ﻣﻄﺎﻟﻌﻪ ﭘﺎراﻣﺘﺮﯾﮏ رﻓﺘﺎر دﯾﻨﺎﻣﯿﮑﯽ ﻣﺨﺎزن ذﺧﯿﺮه ﻣﺎﯾﻌﺎت ﺗﺤﺖ ﺗﺤﺮﯾﮑﺎت ﭘﺎﻟﺲﮔﻮﻧﻪ

Parametric Study on Dynamic Behavior of Liquid Storage Tanks Subjected to Pulse-Like Excitations

ﻣﺨﺎزن ذﺧﯿﺮه ﺳﯿﺎﻻت ﺑﻪ ﻃﻮر ﮔﺴﺘﺮده ﺑﺮاي ذﺧﯿﺮه ﻣﺎﯾﻌﺎت ﻣﺨﺘﻠﻒ ﻫﻤﺎﻧﻨﺪ ﻓﺮآوردهﻫﺎي ﻧﻔﺘﯽ در ﺻﻨﺎﯾﻊ اﺳﺘﻔﺎده ﻣﯽﺷﻮﻧﺪ و ﺻﺪﻣﻪ دﯾﺪن آﻧﻬﺎ ﭘﯿﺎﻣﺪﻫﺎي ﺧﻄﺮﻧﺎﮐﯽ را ﺑﻪ ﻫﻤﺮاه ﺧﻮاﻫﺪ داﺷﺖ. زﻟﺰﻟﻪﻫﺎي ﺣﻮزه ﻧﺰدﯾﮏ ﮔﺴﻞ ﺑﺎ دارا ﺑﻮدن ﭘﺎﻟﺲﻫﺎي ﺷﺪﯾﺪ ﺳﺮﻋﺖ، ﭘﺘﺎﻧﺴﯿﻞ آﺳﯿﺐ زدن ﺑﻪ ﭼﻨﯿﻦ ﺳﺎزهﻫﺎﯾﯽ را دارﻧﺪ. اﯾﻦ ﻧﻮع ﺗﺤﺮﯾﮑﺎت زﻣﯿﻦ ﻣﯽﺗﻮاﻧﻨﺪ ﺑﻪ ﺻﻮرت ﺗﻮاﺑﻊ ﺗﺤﻠﯿﻠﯽ ﭘﺎﻟﺲﮔﻮﻧﻪ اراﺋﻪ ﺷﻮﻧﺪ. در اﯾﻦ ﺗﺤﻘﯿﻖ رﻓﺘﺎر ﻟﺮزهاي ﻣﺨﺎزن ذﺧﯿﺮه ﺳﯿﺎﻻت ﺗﺤﺖ ﭼﻨﯿﻦ ﺗﺤﺮﯾﮑﺎت ﭘﺎﻟﺲﮔﻮﻧﻪ ﺑﺼﻮرت ﭘﺎراﻣﺘﺮﯾﮏ ﺑﺮرﺳﯽ ﻣﯽﺷﻮد. ﺑﺮاي اﯾﻦ ﻣﻨﻈﻮر اﺑﺘﺪا ﻣﺨﺎزن ﺑﺎ ﻣﺪلﻫﺎي ﻣﮑﺎﻧﯿﮑﯽ ﻣﻌﺎدل ﺷﺒﯿﻪﺳﺎزي ﺷﺪه و ﺳﭙﺲ آﻧﺎﻟﯿﺰ دﯾﻨﺎﻣﯿﮑﯽ آﻧﻬﺎ ﺗﺤﺖ اﯾﻦ ﻧﻮع ﺗﺤﺮﯾﮑﺎت اﻧﺠﺎم ﻣﯽﺷﻮد. ﻣﺪل ﺗﺤﻠﯿﻠﯽ ﭘﺎﻟﺲ اﻧﺘﺨﺎب ﺷﺪه ﺑﺮ ﭘﺎﯾﻪ ﺗﻮاﺑﻊ ﻣﻮﺟﮏ ﺑﻮده ﮐﻪ داراي ﭼﻬﺎر وﯾﮋﮔﯽ داﻣﻨﻪ، ﭘﺮﯾﻮد، ﺷﮑﻞ و ﺗﻌﺪاد ﭘﺎﻟﺲ اﺳﺖ. ﺗﺎﺛﯿﺮ ﻫﺮ ﯾﮏ از اﯾﻦ ﻣﺘﻐﯿﺮﻫﺎ در اﻧﻮاع ﭘﺎﺳﺦﻫﺎي دﯾﻨﺎﻣﯿﮑﯽ و ﻧﯿﺰ ﺗﺎﺛﯿﺮ ﻧﺴﺒﺖ اﺑﻌﺎدي ﻣﺨﺰن ارزﯾﺎﺑﯽ ﻣﯽﺷﻮد. ﻧﺘﺎﯾﺞ ﺣﺎﺻﻠﻪ ﺑﯿﺎﻧﮕﺮ اﯾﻦ اﺳﺖ ﮐﻪ ﭘﺎﻟﺲﻫﺎﯾﯽ ﺑﺎ ﭘﺮﯾﻮد ﺑﻠﻨﺪ ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﺑﺎﻻ ﺑﻮدن زﻣﺎن ﺗﻨﺎوب ﻣﻮد ﻧﻮﺳﺎﻧﯽ، ﺟﺎﺑﺠﺎﯾﯽ ﻗﺎﺋﻢ ﺳﻄﺢ آزاد ﺳﯿﺎل و ﭘﺎﻟﺲﻫﺎﯾﯽ ﺑﺎ ﭘﺮﯾﻮد ﮐﻮﺗﺎه ﺑﻪ ﻟﺤﺎظ ﭘﺎﯾﯿﻦ ﺑﻮدن زﻣﺎن ﺗﻨﺎوب ﺿﺮﺑﺎﻧﯽ، ﺑﺮشﭘﺎﯾﻪ و ﻣﻤﺎن واژﮔﻮﻧﯽ را ﺗﺤﺖ ﺗﺎﺛﯿﺮ و ﺗﺸﺪﯾﺪ ﻗﺮار ﻣﯽدﻫﻨﺪ. ﻫﻤﭽﻨﯿﻦ ﺑﺎ اﻓﺰاﯾﺶ ﺗﻌﺪاد ﭘﺎﻟﺲ، ﭘﺎﺳﺦﻫﺎ در ﺣﻮاﻟﯽ ﭘﺮﯾﻮد ﭘﺎﻟﺲ ﻧﺰدﯾﮏ ﺑﻪ زﻣﺎن ﺗﻨﺎوب ﻧﻮﺳﺎﻧﯽ اﻓﺰاﯾﺶ ﭼﺸﻤﮕﯿﺮي ﻣﯽﯾﺎﺑﻨﺪ. اﯾﻦ در ﺣﺎﻟﯽ اﺳﺖ ﮐﻪ ﺷﮑﻞ ﭘﺎﻟﺲ از ﻧﻈﺮ ﻣﺘﻘﺎرن ﯾﺎ ﭘﺎد ﻣﺘﻘﺎرن ﺑﻮدن ﺗﺎﺛﯿﺮ ﻣﺤﺴﻮﺳﯽ ﺑﺮ ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ ﻧﺪارد.

Liquid storage tanks are widely used to store different types of liquids such as petroleum products. Any failure of these structures may cause serious consequences. Near-fault ground motions which may have severe velocity pulses have a destructive potential on these facilities and can be represented by analytical pulse-like functions. In this paper, a parametric study is carried out to investigate the seismic behavior of liquid storage tanks under pulse-like excitations. For this purpose, the liquid storage tanks are modeled using equivalent mechanical models and then dynamic analyses of the models are done using pulse-like excitations. The selected analytical pulse-like excitation is based on the modified Gabor Wavelet transform with four main characteristics: amplitude of the signal, period of the signal, shape (phase) of the signal, and the number of pulses. The effect of each pulse parameter as well as the effect of tank aspect ratio on the various response parameters is investigated. The obtained results indicate that the sloshing motion of the liquid near the free surface is affected more by equivalent pulses with long periods while the base shear and overturning moment are affected more by equivalent pulses with short periods. It is also seen that by increasing the number of pulses, the response parameters increase considerably when the pulse period is near the natural period of the convective mode. However, changing the phase of input signals in order to produce symmetric or anti-symmetric pulses has not any noticeable effect on the obtained results.