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Hysteretic behaviour of steel- and fibre-reinforced elastomeric isolators fitted with superelastic shape memory alloy wire

University of British Columbia

Among different types of earthquake protective mechanisms, elastomeric base isolators, also called rubber bearings (RBs), are one of the most well-known systems that are widely used in buildings and bridges. They can regulate the seismic response of structures, increase the public safety, and reduce the cost of repair and rehabilitation by providing lateral flexibility and dissipating the earthquake’s energy. RBs consist of elastomeric layers which are reinforced with steel shims or fibre-reinforced polymer composites. Seeking performance improvements, as well as cost and weight reduction led scientists to introduce different types of RBs. However, most RBs possess weaknesses such as limited shear strain capacity, un-recovered residual deformation, and instability due to large deformations. Using superelastic (ability to regain original shape upon unloading) shape memory alloy (SMA) in the form of wire, bar, or spring is a solution to partially overcome the aforementioned limitations. Its unique characteristics such as a flag-shaped hysteresis with zero residual deformation, superelastic effect (up to 13.5% recoverable strain) and a suitable fatigue property make it an ideal candidate for such applications. Objectives of this thesis are to propose a new generation SMA wire-based RBs (SMA-RB) and develop a novel constitutive model for such smart isolators in order to accurately capture their shear hysteretic behaviour. With the purpose of evaluating the performance of SMA-RBs in structural applications, the seismic fragility of a highway bridge isolated by SMA-RBs was assessed. First, a number of scaled carbon fibre-reinforced elastomeric isolators (C-FREIs) were manufactured and tested. Then, based on the experimental observations, numerical simulations were generated using finite element method (FEM). Results showed that incorporating SMA wires into natural and high-damping rubber bearings (NRB, HDRB) slightly improves the re-centring capability and energy dissipation capacity. However, equipping lead rubber bearing (LRB) with double cross SMA wires significantly reduces the residual deformation and noticeably enhances the energy damping property. It was also depicted that the developed hysteresis of SMA model can be characterized by three stiffnesses and two shear strain limits upon activation of SMA wires. Findings revealed that SMA wires can increase the reliability of elastomeric bearings and bridge system.

Text

2015-04-30

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/53019

Civil Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/