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About this book

This book introduces readers to the fundamental properties and practical applications of shape memory alloys (SMAs) from the perspective of seismic engineering. It objectively discusses the superiority of this novel class of materials, which could potentially overcome the limitations of conventional seismic control technologies. The results, vividly presented in the form of tables and figures, are demonstrated with rigorous experimental verifications, supplemented by comprehensive numerical and analytical investigations.

The book allows readers to gain an in-depth understanding of the working mechanisms of various SMA-based structural devices and members, including beam-to-column connections, dampers, and braces, while also providing them with a broader vision of next-generation, performance-based seismic design for novel adaptive structural systems. Helping to bridge the gap between material science and structural engineering, it also sheds light on the potential of commercializing SMA products in the construction industry. The cutting-edge research highlighted here provides technical incentives for design professionals, contractors, and building officials to use high-performance and smart materials in structural design, helping them stay at the forefront of construction technology.

Table of Contents

Frontmatter

Chapter 1. Introduction to Shape-Memory Alloys

Abstract
The background information on shape-memory alloys (SMAs) is presented in this chapter. A brief history of the development and application of SMAs is first introduced, which is followed by a detailed discussion on two fundamental properties of SMAs, i.e. superelastic effect (SE) and shape-memory effect (SME). The potential of the two unique properties for civil engineering application is then elaborated together with a demonstration of several existing projects that successfully adopted the SMA technology. The necessary manufacturing procedures ensuring satisfactory thermal–mechanical properties of SMA products are highlighted, and the civil engineering-oriented experimental characterization methods are introduced. Finally, the available constitutive models for SMAs are introduced with a focus on phenomenological modelling approaches, which are more suited to the civil engineering application. Although the information provided in this chapter would suffice for practical civil/structural engineers who are interested in this topic, the reader should recognise that a wealth of knowledge exists on the relevant subjects, which are available in a vast body of literature.
Cheng Fang, Wei Wang

Chapter 2. Shape-Memory Alloy Elements

Abstract
In this chapter, a series of SMA elements, including SMA wires, cables, bars, bolts, helical springs, washer springs and ring springs, are described in detail. These elements are important additions to the ‘arsenal’ against the seismic hazard. For each type of element, the manufacturing process, testing scheme, key mechanical behaviour and analytical expressions are presented. The various SMA elements are shown to have their own unique load–deformation, self-centring and energy dissipation characteristics, catering to different design purposes. The main advantages and possible limitations of these elements are also discussed, with a particular focus on their failure mode and material utilisation efficiency.
Cheng Fang, Wei Wang

Chapter 3. Steel Beam-to-Column Connections with SMA Elements

Abstract
Having gained the necessary knowledge on the behaviour of various SMA elements, this chapter focuses on a series of novel SMA-based self-centring steel beam-to-column connections. Different SMA elements, including SMA bolts, SMA Belleville washer springs and SMA ring springs, are considered as kernel elements for these connections. The combined use of different types of SMA elements is also attempted. The influence of the slab system on the behaviour of self-centring connections is discussed, and the issue of frame expansion is particularly raised and addressed. The available experimental studies on these novel connections are presented, enabling a comprehensive understanding of their key performances such as moment–rotation response, ductility, self-centring capability, energy dissipation and possible failure modes. The design recommendations for some typical connections are also presented in this chapter.
Cheng Fang, Wei Wang

Chapter 4. Self-centring Braces with SMA Elements

Abstract
This chapter proceeds with discussions of the application of SMA elements in self-centring bracing members in framed structures. First, the existing solutions for self-centring braces are briefly introduced, and the potential limitations are also outlined. A series of newly proposed braces, employing SMA wires, tendons or ring springs, are subsequently discussed in detail. The main focus of this chapter is on the design principle, working mechanism, and fundamental mechanical behaviour of the kernel devices for the braces. Some technical issues such as the manufacturing process and annealing scheme are particularly addressed for the devices equipped with SMA ring spring systems.
Cheng Fang, Wei Wang

Chapter 5. Structural Responses: Single-Degree-of-Freedom (SDOF) Systems

Abstract
Following the discussions of the working principle and behaviour of the various SMA elements and SMA-based members and devices, it is time to move on to understand how SMA-based structural systems respond to earthquake excitations. A good starting point is to examine the fundamental dynamic responses of single-degree-of-freedom (SDOF) systems with varying parameters that characterise the basic hysteretic behaviour of the structural systems. This chapter starts with a comprehensive seismic evaluation of SDOF systems with a wide spectrum of structural parameters. The primary objective is to quantify the structural and non-structural performances of conventional and novel self-centring systems under both near-fault (NF) and far-field (FF) earthquakes. The analysis involves 5760 different SDOF models with more than 1.45 million statistical response results being processed. According to the available data, two sets of design models that provide the predictions of the inelastic displacement demand and residual displacement response for various systems are given. The results presented in this chapter can form the basis of the performance-based seismic design of SMA-based self-centring structures.
Cheng Fang, Wei Wang

Chapter 7. Economic Seismic Loss Assessment

Abstract
Economic seismic loss is one of the most important indices that quantify the seismic resilience of a structural system. This chapter provides further insight into the potential of SMA-based self-centring frames for reducing the economic seismic losses. The assessment is conducted based on three prototype steel building frames, namely, conventional moment resisting frame (MRF), buckling-restrained braced frame (BRB frame) and SMA-based self-centring braced frame. The rationale behind the seismic loss assessment framework is explained, and the FEMA P-58 methodology, a procedure which is now widely adopted in the community of seismic engineers, is particularly elaborated. The basic principles of incremental dynamic analysis (IDA) and fragility analysis are also clarified. Based on the existing methodology, the seismic losses of the three types of structures under different levels of earthquakes are obtained, and factors that affect the seismic loss performance are discussed. The assessment can offer more quantitative and rational seismic loss predictions for decision makers, especially in the feasibility analysis stage of construction projects.
Cheng Fang, Wei Wang
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