## 2 Application to Flexible Structures
### Structural Vibration Control
devised an adaptive system focusing on the enhancement of the soundproof performance of car door seals using SMA wires, which was integrated within the seal cavity to reduce the sound [42]. [PERSON] and [PERSON] investigated the nonlinear random vibration of axially moving SMA composite beam subjected to transverse loads as a function of the axial movement velocity. Using the stochastic averaging method, the amplitude frequency response equation under primary resonance and the probability density function under random perturbation were derived [43]. [PERSON] et al. applied the optimized SMA damper to control wave-induced vibrations of fixed jacket platforms where the ideal gas molecule movements method was implemented to minimize the deck displacements under the action of an extreme wave [44]. [PERSON] et al. proposed a single-sided pounding tuned mass damper using SMA sponge to mitigate the transient and force vibrations of a suspended piping system in which the SMA damper was utilized as a passive damper possessing high energy dissipation characteristics [45]. [PERSON] investigated the feasibility of a new approach to obtain more rapid cooling of SMA wires. It was because a steel spring pin placed on the wire induces a first vibration mode driven by an electromagnet when the SMA is cooled [46]. [PERSON] et al. investigated vibration control of a fixed-fixed beam using a piezo-SMA ferrule. The stability of the proposed beam structure could be improved by a self-regulation of the stiffness of the proposed actuator subjected to external excitations [47]. [PERSON] et al. proposed a unique sound absorber to tune the geometry manipulation using the reversible shape-changing ability of an SMP foam in which the micro-structure of foam was recovered to control the sound absorption capability dependent on frequency [48]. [PERSON] et al. applied SMA cables to the girder bridges in order to reduce unwanted vibration and hence increase traffic safety and comfort where both the bending and torsional vibrations were analyzed by the finite element method [49]. [PERSON] et al. investigated the mechanism of load transfer at the interface of SMA and glass fiber-reinforced plastic (GFRP) to detect the crack problem, which can reduce the stiffness of the hybrid composites. The pull-out test was undertaken with the hybrid composite specimens under plain SMA insert exhibiting the micro-cuts [50]. [PERSON] et al. designed a penalty-based sliding mode control law to actively control the flexible bar using an SMA actuator in which control force manipulates SMA to exert the necessary force for deflecting the flexible bar into the desired state [51]. [PERSON] et al. proposed a composite beam reinforced with SMA wires for free vibration control where both the static and dynamic behaviors of the beam with different volumetric fiber fractions were evaluated by analyzing the change of natural frequencies due to heat activation [52]. [PERSON] et al. investigated the free and forced vibration behaviors of a sandwich beam with functionally graded porous core and composite face layers embedded with SMA in which the change of the natural frequencies of the beam was evaluated as a function of the temperature, and vibration amplitude was shown at different external forces [53]. [PERSON] et al. proposed a multi-level SMA/lead rubber bearing isolation system to ensure both isolation efficiency and displacement attenuation under different levels of earthquake excitations in which a four-span continuous box-girder bridge system was designed and analyzed in terms of nonlinear dynamics [54]. [PERSON] et al. proposed SMA-based friction damper consisting of the friction plate and SMA cable for vibration control of civil structures such as bridges where the effects of the loading frequency, displacement amplitude, and number of SMA wires on the hysteretic behavior of the friction damper were investigated using three different structures [55]. [PERSON] et al.