Static structures (e.g. – buildings) – Means compensating earth-transmitted force – Relative motion means between a structure and its foundation
Patent
1998-08-05
2000-11-07
Kent, Christopher T.
Static structures (e.g., buildings)
Means compensating earth-transmitted force
Relative motion means between a structure and its foundation
521671, 521678, 525731, 248638, 248562, 248603, E04B 198
Patent
active
061419192
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to energy absorbers. More particularly this invention relates to a shear damper able to be used in a wide range of applications.
BACKGROUND ART
For the purposes of this specification a shear damper means a cyclic shear energy absorber of the type described in WO94/13974; U.S. Pat. Nos. 4,117,637, 4,499,694; 4,593,502; and 4,713,917, the specifications of which are hereby incorporated by reference. Shear dampers have been used primarily in seismic isolation of structures. Seismic isolation involves increasing the natural period of a structure to outside the period of the exciting motion. This reduces the forces transmitted into a building through decoupling. The addition of a damping mechanism to dissipate the associated energy, thereby controlling the displacements and further reducing the accelerations transmitted to the structure, establishes a seismic protection system. This method of protection is suitable for structures with natural periods of less than 1.5 seconds. More of the principles of seismic isolation are described in Skinner et al, (see references at the end of the description).
Energy absorbers of this type to date have been designed to be weight bearing and are known in the art as lead rubber bearings. That is, the structure or parts of a structure to be damped from induced motion rest on top of the bearing and the bearings themselves rest either on the ground or on another part of the structure. These devices are intended to absorb earthquakes or wind loads, but are resistant to lesser forces.
It has been known for some time that energy absorbers can be used as dampers to control the elastic and plastic deformation of tall structures with natural periods greater than 1.5 seconds (Scawthorn et al, 1995). Dampers can be interposed laterally between structures or parts of structures to damp motion. The vibrations which may be damped may be very small.
It would be useful to be able to take advantage of shear dampers for uses other than as bearings in damping motion induced on structures. For example, shear dampers would be useful in applications such as damping vibrations in machinery, in penstocks of hydro-electric power stations or the like, in rolling stock such as heavy trucks or railway freight cars, carriages or engines or any similar vibrations.
It is an object of this invention to go some way towards achieving this desideratum or at least to offer the public a useful choice.
DISCLOSURE OF INVENTION
The invention may be said broadly to consist in an energy absorber comprising: damper comprising a pair of rigid end plates, a laminated structure of rigid plates able to slide past one another and a core of plastically deformable material in a bore through said rigid plates from the inner face of one end of said end plate to the inner face of the other said end plate, at a hydrostatic pressure at least approaching the shear yield stress of said plastically deformable material, commonly attachable to a first portion of a structure, common end plate being attachable to a second portion of a structure, about 5% to about 95% of the average total cross-sectional area of each said damper, absorber, when attached to a first and second structure or portions of a structure, dampens relative motion therebetween.
Preferably each said core is lead.
Altematively each said core is of high purity aluminium, tin, zinc, indium or iron, or alloys of lead, aluminium, tin, zinc, indium or iron or any superplastic alloy or other material having a low rate of work hardening.
In still a further alternative each said core is densely packed granular material such as is described in U.S. Pat. No. 4,713,917.
Preferably said granular material is steel, glass beads, alumina, silicon carbide or any other similar hard granular material.
Alternatively said granular material is granular iron, lead, aluminium or other similar less hard material.
Preferably said end plates and said rigid plates are of steel.
Alternatively said end plates and said rigid plates are of aluminium or
REFERENCES:
patent: 3134585 (1964-05-01), Trask
patent: 4117637 (1978-10-01), Robinson
patent: 4499694 (1985-02-01), Buckle et al.
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patent: 5201155 (1993-04-01), Shimoda et al.
"High Strain Cyclic Shear of Lead" (thesis), Univ. of Auckland, Michael D. Monti, Jul. 1994, pp. 1-193.
"Lead as a Seismic Energy Dissipator", M.D. Monti et al, Univ. of Auckland, 9 pages.
11WCEE, "A Lead Shear Damper Suitable . . . ", M.D. Monti et al, Acapulco, Mexico, Jun. 23-28, 1996, 8 pages.
"Lead as a Cyclic Motion Damper", M.D. Monti et al, Univ. of Auckland, 1995, 7 pages.
Earthquake Engineering . . . , vol. 10, "Lead-Rubber Hysteretic Bearings . . . ", W.H. Robinson, 1982, pp. 593-604.
Earthquake Engineering . . . , vol. 4, "An Extrusion Energy Absorber Suitable for . . .", W.H. Robinson et al, 1976, pp. 251-259.
ASME/JSME PVP Conference, "Seismic Isolation, the New Zealand Experience", Hawaii, W.H. Robinson, 1995, 10 pages.
Eleventh World Conference . . . , "Latest Advances in Seismic Isolation", W.H. Robinson, Mexico, Jun. 23-28, 1996, p. 800.
EQE Engineering, "Earthquake Loading and Response", Kato et al, Tokyo Univ., Tokyo, Japan, pp. 839-841.
Bulletin of the New Zealand . . . , vol. 8, No. 2, "Base Isolation for Increase . . . ", Skinner et al, pp. 93-101, Jun. 1975.
An Introduction to Seismic Isolation, Skinner et al, 1993, 7 pages.
Journal De Physique IV, "Amplitude-Dependent Internal Friction in Lead at . . . ", Kustov et al, vol. 6, Dec. 1996, pp. C8-265-268.
Dorsey Dennis L.
Kent Christopher T.
Robinson Seismic Limited
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