ارزیابی لرزه ای پل‌های قوسی بتنی غیرمسلح راه‌آهن براساس مشخصات هندسی و مکانیکی آنها

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانشجوی دکتری مهندسی زلزله، پژوهشگاه بین المللی زلزله شناسی و مهندسی زلزله، تهران، ایران

2 دانشیار، دانشکده مهندسی عمران، آب و محیط زیست، دانشگاه شهید بهشتی ، تهران، ایران

3 استادیار،دانشکده مهندسی، دانشگاه اراک، اراک، ایران

چکیده

پل‌های قوسی بنایی به تعداد زیادی در شبکه‌ خطوط راه‌آهن کشور موجود هستند که عمر بیشتر آنها بیش از هفتاد سال است. این سازه‌ها اگرچه تحت اثر بارهای سرویس (قائم) عملکرد خوبی را از خود نشان داده‌اند، اما برای بارهای زلزله (جانبی) طراحی نشده‌اند، بنابراین ارزیابی لرزه‌ای این سازه‌ها برای بدست آوردن سطوح خرابی و سطوح عملکرد آنها امری ضروری به نظر می‌رسد تا در صورت نیاز این سازه‌ها تقویت، و یا از رده خارج شوند. با توجه به رفتار پیچیده این سازه‌ها، نیاز به آزمایش‌های میدانی جهت ارزیابی رفتار آنها امری ضروری است. به علت تعدد این پل‌ها در شبکه راه‌آهن امکان انجام آزمایش‌های میدانی بر روی همه آنها وجود ندارد، بنابراین جهت بررسی و مطالعه رفتار این پل‌ها نیاز به شبیه‌سازی دقیق آنها می‌باشد. برای اینکه بتوان رفتار این پل‌ها را بهم مربوط کرد؛ پارامترهای زیادی از جمله: تعداد دهانه، طول دهانه، مشخصات هندسی قوس، ارتفاع پایه و مشخصات مکانیکی مصالح وجود دارد. در مطالعه حاضر با استفاده از نتایج میدانی انجام گرفته شده بر روی پل‌های قوسی بتنی غیرمسلح، از روش اجزا محدود جهت تحلیل سه بعدی 32 مدل عددی به‌هنگام شده که دارای مشخصات هندسی و فیزیکی متفاوتی هستند، استفاده شده است. در ادامه با استفاده از تحلیل استاتیکی غیرخطی و طیف‌های پیشنهاد شده در آیین‌نامه طرح پل‌های راه و راه‌آهن (نشریه 463)، منحنی‌های تقاضا و ظرفیت مدل‌ها با یکدیگر مقایسه شده است. نتایج بدست آمده نشان می‌دهد که؛ اگرچه رفتار طولی این سازه‌ها نسبت به جهت عرضی آنها تحت اثر زلزله‌های نسبتاً شدید عملکرد بهتری دارد، اما به طور کلی عملکرد لرزه‌ای این سازه‌ها مناسب نبوده و مقاوم‌سازی آنها جهت بهبود عملکردشان ضروری است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Seismic assessment of plain concrete arch bridges by three dimensional simulation using geometrical and mechanical properties

نویسندگان [English]

  • Adel Mahmoudi Moazam 1
  • Nemat Hassani 2
  • Mahdi Yazdani 3
1 PhD candidate in Earthquake Engineering, International Institute of Earthquake Engineering and Seismology, Tehran, Iran
2 Associate professor,Faculty of Civil, Water and Enviromental Engineering, Shahid Beheshti University, Tehran, Iran.
3 Assistant professor, Department of Civil Engineering, Faculty of Engineering, Arak University, Arak, Iran
چکیده [English]

There are numerous old arch bridges in Iran that have been used as railway bridges for more than seventy years. Since most of these bridges are not designed for earthquake excitation, seismic vulnerability of these structures is uncertain. This fact necessitates the investigation of the earthquake resistance of these kinds of bridges. To evaluate complex behavior of these bridges, results of field tests are required. Since it is not possible to perform field tests for all arch bridges, these structures should be simulated correctly by computers for structural assessment. Several parameters are employed to describe the bridges, such as number of spans, length, geometrical and material properties. In this study, results of field tests are used and adapted for 32 three dimensional finite element models with various physical parameters. Modal deformations of bridges at longitudinal and transverse directions is perceived from nonlinear computer simulations. Furthermore, Seismic performance of these bridges is assessed by pushover analysis in two directions and the capacity curves of the structures and linear demand spectrum are obtained using nonlinear static analysis method suggested by the Iranian standard. The crown is selected as a control node in the pushover analysis and its influence on seismic performance of plain concrete arch bridges is considered. Finally, the demand levels of the bridges based on 475 return period earthquakes are determined and compared with capacity curves. The results show that the performance of longitudinal direction is better than transverse direction, but the earthquake resistance of these kinds of bridges totally depends on the material properties and geometry of the structures.

کلیدواژه‌ها [English]

  • plain concrete arch bridge
  • three dimensional finite element modeling
  • Nonlinear static analysis
  • Geometrical Parameters
  • seismic assessment
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