WO1992001134A1

WO1992001134A1 - A damping device for seismic protection of such works as viaducts and the like

Info

Publication number: WO1992001134A1
Application number: PCT/EP1991/001188
Authority: WO
Inventors: Paolo Ripa; Roberto Marnetto
Original assignee: L'asfalto Ansani S.R.L.
Priority date: 1990-07-04
Filing date: 1991-06-26
Publication date: 1992-01-23
Also published as: IT1244379B; EP0537228A1; IT9020856A1; AU8054691A; IT9020856A0

Abstract

A damping device (1) for protecting works, intended for implacement between parts of works, such as between a pier (2) and a beam (3) of a viaduct, comprises a C-shaped strip-like member (6) deformable in an elasto-plastic fashion and being composed of a plurality of superimposed plies (16a-g) having increasing thickness from the innermost ply (16a) to the outermost ply (16g).

Description

A DAMPING DEVICE FOR SEISMIC PROTECTION OF SUCH WORKS AS VIADUCTS A* τ. _ LIKE DESCRIPTION

Tms invention relates to a αaitiDing device as defined in the preamble of Claim 1.

Sucn devices are interposed to structural members, e.g. on viaducts between a pier and a beam, so that the C-shaped element has its flanges bound to the pier and the beam, respectively. Any relative movement of said parts, as caused by earth tremor, would result in one flange being unwound or stretched out and the other flange being wounα or rolled up while the curved section of the C-shape oivots aDout its center. At the curvature transition points, an elasto-plastic deformation takes place which, by virtue of its plastic behavior, additionally to restricting the force transferred, will absorb energy from outside and produce the damping effect sought.

To obtain the highest damping effect for a given volume, the strip-like member is dimensioned to have the largest □ossible thickness, obviously within the limits beyond wnich cold bending around tπe curvature would reach breaking stress.

Larger thicknesses could be adopted for the C-shaped memoer provided that the radius of curvature of the arcuate portion of the C-shaped member be increased concurrently. However, sucn an increase in the radius of curvature would eviαently result in increased bulk of tne αevice, and hence more difficult installation thereof, if not altogether unorooosaDLe as is tne case wnen tne installation is to be oerfor ed on existing WOΓKS.

It follows, in otner worαs, tnat cπor αevices are forcinly limiteα in their αamoing capacity wnerever sσace is at a premium. - 2 -

as in most cases.

The problem that underlies this invention is to provide a damping device of the type specified above, which has sucn structural and functional features as to overcome the aforementioned drawbacks.

This problem is solved by a damping device as defined in the characterizing part of Claim 1.

Further features and the advantages of the damping device according to this invention will become apparent from the following detailed description of a preferred embodiment thereof, given by way of non-limitative example with reference to the accompanying drawing whose single figure shows a sectional elevation view of a damping device according to the invention.

With reference to the accompanying drawing figure, generally shown at 1 is a damping device implaced between parts of works, e.g. between a pier 2 and a beam 3 of a viaduct.

Its function is one of dissipating the energy released to the works by earth tremor, thus reducing the stresses applied to its various parts.

The device 1 comprises two juxtaposed plate-like bases, of which a lower base 4 is fastened to the pier 2 and an upper base, generally indicated at 5, is associated with the beam 3.

Between the bases 4 and 5 there extends a C-shaped strip-like member 6 which is deformable elasto-plastically and laid on a perpendicular plane to the bases to extend along a direction X-X.

It should be noted that the upper base 5 comprises two ciates, a top one 7 attached to the beam 3 and a bottom one 8, which are coupled slidably together by means of a guide 9 which extends along a direction Y-Y perpendicularly to X-X.

The member 6 has a straight upper run 10 and a straight lower run 11 which extend from respective ends 10a and 11a and join each other at an arcuate portion 12.

The end 10a is secured firmly on the plate 8, being specifically held between the latter and a bracket 13 by screws 14, and is further held in place by pins 15. In quite a similar manner, the end 11a is secured firmly on the base 4 by means of a bracket 13, screws 14, and pins 15.

In the device 1 of this invention, the C-shaped member 6 is formed of a plurality of superimposed plies, seven in the example shown, as indicated at 16a, b, c, d, e, f, g.

The plies 16a-g have a small thickness dimension which increases gradually from a minimum to a maximum, from the innermost ply 16a to the outermost ply 16g.

The C-shape is obtained for each ply 16a-16g by a cold bending step starting from a straight blank.

In relation to a predetermined curvature of the arcuate portion, the thickness of each ply is selected for the largest possible value, consistent with the requirement that the outermost fibers in the cross-sect on of each ply should undergo plasticization or yield stresses, in no case breaking stresses.

The device 1 comprises a further C-shaped memoer, indicated at 17, αuite identical with the C-shaped member 6 and arranged in mirror-image arrangement to form in cooperation therewith a loop structure 18 defining a hollow 19 on its interior.

Those parts of the members 6 and 17 which are similar in construction and function will be denoted by the same references hereinafter.

The hollow or cavity 19, in particular, is bound in the direction X-X by the arcuate portions 12 of the C-shaped members 6 and 17, and in the vertical direction by the mounting brackets 13 for said members.

The cavity 19 is occupied by a rigid insert 20 which extends in the direction X-X and has arcuate opposed ends 21 to match the arcuate portions 12 and a flattened mid-portion 22 interposed to the brackets 13.

An antiscuff lining 23 is associated with the insert 20. Specifically, the lining covers the arcuate ends 21 and the flattened mid-portion 22 of the insert.

In operation of the device 1, a relative displacement of the bases 4 and 5 brought about by earth tremor ard taking place along the direction X-X would be accompanied by the desired damping effect to be explained, whereas a displacement occurring along the direction Y-Y would be unrestricted thanks to the guide 9.

The displacement along the direction X-X causes progressive bending deformation of the plies 16a-g at the runs 10 and 11 due to their progressive arching or curling up into the arcuate shape at the start of the arcuate portion 12, or their progressive straightening up or extending back into the straight shape at the end of the arcuate portion.

Thus, the desired damping effect originates from plasti cization of the C-shaped member plies in those sections where the transition in curvature occurs on account of the straight shape turning into the arcuate one, or vice versa.

During the displacement movement along the direction X-X, tne rigid insert 20 ensures, by its arcuate enαs 21, tnat the arcuate portions 12 will retain their shape, from tne innermost ply 16a to the outermost one 16g.

Because of the rigid insert 20 provided, each ply, from the innermost one, will behave as a rigid insert for its adjacent one in the plurality of plies, thus ensuring that its shape will be retained, and so on to the outermost ply.

Adjacent ones in the plurality of plies remain stationary relatively to each other, thereby no damage is caused to their confronting surfaces.

The insert 20 interposed with its flattened mid-portion 22 between the brackets 13 also imparts to the device 1 an ability to withstand vertical loads.

Said functions served by the insert 20 are bcth assisted by the antiscuff lining 23 preventing damage to the surfaces of the arcuate portions and the brackets and to the surface of the insert itself.

A major advantage of the damping device of this invention resiαes in its compact design, as brougnt about by the small thickness of the plies which comprise the C-shaped members affording a uniquely reduced radius of curvature for the C-shaped member.

A further advantage of the device according to the invention resides in the constancy of its performance being ensured by the rigid insert provided, which insert is effective to keep the ply snapes uncnanged both at the runs and the arcuate portions, and this even after repeated working cycles.

Still another advantage of the inventive device is that is that it can withstand vertical loads.

Of course, the device described in the foregoing may be altered and modified in various ways by the skilled one to meet specific, contingent demands, without departing from the invention scope as set forth in the appended claims.

Claims

1. A damping device (1) for seismic protection of works, intended for implacement between parts of works, such as between a pier (2) and a beam (3) of a viaduct, being of a type which comprises a C-shaped strip-like member (6) deformable in an elasto-plastic fashion, and characterized in that said C-shaped strip-like member (6) is formed of a plurality of superimposed plies (16a-g).

2. A damping device (1) according to Claim 1, characterized in that the plies (16a-g) have gradually increasing thickness from a minimum to a maximum, from the innermost ply (16a) to the outermost ply (16g).

3. A damping device (1) according to Claim 2, characterized in that it comprises a further C-shaped member (17) identical with the first-meπtior.ed one and arranged in mirror-image relationship therewith to provide a loop structure (18) defining a cavity (19).

4. A damping device (1) according to Claim 3, characterized in that it comprises a rigid insert (20) occupying said cavity (19).

5. A damping device (1) according to Claim 4, characterized in that a lining (23) of an antiscuff material is associated with the insert (20).