ارزیابی عملکرد لرزه‌‌ای پایه‌‌های پل بتنی طراحی شده به روش طراحی مستقیم بر اساس تغییرمکان

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه مهندسی سازه و زلزله، دانشکده مهندسی عمران، دانشگاه صنعتی نوشیروانی بابل، بابل، ایران

چکیده

در طراحی مستقیم بر اساس تغییرمکان، هدف عملکردی رسیدن به تغییرمکان طرح (تغییرمکان هدف) است و سختی و مقاومت سازه به‌‌گونه‌‌ای تعیین می‌‌شود که بیشینه تغییرمکان سازه در زلزله به این تغییرمکان برسد. بدین منظور برش پایه طراحی بر اساس 3 پارامتر کلیدی میرایی معادل، فاکتور اصلاح میرایی و اثر پی-دلتا تعیین می‌‌شود. با توجه به تعدد روابط موجود برای هر یک از این پارامترها، در این تحقیق تاثیر استفاده از روابط مختلف بر برآورده شدن اهداف عملکردی مورد بررسی قرار گرفته است. در این مطالعه، ابتدا چند پایه پل دارای 2 ارتفاع و 2 طول دهانه متفاوت در 2 منطقه با سطوح خطر لرزه‌‌ای متفاوت طراحی شد. جهت طراحی پایه‌ها از طیف طرح تغییرمکان به دست آمده از طیف طرح شتاب آیین‌نامه آشتو استفاده شده است. سپس هر یک از این 8 پایه‌‌ برای 27 مسیر مختلف طراحی ناشی از 3 رابطه متمایز برای هر یک از 3 پارامتر کلیدی فوق طراحی شدند که در مجموع 216 پایه پل به روش طراحی مستقیم بر اساس تغییرمکان طراحی شد. در ادامه جهت ارزیابی عملکرد لرزه‌‌ای پایه‌‌ها، هر یک از 216 پایه در نرم افزار اپن‌‌سیس مدل‌‌سازی و تحت 14 نگاشت دور از گسل مقیاس شده بر روی طیف طرح قرار گرفتند. پس از تعیین بیشینه تغییرمکان هر پایه تحت زلزله، نزدیک بودن این تغییرمکان به تغییرمکان هدف به عنوان شاخص برآورده شدن هدف عملکردی مورد مطالعه قرار گرفت. نتایج تحلیل‌‌ها نشان می‌‌دهد که استفاده از روابط مختلف طراحی، تاثیر قابل توجهی بر عملکرد لرزه‌ای و هزینه ساخت پایه‌ها دارد. به طوری که در بسیاری از پایه‌های طراحی شده، استفاده از روابط مختلف موجب 20% کاهش یا افزایش بیشینه تغییرمکان نسبت به تغییرمکان هدف و تا حدود 40% تغییرات در هزینه ساخت می‌‌شود. در میان 27 مسیر انتخابی از روابط ارائه شده، استفاده از رابطه پریستلی برای میرایی معادل، رابطه آیین‌‌نامه ژاپن برای ضریب اصلاح میرایی و رابطه پتینگا و پریستلی برای اثر پی-دلتا، عملکرد مناسب‌تری را برای کلیه پایه‌های پل با ارتفاع، طول دهانه و سطح خطر مختلف نشان می‌دهد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Seismic performance evaluation of RC bridge piers designed with direct displacement-based design

نویسندگان [English]

  • Alireza Sepahvand
  • Horr Khosravi
Department of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran
چکیده [English]

In Direct Displacement-Based Design (DDBD), the performance objective is to achieve the design displacement (target displacement), and the stiffness and strength of the structure are determined in such a way that the maximum displacement of the structure in an earthquake reaches this displacement. For this purpose, the design base shear is determined based on 3 key parameters equivalent damping, damping modification factor, and P-Delta effect. Due to the variation of relationships for each of these parameters, in this study, the influence of using different relations on achieving performance objectives is investigated. In this study, 8 bridge piers with 2 different heights, 2 different span lengths, and 2 seismic hazard levels were selected. In order to design the piers, the displacement design spectra were extracted from AASHTO acceleration design spectra. Then, each of these piers was designed for 27 different design paths resulting from 3 distinct relationships for each of the 3 key parameters, and a total of 216 bridge piers were designed by the DDBD approach. Then, to evaluate the seismic performance of the piers, each of the 216 piers was modeled in OpenSees software and subjected to 14 far-field earthquake records scaled on the design spectrum. After determining the maximum displacement of each pier, the proximity of this displacement to the target displacement was studied as a performance objective indicator. The results of the analysis show that the use of different design relations has a significant effect on the maximum displacement of piers and their construction cost. So for the most designed bridge piers, the use of different relationships causes a 20% decrease or increase in the maximum displacement compared to the target displacement and up to 40% changes in the construction cost. Among 27 design paths, using the Priestley relationship for equivalent damping, the Japanese regulation formula for the damping modification factor, and the Pettinga and Priestley formula for the P-Delta effect, provides a more suitable performance for all bridge piers designed with different heights, different span lengths and different seismic hazard levels.

کلیدواژه‌ها [English]

  • Direct Displacement-Based Design Method
  • RC Bridge Pier
  • Equivalent Viscous Damping
  • P-Δ Effect
  • Nonlinear Dynamic Analysis
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