ﺑﺮرﺳﯽ اﺛﺮ ﻣﯿﺮاﯾﯽ ﻫﯿﺴﺘﺮﺗﯿﮏ آﻟﯿﺎژﻫﺎي ﻫﻮﺷﻤﻨﺪ ﺑﺮ ﻋﻤﻠﮑﺮد ﻟﺮزه اي ﻣﯿﺮاﮔﺮ ﺟﺮﻣﯽ ﺗﻨﻈﯿﻢ ﺷﺪه

Evaluation of Effects of Hysteretic Damping of Shape Memory Alloys on Seismic Performance of Tuned Mass Damper

ﻣﯿﺮاﮔﺮ ﺟﺮﻣﯽ ﺗﻨﻈﯿﻢ ﺷﺪه اﺑﺰاري راﯾﺞ در ﮐﻨﺘﺮل ﻏﯿﺮﻓﻌﺎل اﺳﺖ ﮐﻪ در ﺑﺴﯿﺎري از ﺳﺎزه ﻫﺎ ﻣﻮرد اﺳﺘﻔﺎده ﻗﺮار ﮔﺮﻓﺘﻪ اﺳﺖ. ﺑﺎ اﯾﻦ ﺣﺎل، ﺑﺎ ﺗﻤﺎم وﯾﮋﮔﯽﻫﺎي ﻣﻨﺎﺳﺒﯽ ﮐﻪ در اﯾﻦ ﻣﯿﺮاﮔﺮ وﺟﻮد دارد، ﻣﻬﻤﺘﺮﯾﻦ ﻣﺤﺪودﯾﺖ ﻋﻤﻠﮑﺮدي آن، ﺿﻌﻒ در ﺑﺮاﺑﺮ ﺗﺤﺮﯾﮏﻫﺎي ﺑﺎ ﻣﺤﺘﻮاي ﻓﺮﮐﺎﻧﺴﯽ ﺑﺎﻻ اﺳﺖ. روشﻫﺎي ﻣﺨﺘﻠﻔﯽ ﺑﺮاي ﻏﻠﺒﻪ ﺑﺮ اﯾﻦ ﻣﺸﮑﻞ ﭘﯿﺸﻨﻬﺎد ﺷﺪهاﻧﺪ ﮐﻪ در ﻣﯿﺎن آﻧﻬﺎ اﺳﺘﻔﺎده از ﻣﯿﺮاﯾﯽ ﻫﯿﺴﺘﺮﺗﯿﮏ ﻣﺼﺎﻟﺢ ﺑﺎ رﻓﺘﺎر ﻏﯿﺮﺧﻄﯽ ﺑﻪ ﻋﻨﻮان ﯾﮏ روش ﻣﻮﺛﺮ ﺷﻨﺎﺧﺘﻪ ﺷﺪه اﺳﺖ. در ﻣﯿﺎن ﻣﺼﺎﻟﺢ ﺑﺎ رﻓﺘﺎر ﻏﯿﺮﺧﻄﯽ آﻟﯿﺎژﻫﺎي ﺣﺎﻓﻈﻪ ﺷﮑﻠﯽ داراي وﯾﮋﮔﯽﻫﺎي ﻣﻨﺎﺳﺐ و ﺣﻠﻘﻪﻫﺎي رﻓﺘﺎري ﻫﯿﺴﺘﺮزﯾﺲ وﺳﯿﻊ ﻫﺴﺘﻨﺪ. از اﯾﻦ رو در اﯾﻦ ﻣﻘﺎﻟﻪ ﺑﺎ اﺳﺘﻔﺎده از ﺳﺨﺘﯽ ﻏﯿﺮﺧﻄﯽ و ﻣﯿﺮاﯾﯽ ﻫﯿﺴﺘﺮﺗﯿﮏ ﯾﮏ ﻓﻨﺮ از ﺟﻨﺲ آﻟﯿﺎژ ﺣﺎﻓﻈﻪ ﺷﮑﻠﯽ، ﺳﺨﺘﯽ ﺧﻄﯽ و ﻣﯿﺮاﯾﯽ وﯾﺴﮑﻮز ﻣﯿﺮاﮔﺮﻫﺎي ﺟﺮﻣﯽ راﯾﺞ ﺟﺎﯾﮕﺰﯾﻦ ﻣﯽﺷﻮﻧﺪ. ﺳﭙﺲ ﻣﯿﺮاﮔﺮ ﺟﺮﻣﯽ ﺗﻐﯿﯿﺮ ﯾﺎﻓﺘﻪ ﺑﺮاي ﮐﻨﺘﺮل ﭘﺎﺳﺦﻫﺎي ﺳﺎزهﻫﺎي ﯾﮏدرﺟﻪ آزادي ﺗﺤﺖ ﺗﺤﺮﯾﮏ ﻫﺎرﻣﻮﻧﯿﮏ ﻣﻮرد اﺳﺘﻔﺎده ﻗﺮار ﮔﺮﻓﺘﻪ و اﺛﺮ داﻣﻨﻪ ﺑﺎرﮔﺬاري ﺑﺮ ﮐﻨﺘﺮل ﭘﺎﺳﺦ-ﻫﺎي ﺳﺎزهاي ﺗﻌﯿﯿﻦ ﻣﯽﺷﻮد. ﭘﺲ از آن ﻣﯿﺮاﮔﺮ ﺑﺮاي ﮐﻨﺘﺮل ﭘﺎﺳﺦﻫﺎي ﻟﺮزهاي ﺳﺎزهﻫﺎي ﯾﮏدرﺟﻪ آزادي ﺑﻪ ﮐﺎر ﻣﯽرود ﺗﺎ ﻋﻤﻠﮑﺮد آن ﺗﺤﺖ ﺗﺎﺛﯿﺮ ﺑﺎرﮔﺬاريﻫﺎي ﻟﺮزهاي داراي ﻣﺤﺘﻮاي ﻓﺮﮐﺎﻧﺴﯽ ﺑﺎﻻ ﺑﺎ ﻋﻤﻠﮑﺮد ﻣﯿﺮاﮔﺮﻫﺎي ﺟﺮﻣﯽ ﻣﻌﻤﻮل ﻣﻘﺎﯾﺴﻪ ﮔﺮدد. ﻧﺘﺎﯾﺞ اﯾﻦ ﺗﺤﻠﯿﻞﻫﺎ ﻧﺸﺎن ﻣﯽ دﻫﻨﺪ ﮐﻪ وﯾﮋﮔﯽﻫﺎي آﻟﯿﺎژﻫﺎي ﺣﺎﻓﻈﻪ ﺷﮑﻠﯽ ﻣﯽﺗﻮاﻧﻨﺪ ﺑﻪ ﻧﺤﻮ ﻗﺎﺑﻞ ﻗﺒﻮﻟﯽ ﺗﺎﺛﯿﺮ داﻣﻨﻪ ﺑﺎرﮔﺬاري را ﺑﺮ ﻋﻤﻠﮑﺮد ﻣﯿﺮاﮔﺮ ﺟﺮﻣﯽ ﻏﯿﺮﺧﻄﯽ ﮐﻨﺘﺮل ﻧﻤﺎﯾﻨﺪ. ﻫﻤﭽﻨﯿﻦ ﺣﻀﻮر ﻣﯿﺮاﯾﯽ ﻫﯿﺴﺘﺮﺗﯿﮏ ﻣﯽﺗﻮاﻧﺪ ﺑﻪ ﻣﯿﺰان ﻗﺎﺑﻞ ﻣﻼﺣﻈﻪاي ﮐﻨﺘﺮل ﭘﺎﺳﺦﻫﺎي ﻟﺮزهاي ﺳﺎزهﻫﺎي ﯾﮏدرﺟﻪ آزادي را ﻧﺴﺒﺖ ﺑﻪ ﻣﯿﺮاﮔﺮﻫﺎي ﺟﺮﻣﯽ ﻣﻌﻤﻮل ﺑﻬﺒﻮد ﺑﺨﺸﺪ ﺑﻪ ﺷﺮﻃﯽ ﮐﻪ وﯾﮋﮔﯽﻫﺎي دﯾﻨﺎﻣﯿﮑﯽ ﻣﯿﺮاﮔﺮ ﻏﯿﺮﺧﻄﯽ ﻣﻘﺎدﯾﺮ ﺑﻬﯿﻨﻪ ﺧﻮد را اﺧﺘﯿﺎر ﮐﻨﻨﺪ.

Tuned mass damper is a common tool in passive control, which is used in many structures. However, with all the proper features, its most important functional limitation is the weakness against broad band excitation. Various methods have been proposed to overcome this problem, among which using hysteretic damping of materials with nonlinear behavior is known effective. Among materials with nonlinear behavior, shape memory alloys have good features and large hysteresis loops. Hence, in this paper, using nonlinear stiffness and hysteretic damping of a shape memory alloy spring, linear stiffness and viscous damping of a common tuned mass damper are replaced. Then, the modified damper has been used to control responses of a single degree of freedom structure under harmonic loadings and the effect of the loading amplitude on the control of the structural responses was determined. Subsequently, the damper has been used to control seismic responses of single degree of freedom structures to compare its performance under broad band seismic loadings with the performance of conventional tuned mass dampers. Results of the analyses show that the characteristics of shape memory alloys can adequately control the impact of the loading amplitude on the performance of nonlinear mass dampers. Also, the presence of hysteretic damping can significantly improve control of seismic responses of single degree degrees of freedom structures compared to conventional tuned mass dampers, provided that dynamic properties of the nonlinear mass damper take their optimal values.