بررسی عملکرد لرزه‌ای کوله پل‌های نامنظم در ارتفاع بر اثر اعمال زلزله در راستاهای مختلف

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانش‌آموخته کارشناسی ارشد، دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره)، قزوین، ایران

2 استادیار، گروه عمران، دانشکده فنی و مهندسی، دانشگاه بین‌المللی امام خمینی (ره)، قزوین

چکیده

ارزیابی پل­های بزرگراهی، به منظور سنجش عملکرد لرزه­ای برای برنامه­ریزی یک سیستم حمل­و­نقلی، قبل و پس از وقوع زلزله اهمیت زیادی دارد. سازه­های نامنظم، به­دلیل رفتار لرزه­ای پیچیده­تر اعضا، همواره در کانون توجه پژوهشگران و طراحان بوده­اند. در این مطالعه، مدل سه­بعدی کوله­های زینی در مجموعه­ای از پل­های نامنظم در ارتفاع با استفاده از نرم­افزار اجزای محدود OpenSees تشکیل شده است. با توجه به اینکه نامنظمی در ارتفاع پایه­ها منجر به تفاوت در سختی آن­ها می­شود، توزیع نیروی زلزله بر هر پایه نامتوازن خواهد بود. از سوی دیگر، میزان نیرویی که متوجه کوله­ها می­شود، به مقاومت و سختی پایه­های میانی نیز بستگی دارد. علاوه بر نقش نامنظمی، تأثیر دو رویکرد مجزا برای مدل‏سازی شرایط تکیه­گاهی پایه­های میانی، اعم از تکیه­گاه گیردار و انعطاف­پذیر (اندرکنش خاک­و­سازه) در تحلیل ملاحظه شده است. همچنین، لازم است برای پل­های دارای پیچیدگی­های رفتاری که تحت اثر تحریکات زلزله به­وسیله دو مؤلفه افقی متعامد هستند، تعداد کافی شتابنگاشت با زوایای مختلف به سازه اعمال شود تا بیشترین تقاضای اعضای آن به‏دست آید. بنابراین، هر یک از مدل­ها به ازای یک مجموعه شتابنگاشت که هر کدام در هفت زاویه گوناگون دوران داده شده­اند، تحت تحلیل دینامیک افزاینده قرار گرفته است. تحلیلدو سطح ظرفیتی مختلف مشخص کرد که نوع و میزان نامنظمی پل، اندرکنش خاک و سازه و زاویه اعمال تحریکات زلزله (سوئگی) سه عامل مهمی هستند که هر یک می­توانند در به‏دست آوردن پاسخ شکنندگی اعضای تشکیل دهنده کوله نقش چشمگیری ایفا کنند. بدون استثنا، در تمامی مدل­ها، فرض تکیه­گاه گیردار برای پایه­های میانی باعث ایجاد پاسخ محافظه­کارانه­ در اعضای کوله در مقایسه با حالت اندرکنش خاک­و­سازه می­شود. در حالی که تأثیر زاویه اعمال شتابنگاشت بر بحرانی شدن شکنندگی هر یک از اعضای کوله می­تواند از یک مدل به مدل دیگر و به ازای حالت­های ظرفیتی مختلف، متغیر باشد.

کلیدواژه‌ها


عنوان مقاله [English]

Seismic Performance Assessment of Abutment in Bridges with Altitudinal Irregularity Subjected to Ground Motion Directionality Effects

نویسندگان [English]

  • soheil soltanieh 1
  • Mohammad Mahdi Memarpour 2
  • Fouad Kilanehei 2
1 Graduated MSc. of Earthquake Engineering, Imam Khomeini International University, Qazvin, Iran
2 Assistant Professor, Department of Civil Engineering, Faculty of Engineering & Technology, Imam Khomeini International University, Qazvin, Iran
چکیده [English]

Evaluation of highway bridges is a matter of importance in terms of seismic performance analysis for pre-and post-earthquake planning of a transportation system. Irregular structures have always been in the spotlight of researchers and engineers. In this study, a three-dimensional model of seat-type abutments is generated in a set of irregular bridges with unequal height of piers using OpenSess finite element software. Since altitudinal irregularity leads to different stiffness of individual piers, the distribution of seismic forces will be dissimilar for each pier. On the other hand, the proportion of seismic forces absorbed by the abutments is dependent on strength and stiffness of central piers. In addition to irregularity effects, the influence of two distinct approaches of pier support modeling such as fixed-base and flexible-base (soil-structure-interaction) is taken into account in the analyses. In addition, in order to obtain maximum demand on bridge members with complex behavior, subjected to the ground motion by orthogonal components, nonlinear time-history analysis using multiple earthquake records should be applied in different directions. Therefore, incremental dynamic analysis is performed on each bridge model for a set of seismic records each rotated in seven various directions. By processing the outcomes obtained from analysis of two levels of damage states, it is determined that the irregularity ratio and configuration, soil-structure-interaction, and incident angle of seismic motions are three important factors in evaluation of fragility characteristics of abutment constitutive members. With no exceptions in the investigated models, the fixed-base assumption of central piers produces conservative response of the abutment components in comparison to soil-structure-interaction consideration. However, the effects of ground motion directionality on the fragility characteristics of individual members of abutment vary for different damage states from one model to another.

کلیدواژه‌ها [English]

  • Bridge abutment
  • Irregular bridges
  • Ground motion directionality
  • Soil-structure-interaction
  • Incremental Dynamic Analysis
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