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Materials Science and Nanotechnology | Volume: 03
WORLD CONGRESS ON SMART MATERIALS AND STRUCTURES
&
3
rd
International Conference on
POLYMER CHEMISTRY AND MATERIALS ENGINEERING
November 21-22, 2019 | Singapore
Joint event on
Modern seismic design philosophy allows buildings to
experience significant plastic responses to dissipate energy at
plastic hinge regions when subjected to moderate-to-strong
earthquakes. Even though the performance target (e.g.,
Collapse Prevention) of these buildings can be successfully
met, such a design philosophy may result in permanent
damage concentrated in the selected “sacrificial” regions after
earthquakes. The damaged buildings are often demolished
because too large residual deformation makes the repair
economically unviable. For example, approximately 60% of
RC buildings after 2011 New Zealand Christchurch earthquake
were demolished because of forbidden repair cost, although
most of them did not collapse during the earthquake. The
government estimated the total losses would be as much as
NZ$40 billion. Furthermore, the central business district was
closed for over 2 years and some tall buildings underwent
a long-demolished period. A recent study concluded that
residual drift ratio greater than 0.5% makes rebuilding a
new structure more economical rather than retrofitting the
damaged structure. For this reason, new seismic protection
concepts, such as resilience-based design (RBD) have recently
emerged to minimize structural damage through new
technologies or high-performance materials.
As a high-performance metallic material, shape memory
alloys (SMAs) can undergo large strains and recover their
initial shape through heating (shape memory effect) or
unloading (superelastic effect). The schematic of stress-strain
responses of superelastic and shape memory behaviors. The
stress-strain behavior of SMA is similar to the conventional
steel with fat hysteresis loop and remarkable residual strain
at a temperature below the martensite finish temperature
T < Mf ; however, residual strain can be recovered through
temperature increase. When the temperature above the
austenite finish temperature T > Af , SMA exhibits superelastic
behavior with little or no residual strain caused by a stress-
induced phase transformation from austenite to martensite.
Moreover, excellent corrosion resistance performance and
high fatigue resistance of NiTi SMAs can overcome the aging,
durability, and maintenance issues in a life-cycle design of
civil infrastructures. The superelasticity of SMA is appealing
to the earthquake engineering research community because
flag-shaped hysteresis is associated with minimal residual
deformation under cyclic loading.
The lecture highlights the research on seismic applications of
superelastic SMAs, from material level, structural member
level, to structural system level. The major content includes
the thermomechanical constitutive model of SMA, SMA-
based dampers and braces, self-centering reinforced concrete
walls, high-performance steel rocking columns, shake table
test study of a steel frame with SMA braces, and performance-
based seismic design method. From the perspective of
seismic design, SMA-based structural members and systems
exhibit satisfactory and stable flag-shaped hysteretic loops
with excellent self-centering capability and sufficient energy
dissipation capability. Detailed experimental studies and
numerical analyses show superelastic SMAs can provide a
promising solution to high-performance structural systems to
achieve modern resilient and sustainable civil infrastructure.
Biography
Songye Zhu received his B.Eng. and
M.Sc. degrees in Structural Engineering
from Tongji University, China in 2000 and 2003, respectively, and his
Ph.D. degree in Civil Engineering from Lehigh University, USA in 2007.
He is currently an Associate Professor in the Department of Civil and
Environmental Engineering and the Hong Kong Branch of National Rail
Transit Electrification and Automation Engineering Technology Research
Center at The Hong Kong Polytechnic University. He also serves as Editor
of Advances in Structural Engineering (an international journal), Associate
Editor of International Journal of Nano and Smart Materials, and Immediate
Past President of American Society of Civil Engineers – Hong Kong Section
(2018-2019).
e:
songye.zhu@polyu.edu.hkSongye Zhu
The Hong Kong Polytechnic University, Hong Kong
Using superelastic shape memory alloys to achieve earthquake resilience
Mater Sci Nanotechnol, Volume: 03