Earthquake-protective building buffer

Abstract

A manufacture called “earthquake buffer” to protect a building structure from destructive earthquakes as well as to secure its stability under strong winds, comprising two non-resonant rolling friction slide layers positioned above each other on a building footing and consisting of a plurality of cylindrical rollers stretched parallel in a direction of one of the main building axes while being orthogonal to the bars in an alternative slide layer. The slide layers are interlaid with a distributive plate and topped with an inertia block connected to a rigid first floor diaphragm and the building superstructure. With a magnitude of earth movement exceeding a certain threshold, the earthquake buffer permits practically unlimited horizontal excursions of the footing relative to the superstructure while transmitting a dramatically reduced shearing force upwards and preventing any sizable lateral resonant effects in the protected building.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to earthquake protection of building structures. More particularly, the invention relates to seismic isolation techniques.

[0003] 2. Description of the Prior Art

[0004] The concept of suppression or diverting the seismic energy flow from entering a building structure is known as a seismic or base isolation. Normally, this technique needs some pads to be inserted into all major load-carrying elements in a base of the building. It also requires creating additional rigidity diaphragms in the basement of the building and a moat around the building, as well as making additional provisions against overturning and/or P-D effect. Potential benefits of the base isolation technique should not be taken for granted: they depend on many factors and are, sometimes, questionable (visit http://www.ecs.csun.edu/˜shustov/Topic4.htm).

[0005] There are the following major reasons why the existing buildings, which incorporating seismic isolators, performed below the expectations during the recent earthquakes:

[0006] 1. Predictions of their earthquake performances were made in assumption of the whole building structure acting as an absolutely rigid body rocking on their seismic isolators, while the higher natural modes of vibration were, practically, neglected.

[0007] 2. Possibility of a negative effect of a heavy damping mechanism of those isolators, that could generate short pulses of a high intensity, was overlooked.

[0008] 3. The buildings that were erected on seismic isolators remained essentially resonant systems in a wide range of earthquake frequencies.

[0009] However, if the existing buildings on seismic isolators happen to do their job properly and survive the earthquake impacts successfully, there is the opposite challenge: an earthquake safe, due to a perfect seismic isolation, structure may become vulnerable to a strong wind.

BRIEF DESCRIPTION OF THE DRAWING

[0010] In the description of invention herein presented, references are made to the accompanying drawings, in which:

[0011] FIG. 1 is a perspective view of an earthquake buffer on a footing.

[0012] FIG. 2 depicts an exploded perspective view of an earthquake buffer divided into several functional strata.

DESCRIPTION OF THE PREFERED EMBODIMENT

[0013] The present invention will be described with reference to the accompanying drawings. As illustrated at FIG. 1 and FIG. 2, the earthquake buffer according to the invention is positioned on each individual column footing (1) of a building and has two non-resonant and low friction horizontal slide layers consisting of a plurality of identical cylindrical rollers, namely, a lower layer (2) and upper layer (4), which are interlaid with a horizontal distributive plate (3) and are topped with an inertia block (5) that supports the first floor diaphragm (6) and the building superstructure (7). The cylindrical rollers of the layers (2) and (4) are distanced from each other and running parallel in a direction of one of two main building axes. The direction of rollers in the layer (2) is orthogonal to the direction of rollers in the layer (4). The rollers of the lower layer (2) rest on a flat top surface of the footing (1) that supports the particular earthquake buffer. The weight of the inertia block (5) of the buffer should be enough to suppress the potentially damaging higher frequency pulses of vibration being transmitted from the footing (7) into the superstructure (7) and to create a friction force that can resist a lateral strong wind pressure.

[0014] During an earthquake, any two-dimensional horizontal movement of the footing (7) is resolved, while transmitted upwards, into two orthogonal components, by the following steps: first, the plate (3) will slide up in one of the orthogonal directions relative to the footing (1); then, the block (5) will slide up in another orthogonal direction. Finally, a two-dimensional acceleration will be developed and applied to the bottom of the building superstructure (7) but being dramatically scaled down due to a low value of the rolling friction in the layers (2) and (4).

[0015] The material, length, diameter and a number of rollers in each layer should satisfy both a requirement of sufficient vertical load bearing capacity and that of an adequate shearing force being transmitted through the earthquake buffer into the superstructure.

Claims

1. A system of properly manufactured earthquake buffers adapted to separate a building superstructure from its foundation for protection against damaging effect of strong earthquakes and, at the same time, to prevent such separation under a strong wind or minor earthquakes, each of said devices comprising:

two non-resonant rolling friction horizontal slide layers positioned above each other on a building footing and consisting of a plurality of identical cylindrical rollers distanced from each other and running parallel in a direction of one of the main building axes, said rollers in one of said layers are orthogonal to said rollers in another said layer in order to provide an adequate separating effect for any horizontal component of earth movement;

a horizontal distributive plate between said two slide layers to provide a better gravity load application to contacting surfaces of said layers;

an inertia block located on top of the upper of said slide layers and supporting a rigid first floor diaphragm and said superstructure, said inertia block together with said floor diaphragm having a mass comparable to a mass of said superstructure in order to prevent any higher frequency pulses to be transmitted from said footing to said superstructure and to create a friction force that can resist any possible strong wind pressure.