Self-Centering Braced Frame for Seismic Resistance in Buildings

Abstract

An elongated tension-only or centering brace for a structural frame is provided where the brace is anchored at a first attachment point and to a second attachment point that is removed from the first attachment point. The elongated tension-only brace has one or more elastic restoring force elements that have effective lengths greater than the length of the tension only brace between the attachment points.

Description

BACKGROUND OF THE INVENTION[0001]The present invention provides a self-centering system for the structural frame of a building, in particular, the present invention provides a tension brace that provides elastic restoring forces to the frame of the building.[0002]After an earthquake, permanent damage in even properly designed structures may allow for a building to come to rest in an out-of-plumb condition, which is often referred to as “residual (horizontal) displacement”. At best this can lead to loss of use (red tag) and at worst complete collapse in subsequent aftershocks. In recent years state-of-the-art earthquake resistant design research has focused on systems that are capable of ensuring that after an earthquake a building would have little, if any, residual displacement, thus they are “self-centering”. The proposed invention is such a system.[0003]Various types of self-centering systems have been proposed. Inherent in the self-centering philosophy is the need for something ...

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Benefits of technology

[0021]This object could also be achieved by adding pulleys located at different points along the elongat

Problems solved by technology

At best this can lead to loss of use (red tag) and at worst complete collapse in subsequent aftershocks.

For this to happen the pre-stressed element must remain elastic (unyielding) even as it is stretched under the combined demands of the pre-stressing and the supplemental strain induced by building deformations during an earthquake, and it is in meeting these combined strain demands by stretching without yielding that many of the difficulties of designing such systems are encountered.

One of the challenges of self-centering systems is configuring the geometry of the building and the self-centering system in such a way that the strain induced in the elastic restoring force elements that provide the force necessary to pull the building back to its original position (this is called the “restoring force”) does not exceed the yield strain for the materials from which the elastic force restoring elements are made.

One researcher, Alan Jamal Stewart, has found that tendon yielding and loss of elasticity can still be a problem with moment-resisting frames designed with gap opening behavior at the beam-column joints.

Self-centering moment frame systems that rely on the gap-opening behavior of beam-to-column joints to dissipate energy also have a problem i

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