ﮐﻨﺘﺮل ارﺗﻌﺎﺷﺎت ﻧﺎﺷﯽ از ﺑﺎد ﺑﺮج ﻫﺎي ﺗﻠﻮﯾﺰﯾﻮﻧﯽ ﺑﻠﻨﺪ ﺑﺎ ﺑﻪ ﮐﺎرﮔﯿﺮي ﺑﺨﺸﯽ از ﺳﺎزه اﺻﻠﯽ ﺑﻪ ﻋﻨﻮان زﯾﺮﺳﺎزه ﺟﺎذب ارﺗﻌﺎش

Wind-Induced Vibration Control of Tall TV Towers using a Part of the Main Structure as a Vibration Absorber Substructure

در اﯾﻦ ﻣﻄﺎﻟﻌﻪ، روش ﺟﺪﯾﺪي ﺑﺮاي ﮐﻨﺘﺮل ﭘﺎﺳﺦ ﺑﺮجﻫﺎي ﺗﻠﻮﯾﺰﯾﻮﻧﯽ ﺑﻠﻨﺪ در ﻣﻘﺎﺑﻞ ﻧﯿﺮوﻫﺎي دﯾﻨﺎﻣﯿﮑﯽ ﺑﺎد ﭘﯿﺸﻨﻬﺎد ﮔﺮدﯾﺪ. ﻣﻄﺎﺑﻖ اﯾﺪه ﭘﯿﺸﻨﻬﺎدي، ﺑﺨﺸﯽ از ﺳﺎزه اﺻﻠﯽ ﺑﺮج از آن ﺟﺪا ﮔﺮدﯾﺪ و ﺑﻪ ﻋﻨﻮان زﯾﺮﺳﺎزه ﺟﺎذب ارﺗﻌﺎش دﯾﻨﺎﻣﯿﮑﯽ در ﻧﻈﺮ ﮔﺮﻓﺘﻪ ﺷﺪ. ﺟﻬﺖ ارزﯾﺎﺑﯽ روش ﭘﯿﺸﻨﻬﺎدي، ﺑﺮج 310 ﻣﺘﺮي ﻧﺎﻧﺠﯿﻨﮓ در ﮐﺸﻮر ﭼﯿﻦ ﮐﻪ داراي دو ﺳﮑﻮي ﺗﻤﺎﺷﺎ در ارﺗﻔﺎعﻫﺎي 180 و 240 ﻣﺘﺮي ﻣﯽﺑﺎﺷﺪ، ﻣﻮرد ﻣﻄﺎﻟﻌﻪ ﻗﺮار ﮔﺮﻓﺖ. ﭘﺎﺳﺦ ﺳﺎزه ﺑﺮاي ﺳﻪ ﺣﺎﻟﺖ ﮐﻨﺘﺮل ﻧﺸﺪه، ﮐﻨﺘﺮل ﺷﺪه ﺑﺎ ﻣﯿﺮاﮔﺮ ﺟﺮﻣﯽ ﺗﻨﻈﯿﻢ ﺷﻮﻧﺪه ﯾﺎTMD ، و ﮐﻨﺘﺮل ﺷﺪه ﺗﻮﺳﻂ ﯾﮏ زﯾﺮﺳﺎزهي ﺟﺪا ﺷﺪه از ﺳﺎزه اﺻﻠﯽ در ﻣﺤﻞ ﺳﮑﻮي ﺗﻤﺎﺷﺎي ﻓﻮﻗﺎﻧﯽ، ﻣﻮرد ﺗﺤﻠﯿﻞ ﻗﺮار ﮔﺮﻓﺖ. ﺳﺎزه ﺑﺮج ﺑﻪﺻﻮرت ﺗﯿﺮ ﻃﺮهاي ﻗﺎﺋﻢ ﭼﻨﺪ درﺟﻪ آزادي در ﻧﻈﺮ ﮔﺮﻓﺘﻪ ﺷﺪ و زﯾﺮﺳﺎزه ﺟﺎذب ارﺗﻌﺎش ﺑﻪﺻﻮرت ﺟﺮم ﻣﺘﻤﺮﮐﺰ ﺗﻮﺳﻂ ﺳﯿﺴﺘﻢ ﻣﻮازي ﺳﺨﺘﯽ و ﻣﯿﺮاﯾﯽ ﺑﻪ ﺳﮑﻮي ﻓﻮﻗﺎﻧﯽ ﻣﺘﺼﻞ ﮔﺮدﯾﺪ. ﮐﻠﯿﻪ ﻣﺮاﺣﻞ ﺗﺤﻠﯿﻞ ﺣﻮزه ﻓﺮﮐﺎﻧﺲ، ﺑﻬﯿﻨﻪﺳﺎزي ﺳﯿﺴﺘﻢ، ﺷﺒﯿﻪﺳﺎزي ﺗﺎرﯾﺨﭽﻪ زﻣﺎﻧﯽ ﺳﺮﻋﺖ ﺑﺎد و ﺗﺤﻠﯿﻞ ﺣﻮزه زﻣﺎن، از ﻃﺮﯾﻖ ﺑﺮﻧﺎﻣﻪﻧﻮﯾﺴﯽ در ﻣﺤﯿﻂ ﻧﺮماﻓﺰار ﻣﺘﻠﺐ اﻧﺠﺎم ﮔﺮدﯾﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن ﻣﯽدﻫﺪ روش ﭘﯿﺸﻨﻬﺎدي ﻧﺴﺒﺖ ﺑﻪ ﺳﯿﺴﺘﻢ TMD داراي ﻗﺎﺑﻠﯿﺖ ﺑﯿﺸﺘﺮي در ﮐﻨﺘﺮل ارﺗﻌﺎﺷﺎت ﺳﺎزه دارد، اﯾﻦ ﺳﯿﺴﺘﻢ ﺑﻪ ﻃﻮر ﻣﻮﺛﺮي ﭘﺎﺳﺦ ﺷﺘﺎب ﺳﺎزه را ﮐﺎﻫﺶ ﻣﯽدﻫﺪ و ﻧﻘﺶ ﻣﻬﻤﯽ در ﺗﺎﻣﯿﻦ آﺳﺎﯾﺶ ﺳﺎﮐﻨﯿﻦ در ﺷﺮاﯾﻂ ﺑﺤﺮاﻧﯽ ﻧﯿﺮوﻫﺎي دﯾﻨﺎﻣﯿﮑﯽ ﺑﺎد اﯾﻔﺎ ﻣﯽﮐﻨﺪ. ﻫﻤﭽﻨﯿﻦ ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ اﯾﻨﮑﻪ در روش ﭘﯿﺸﻨﻬﺎدي، ﺑﺨﺸﯽ از ﺟﺮم ﺳﺎزه اﺻﻠﯽ ﺑﻪ ﻋﻨﻮان ﺟﺎذب ارﺗﻌﺎش ﻋﻤﻞ ﻣﯽﻧﻤﺎﯾﺪ، ﻣﺤﺪودﯾﺖﻫﺎي ﺑﻪﮐﺎرﮔﯿﺮي ﺳﯿﺴﺘﻢ TMD ﺷﺎﻣﻞ ﻧﯿﺎز ﺑﻪ اﺧﺘﺼﺎص ﺑﺨﺶ ﺑﺎ ارزﺷﯽ از ﻓﻀﺎي ﺑﺮج ﺑﻪ ﺟﺎدادن ﯾﮏ ﺟﺮم اﺿﺎﻓﯽ ﺳﻨﮕﯿﻦ و ﻓﻀﺎي ﻻزم ﺑﺮاي ارﺗﻌﺎش آن، ﻣﺮﺗﻔﻊ ﻣﯽﮔﺮدد.

The present paper proposes a new control strategy to mitigate wind-induced vibrations of tall TV towers. Based on the proposed idea, a part of the main structure of the tower is isolated and regarded as a dynamic vibration absorber. In order to investigate the effectiveness of the proposed system, the 310-m tall Nanjing TV tower in China, which has two observation decks at the heights 180 m and 240 m, is studied. The wind-induced responses are obtained for the following cases: uncontrolled structure; controlled structure equipped with the TMD system; and the controlled structure with an isolated substructure at the upper observation deck level. The structure is modelled as a multi-degree-of-freedom (MDOF) lumped mass vertical cantilever beam. The TMD system and the isolated substructure are modelled as a lumped mass connected to the upper observation deck by a parallel stiffness and damper system. All the calculation works related to the frequency-domain analysis, optimizing the system, simulating the wind velocity, and the time-domain analysis are carried out using the MATLAB software. The results indicate that the proposed self-control structural system has higher vibration control capacity than the TMD system. The proposed system can effectively reduce the acceleration response of the structure and improve occupant comfort during critical wind speed. In the proposed system, since a part of the main structure performs as a vibration absorber, it is not required to assign a valuable space of the observation deck for the installation of an additional mass damper and the corresponding clearance to accommodate its large strokes.