بررسی تأثیر سختی بر رفتار سازه های بلند مرتبه جداسازی شده

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی عمران، دانشگاه آزاد اسلامی، خمینی شهر، ایران

2 استادیار، دانشکده مهندسی عمران، دانشگاه آزاد اسلامی، خمینی شهر، ایران

چکیده

اساس کار جداسازهای لرزه‌ای در کاستن از شتاب اعمال شده به سازه‌ها، بر مبنای افزایش پریود طبیعی ارتعاش سازه است. در سازه‌های بلند مرتبه پریود طبیعی به خودی خود زیاد است. در این صورت ممکن است نرم بودن قسمت روسازه، با اصل الاستیک ماندن آن هنگام زلزله در تعارض باشد. در تحقیق حاضر با مدل‌سازی و آنالیز تاریخچة زمانی 240 سازه در گام نخست به این سؤال پرداخته شد که آیا افزودن یا کاستن سختی قسمت‌های زیرسازه و روسازه (به ترتیب به میزان 1 تا 100 برابر و 0/001 تا 1 برابر) تأثیری بر توزیع شتاب این قسمت‌ها دارد یا نه؟ نتایج تحلیل سازه‌ها که از 5 نوع پالن و در ارتفاعات 10 ،15 ،20 ،24 و 28 طبقه بودند نشان داد که افزودن سختی روسازه می‌تواند منجر به کاهش حدود 30 درصدی شتاب حداکثر بام (نسبت به سازه جداسازی شده بدون افزایش سختی روسازه) شود. این در حالی است که استفاده از جداسازی پایه در سازه های مورد بررسی به طور متوسط حدود 50 %شتاب بام را کم کرده است. کاهش چشمگیر شتاب بام مربوط سازه‌های با افزایش 10 برابری سختی روسازه نسبت به سازه عادی بود. در گام بعد با آنالیز پوش‌آور 15 سازه از این مجموعه مشخص شد که در تمام سازه‌ها (با سختی‌های مختلف) قسمت روسازه در حالت الاستیک خواهد ماند و هیچ یک از مفاصل تشکیل شده در اعضاء از ناحیة IO رد نشده بود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

The effect of Stiffness on Behavior of Isolated Tall Buildings

نویسندگان [English]

  • Hamidreza Sharifi 1
  • Sayed Behzad Talaeitabab 2
1 MSc Graduated, Civil Department/Khomeinishahr barch of Azad Islamic University
2 Assistant professor, Civil Department/Khomeinishahr barch of Azad Islamic University
چکیده [English]

The basis of seismic isolation in reducing the acceleration applied to structures is based on an increase in the natural period. In high-rise structures, the natural period itself is high. In this case the flexibility of superstructure may be in conflict with its elastic behavior. In the present study, 240 structures were modeled and analyzed in the first step to the question of whether the addition or reduction of the stiffness of the substructure and superstructure (1-100 times and 0.001 to 1 times respectively) affected the floors acceleration distribution or not? The results of the analysis of structures that were of five types of plans and at elevations 10, 15, 20, 24 and 28 floors showed that adding the stiffness of the superstructure can lead to a decrease of about 30 and 55 percent of the maximum roof acceleration and average acceleration of floors respectively (relative to the isolated structure without increasing the stiffness of the superstructure); However, the use of base isolation in the structures decreased about 50% of roof acceleration. The significant decrease in roof acceleration was related to structures with a 10 times increase in the stiffness of the superstructure compared to normal structure. In the next step, with the push-over analysis of 15 structures of this set, it was determined that in all isolated structures (with varying stiffness), the superstructure will remain in elastic state. The number of plastic hinges in the elastic region (before IO performance level) increased by 50% in isolated structures compare to fixed base and none of the plastic hinges formed in the members, exceeded from IO region.

کلیدواژه‌ها [English]

  • Base Isolation
  • tall buildings
  • redundancy factor
  • stiffness
  • Acceleration
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