تاثیر حرکات پالس‌مانند زلزله‌های حوزه نزدیک گسل دارای خصوصیت جهت‌پذیری پیش‌رونده بر پاسخ سازه‌های بتنی

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دکترای ژئوتکنیک، دانشکده مهندسی عمران و محیط زیست، دانشگاه صنعتی شیراز، شیراز، ایران

2 استادیار، دانشکده مهندسی عمران، واحد شهرکرد، دانشگاه آزاد اسلامی، شهرکرد، ایران

3 دانش آموخته کارشناسی ارشد سازه، دانشکده مهندسی عمران، شیمی، محیط زیست و مصالح، دانشگاه بولونیا، بولونیا، ایتالیا

4 کارشناس ارشد سازه‌های دریایی، دانشکده مهندسی عمران و محیط زیست، دانشگاه امیرکبیر (پلی تکنیک)، تهران، ایران

چکیده

خصوصیات زلزله‌ها برای ساختگاه‌های نزدیک به چشمه لرزه‌زا و دور از آن، هم به لحاظ دامنه و هم محتوای فرکانسی متفاوت است. مطالعه رفتار سازه‌ها تحت اثر زلزله‌های حوزه نزدیک در مقایسه با زلزله‌های دور از گسل بیانگر اثرات بیشتر این نوع زلزله بر سازه بوده‌اند. عمده این اثرات به خصوصیات جهت‌پذیری پیش‌رونده و حرکت پرتابی دارای اثر تغییرمکان ماندگار وابسته است. از اینرو خصوصیات زلزله‌های نزدیک گسل باید در طراحی و تحلیل سازه‌ها در نظر گرفته شود. هدف تحقیق حاضر بررسی اثر جهت‌پذیری پیش‌رونده زلزله‌های حوزه نزدیک بر پاسخ سازه‌های بتنی می‌باشد. بدین منظور رکوردهای حاصل از ایستگاه‌های مختلف زلزله چی‌چی به‌عنوان شتابنگاشت‌های مبنا انتخاب شد. سپس با استفاده از روش‌های تحلیلی، طیف پاسخ این رکوردها با در نظر گرفتن اثر جهت‌پذیری پیش‌رونده و بدون آن (حذف پالس‌های غالب) در جهت‌های شرق-غرب و شمال-جنوب تعیین شد. در ادامه با تحلیل تاریخچه زمانی بر روی دو سازه 10 طبقه و 15 طبقه بتنی، برای هفت رکورد زلزله چی‌چی، دریفت (جابجایی نسبی) و برش پایه طبقات در سازه‌های مذکور بررسی شد. نتایج نشان داد که با توجه به ماهیت غیرقابل پیش‌بینی زلزله، پاسخ دریفت و برش پایه طبقات در سازه‌های مورد مطالعه در جهات مختلف در برخی موارد افزایش و یا کاهش یافته است. بنابراین می‌توان دریافت که جهت‌پذیری همیشه تاثیر یکنواختی بر رفتار سازه نداشته و از الگوی ثابتی پیروی نمی‌کند. علاوه بر این، نتایج نشان داد که با افزایش ارتفاع سازه و در نتیجه افزایش پریود آن، تاثیر جهت‌پذیری رکورد زلزله بر پاسخ سازه افزایش می‌یابد. این در حالی است که در سازه‌های کوتاه‌تر در بسیاری از موارد جهت‌پذیری رکورد زلزله، تاثیر چندانی بر پاسخ سازه نداشته و حتی در برخی موارد، باعث کاهش آن می‌گردد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

The effects of pulse-like motions of near-fault earthquakes with forward-directivity characteristic on the response of concrete structures

نویسندگان [English]

  • Meisam Mahboubi Niazmandi 1
  • Sohrab Mirassi 2
  • Mohammad Momeni 2
  • Mohammad Bakhshandeh 3
  • Hossein Lotfi 4
1 Ph.D Graduated, Department of Civil and Environmental Engineering, Shiraz University of technology, Shiraz, Iran
2 Assistant Professor, Department of Civil Engineering, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran
3 Ms.C Graduated, Department of Civil, Chemical, Environmental, and Materials Engineering (DICAM), Bologna University, Bologna, Italy
4 Ms.C Graduated, Department of Civil and Environmental Engineering, Amirkabir (Polytechnic) University, Tehran, Iran
چکیده [English]

Studies on behavior of structures under the effect of earthquakes in the near-field earthquakes, compared to far-field earthquakes, have shown more effects of this type of earthquake on the structure. Most of these effects depend on the characteristics of forward-directivity and flip-step with permanent displacement effect. The characteristics of near-filed earthquakes should be considered in the design and analysis of structures. The present research, aimed to investigate the effect of directivity characteristics of near-field earthquakes on the response of concrete structures. To this aim, first the different records of ChiChi earthquake in different stations have been determined as the basis for selecting accelerograms. Then, using analytical methods, the response spectrum of these records, considering the effect of forward-directivity and without it (removing dominant pulses) in the east-west and north-south directions was determined. Next, using time history analysis on two concrete structures of 10 and 15 stories, the drift (relative displacement) and the inter-story base shear in the structures was investigated for seven records of ChiChi earthquake. The results showed that due to the unpredictable nature of the earthquake, the drift and base shear responses of stories in both structures have been increased or decreased in different directions in some cases. Therefore, it can be seen that directivity does not always have a uniform effect on the behavior of the structure and does not follow a fixed pattern. Also, the results showed that by increase in the height of the structure and as a result of increasing its period, the effect of forward-directivity on the response of the structure increases. This is despite the fact that in many cases of shorter structures, the directivity does not have much effect on the response of the structure and even in some cases; it has caused a decrease in the response.

کلیدواژه‌ها [English]

  • Near-field earthquake
  • forward-directivity effect
  • ChiChi earthquake
  • Seismic responses of concrete structures
  • Drift and shear base of stories
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