تحلیل دینامیکی پاسخ طولی باد و تعیین ضریب بارگذاری تندباد برای بیلبوردهای تک‎ستونی بزرگ

نوع مقاله : مقاله پژوهشی

نویسنده

گروه مهندسی سازه، دانشگاه آزاد اسلامی، واحد خورموج، خورموج، ایران

چکیده

نقش موثر بیلبوردها برای تبلیغات، موجب گسترش استفاده آن‎ها در فضاهای باز و عمومی شده است. سطح بادگیر بزرگ و وزن کم بیلبوردها، موجب حساسیت آن‏ها در برابر باد شده و موارد متعدد خرابی آن‎ها در سال ‎های اخیر گزارش شده است. طراحی سازه‎ها در برابر باد، عموما با روش ضریب بارگذاری تندباد انجام می ‎شود، ولی این روش، در اکثر آیین نامه‎ ها مختص ساختمان ها و ملحقات آن‎ها و سازه‎های بلند است و روابطی برای بیلبوردها ارائه نشده است. در این تحقیق، پاسخ ‎های استاتیکی و دینامیکی طولی باد و ضریب بارگذاری تندباد برای بیلبوردهای تک‎ستونی بزرگ، با استفاده از تحلیل حوزه فرکانس مدل‎ های چند درجه آزادی، با برنامه‎نویسی در نرم‎افزار متلب محاسبه شد. نخست، مثالی از بیلبورد بلند ارائه گردید و پاسخ سازه و ضریب تندباد برای آن تعیین شد و تاثیر سرعت مبنای باد و زبری ناحیه در پاسخ سازه بررسی گردید. سپس، بیلبوردهایی با مشخصات هندسی مختلف طراحی شدند و در برابر باد تحلیل گردیدند. طبق نتایج، میرایی آیرودینامیکی از عوامل مهم محدودکننده ارتعاش بویژه در نواحی با زبری کم و سرعت باد بالا بود. با افزایش زبری زمین و همچنین با کاهش ارتفاع سازه، آشفتگی باد بیشتر و سرعت میانگین باد و میرایی آیرودینامیکی سازه کم می شد که با افزایش ضریب بارگذاری تندباد همراه بود، به نحوی که برای محدوده شهری و ارتفاع بیلبورد 10 متر، ضریب مذکور به عدد4/71 رسید که حاکی از اهمیت بالای ارتعاشات بیلبورد در این شرایط بود. بنابراین، با توجه به پاسخ دینامیکی بالا، طراحی ایمن و مقاوم بیلبوردها، مستلزم تعیین دقیق ضریب تندباد است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Along-Wind Dynamic Analysis and Determination of Gust Loading Factor (GLF) for Large Single-Column Billboards

نویسنده [English]

  • Nahmat Khodaie
Department of civil engineering, Islamic Azad University, Khormouj Branch, Khormouj, Iran.
چکیده [English]

The effective role of billboards in advertising has led to the expansion of their use in open spaces and public places. The large panel area and light weight have made billboards sensitive to wind, and many cases of their damage have been reported recently. The design of structures against wind force is generally done with the gust loading factor (GLF) method. However, this method is specific to tall structures in most codes and standards, and there are no relations for billboards. In this research, the along-wind responses and the GLF have been calculated for large single-column billboards using frequency domain analysis of MDOF models using MATLAB software. First, an example of a tall billboard was presented and the responses of the structure and the GLF were determined for it, and the effect of basic wind speed and area roughness on the GLF was investigated. Then, billboards with different geometric specifications were designed and analyzed against wind load. According to the results, aerodynamic damping was one of the important factors limiting vibration, especially in rough areas. The GLF increased with the decrease of the structure’s height and increase of ground roughness, in such a way that it reached 4.71 for the urban area and 10 meters high billboard, which indicates the high importance of vibrations of billboard is in this situation. Due to the high dynamic response, the safe and resistant design of these structures requires the accurate determination of the GLF.

کلیدواژه‌ها [English]

  • Gust Loading Factor
  • Along-Wind Response
  • Large Billboards
  • Aerodynamic Damping
  • Frequency Domain Analysis
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