scholarly journals Response Statistics of a Shape Memory Alloy Oscillator with Random Excitation

2021 ◽  
Vol 11 (21) ◽  
pp. 10175
Author(s):  
Rong Guo ◽  
Qi Liu ◽  
Junlin Li ◽  
Yong Xu
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Perturbation Technique ◽  
Time History ◽  
Multiple Scale ◽  
Harmonic Excitation ◽  
Random Excitation ◽  
Random Fluctuation ◽  
Steady State Probability ◽  
Approximate Analytical Solutions

This paper aimed to explore analytically the influences of random excitation on a shape memory alloy (SMA) oscillator. Firstly, on the basis of the deterministic SMA model under a harmonic excitation, we introduce a stochastic SMA model with a narrow-band random excitation. Subsequently, a theoretical analysis for the proposed SMA model was achieved through a multiple-scale method coupled with a perturbation technique. All of the obtained approximate analytical solutions were verified by numerical simulation results, and good agreements were observed. Then, effects of the random excitation and the temperature value on the system responses were investigated in detail. Finally, we found that stochastic switch and bifurcation can be induced by the random fluctuation, which were further illustrated through time history and steady-state probability density function. These results indicate that the random excitation has a significant impact on dynamics of the SMA model. This research provides a certain theoretical basis for the design and vibration control of the SMA oscillator in practical application.

Seismic analysis and evaluation of several recentering braced frame structures

2013 ◽  
Vol 228 (5) ◽  
pp. 781-798 ◽  
Author(s):  
Jong Wan Hu
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Seismic Analysis ◽  
Time History ◽  
Frame Structures ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Economic Point ◽  
Conventional Steel ◽  
Steel Bracing

After earthquakes, residual inter-story drifts greater than 0.5% in buildings may indicate a complete loss of the structure from an economic point of view. Recently, research efforts have been extended to the utilization of superelastic shape memory alloy materials for the smart control systems that can automatically reduce the plastic deformation of the structure subjected to strong seismic loading. Superelastic shape memory alloys are unique metallic alloys that undergo substantial inelastic deformations and regain their original conditions when applied loads are removed, thus alleviating the problem of permanent deformation. The frame structures make the best use of such shape memory alloy’s recentering capability if the superelastic shape memory alloy segments used to replace the steel segments are installed at the part where large deformation is likely to occur. The primary focus of this study is on the seismic response of special steel concentrically braced frames and buckling-restrained braced frames, utilizing superelastic shape memory alloy braces. In order to examine the comparative residual inter-story drift response of both braced frames, 3- and 6-story buildings were designed in accordance with current code specifications, and then nonlinear time-history analyses for two seismic hazard levels were conducted on 2D analytical frame models. The braced frames with superelastic shape memory alloy bracing systems were also compared to those with conventional steel bracing systems. Overall, analysis results show that the superelastic shape memory alloy bracing systems are more effective in decreasing residual inter-story drifts than the conventional steel bracing systems.

Random Characteristics of Vehicle-Bridge System Vibration by an Optimized Pseudo Excitation Method

2020 ◽  
Vol 20 (05) ◽  
pp. 2050069
Author(s):  
Siyu Zhu ◽  
Yongle Li
Keyword(s):  
Excitation Frequency ◽  
Time History ◽  
Harmonic Excitation ◽  
Random Excitation ◽  
Computational Effort ◽  
Cumulative Distribution ◽  
Pseudo Excitation Method ◽  
Rail Irregularities ◽  
Pseudo Excitation ◽  
Excitation Method

The pseudo excitation method (PEM) is improved for its efficiency by incorporating the self-adaptive Gauss integration (SGI) technology as a new combining integration. The PEM can transform the random rail irregularities into some pseudo harmonic excitation, which is a mature approach to deal with the random excitation for vehicle–bridge systems. The SGI was used to distinguish the significant from the insignificant parts of an integral section for the random excitation frequency on the stochastic response of the system, thereby reducing the computational effort required for the random vibration analysis of the system. Also, the SGI can intelligently handle the recognized integral section, by subdividing the important sections into several necessary frequency points, making rough decomposition, and allowing the unimportant regions to be eliminated. Based on selected frequency points, the deterministic pseudo harmonic excitations were generated, and then the standard deviation (SD) of the time history for the system was calculated by the PEM. The vehicle subsystem was simulated as a 23-degree of freedom model, and the bridge subsystem as a three-dimensional finite element model. The time-varying power spectral density (PSD) plots of the system were presented. Besides, the cumulative distribution function (CDF) of the response was calculated using Poisson’s crossing assumption. The random characteristics for the vehicle–bridge vibrations for different speeds and rail irregularities were calculated.

Mitigation of Vertical and Horizontal Seismic Excitations on Bridges Utilizing Shape Memory Alloy System

2013 ◽  
Vol 831 ◽  
pp. 90-94 ◽  
Author(s):  
H. Aryan ◽  
M. Ghassemieh
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Three Dimensional ◽  
Time History ◽  
Alloy System ◽  
Practical Method ◽  
Nonlinear Time History Analysis ◽  
Vertical Acceleration ◽  
Three Dimensional Model ◽  
Seismic Excitations

Vertical seismic excitation has a tremendous effect on bridges and many researchers have pointed out bridges damages occurred during the past significant earthquakes which were direct results of ignoring vertical acceleration of ground motions. Many studies have emphasized the importance of extending practical methods to reduce effects of vertical acceleration of earthquakes besides effects of horizontal accelerations; but no practical method has proposed up to now. In this article, an innovative shape memory alloy system is proposed for bridges that can simultaneously controls effects of vertical and horizontal seismic excitations on bridge and reduce them. To evaluate the effectiveness of the shape memory alloy system, a nonlinear time history analysis is conducted on a detailed three-dimensional model of a multi-span simply supported bridge using a representative ground motion. The results show that the proposed new system is very effective for reducing effects of vertical and horizontal seismic excitations on bridges.

scholarly journals Theoretical Study on Vibration Control of Symmetric Structure with Shape Memory Alloy (SMA)-Friction Damper

2014 ◽  
Vol 8 (1) ◽  
pp. 803-808
Author(s):  
Yunli Gao ◽  
Wenjie Ren
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Vibration Control ◽  
Time History ◽  
Response Analysis ◽  
Analysis Program ◽  
Friction Damper ◽  
Symmetric Structure ◽  
In Series ◽  
Dissipation Elements

The paper proposed an innovative shape memory alloy (SMA)-friction damper. The damper consisted of the superelastic SMA wire and the friction element in series. According to the working mechanism of the damper, the paper set up the mechanical model of the damper. Seismic elastic-plastic time history response analysis program and energy analysis program of the damped structure were designed. The numerical calculations of the vibration control of a threestory shear-type symmetric structure with the damper were carried out. The results indicated that the damper can decrease the displacement and the inter-story displacement of the structure effectively, but increase the acceleration of the structure comparing with uncontrolled structure. The SMA-friction damper can not only adjust the working status of the energy dissipation elements automatically according to the seismic responses of the structure, but also has some advantages as simple configuration and economical application.

scholarly journals Life-cycle cost evaluation of steel structures retrofitted with steel slit damper and shape memory alloy–based hybrid damper

2018 ◽  
Vol 22 (1) ◽  
pp. 3-16 ◽  
Author(s):  
Mohamed NourEldin ◽  
Asad Naeem ◽  
Jinkoo Kim
Keyword(s):  
Life Cycle ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Life Cycle Cost ◽  
Time History ◽  
Steel Structures ◽  
Cost Evaluation ◽  
Nonlinear Time History Analysis ◽  
Analysis Model ◽  
Hybrid Damper

In this study, the seismic capacity of a hybrid damper, composed of a steel slit plate damper and two shape memory alloy bars, is investigated through fragility analysis and life-cycle cost evaluation of a steel frame retrofitted with the damper. The nonlinear time history analysis model frames show that the seismic responses of the frames equipped with hybrid damper are significantly lesser than the frames retrofitted with conventional slit dampers. The enhancement in the seismic performance of frames retrofitted with hybrid damper is because of extra stiffness, energy dissipation, and self-centering capability provided by the shape memory alloy bars. It is also observed that the life-cycle cost of the frames equipped with hybrid dampers is smallest compared with the life-cycle cost of the bare frames and the frames equipped with slit dampers, even though the initial cost is of the hybrid damper is higher than that of the conventional slit damper.

Rocking isolation of bridge pier using shape memory alloy

2021 ◽  
Vol 16 (2-3) ◽  
pp. 85-103
Author(s):  
Rajesh R. Rele ◽  
Ranjan Balmukund ◽  
Stergios A. Mitoulis ◽  
Subhamoy Bhattacharya
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Lateral Displacement ◽  
Plastic Hinge ◽  
Time History ◽  
Bridge Pier ◽  
Bridge Piers ◽  
Isolation Technique ◽  
Residual Drift ◽  
Dynamic Time

The conventional design philosophy of bridges allows damage in the pier through yielding. A fuse-like action is achieved if the bridge piers are designed to develop substantial inelastic deformations when subjected to earthquake excitations. Such a design can avoid collapse of the bridge but not damage. The damage is the plastic hinge formation formed at location of maximum moments and stresses that can lead to permanent lateral displacement which can impair traffic flow and cause time consuming repairs. Rocking can act as a form of isolation by means of foundation uplifting which act as a mechanical fuse, limiting the forces transferred to the base of the structure. In this context, this paper proposes a novel resilient controlled rocking bridge pier foundation, which uses elastomeric pads incorporated beneath the footing of the bridge piers and external restrainer in the form of shape memory alloy bar (SMA). The rocking mechanism is achieved by restricting the horizontal movement of footing by providing stoppers at all sides of footing. The pads are designed to remain elastic without allowing their shearing. The pier, the footing and the elastomeric pads are assumed to be supported on firm rigid concrete sub base resting on hard rock. By performing nonlinear dynamic time history analysis in the traffic direction of the bridge, the proposed pier with the novel resilient foundation is compared against a fixed-based pier and classical rocking pier (CC). The proposed pier rocking on elastomeric pads and external restrainer (CP+SMA) has good re-centering capability during earthquakes with negligible residual drift and footing uplift. In this new rocking isolation technique, the forces in the piers are also reduced and thus leading to reduced construction cost with enhanced post-earthquake serviceability.

Nonlinear Forced Vibration for Shape Memory Alloy Spring Oscillator

2011 ◽  
Vol 250-253 ◽  
pp. 3958-3964 ◽  
Author(s):  
Ze Jin Shang ◽  
Zhong Min Wang
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Forced Vibration ◽  
Time History ◽  
Exciting Force ◽  
Damping Coefficient ◽  
Dimensionless Temperature ◽  
Nonlinear Dynamic Model ◽  
Chaotic Motions ◽  
Nonlinear Forced Vibration

The recovery force of shape memory alloy spring is described by using polynomial constitutive equation. The nonlinear dynamic model of forced vibration for the shape memory alloy spring oscillator is derived. Numerical simulations are performed by a fourth-order Runge-Kutta method. The bifurcation diagram and Lyapunov-exponent spectrum are presented while the dimensionless temperature, the dimensionless damping coefficient or the dimensionless amplitude of exciting force is varied respectively, thus the bifurcation of the system is investigated. Furthermore, the periodic and chaotic motions of the system are analyzed by means of the displacement time history diagram, the phase portrait, the Poincare section diagram and the power spectrum with different parameters. The results show that the periodic or chaotic motion of the system occur by changing temperature, damping coefficient and amplitude of exciting force, thus the vibration of the system could be controlled.

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