Abstract




 
   

IJE TRANSACTIONS A: Basics Vol. 29, No. 4 (April 2016) 464-472   

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  INTRODUCTION OF AIR CUSHION TO REDUCE SEISMIC DEMAND IN CYLINDRICAL WATER STORAGE TANKS
 
F. Ashrafzadeh, S. Tariverdilo and M. R. Sheidaii
 
( Received: December 20, 2015 – Accepted in Revised Form: April 14, 2016 )
 
 

Abstract    Water storage tanks not designed explicitly for seismic loading could require retrofit. One of the common ways of retrofit include some structural change in the lateral load resisting system that could be expensive and requires the tank to be out of service for relatively long time. This paper introduces a novel method to reduce seismic demand on tank’s wall without structural intervention. This is done by employing air cushions adjacent to the wall. The paper investigates the effect of air cushion system on the seismic response of the cylindrical water storage tanks. While in tank without air cushion, the boundary condition adjacent to tank wall is kinematic with no control on the wall pressure, in the proposed method this boundary condition becomes kinetic, enabling control of dynamic fluid pressure on the tank walls. The response parameters of the tank is developed in terms of wall pressure, wave height, base shear, and overturning moment in cylindrical tanks of different sizes with and without air cushions under the far field and near source ground motions. The results demonstrate that the proposed method is an effective way to reduce sloshing force demand.

 

Keywords    Keywords: Cylindrical water storage tanks, Air cushion, Seismic response, boundary condition, Wall pressure.

 

چکیده    مخازن ذخیره آب که برای بارهای لرزه ای طراحی نشده اند، اغلب نیازمند بهسازی هستند. روش‌ معمول بهسازی لرزه‌ای در برگیرنده تغییراتی در سیستم سازه‌ای مخازن می‌باشد که هزینه­بر بوده و توام با خروج از سرویس مخزن برای زمان طولانی است. مقاله حاضر روشی جدید مبتنی بر کاهش نیاز در دیواره‌های مخازن تحت بارگذاری لرزه‌ای معرفی مي­نمايد که نيازمند تغییر در سازه مخزن نیست. اين امر با تعبیه بالشتک هوا در حد فاصل ديوار مخزن و سيال انجام مي­شود. در مخازن عادی (بدون بالشتک) شرایط مرزی دیواره مخزن سینماتیکی است و هیچ‌گونه کنترلی روی فشار سیال وارد بر دیواره مخزن وجود ندارد. با تعبیه بالشتک، شرایط مرزی در دیواره سینتیکی شده، امکان کنترل فشار سیال بر روی دیواره مخزن ایجاد مي­گردد. در اين مقاله، پاسخ مخزن شامل فشار سیال بر دیواره، ارتفاع موج، برش و لنگر خمشی در مخازن استوانه‌ای به ابعاد مختلف با و بدون بالشتک هوا برای زلزله‌های حوزه دور و نزدیک ارائه شده و کارایی سيستم پيشنهادی بررسی شده است. نتایج نشانگر آن است که روش ارائه‌شده یک روش مؤثر برای کنترل نیروی ناشی از مواج شدگی است.

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