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Journal of Materials Science and Nanotechnology | Volume 3
February 25-26, 2019 | Paris, France
Materials Science and Engineering
2
nd
International Conference on
Rocking frame reinforced with superelastic Nickel-Titanium shape memory alloy
Raafat El Hacha
1
and
Fadi Oudah
2
1
University of Calgary, Canada
2
Dalhousie University, Canada
Conventional seismic design systems rely on the inelastic
behaviour of certain members to dissipate the seismic energy.
This research takes a deeper look into retrofitting steel
structures using the rocking structures method. This is an
innovative technique where the designer is allowing for the
structure to rock back and forth with the seismic loading, taking
advantage of the weakening of the structure. Rocking columns
reduce the strength of the structure causing it to yield sooner,
thus reducing the maximum structural accelerations. However,
though the maximum acceleration due to ground excitations is
reduced, the rocking increases the inter-storey displacements.
Shape Memory Alloys (SMA) has been attracting researchers
from different fields, it is a unique class of alloy with the ability
to undergo large deformations (up to 8%) and return to its
original shape through stress removal. The main objective of
this research is to investigate the effectiveness and feasibility of
active techniques for seismic retrofitting of steel braced frames
using the rocking structures combined with pseudoelastic (PE)
nickel-titanium (Ni-Ti) SMA wires. To observe the behaviour
of the retrofitted steel braced frame a free vibration test to
determine the natural frequency of the system and a cyclic
test were performed to demonstrate the effects of a rocking
structure with PE Ni-Ti SMA wires to dissipate and recenter
the structure when subject to an earthquake. The use of
the rocking columns combined with the shape memory
alloys proposed in this research not only controls where the
damage occurs but limits it to be very insignificant, where no
structural elements would need replacing. Results from the
free vibrations test suggest that the stiffness of the system is
dependent on the rigidity of the column-foundation connection
than the rigidity of the cross bracing. The in-plane cyclic tests
found that the Ni-Ti wires have significant pseudoelastic
properties that had almost zero residual strain at 4% drift and
the potential for moderate energy dissipation. Findings of this
research are expected to add valuable knowledge to the field
of seismic retrofitting of RC structures and widen the potential
applications of the SMA in the structural engineering field.
e:
relhacha@ucalgary.ca