• Smart Structures and Systems
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• v.24 no.1
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• pp.1-14
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• 2019

Transmission tower-line system is one of most critical lifeline systems to cities. However, it is found that the transmission tower-line system is prone to be damaged by earthquakes in past decades. To mitigate seismic demands, this study introduces a tuned-mass damper (TMD) using superelastic shape memory alloy (SMA) spring for the system. In addition, considering the dynamic characteristics of both tower-line system and SMA are affected by temperature change. Particular attention is paid on the effect of temperature variation on seismic behavior. In doing so, the SMA-TMD is installed into the system, and its properties are optimized through parametric analyses. The considered temperature range is from -40 to $40^{\circ}C$. The seismic control effect of using SMA-TMD is investigated under the considered temperatures. Interested seismic performance indices include peak displacement and peak acceleration at the tower top and the height-wise deformation. Parametric analyses on seismic intensity and frequency ratio were carried out as well. This study indicates that the nonlinear behavior of SMA-TMD is critical to the control effect, and proper tuning before application is advisable. Seismic demand mitigation is always achieved in this wide temperature range, and the control effect is increased at high temperatures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.377-387
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• 2014

This study mainly treats a new type of the bracing friction damper system, which is able to minimize structural damage under earthquake loads. The slotted bolt holes are placed on the shear faying surfaces with an intention to dissipate considerable amount of friction energy. The superelastic shape memory alloy (SMA) wire strands are installed crossly between two plates for the purpose of enhancing recentering force that are able to reduce permanent deformation occurring at the friction damper system. The smart recentering friction damper system proposed in this study can be expected to reduce repair cost as compared to the conventional damper system because the proposed system mitigates the inter-story drift of the entire frame structure. The response mechanism of the proposed damper system is firstly investigated in this study, and then numerical analyses are performed on the component spring models calibrated to the experimental results. Based on the numerical analysis results, the seismic performance of the recentering friction damper system with respect to recentering capability and energy dissipation are investigated before suggesting optimal design methodology. Finally, nonlinear dynamic analyses are conducted by using the frame models designed with the proposed damper systems so as to verify superior performance to the existing damper systems.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1025-1037
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• 2015

Flexible base isolation bearings that separate superstructure from ground have been widely used in the construction field because they make a significant contribution to increasing the fundamental period of the structure, thereby decreasing response acceleration transmitted into the superstructure. However, the established bearing devices installed to uphold the whole building give rise to some problems involved with failure and collapse due to lack of the capacity as modern structures are getting more massive and higher. Therefore, this study suggests new isolation bearings assembled with additional restrainers enabled to reinforcing and recentering, and then evaluates their performance to withstand the seismic load. The superelastic shape memory alloy (SMA) bars are installed into the conventional lead-rubber bearing (LRB) devices in order to provide recentering forces. These new systems are modeled as component spring models for the purpose of conducting nonlinear dynamic analyses with near fault ground motion data. The LRB devices with steel bars are also designed and analyzed to compare their responses with those of new systems. After numerical analyses, ultimate strength, maximum displacement, permanent deformation, and recentering ratio are compared to each model with an aim to investigate which base isolation models are superior. It can be shown that LRB models with superelastic SMA bars are superior to other models compared to each other in terms of seismic resistance and recentering effect.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.2
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• pp.154-162
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• 2017

CanSat Competition has been annually held in South Korea since 2012 to give students an opportunity for better understanding of system design and operation processes of satellite. SCSky CanSat(Smart Call from the Sky Can Satellite) proposed in this study is a name of CanSat that was participated in 2016 CanSat competition. Its main mission objective is to obtain flight imaging data of inside and outside the CanSat through the video call using on-board smart phone in the CanSat. To implement this mission, we developed a remote touch system using SMA(Shape Memory Alloy) wire. In addition, a wide scan camera mechanism using SMA spring was developed to obtain ground imaging data during the mission. This study introduced the mission of the SCSky CanSat, as well as the description of on-board payloads, system design results, and flight test results.

• Smart Structures and Systems
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• v.28 no.6
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• pp.745-760
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• 2021

Dynamic buckling of structure is one of the failure modes that needs to be considered since it may result in catastrophic failure of the structure in a short period of time. For a thin fiber-reinforced polymer (FRP) plate under compression, buckling is an inherent hazard which will be intensified by the existence of defects like holes, cracks, and delamination. On the other hand, the growth of the delamination is another prime concern for thin FRP plates. In the current paper, reinforcing the plates against buckling is realized by using SMA wires in the form of stitches. A numerical framework is proposed to simulate the dynamic instability emphasizing the effect of the SMA stitches in suppressing delamination growth. The suggested algorithm is more accurate than the other methods when considering the transformation point of the SMA wires and the modeling of the cohesive zone using simple and yet reliable technique. The computational design of the method by producing the line by line orders leads to a simple algorithm for simulating the super-elastic behavior. The Lagoudas constitutive model of the SMA material is implemented in the form of user material subroutines (VUMAT). The normal bilinear spring model is used to reproduce the cohesive zone behavior. The nonlinear finite element formulation is programmed into FORTRAN using the Newmark-beta numerical time-integration approach. The obtained results are compared with the results obtained by the finite element method using ABAQUS/Explicit solver. The obtained results by the proposed algorithm and those by ABAQUS are in good agreement.

• The korean journal of orthodontics
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• v.36 no.5
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• pp.349-359
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• 2006

Objective: Nickel-titanium alloy wire possesses excellent spring-back properties, shape memory and super-elasticity. In order to adapt this wire to clinical use, it is necessary to bend as well as to control its super-elastic force. The purpose of this study is to evaluate the effects of heat treatment on the load-deflection properties and transitional temperature range (TTR) of nickel-titanium wires. Methods: Nickel-titanium wires of different diameters ($0.016"\;{\times}\;0.022"$, $0.018"\;{\times}\;0.025"$ and $0.0215"\;{\times}\;0.028"$) were used. The samples were divided into 4 groups as follows: group 4, posterior segment of archwire (24 mm) without heat treatment; group 2, posterior segment of archwire (24 mm) with heat treatment only; group 3, anterior segment with bending and heat treatment; group 4, anterior segment with bending and 1 sec over heat treatment. Three point bending test was used to evaluate the change in load-deflection curve and obtained DSC (different scanning calorimetry) to check changes in $A_f$ temperature. Results: In the three point bending test, nickel-titanium wires with heat treatment only had higher load-deflection curve and loading and unloading plateau than nickel-titanium wires without heat treatment. Nickel-titanium wires with heat treatment had lower Af temperature than nickel-titanium wires without heat treatment. Nickel-titanium wires with heat treatment and bending had higher load-deflection curve than nickel- titanium wires with heat treatment and nickel-titanium wires without heat treatment. Nickel-titanium with heat treatment of over 1 sec and bending had the highest load-deflection curve. Nickel-titanium wires with heat treatment and bending had lower Af temperature, Nickel-titanium wires with heat treatment of over Af sec and bending had the lowest Af temperature. Conclusion: From the results of this study, it can be stated that heat treatment for bending of Nickel-titanium wires does not deprive the superelastic property but can cause increased force magnitude due to a higher load-deflection curve.