TITLE: DAMPING DEVICE FOR ANTI-SEISMIC STRUCTURES

DESCRIPTION

The present invention relates to a damping device for anti-seismic structures.

At present, during the construction of residential, industrial or similar buildings, or also the construction of bridges, the use of anti-seismic structures incorporating at certain points damping devices may be envisaged, said devices performing the function of limiting the forces, in particular the planar shearing action resulting from the movement of the structure following a seismic event. As is known, these types of dampers include, for example, those of the elastomer and inverted pendulum type and may be inserted inside the anti-seismic structure for example at the point where the pillar is fixed onto an associated bearing structure such as a base or the like.

These types of dampers have various drawbacks, including their constructional complexity, the need for frequent maintenance operations, which therefore have a negative effect on their operating efficiency, and a certain complexity as regards use.

The object of the present invention is to overcome the drawbacks of the dampers for anti-seismic structures by means of a damping device for anti-seismic structures, characterized in that it comprises a support having, formed at the bottom thereof, a seat housing first vertical damping means mounted at the bottom on a foot supported by suitable bearing means fixed to a structure supporting a pillar of an anti-seismic structure: this foot is able to shift or pivot with respect to these bearing means and this support has an upper part co-operating with second horizontal damping means fixed on one side to this upper part of this support and on the other side to the inner side wall of a seat for housing this upper part, formed internally at the base of the pillar or externally between the base of the pillar and this support structure; this pillar has, at the base, a plate with a suitably shaped central hole inside which an end or

middle section of this support engages.

Further characteristic features and advantages of the present invention will be better understood during the course of the following description, considered by way of a non-limiting example with reference to the accompanying drawings in which:

- Fig. 1 shows a side elevation and cross-sectional view of a preferred embodiment of a damping device for anti-seismic structures according to the present invention;

- Fig. 2 shows a further view, on a large scale, of the present damping device according to the embodiment of Fig. 1 ;

- Fig. 3 shows a top plan and cross-sectional view of the present anti-seismic device according to the embodiment shown in Figs. 1 and 2; and

- Fig. 4 shows a side elevation and cross-sectional view of a constructional variant of the present damping device for anti-seismic structures.

With reference to these accompanying drawings and in particular to Fig. 1 thereof, 1 denotes a pillar having at the base a part 101 with a larger cross-section inside which a recess 2 for housing a part of the damping device according to the present invention is formed. This pillar 1 at said base intersects a certain number of beams 3 which form together therewith and other similar pillars the load-bearing anti-seismic structure for a building. A steel disk 4 is shown below this pillar and the recess 2 and is situated on a bearing structure 16 of the pillar 1 which may be, for example, a foundation or the like. This disk 4 has at the top a circular part 104 with a certain concavity on which a foot 5 with a bottom surface having a shape matching said concave circular part 104 rests. A vertical damper 6 is shown on the top of said foot

5 having substantially the form of an overturned T and consists for example of a stack of Belleville springs housed inside an associated seat 107 which is open at the

bottom and formed inside a support 7 in the form of a semi-spherical cap. This semi- spherical support 7 comprises at the top a shank 207 which has, connected to its top end, the inner ends of a series of horizontal dampers 8, of which only two diametrically opposite ones, arranged radially and perpendicularly with respect to said shank 207, are shown in the figure. These horizontal dampers 8 are connected at their associated outer ends to the side wall 102 of the recess 2. A plate 9 rests on this semi-spherical support 7 and comprises a central hole 109 with a circular cross- section and shape matching the semi-spherical outer wall of said support 7. This plate 9 with said through-hole 109 and this semi-spherical support 7 thus form substantially a semi-spherical joint which constitutes the bearing and connection point of the pillar 1 and the terminal part of the beams 3 which intersect it with the underlying support structure 16. By means of this disk 4 with the circular and concave central part 104 this foot 5 and therefore the semi-spherical support 7 are able to pivot with respect to the pillar 1 through 360° in any direction.

Fig. 2 shows on a larger scale the present damping device described in Fig. 1. A plate 11 is fixed by means of a pin 10 onto the top part of the shank 207: a series of seats 12 are formed between the bottom surface of said plate 11 and the side wall of said shank 207 close to its top end, only two of said seats, diametrically opposite to each other, being visible in the figure and each housing a ball 13 fixed to a cylinder 108. Each of these cylinders 108 is therefore basically connected to said shank 207 by means of a ball joint formed by the associated ball 13 inserted inside the associated seat 12. 208 denotes a piston able to slide inside the cylinder 108 and having a head 308 which is inserted inside said cylinder 108 and is able to come into contact against the bottom of the latter, in order to allow said piston 208 to perform a certain travel inside said cylinder 108 but without coming out of it. This piston 208 is internally hollow and a rod 408 able to slide inside said piston 208 is housed inside it, opposing the action of a recall spring 14 which is wound around it and engaged on one side with the base of said piston 408 and on the other side with a head 508 with a larger cross-section formed at the terminal end of said rod 408. This rod 408

protrudes partially from said piston 408 on the side facing the side wall 102 of the recess 2 formed at the base of the pillar 1 and has at one end a ball 15 housed inside an associated seat 202 formed in said side wall 102. Basically, therefore, each of the rods 408 shown in the figure and diametrically opposite each other is connected to the side wall of the recess 2 by means of a ball joint formed by the associated ball 15 inserted inside the associated seat 202.

In the view according to Fig. 3 it can be seen that the recess 2, and therefore also the associated side wall 102, formed at the base of the pillar 1 has a cylindrical shape and the semi-spherical support 7 is housed in the centre thereof. In this embodiment by way of example six horizontal dampers are shown, being arranged radially with respect to said semi-spherical support and positioned, in their rest position, so that they are diametrically opposite each other in pairs (see, for example, the horizontal dampers indicated by 8'). In the figure a displacement of the present damping device due to a seismic event has been assumed and therefore, as can be noted, the top part of the semi-spherical support 7 is situated off-centre with respect to the recess 2 of the pillar 1 : this off-centred position is due to pivoting of the foot 5 (see Figs 1 and 2) of the present device with respect to the underlying disk 4 on which it rests, following forces produced by said seismic event. The semi-spherical support 7 therefore pivots on said disk 4 relative to the fixed plate 9 on which the pillar 1 and the terminal part of the beams 3 rest. The vertical components of the forces resulting from said seismic event are damped by the vertical damper 6 inserted inside the seat 107 formed at the bottom of said semi-spherical support, while the horizontal components of said forces are damped by said horizontal dampers 8 which must be arranged radially and at regular intervals with respect to said semi-spherical support and in pairs, as mentioned, which are diametrically opposite each other. Depending on the direction and the degree of pivoting of the foot 5 of the semi-spherical support 7 with respect to the disk 4, the various pistons 208, as can be understood, will slide to a greater or lesser degree inside the associated cylinders 108, as will the rods 408 inside the associated pistons 208. Considering for example the horizontal dampers 8

situated, when viewing Fig. 2, to the right and left of the shank 207, when the shank 207 of the semi-spherical support 7, which in the figure is shown in the vertical rest position, is inclined for example to the left, following tilting of said semi-spherical support 7, the cylinder 108 of the horizontal left-hand damper 8 slides along the piston 208 and the stem 408 remains at a standstill, while the piston 208 of the right- hand damper 8 slides, since the associated head 308 is in contact against the bottom of the associated cylinder 108, along the rod 408 of said right-hand damper 8, compressing the associated recall spring 14; when the forces at play produced by the seismic event cease, the semi-spherical support 7 returns with the shank 207 into the vertical rest position owing to the action of the recall spring 14 of the right-hand damper 8 which will bring the right-hand piston 208 and the cylinder 108 of the left- hand damper 8 into the rest positions shown in Fig. 2.

Fig. 4 shows a variation of embodiment of the present damping device. This damping device is housed inside a cylindrical seat 17 positioned outside the pillar 1 , namely between the base of the latter and the bearing structure 16. A disk 18 is positioned coaxially above this cylindrical seat 17, said disk consisting of two shells 118' and 118" which have, formed internally, cavities able to provide, once these shells 118' and 118" are fixed and positioned in a manner facing each other as shown in the figure, an annular chamber 19 situated inside said disk 18 and able to house the horizontal dampers 8 described above and positioned, in pairs, diametrically opposite each other. The outer annular edge of said disk 18 has, formed therein, seats 20, entirely similar to the seats 202 which can be seen in Fig. 2, for housing balls 15 connected to the rods 408 of said horizontal dampers 8. This cylindrical seat 17 outside the pillar rests on a steel plate 21 with a flat upper surface, on which the foot 5' of the damping device rests, inside said seat 17 and in a central position. This foot 5' comprises a base 105' and at the top a shank 205' having, wound around it, the vertical damper 6' engaged at one end on said base 105' and inserted at the other end inside the seat 107' formed at the bottom of the support 7' which in this variant has a cylindrical shape. A second seat 307' is formed coaxially

above said first seat 107' inside this cylindrical support T, said second seat having a smaller diameter than said first seat 107' and receiving, partially inserted therein, said shank 205' of said foot 5'. This support T is inserted partially inside a cylindrical through-hole 22 formed centrally in the disk 18 and has at the top an end section 407' with a smaller diameter so as to form a kind of step on which a disk 23 rests, said disk having a central through-hole which is fitted onto said smaller-diameter end section 407' of the cylindrical support 7'. The outer edge of said disk 23 has, formed therein, seats 24, which are entirely similar to the seats 12 described in Fig. 2, for housing balls 13 of the cylinders 108 of the horizontal dampers 8. A shank 207' is provided coaxially above the support 7', protruding from said cylindrical hole 22 in the disk 18, and is fixed by means of suitable pins 25 to said smaller-diameter end section 407' of the support 7'. The pillar 1 comprises at the bottom, similar to that seen above, a plate 9' which has centrally a through-hole 109' inside which the end part of the shank 207' is inserted. A series of reinforcing ribs 26, arranged at regular intervals and in pairs diametrically opposite each other, are provided around this shank 207'. As regards operation of the damping device according to this variation of embodiment, the base 105' of the foot 5' is able to slide horizontally to the right or left on the plate 21 , while the horizontal dampers 8 operate in a manner entirely similar to that described above.

Advantageously, therefore, by means of the present damping device for anti-seismic structures described above, it is possible to control in an optimum manner the vertical period of the anti-seismic structure in the case of a seismic event; moreover, this semi-spherical support 7 co-operating with said horizontal dampers 8 always ensures a centring force which allows the device to return into the rest position once this seismic action has terminated. The various device parts described, such as the plate 9, the disk 4 or 4', the semi-spherical support 7, the foot 5 or 5' and the various horizontal dampers 8 or vertical dampers 6 and the springs, preferably consist of rigid metal parts which require practically zero maintenance or alternatively parts with controlled-friction materials.