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SPECIAL SECTION ON DAMPING OF SHAPE MEMORY ALLOYS, COMPOSITES, AND FOAMS

Theoretical and Experimental Studies for the Application of Shape Memory Alloys in Civil Engineering

[+] Author and Article Information
Mauro Dolce

DiSGG,  University of Basilicata, 85100 Potenza, Italydolce@unibas.it

Donatello Cardone

DiSGG,  University of Basilicata, 85100 Potenza, Italydonatello.c@tiscali.it

J. Eng. Mater. Technol 128(3), 302-311 (Jan 25, 2006) (10 pages) doi:10.1115/1.2203106 History: Received August 31, 2005; Revised January 25, 2006

Shape memory alloys (SMAs) have great potential for use in the field of civil engineering. The authors of this paper have been involved, from 1996, in several experimental and theoretical studies of the application of SMAs in civil engineering, for national and international research projects. This paper provides an overview of the main results achieved, consisting of the conceptual design, implementation, and testing of three families of SMA-based devices, namely: (i) special braces for framed structures, (ii) seismic isolation devices for buildings and bridges, and (iii) smart ties for arches and vaults. The main advantage of using SMA-based devices in the seismic protection of structures comes from the double-flag shape of their hysteresis loops, which implies three favorable features, i.e., self-centering capability, good energy dissipation capability, and high stiffness at small displacements. The main advantage of smart ties comes from the thermal behavior of SMA superelastic wires, which is opposite to that of steel rod. This implies a strong reduction of the force changes caused by variations of air temperature.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Seismic isolation of (a) buildings and (b) bridges. (c) Energy dissipating braces for framed structures.

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Figure 2

(a) Functional scheme of a complete device, including both functional groups of SMA wires, (b) idealized force-displacement relationships of a device including both groups of SMA wires (7)

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Figure 3

Experimental cyclic behavior of a reduced-scale brace, equipped with (a) 12 SMA “recentering” 1mm dia wire loops prestrained at about 2.5%, (b) 8 SMA “dissipating” 1mm dia wire double loops prestrained at about 3.5% and (c) both

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Figure 4

Equivalent viscous damping ratio of SMA braces as a function of displacement amplitude (T=20°C, f=1Hz)

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Figure 5

(a) Cyclic behaviors of the isolation device equipped with 118 1.84mm dia SMA wire loops, prestrained at about 2%, and (b) equivalent viscous damping of the isolation device only and of the complete isolation system

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Figure 6

(a) Displacement-time history during the pushing phase and (b) free damped vibrations of the structure after releasing

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Figure 7

(a) Quarter-scale structural model tested on shaking table (units are centimeter) and (b) scaled acceleration-time history (10)

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Figure 8

(a) Bracing layout and (b) arrangement of the SMA wires inside the device and typical force-displacement behavior (10)

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Figure 9

Changes in the fundamental frequency of vibration of unbraced and SMA-braced models, while increasing PGA

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Figure 10

(a) Minimum frequency of vibration and (b) effective damping exhibited by unbraced and SMA-braced model during the tests, as a function of the corresponding maximum roof displacement

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Figure 11

Force-displacement behaviors exhibited by SMA braces during the test at 0.88g PGA

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Figure 12

Floor displacement-time histories, recorded during the test at 0.88g PGA, on the SMA-braced model

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Figure 13

Comparison between the thermal behavior of a steel tie-rod with and without TCB

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Figure 14

Hysteresis subloops of a SMA wire sample during tensile test at 1Hz frequency of loading, representing the cyclic behavior of TCB during an earthquake

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