Seismic protection by rocking with superelastic tendon restraint

Abstract

This article introduces an innovative system for enhancing the seismic performance of a structure through facilitating large rotational (rocking) motion to occur without risking overturning. The innovation of this study is in the use of tendons consisting of Nickel‐Titanium (superelastic) alloy connected in series with steel to impose partial restraints to the structure when experiencing rocking motion. Importantly, the large rotational motion is fully recoverable. Existing installations which can be made to rock may also be retrofitted with the device for improving its seismic resistance. The original contributions of the article are the derivation, and experimental validation, of an analytical model for simulating the seismic performance of a system that has been fitted with the restraining device. In a parametric study employing the newly developed modelling techniques, major trends in the seismic response behaviour of the structure have been identified.

Seismic internal force in rocking shear frame with superelastic tendon restraint

“…In application, 𝐹 𝑇 can be represented by Equation ( 17) 32 and analysed by a stepwise method as described below.…”

“…As shown on the test schedule (Table 2), different styles of excitations were applied to the specimen, including freerelease (pluck) tests, single impulse and double impulse excitation tests (emulating near-fault ground motions 11,32,46 ). Single impulse excitations of varying amplitudes were applied to each of the test setups (refer test no.…”

“…This paper is to report the study on seismic response of a rocking shear frame. The superelastic tendon restraint, which is an added‐on feature to the rocking system, has the merit of recovering whole body rotation of the structure and at the same time, increasing the rate of energy dissipation 32,33 . The NiTi alloy 34–38 tendon which is connected in series with the steel tendon forms the superelastic tendon restraint in this study.…”

“…The superelastic tendon restraint, which is an added-on feature to the rocking system, has the merit of recovering whole body rotation of the structure and at the same time, increasing the rate of energy dissipation. 32,33 The NiTi alloy [34][35][36][37][38] tendon which is connected in series with the steel tendon forms the superelastic tendon restraint in this study. The proposed system is different from the existing technology that adopts the superelastic material in the form of short-length bars installed at the base of precast columns.…”

“…It may not impose effective prestressing force on the structure by itself and the recoverable limits are controlled by the steel tendon, which yields under a small rotation, for instance, 1.1 • rotation for a structure with 5:1 aspect ratio. In contrast, when the superelastic wire is connected in series with a steel wire, 32 as investigated in this study, the structure can be prestressed, and a larger recoverable elongation can be facilitated. The recoverable rotation can be 9.5 • for a 5:1 aspect ratio structure when one-third length of the tendon is made of NiTi alloy wire.…”