Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Civil and Environmental Engineering

Supervisor

Maged A. Youssef

Abstract

Although conventional earthquake-resisting structural systems provide the life safety level during earthquakes, they experience significant structural damage when exposed to strong ground shaking that render structural retrofitting as uneconomical. Superelastic shape memory alloys (SMAs) can be used in steel structures to reduce the residual deformations due to their recentering capability, which can facilitate post-seismic retrofitting. The primary aim of this thesis is to enhance the seismic performance of both regular and modular steel structures using an optimum amount of superelastic SMAs material in terms of maximum inter-storey drift, residual drift, and damage scheme.

First, a simplified method based on pushover analysis is proposed to identify the severely damaged floor of a typical SMRF. It was validated with the studies by other researchers. Three and ten-storey SMRFs are considered to further validate the method. The predicted location of damage for the SMRFs using this method is compared to the results of static pushover and nonlinear dynamic analyses. The method accurately identified the severely damaged floors of SMRFs.

The proposed simplified method as well as incremental dynamic analysis is then utilized to determine the best locations of SMA connections to improve the seismic performance of SMRFs. Six different SMA frames are examined using nonlinear dynamic analyses. Among all SMA frames, the frame using SMA connections at the critical first and fourth floors showed very good seismic performance compared with the steel frame.

The seismic performance of modular steel braced frames (MSBFs) is significantly different from regular steel braced frames because of their unique detailing and construction procedure. An analytical model that can accurately predict the seismic behaviour of MSBFs equipped with buckling restrained SMA braces is first developed. This model is then implemented to identify the locations of SMA braces to improve the seismic performance of MSBFs. The study highlighted the need to use SMA braces at all floors.

The study also examines the seismic performance of MSBFs utilizing superelastic SMA bolts at the vertical connections between the modules. It was observed that the seismic performance of a MSBF can be improved by using SMA connections at the right locations.


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