پاسخ برشگیر پل‌های واقع بر خاک‌های غیرچسبنده تحت اثر زلزله‌های با محتوای فرکانسی متفاوت

نوع مقاله : علمی - پژوهشی

نویسندگان

1 گروه مهندسی عمران، واحد بوشهر، دانشگاه آزاد اسلامی، بوشهر، ایران

2 گروه مهندسی عمران، دانشگاه خلیج‌فارس، بوشهر، ایران

چکیده

چکیده
پل‌ها به عنوان یکی از سازه‌های مهم نقش بارزی را در آبادانی به عنوان شاهرگ‌های حیاتی هر کشور بر عهده دارد. در چند دهه اخیر مطالعات متعددی در زمینه رفتار لرزه‌ای پل‌ها تحت زلزله‌های مختلف صورت گرفته است که در آن‌ها برشگیرها را به عنوان عناصر فیوز مانند جهت جلوگیری از دررفتگی عرشه پل از روی زیر سازه در نظر می‌گرفتند. اما موضوع مهمی که در این مطالعات به آن توجه چندانی نشده است، تأثیر رفتار ساخت گاه بر پاسخ تنش‌های ایجادشده در برشگیرها تحت اثر برخورد شاه‌تیرها به برشگیرها در زمان وقوع زلزله‌های با محتوای فرکانسی متفاوت به‌صورت واقع‌بینانه و در شرایط سه‌بعدی می‌باشد. در مطالعه حاضر پس از اعتبار سنجی مدل‌سازی یک پل به‌صورت سه‌بعدی با یک پژوهش معتبر، و در نظر گرفتن شرایط نزدیک به واقعیت با مدل‌سازی عددی سه‌بعدی در نرم‌افزار اجزاء محدود آباکوس، رفتارسنجی پاسخ‌ها در پل و برشگیرها به‌صورت جداگانه تحت اثر زلزله‌های با محتوای فرکانسی متفاوت در شرایط بدون در نظر گرفتن اندرکنش خاک – سازه و با در نظر گرفتن آن مورد ارزیابی قرار می‌گیرد. نتایج حاصل از این تحقیق نشان‌دهنده کاهش شتاب در سازه پل در حالت با در نظر گرفتن اندرکنش خاک – سازه در خاک‌های غیرچسبنده می‌باشد. این میزان کاهش برای زلزله‌های با تاریخچه زمانی مختلف، متفاوت می‌باشد. مشاهده می‌گردد، با در نظر گرفتن اثرات خاک در برخی زلزله‌ها حوزه بیشتری در مقادیر تنش‌ها در برشگیر پل‌ها نسبت به زلزله‌های دیگر و سازه واقع بر بستر سنگی مشاهده شده است. به عبارتی عدم فرض اندرکنش خاک-سازه در تحلیل لرزه‌ای پل‌ها سبب ارائه نتایج غیرواقع‌بینانه و از اعتبار کمی برخوردار خواهد شد. لذا فرض لحاظ نمودن اندرکنش خاک- سازه به اقتصادی شدن طرح پل ها در برخی تحلیل های لرزه ای کمک شایانی خواهد نمود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

The response of bridges shear key located on cohesionless soils under earthquakes with different frequency content

نویسندگان [English]

  • Hadi Dashti 1
  • Afshin Hefzi 1
  • Alireza Fiouz 2
1 Department of Civil Engineering, Bushehr Branch, Islamic Azad University, Bushehr, Iran
2 School of Engineering, Persian Gulf University, Bushehr, Iran
چکیده [English]

Abstract

Bridges, as one of the most important structures, play a prominent role in the development of each country as vital vessels. In recent decades, several studies have been conducted on the seismic behavior of bridges under different earthquakes, in which the shear keys were considered as fuse-like elements to prevent collapsing of the deck on the substructure. However, an important issue that has not been addressed in these studies is the effect of site behavior on the stress response in the shear keys that is, the analysis at the earthquakes of varying frequency content is realistic and in three-dimensional terms and with the effect of soil, due to the impacts of the shear keys on the girder. In the present study, after validating a three-dimensional bridge with a valid research, and considering conditions close to reality with three-dimensional numerical modeling in ABAQUS finite element software, the response behavior in bridges and shear keys is evaluated by considering different frequency content earthquakes under conditions with and without considering soil-structure interaction.The results of this study show that the acceleration decrease in bridge structure with respect to soil-structure interaction in cohesionless soils. This rate is different for with different frequency content. Also taking into account the effects of soil-structure interaction in far field earthquakes, we see a greater reduction in stress values in shear keys than some earthquakes and structures located on bed rock. In other words, not assuming soil-structure interaction in the seismic analysis of bridges will lead to unrealistic results.

کلیدواژه‌ها [English]

  • Shear Keys
  • Bridges
  • frequency content
  • Numerical
  • Soil-Structural Interaction
  • cohesionless soil
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