Applications of shape memory alloys in civil structures
G. Song a,∗ , N. Ma a , H.-N. Li b
a Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA b School of Civil and Hydraulic Engineering, Dalian University of Technology, Dalian, 116024, China
Received 24 June 2004; received in revised form 19 December 2005; accepted 26 December 2005 Available online 17 April 2006
Abstract Shape memory alloy (SMA) is a novel functional material and has found increasing applications in many areas. Recently, research efforts have been extended to using SMA for control of civil structures. This paper presents a review of applications of the SMA materials for passive, active and semi-active controls of civil structures. First, an overview of the characteristics of SMA is presented. The shape memory effect (SME) and pseudoelasticity, two major properties of SMA associated with the thermal-induced or stress-induced reversible hysteretic phase transformation between austenite and martensite, are reviewed. These unique properties enable SMA to be used as actuators, passive energy dissipators and dampers for civil structure control. This paper then reviews current research using SMA-based devices for passive, semi-active or active control of civil structures. The operation mechanism, design and experimental results of these SMA-based devices are also presented in the paper. c 2006 Elsevier Ltd. All rights reserved. Keywords: Shape memory alloy; Structural control; Passive vibration damping; Structural rehabilitation
1. Introduction Smart systems for civil structures are described as systems that can automatically adjust structural characteristics in response to external disturbances and/or unexpected severe loading toward structural safety, extension of the structure’s life time, and serviceability . One key technology toward this goal is the development and implementation of smart materials, which can be integrated into structures and provide functions such as sensing, actuation and information processes essential to monitoring, self-adapting and healing of structures. Some examples of smart materials are piezoceramics, shape memory alloys (SMAs), magneto-rheological (MR) ﬂuids, and electrorheological (ER) ﬂuids. SMAs have found applications in many areas due to their high power density, solid state actuation, high damping capacity, durability and fatigue resistance. When integrated with civil structures, SMAs can be passive, semi-active, or active components to reduce damage caused by environmental impacts or earthquakes. Though most of the research activities ∗ Corresponding author. Tel.: +1 713 743 4525; fax: +1 713 743 4503.
of SMAs’ applications in civil structures are still in laboratory stage, a few have been implemented for ﬁeld applications and found effective . 2. Basics about Nitinol shape memory alloys 2.1. Basics about shape memory alloys In 1932, Chang and Read observed a reversible phase transformation in gold–cadmium (AuCd), which is the ﬁrst record of the shape memory transformation. It was after 1962, when Buechler and co-researchers discovered the shape memory effect (SME) in nickel–titanium at Naval Ordnance Laboratory (they named the material Nitinol after their workplace), that both in-depth research and practical applications of shape memory alloys emerged. Up to date, many types of shape memory alloys have been discovered. Among them, Nitinol possesses superior thermomechanical and thermoelectrical properties and is the most commonly used SMA . In this paper, SMAs are referred to as Nitinol SMAs unless another type of SMA is speciﬁed. The following reviews two important properties of Nitinol SMAs: the shape memory effect and the superelasticity.
E-mail address: email@example.com (G. Song). 0141-0296/$ - see front matter c 2006 Elsevier Ltd. All rights reserved....