity envisaged for that determinate zone and consequently on the design specifications.
It comes within the framework of the invention to provide parallel plane separation elements, separation elements with the central part absent, and also separation elements having different sections, possibly differentiated gradually, between periphery and center.
It comes within the framework of the invention to make at least part of the pillar work by means of oscillation around a hinge.
A variant of the invention makes at least part of the pillar work around a median axis to the cross section of the pillar.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

fig. 1a is a section view of a pillar for building constructions according to the present invention;
fig. 1b is a section view of a pillar for building constructions in a second form of embodiment;
fig. 2 is a section view of fig.1 along the line II;
fig. 3 is a first variant of fig. 1;
fig. 4 is a second variant of fig. 1;
fig. 5 is a view of a detail in fig. 1 according to some forms of embodiment;
fig. 6 is a schematic representation of how the invention works;
fig. 7 is a variant of fig. 1b;
fig. 8 is a variant of a detail of fig. 3;
fig. 9 shows a separator element without the central part, of a toroidal shape in the case shown;
fig. 10 shows a separator element with a differentiated section and with an oscillation pin within the internal area of the pillar;
fig. 11 shows a pillar with a separator element and two bearing plates with respective dissipator elements;
fig. 12 is a variant of fig. 4.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one form of embodiment can conveniently be incorporated into other forms of embodiment without further clarifications.

DETAILED DESCRIPTION OF SOME PREFERENTIAL FORMS OF

EMBODIMENT

With reference to figs. 1a and 1b, a pillar for building constructions, which can be the normal type with internal reinforcement, or the mixed steel-concrete type, or the only encircled type, is indicated in its entirety by the reference number 10, and comprises a metal reinforcement 14, consisting of reinforcement rods joined to each other in a cage in a known manner, the reinforcement 14 being immersed in a cast of concrete 16.
According to the invention, a separator element 12, substantially of the plate type, is disposed in a substantially orthogonal direction with respect to the axis of the pillar 10, while the reinforcement 14 has the rods which pass through it (figs. 1b, 3, 4 and 7).
According to a variant (fig. 9), the central part of the separator element 12 is eliminated.
According to another variant (fig. 10), the separator element 12 has a differentiated section. Furthermore, in association with the differentiated section it is provided that the oscillation of the mobile part of the pillar 10 occurs in a cradle shape which carries the oscillation inside the section of the pillar, preventing concentrated loads, advantageously near the central zone.
The separator element 12 can be applied near an interconnection joint 20 as shown in fig. 1 a, or in an intermediate position of the longitudinal extension of the pillar 10 as shown in fig. 1b, or again (fig. 4), in proximity to the connection of the pillar 10 to the base plate of the foundations 30.
The separator element 12 (figs. 1-3) can cooperate with bearing plates or structures 22, suitable to position and support beams 17 of a floor, in which case the bearing plates 22 can have compartments for the transit of the connection rods 18.
According to the invention (figs. 1, 2, 5 and 7), the pillar 10 can comprise an external jacket 13 which may have only a containing function or it may cooperate in supporting the load; when the concrete is cast, the jacket 13 may act as a form work to make the finished pillar 10.
In the forms of embodiment shown in figs. 1a, 1b and 5, it is provided that the pillar 10 may comprise a second plate 24, disposed in contact against a surface of the separator element 12, the function of which is to distribute equally the load supported by the pillar 10.
The second plate 24 can completely cover the whole cross section of the pillar 10, and the end of the external jacket 13 can be welded to it.
The rods of the reinforcement 14 (figs. 1a and 5) may be made solid both with the bearing plate and with the second plate 24, or they may be made solid only with the second plate 24, taking away, or at least reducing, their deforming capacity.
The second plate 24 is disposed in contact against a surface of the separator element 12, opposite the contact surface with the bearing plate 22.
The second plate 24 is provided with through holes made near the points where first dissipator elements 15 pass through, which in turn pass through the second plate 24 without anchoring to it, since they anchor to the bearing plate 22.
If the invention is applied in an intermediate position of the pillar 10 (figs. 1b, 7), the separator element 12 is passed through by the rods of the reinforcement 14, and disposed between a first cast of concrete 16a and a second cast of concrete 16b.
Specifically, the pillar 10 comprises two second plates 24 disposed on the two opposite surfaces of the separator element 12 and extending for the whole cross section of the pillar 10. In this case too the external jacket 13 is interrupted transversely near the two second plates 24, leaving the rods of the reinforcement 14 with the possibility of deforming in the event of seismic phenomena.
In this case, moreover, the second plate 24 disposed under the separator element 12 functions as a support element for the separator element 12.
According to a variant of the present invention (fig. 7), dissipator elements 15 consisting for example of steel round pieces or bars, may be disposed through the second plates 24, and are made solid with at least one of them.
According to another variant (fig. 11), the rods of the reinforcement 14, on the lower part and the upper part of the pillar 10, terminate and anchor respectively in correspondence with the bearing plate 22 and the second plate 24, not passing through the separator element 12.
In this case the first dissipator elements 15, anchored, start from one and the other plate 22, 24, pass through the other plate 24, 22, and extend into the other cast of concrete (fig. 11).
Figs. 3 and 4 show a pillar 10 without the external steel jacket 13.
The section of the pillar 10 can be any shape whatsoever depending on design specifications.
Not only the rods of the reinforcement 14 can be anchored to the bearing plate 22, but also the first dissipator elements 15, which extend into the cast of concrete 16 and pass through the separator element 12.
The first dissipator elements 15 can be made solid with the bearing plate 22 in any way whatsoever.
The free ends, which extend into the concrete, of the first dissipator elements 15 are provided with anchoring means 23, in this case mushroom shaped, and in the event of an earthquake, prevent the first dissipator elements 15 from coming out of the cast of concrete 16.
The first dissipator elements 15 and possibly the rods of the reinforcement 14 are made solid with the bearing plate 22 in correspondence with an upper anchoring plane 27 (fig. 1) or a lower anchoring plane 31 or on both planes of the bearing plate 22.
In other forms of embodiment, the separator element 12 and the first dissipator elements 15 may be disposed, as described above, also on the bearing plate 22 opposite the one described with reference to fig. 1, that is, on one side of the bearing plate opposite the one described in previous forms of embodiment. An example of this application is shown in fig. 12 where the bearing plate 22 is disposed in contact against the lower surface of a floor 36 and anchoring rods 37 provide to keep the pillar 10 anchored to the base of the floor. The separator element 12, in this form of embodiment, is disposed at the top of the pillar 10.
In the event of seismic activity, the rods of the reinforcement 14 and/or the first dissipator elements 15 are suitable to absorb, to the extent desired by the designer, the stresses that occur in conditions of flexion and/or flexion-torsion.
In another form of embodiment (fig. 4), the separator element 12 can be provided in proximity to the bearing plate 22 of the pillar 10, that is, in the connection zone with the foundations 30 by means of reinforcement rods 32.
In another form of embodiment, the separator element 12 can be disposed under the bearing plate 22.
Fig. 6 shows how one solution according to the invention works.
During seismic activity, the pillar 10 oscillates with respect to the separator element 12. The pillar 10 rests on the bearing plate 22, pressing the separator element 12 and rotating around an oscillation point 28, in this case hinge-wise, according to an angle of divarication α.
Due to the angle of divarication α, the rods of the reinforcement 14 and the first dissipator elements 15 are tensed by the cast of concrete 16 which incorporates them, stressing them under traction.
Fig. 10 shows a variant of how the pillar 10 can work. In this variant, the oscillation point 28 is located near the central zone of the pillar 10.
The traction stress finds a resisting strenght in the rods of the reinforcement 14 and the first dissipator elements 15, which give a determinate flexional resistance capacity, absorbing some of the stresses in play. When the stresses in play exceed the elastic limit of the dissipator elements 15 and/or the rods of the reinforcement 14, the condition is reached where one and/or the other dissipator element is destroyed.
The first dissipator elements 15 may also have other shapes, all suitable to function as above.
For example (fig. 5), the first dissipator elements 15 can comprise a tubular element 25, incorporated in the cast of concrete 16 and cooperating with the first dissipator element 15 which has deformation means 33, which functions as a separator element to make the first dissipator elements 15 non-adherent to the cast of concrete 16.
The tubular element 25, in another form of embodiment, may also have an external jacket 26, which leaves space for the deformation of the tubular element 25, preventing the cast of concrete 16 from preventing or slowing down the deformation. In this case it is the tubular element 25, or also the tubular element 25, which constitutes the dissipator element. If the tubular element 25 constitutes the dissipator element, it will be anchored only in the concrete.
Similarly, the parts of the rods of the reinforcement 14 that cooperate with the plate 22 may also be provided with a tubular element 25 as described above, to allow said deformation.
The tubular element 25 may be made of metal, wood, plastic or other material.
According to a variant of the present invention (fig. 8), both the rods of the reinforcement 14 and the first dissipator element 15 are each provided with a covering element 35 which, like the tubular element 25 described above, functions as a separator element, rendering the rods of the reinforcement 14 and the first dissipator elements 15 non-adherent to the cast of concrete 16 for a predetermined length.
The length of the covering element 35 is comprised, simply to give an example, between about 10 cm and about 100 cm, even if this length is proportional to the extension of the pillar 10 and to the load that the absorbing system has to support.
The covering element 35 prevents the cast of concrete 16 surrounding the first dissipator elements 15 and/or the rods of the reinforcement 14 from contrasting the dissipating action, since it too is affected in terms of destruction during a seismic event.

Claims

Pillar for building constructions, suitable to absorb external stresses generated by oscillatory or undulatory phenomena, comprising a cast of concrete (16) having a substantially vertical development, characterized in that at least a separator element (12) made of deformable material is disposed transversely to said cast of concrete (16) in order to obtain a vertical discontinuity in said cast of concrete (16), wherein said separator element (12) is passed through by at least an energy dissipator element (14, 15, 25), having a coefficient of elasticity greater than that of said cast of concrete (16), at least partly incorporated in said cast of concrete (16) and anchored to the latter by anchoring means (14, 22, 23, 24, 33) having, on the other side of said separator element (12) and opposite to the part anchored to the cast of concrete (16), anchoring means independent of said cast of concrete (16).
Pillar as in claim 1, characterized in that said at least one dissipator element consists of the metal reinforcement (14) embedded in said cast of concrete (16).
Pillar as in claim 1 or 2, characterized in that said at least one dissipator element comprises a first dissipator element (15) different from the metal reinforcement (14) embedded in said cast of concrete (16).
Pillar as in any claim hereinbefore, characterized in that said at least one dissipator element is tubular shaped (25, 26).
Pillar as in any claim hereinbefore, characterized in that said anchoring means comprise a bearing plate (22) disposed in contact with said cast of concrete (16), on one side of said separator element (12) and to which said dissipator elements (14, 15) are solidly connected, which are embedded in said cast of concrete (16) at least on the other side of said separator element (12), with respect to said bearing plate (22), after having passed through it.
Pillar as in any claim hereinbefore, characterized in that said dissipator element (14, 15) comprises a separator element (25, 35), in proximity to its anchoring end, suitable to render it at least partly non adherent to said cast of concrete (16).
Pillar as in any claim hereinbefore, characterized in that said separator element (12) is made of deformable material such as neoprene or similar materials and has a thickness comprised in a range from 0.8 mm to 150 mm.
Pillar as in any claim hereinbefore, characterized in that it has an oscillation or hinge point (28) near the perimeter of the pillar.
Pillar as in any claim from 1 to 7, characterized in that it has an oscillation point (28) near the central part of the transverse section.
Method to dissipate the energy coming from an earthquake by making use of a pillar (10) as claimed in claim 1, made of mixed steel and cement comprising a metal reinforcement (14) with a longitudinal development immersed in a cast of concrete (16), characterized in that said pillar (10) is made to operate at least with a hinge or oscillation point (28) disposed peripherally between a separator element (12) and a support element (22, 16b), at least part of at least one dissipator element (14, 15, 25) being stressed with axial deformation while at least part of said separator element (12) is subjected to differentiated deformation.
Method as in claim 10, characterized in that the at least one oscillation point (28) cooperates with an anchoring plane (27) present in a bearing plate (22).
Method as in claim 11, characterized in that said cast of concrete (16), in proximity to the oscillation point (28), at least compresses said separator element (12) before cooperating with the anchoring plane (27).
Method as in claim 10, 11 or 12, characterized in that the oscillation point (28) cooperates with the proximity of a central zone of the section of the pillar (10).
Method as in any claim from claim 10 to 13, characterized in that the dissipator elements (14, 15, 25) are prevented from moving axially inside said cast of concrete (16) by anchoring elements.
Method as in any claim from claim 10 to 14, characterized in that the dissipator elements (14, 15, 25) absorb the energy by means of axial deformation.