IJE TRANSACTIONS A: Basics Vol. 27, No. 10 (October 2014) 1547-1556   

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M. Shahmardani, J. Mirzapour and S. Tariverdilo
( Received: January 10, 2014 – Accepted: June 26, 2014 )

Abstract    An analytical approach is presented to assess the response of offshore structures under seismic excitation. This paper evaluates the impacts of different fluid field models and the mass of equipment at the top of offshore structure which is simulated as lumped mass on the responses of offshore structures. To do this, two and three dimensional fluid field models are developed. In three dimensional models different approximation regarding the free surface boundary condition associated with high and low frequency excitations are adopted. Then the alternation of response of structure with changing in the value of lumped mass is calculated. Finally the impacts of different models on the value of maximum displacement for Kobe earthquake are evaluated. It is shown that different approximations regarding the fluid field could largely change the value of maximum displacement evaluated by the models.


Keywords    vertical circular cylinder, Seismic Excitation, lumped mass, added mass


چکیده    چكيده يک روش تحليلی برای ارزيابی پاسخ سازه­های دريايی تحت اثر بار زلزله ارائه شده است. اين مقاله اثرات مدل­های مختلف ميدان سيال و جرم تجهيزات در بالای سازه دريايی را که بصورت جرم متمرکز مدل شده را بر روی پاسخ سازه دريايی ارزيابی می­کند. مدل دو و سه بعدی ميدان سيال بسط داده شده است. در مدل­های سه بعدی تقريب­های مختلف با توجه به شرايط مرزی سطح آزاد در ارتباط با تحريک فرکانس بالا و پايين اتخاذ شده است. سپس تغييرات پاسخ سازه همراه با تغيير در مقدار جرم متمرکز محاسبه شده است. در نهايت اثرات مدل­های مختلف به مقدار حداکثر جابجايي برای زمين­لرزه کوبه ارزيابی شده است. نشان داده شده است که تقريب­های مختلف در رابطه باميدان سيال تا حد زيادی می­تواند مقدار حداکثر جابه جايي با مدل­های ارزيابی شده را تغيير دهد.



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