فهرست مطالب

علوم و مهندسی زلزله - سال نهم شماره 3 (پیاپی 32، پاییز 1401)

مجله علوم و مهندسی زلزله
سال نهم شماره 3 (پیاپی 32، پاییز 1401)

  • تاریخ انتشار: 1401/09/16
  • تعداد عناوین: 10
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  • راضیه عباس پور، سید مرتضی موسوی*، محمدمهدی خطیب، احمد رشیدی صفحات 1-17

    این پژوهش به بررسی شواهد و آثار فعالیت های زمین ساختی جوان بر مبنای محاسبه میزان تغییرات قایم رخ داده در چین خوردگی ها و راندگی ها در باختر فرازمین شتری می پردازد. تحلیل کمی تغییرات عمودی سطح زمین در بخش باختری فرازمین شتری و بررسی عوامل تاثیرگذار بر میزان این تغییرات از اهداف این پژوهش بوده است. به منظور تحلیل تغییرات قایم رخ داده توسط چین خوردگی های جوان، گسل های راندگی و   پدیده های غیر زمین ساختی در منطقه از تصاویر راداری سنتینل 1 به روش تداخل سنجی راداری در محیط نرم افزار LiCSBAS استفاده شده است. بر اساس تفسیر داده ها، نرخ تغییرات قایم در طاقدیس فهلنج حدود 7/1 میلی متر و طاقدیس سردر حدود 1/28 میلی متر می باشند که به ترتیب بیشترین و کمترین تغییرات قایم را نشان می دهند. به طورکلی، تغییرات قایم در بخش باختری فرازمین شتری از شمال به سمت جنوب (پایانه ی شمالی گسل نایبند) افزایش چشمگیری دارد. نرخ و دامنه زیاد تغییرات در بخش باختری فرازمین شتری، به ویژه در چین خوردگی ها و گسل های راندگی جوان به دلیل بالا نبودن میزان دگرشکلی بین لرزه ای و عدم رخداد زمین لرزه با بزرگای بالا در دوره زمانی تفسیر تصاویر مورد استفاده در این مطالعه، دلیل مهم غیر زمین ساختی دارد. در منطقه مورد نظر، عامل بسیار تاثیرگذار در شکل گیری چنین تغییراتی، وقوع سیلاب های شدید فصلی و نشست رسوبات حمل شده توسط آنها در منطقه می باشد؛ اما شواهد ریخت زمین ساختی مشاهده شده در منطقه بر فعالیت کنونی گسله ها، فراخاست و رشد چین های جوان منطقه تاکید دارد. شواهدی همچون رودخانه های ماندری، رودخانه های منحرف شده و سربریده، دره های باریک و ژرف، پادگانه های آبرفتی بالاآمده بر فراز چین های نیوژن، چینه های رویشی از رسوبات آبرفتی جوان بر فراز یال طاقدیس های جوان منطقه، فعالیت کنونی گسله ها، فراخاست و رشد چین های جوان.

    کلیدواژگان: تکتونیک فعال، تداخل سنجی راداری، تغییرات قائم پوسته زمین، فرازمین شتری، طبس
  • نیلوفر باباآدم، علی ارومیه ای*، عبدالله سهرابی بیدار، ابراهیم حق شناس، شهرام مقامی صفحات 19-35

    در این پژوهش رفتار لرزه ای عوارض توپوگرافی شامل دره ها و تپه های نیم سینوسی دو بعدی به دو صورت متقارن و نامتقارن با نسبت شکل و نسبت تقارن متفاوت مورد بررسی قرار گرفته است. در عوارض متقارن، ارتفاع/عمق و در عوارض نامتقارن، نیم پهنا فاکتور متغیر می باشد. عوارض توپوگرافی به صورت همگن در نظر گرفته شده اند و مدل سازی عددی تحت موج مهاجم قایم SV ریکر با فرکانس های غالب 3 و 5 هرتز و با استفاده از روش اجزای مرزی انجام شده است. در این مطالعه تحلیل ها همگی در سطح زمین و در حوزه زمان به دست آمده است که با اعمال تبدیل فوریه به حوزه فرکانس منتقل شده است. نتایج به دست آمده در این پژوهش حاکی از آن است که در عوارض متقارن، افزایش نسبت شکل سبب تشدید در بزرگ نمایی تاج در تپه ها و کوچک نمایی در کف دره ها می شود؛ درحالی که در عوارض نا متقارن، افزایش نسبت تقارن موجب کاهش بزرگ نمایی بالای تپه ها و همچنین کوچک نمایی کف دره های مورد مطالعه می شود. همچنین در پایان اشاره ای به چگونگی بررسی عوارض توپوگرافی در آیین نامه های ساختمانی شده است که بیان می کند، مقادیر بزرگ نمایی های به دست آمده برای عوارضی با نسبت شکل های مختلف با مقادیر پیشنهاد شده توسط آیین نامه های ساختمانی مورد مقایسه قرار گرفته و نتایج، گواه بر این موضوع است که میزان تاثیر ابعاد عارضه و عدم تقارن، بر پاسخ لرزه ای عوارض توپوگرافی به مقدار چشمگیری بیش از ضرایب در نظر گرفته شده در این آیین نامه هاست.

    کلیدواژگان: عوارض توپوگرافی، نسبت شکل، نسبت تقارن، دو بعدی، موج مهاجم SV
  • اسماعیل محمدی ده چشمه، وحید بروجردیان* صفحات 37-55
    سیستم های نوین باربر جانبی مرکزگرا، با متمرکز کردن خرابی ها در اعضای فیوز، باعث کاهش هزینه های تعمیر شده و امکان بهره برداری بدون وقفه را فراهم می‎آورند. دیوار برشی بتنی مرکزگرای گهواره ای جزو این سیستم ها محسوب می شود. در تحقیق حاضر، رفتار دیوارهای پایه-گهواره ای مرکزگرا تحت 25 شتاب‎نگاشت نزدیک گسل پالس مانند بررسی شد. اثر شتاب نگاشت های مزبور بر روی سازه ها در دو حالت با و بدون مولفه دورانی زلزله مورد بررسی قرار گرفت. به منظور مقایسه و در نظر گرفتن مولفه های دورانی، شش ترکیب بارگذاری لرزه ای در نظر گرفته شده است. برای تحلیل تاریخچه زمانی غیرخطی، سازه‎های دارای 4، 8، 12، 16 و 20 طبقه انتخاب شدند. مدل سازی‎ها در نرم افزار OpenSees  به صورت دو بعدی انجام شدند. نتایج نشان داد لحاظ مولفه دورانی زلزله می تواند پاسخ های سازه را افزایش دهد. به طوری که حداکثر شتاب، جابه جایی نسبی، خمش، برش طبقات، جابه جایی نسبی پسماند بام و نسبت تنش حداکثر کابل به ترتیب برابر با 24/6، 9/3، 10/4، 9/6، 623 و 11 درصد با لحاظ مولفه دورانی زلزله به صورت حداکثر، افزایش یافته است. در سیستم های دیوار پایه-گهواره ای مورد بررسی، حداکثر جابه جایی پسماند برابر با 0/01 درصد بود. در پایان می توان گفت در سیستم های پایه -گهواره ای مرکزگرا، زاویه شتاب نگاشت با مولفه گهواره ای حداکثر نسبت به زاویه شتاب نگاشت با مولفه افقی حداکثر، ممکن است پاسخ های بیشتری را ایجاد کند.
    کلیدواژگان: سیستم مرکزگرا، دیوار گهواره ای، زلزله حوزه نزدیک، مولفه دورانی زلزله، تحلیل دینامیکی غیرخطی
  • سعید قشلاقی، فریبرز ناطقی الهی* صفحات 57-76
    مهاربند کمانش ناپذیر با قابلیت برگشت به موقعیت اولیه که با عنوان SC-BRB شناخته می شود، اخیرا به منظور طراحی لرزه ای سازه ها و کنترل خسارت تحت اثر زمین لرزه های شدید، مورد توجه پژوهشگران قرار گرفته اند. در این نوع مهاربندها، فاز بازگشت توسط تاندون های پلیمری تامین می گردد. در این راستا پژوهش حاضر سعی در ارزیابی رفتار این نوع مهاربند و مقایسه آن با قاب خمشی فولادی و قاب مهاربندی شده دارد. برای این منظور توسعه مدل عددی بر مبنای مطالعه آزمایشگاهی استوار بوده است. همچنین مقایسه ای میان عملکرد قاب خمشی ساده، قاب مهاربندی شده، قاب با مهاربندی کمانش ناپذیر و قاب مهاربندی شده با سیستم SC-BRB انجام شد. در نهایت عملکرد لرزه ای قاب به همراه مهاربند SC-BRB صورت پذیرفت. نتایج بیانگر رفتار بسیار مناسب مهاربندهای SC-BRB بوده که استفاده از آن در سازه سبب بالا رفتن بسزای ظرفیت باربری و شکل پذیری سازه شده است. اعمال مهاربند SC-BRB در قاب خمشی سبب شد تا ظرفیت باربری جانبی قاب یک طبقه یک دهانه از 1248 کیلونیوتن با 2/8 برابر رشد به 3576 کیلونیوتن افزایش یابد. همچنین مقاومت سازه پنج طبقه با استفاده از مهاربند SC-BRB در دهانه های وسط و دهانه های جانبی نسبت به قاب خمشی ساده به ترتیب 21 درصد و 38 درصد بیشتر بوده است.
    کلیدواژگان: مهاربند کمانش ناپذیر، SC-BRB، تحلیل هیسترزیس، تحلیل لرزه ای، روش اجزای محدود
  • زهرا تورنگ*، امید بهار صفحات 77-94
    هنگامی که سازه ها تحت بارهای متوسط تا شدید محیطی آسیب می بینند، مشخصات فیزیکی آنها مانند سختی، میرایی و در نتیجه شکل مودهای ارتعاشی آنها تغییر می نماید. تقریبا همه روش های عددی موجود برای شناسایی آسیب سازه ها از مولفه های انتقالی شکل مودی برای برآورد آسیب استفاده می نماید. در این مقاله با استفاده از مولفه های انتقالی و دورانی اشکال مودی و تعریف توابع هدف مختلف بر این اساس، به شناسایی آسیب پرداخته شده است. به این منظور، یک الگوریتم به روزرسانی اتوماتیک تکرارشونده در نرم افزار MATLAB ایجاد شده که از نرم افزار OpenSees به عنوان موتور تحلیل اجزای محدود استفاده می کند. جهت ارزیابی عملکرد روش پیشنهادی، دو سازه فلزی با قاب خمشی و مهاربندی برای سه سناریوی مختلف آسیب آنالیز گردیدند. برداشت داده ها به سه صورت مولفه های انتقالی شکل مودی، مولفه های دورانی و کل مولفه های شکل مودی انجام گرفته است. تفاضل فرکانس های طبیعی و اشکال مودی، معیار ارزیابی شاخص مودی و ماتریس نرمی به عنوان توابع هدف مورد استفاده قرار گرفتند. نتایج تحلیل های گسترده نشان می دهد که استفاده از مولفه های دورانی در تعیین دقیق موقعیت و شدت آسیب ها تاثیر به سزایی دارد. همچنین بررسی نتایج تحلیل حاکی از کارآمدی روش در شناسایی آسیب حتی با داده های آغشته به نوفه می باشد.
    کلیدواژگان: روش به روزرسانی، بهینه سازی تکرارشونده، روش شناسایی آسیب، درجات آزادی انتقالی، درجات آزادی دورانی
  • مسعود محمودآبادی*، سید محمدرضا حسنی، بابک تقوی صفحات 95-109

    در این مقاله، با روشی جدید و با رسم نمودار تغییرات فرکانس های طبیعی تیرهای خمشی منشوری بر حسب پارامتری که متناسب با جذر فرکانس زاویه ای این سیستم هاست، فرکانس های طبیعی این تیرها شناسایی شده است. در این تحقیق، از توابع درون یابی جدیدی که متشکل از توابع مثلثاتی و نمایی است، به جای توابع درون یابی متعارف که شامل چند جمله ای های درجه سه می باشند، استفاده شده است. مقادیر آرگومان این توابع شامل پارامتری موسوم به بتا است که متناسب با جذر فرکانس زاویه ای تیر خمشی می باشد. با تغییر این پارامتر در محدوده ای مناسب و با گامی مشخص، فرکانس های تیر خمشی با محاسبه ماتریس های سختی و جرم و به ازای مقادیر مختلف بتا محاسبه شده و نمودار تغییرات فرکانس های تیر خمشی بر حسب بتاهای مختلف رسم می گردد. از دیدگاه اجزای محدود، این تیرها دارای درجه آزادی معینی هستند که به تعداد این درجات آزادی و به ازای یک بتا مشخص، می توان برای آنها فرکانس طبیعی ارتعاشی محاسبه نمود. با بررسی نمودارهای فرکانس های مختلف تیر خمشی مورد نظر بر حسب پارامتر بتا و نیز با داشتن فرکانس هایی تقریبی که با روش اجزای محدود متعارف به دست می آید و مقایسه آنها با یکدیگر، می توان فرکانس های تیر را با دقت بالاتری به دست آورد. در این مقاله، سه نوع تیر خمشی منشوری با شرایط تکیه گاهی مختلف به تفصیل مورد بررسی قرار گرفتند و فرکانس هایی که از این روش ابتکاری برای آنها به دست آمد در مقایسه با روش اجزای محدود متعارف دارای دقت بالاتری مخصوصا برای مدهای ارتعاشی بالاتر بودند.

    کلیدواژگان: فرکانس های طبیعی، تیرهای خمشی منشوری، جزء محدود، توابع درون یابی، ماتریس های جرم و سختی
  • سروش نودهی، مهدی زهرایی* صفحات 111-130
    جمع آوری اطلاعات آماری از ساختمان های موجود به ویژه شهر تهران و طبقه بندی آنها کمک شایانی در مدیریت بحران جهت کاهش خسارات لرزه ای می نماید. حذف میان قاب در طبقه همکف به دلیل مزایای کاربردی، به طور گسترده دیده می شود. مطالعات صورت گرفته روی این ساختمان ها، عملکرد ضعیف آنها به علت تشکیل طبقه نرم را نشان می دهد. در این پژوهش ابتدا اطلاعات آماری از ساختمان های نوساز در مناطق 9 و 11 شهر تهران که بر اساس ضوابط لرزه ای طراحی شده جمع آوری و بر اساس علل تشکیل طبقه نرم طبقه بندی گردید. بر این اساس با فرض اجرای صحیح، تنها عامل ممکن در ایجاد طبقه نرم در این سازه ها حذف میان قاب در طبقه همکف می باشد. جهت بررسی این عامل یک ساختمان شش طبقه بتنی نمونه، در حالت سه بعدی در OpenSees مدل سازی شده که در حالت های مختلف چینش میان قاب در طبقه همکف و اعمال زلزله در زوایای مختلف، رفتار سازه ارزیابی گردید. نتایج تحلیل های دینامیکی غیرخطی نشان داد به دلیل آنکه این سازه ها بر اساس ضوابط لرزه ای طراحی شده ، حذف میان قاب در طبقه همکف باعث تشکیل طبقه نرم نشد و با توزیع یکنواخت خسارت در همه طبقات، عملکرد سازه بهبود یافت. همچنین حالت های مختلف چینش میان قاب در طبقه همکف، رفتار سازه را تغییر داده و اهمیت مدل سازی میان قاب و اعمال زلزله در زوایای مختلف را جهت تعیین رفتار واقعی سازه در هنگام زلزله نشان داد.
    کلیدواژگان: مطالعات آماری، طبقه نرم، میان قاب، OpenSees، تحلیل های غیرخطی سه بعدی
  • محسن رستمی*، زینب ولی پوری، فاطمه گرجی سینکی، عبدالرضا سروقد مقدم صفحات 131-140
    آسیب های ناشی از زلزله در سازه های بتنی باعث شده است که روش های نوینی برای طراحی و ساخت سازه های بتنی مقاوم در برابر زلزله توسعه پیدا کنند اما زلزله های اخیر نشان داده اند که ساختمان های بتنی تحت اثر زلزله دچار آسیب هایی می شوند که تعمیر آنها را بسیار دشوار و حتی غیر ممکن می گرداند؛ لذا در این پژوهش به معرفی سیستم نوینی پرداخته شده است که با استفاده از سازوکار حرکت گهواره ای در دیوارهای برشی سازه، آسیب را به فیوزهای سازه منتقل می کند و باعث می شود سازه بتنی در حین زلزله و پس از آن ایمن باقی بماند و تعمیرپذیری بسیار ساده ای داشته باشد. جزییات دقیق اتصالات و طراحی این سیستم در نرم افزار ABAQUS و تحلیل غیر خطی سازه های 4 طبقه بتنی منظم مجهز به دیوار برشی دارای حرکت گهواره ای در نرم افزار SAP و تحت هفت رکورد لرزه ای حوزه نزدیک گسل انجام شده است. نتایج نشان می دهد که استفاده از سیستم دیوارهای برشی دارای حرکت گهواره ای در مقایسه با سازه های بتنی فاقد آن به طرز موثری آسیب وارده به سازه را در اثر اعمال رکوردهای لرزه ای کاهش داده و سازه بتنی مجهز به آن سالم باقی مانده است. همچنین سطوح عملکردی سازه مجهز به دیوارهای برشی دارای گهواره ای نیز در ناحیه خدمت رسانی بی وقفه باقی مانده است اما در سازه بتنی فاقد آن مفاصل پلاستیک حتی وارد ناحیه فروریزش شده است. بهبود رفتار لرزه ای سازه مجهز به دیوار برشی دارای حرکت گهواره ای به میزان 30 درصد بیشتر از سازه مشابه فاقد آن بوده است.
    کلیدواژگان: خسارت محدود، ساختمان تعمیرپذیر بتنی، دیوار برشی دارای حرکت گهواره ای
  • اکبر واثقی*، مهدی پورنداف حقی صفحات 141-152
    پل های تیر و دال چند دهانه با تکیه گاه های ساده از متداول ترین پل های بزرگراه های کشور می باشند. در این پل ها معمولا درزهای انبساط در پایه های میانی و کوله ها به منظور تامین حرکت طولی ناشی از تغییرات دما تعبیه می گردد. در هنگام بهره برداری از پل، وجود درزهای انبساط باعث مشکلات فراوانی از قبیل پر شدن فاصله درز، اختلاف تراز دو طرف درز و خسارت جدی به پایه های میانی به واسطه نشت آب های سطحی از میان درز و در نتیجه از بین رفتن پوشش بتن و خوردگی آرماتورهای تیر سرستون می شوند. این خسارات در بسیاری از پل های چند دهانه کشور به دلیل تعمیر و نگهداری نامناسب شدید می باشد. حذف درز انبساط در پایه های میانی از رویکردهای پژوهشی اخیر در جهان بوده است. این پژوهش ها منجر به ارایه سیستم جدیدی شده است که در آن تیرهای تابلیه دو سر ساده محاسبه و اجرا می گردند ولی دال عرشه در محل پایه های میانی به صورت یکسره اجرا می شود. دال یکسره در محل درز میانی «دال پیوند» نامیده می شود و وجود آن مشخصات دینامیکی و رفتار لرزه ای پل را تغییر می دهد. در این مقاله نتایج تحلیل های لرزه ای پل های تیر و دال بتنی چهار دهانه و هفت دهانه با دال پیوند و بدون دال پیوند ارایه شده است. مطالعه تحلیلی به صورت تحلیل طیفی در هر دو جهت طولی و عرضی پل ها انجام شد و رفتار لرزه ای پل ها با مقایسه تقاضای لرزه ای در زیرسازه پل برای حالات مختلف چیدمان دال پیوند و درز انبساط بررسی گردید. نتایج این مطالعه نشان می دهد که یکسره کردن دال عرشه پل و استفاده از دال پیوند تاثیر قابل توجهی بر رفتار لرزه ای پل ها می گذارد. طول پل و نحوه چیدمان درزهای انبساط و دال پیوند، عوامل موثر در تغییر رفتار لرزه ای پل و توزیع برش پایه به عناصر زیر سازه است.
    کلیدواژگان: پل، سازه، بتن، زلزله، دال پیوند
  • شاهرخ پوربیرانوند* صفحات 153-163

    امروزه کاربردهای بسیاری برای اطلاعات میدان تنش وجود دارد. شناسایی و مدیریت مخزن، پایداری معادن، تونل، گمانه ها و مکان های دفن زباله، کالیبراسیون مدل های ژیومکانیکی- عددی، شبیه سازی های چهاربعدی هیدروترمومکانیکی و ارزیابی خطر زلزله با استفاده از لغزش گسلی و تجزیه وتحلیل پتانسیل شکست مثال هایی از این کاربردها هستند. با توجه به پروژه های جاری در زمینه ارزیابی تحلیل خطر زلزله در منطقه مورد مطالعه با رهیافت مطالعات نرخ لغزش و دگرشکلی توزیع شده، بر اهمیت استفاده از پایگاه داده اطلاعات تنش به صورت به روزشده و جامع، افزوده است. در این مطالعه کوشش شده است که اطلاعات موجود درباره میدان تنش در منطقه مکران شامل داده های سازوکار کانونی زمین لرزه ها و وارون سازی آنها به پایگاه داده موجود که در پروژه جهانی تنش در دسترس قرار گرفته است، اضافه شود. به این ترتیب پایگاه داده های تنش در منطقه مورد نظر تا حد ممکن تکمیل شده و زمینه برای بهبود مطالعات مربوطه فراهم آمده است. در آخر نتایج به دست آمده با مطالعات انجام شده در منطقه به روش وارون سازی تنش مقایسه شده و همخوانی مناسبی بین نتایج مشاهده شده است.

    کلیدواژگان: تنش تکتونیکی، زمین لرزه، سازوکار کانونی، مکران، نقشه ی جهانی تنش
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  • Razieh Abbaspour, Seyed Morteza Mousavi *, MohammadMehdi Khatib, Ahmad Rashidi Pages 1-17

    This study examines the evidence and effects of young tectonic activities based on the calculation of vertical changes in folds and thrusts in the western part of the Horst Shotori. Quantitative analyses of vertical changes in the western part of the Shotori and the study of factors affecting the extent of these changes have been the objectives  of this study. In order to quantitatively analysis the vertical changes caused by young folds, thrust faults and non-tectonic phenomena in the region, Sentinel 1 radar images were used by radar interferometry method in LiCBAS software. Based on the interpretation of the data, the rate of vertical changes in the Fahlonj anticline is about 7.1 mm and the Sardar anticline is about 1.28 mm, which show the most and the least vertical changes, respectively. In general, vertical changes in the western part of the Horst Shotori, from north to south (northern end of Nayband fault) increase significantly.The high rate and range of changes in the western part of the Camel Plateau, especially in folds and young thrust faults, due to the low rate of inter-seismic deformation and the absence of high-magnitude earthquakes in the time period of the interpretation of the images used in this study, is an important non-tectonic reason. The absence of high magnitude earthquakes in the interpretation period of the images used in this study has an important non-tectonic reason. In the region, a very influential factor in the formation of such changes is the occurrence of severe seasonal floods and the deposition of sediments carried by them in the region. However, the evidence of tectonic morphology observed in the region underscores the current activity of faults, uplift, and the growth of the region's young folds. Evidence such as: Meanderi rivers, Beheaded and Deflected Streams, narrow and deep valleys, alluvial fans rising above the Neogene folds, strata of young alluvial sediments above the limbs of young anticlines in the region, the current activity of faults, uplift and growth of young anticlines.

    Keywords: Active Tectonic, Radar interferometry, Vertical Changes earth's crust, Horst Shotori, Tabas
  • Niloufar Babaadam, Ali Uromeihy *, Abdollah Sohrabi-Bidar, Ebrahim Haghshenas, Shahram Maghami Pages 19-35

    In recent years, many reports of damages caused by earthquakes have been observed in different parts of the world, especially after observing the severity of damage in the Mexico City earthquake in 1985, special attention was paid to the discussion of site effect, and many researchers have investigated this issue in Mexico City and also investigated the site effect on the seismic response in other regions. The effects of topography have been stated as an important factor in the amplification of earthquake waves. Due to the great importance of the effect of these features, including valleys and hills, on the seismic response, many researchers investigated this field, while most research on the effect of topography on seismic behavior has been focused on symmetric topographic features.In this research, the seismic behavior of topographic features, including symmetrical and asymmetrical semi-sine valleys and hills with different shape ratios, has been studied. The reason for choosing semi-sine features is that they are the most common form of topographic features in nature, and this is very important in applying the results of the studies. The most important reason for the current study is that in nature, topographic features are rarely seen symmetrically, and studying asymmetric features in seismic studies is necessary.The results in this research have been obtained by using numerical modeling, in order to carry out numerical modeling, the Boundary Element Method (BEM) has been used, which has shown very high accuracy in modeling the distribution of seismic waves among the existing numerical methods.The main goal of this research is to investigate the seismic behavior of symmetric and asymmetric homogeneous two-dimensional semi-sine topographic features. According to the literature review, different studies have investigated the seismic response in different parts of the topographic features, and have pointed out the importance of the topographic shape in the seismic response. In this regard, two symmetric and asymmetric semi-sine topographic features have been studied and their effects on seismic waves with frequency domains of 3 and 5 Hz have been investigated. The symmetrical features consist of eight valleys and semi-sine hills with a half-width of 500 meters and different heights of 125, 250, 375, and 500 meters, which have shape ratios of 0.25, 0.5, 0.75, and 1 respectively. The seismic response has been examined at three points at the top, middle, and bottom of the features. The second part of the study is investigating the seismic behavior of homogeneous and asymmetric topographic features. For this purpose, 10 asymmetric valleys and hills with the same height of 500 meters and different half-widths of 125, 250, 500, 1000, and 2000 meters, have symmetry ratios of 0.25, 0.5, 1, 2, and 4, respectively.In this research, the amplification obtained for features with different shape ratios has been compared with the values suggested by the building codes and the results prove that the effect of features dimensions and asymmetry on the seismic response of topographic features is significantly more than the suggested coefficients in these codes.In the following, the most important results of this study are briefly discussed:In symmetrical hills, the effect of the shape ratio on the spectral amplification increases from the foot to the top of the hills. In addition, the period of the maximum spectral amplification increases with the increase of the aspect ratio.In symmetrical valleys, increasing the shape ratio causes a decrease in the minimum spectral amplification inside the valleys. By moving away from the valleys, a fluctuation of amplification and de-amplification is seen in the seismic wave, which increases the number of these fluctuations with the increase of the shape ratio.The study of the seismic behavior of asymmetric hills shows that as the symmetry ratio increases, the effect of topography on the seismic behavior decreases, especially at the top of the hill, this is clearly visible. In addition, the highest spectral amplification in each symmetry ratio is in the asymmetric part of the hill (the slope with different symmetry ratios).Asymmetric valleys show the effect of asymmetry in the form of intensification in the fluctuation of amplification and de-amplification at the edge that has a greater slope. In addition, in the valley, decreasing in de-amplification is seen with the increase in the symmetry ratio (the symmetry ratio and de-amplification show an opposite relationship).In asymmetric valleys, a side of the valley that has a constant symmetry ratio shows the same behavior in all valleys (valleys with different symmetry ratios), while in asymmetric hills, it can be seen that the asymmetry affects the seismic behavior of the side of the hill that has a constant symmetry ratio.

    Keywords: Topographic Features, Shape Ratio, Asymmetric Ratio, 2-Dimensional, SV Incident Wave
  • Esmaeil Mohammadi Dehcheshmeh, Vahid Broujerdian * Pages 37-55
    Nowadays, self-centering (SC) lateral resistant systems are able to reduce residual displacement and post-earthquake repairing costs. By concentrating damages on fuse elements, these systems reduce repair costs and allow immediate occupancy. To resist against lateral load, the SC systems have two mechanisms including: 1) restoring force mechanism, 2) energy dissipation (ED) mechanism. Both mechanisms are needed to provide flag shape pushover behavior. The restoring force mechanism provided with post-tensioned (PT) prestressed core to supply prestressed used unbounded tendons. The reason using unbounded tendons is to prevent their yielding suddenly and creating cracks in core. Usually, the restoring force mechanism is accompanied by gap opening in systems. This gap opening can cause damage to other structural and nonstructural members. Then, the system should be isolated in location of joints. The ED mechanism provided with fuses. Fuses can have different types, including:  1) hysteric, 2) viscous, and 3) shape memory alloy (SMA) dampers. Among these dampers, hysteric elements are more used due to their low price than other fuses. The SC systems implemented in different types, including: 1) rocking cores, or frames, 2) moment frames, and 3) braces. The moment frames and braces need specially detailing, and expert worker for building and construction. Furthermore, rocking frames needed total system rotated that is constructive details difficult. Among these systems, rocking cores have mostly been used and studied. The rocking cores are made with three cores of concrete shear wall, wooden wall and bracing frame.According to seismic codes, lateral resistant system must have the necessary strength to withstand earthquakes. The records of earthquakes have three translational and three rotational components. Usually, the structures investigated under translational component and rotational component ignored. To produce the rotational component, there are two methods, including single station procedure (SSP) and multiple stations procedure (MSP) or geodetic method. The SSP method extracts the rotational components from the translational ones. In this method, many researchers employ the information of a single station individually to obtain the rotational components. In the MSP method, the rotational components use translational recorded data by the numerous ground motions distributed in a closely dense zone. Utilizing this method requires a vast range of information of many ground motions, which was unreachable for the authors of this manuscript. Therefore in this research, to produce the rotational components of ground motions use SSP method. Furthermore, near-fault ground motions were considered for time history analysis. Near-field ground motions have some characterizations that make them different from far-field ground motions. The most remarkable characterization of these records includes: 1) distance less than 10 km from the fault, 2) the existence of long-period pulses in their velocity time series, 3) high Peak Ground Acceleration (PGA), and 4) high Peak Ground Velocity (PGV).In current study, the behavior of SC base-rocking walls under 25 near pulse-like ground motions was investigated. The structures were studied in two states depending on considering or ignoring the rotational component of the ground motions. In order to compare and consider the rotational components, six seismic load combinations were considered. 2D frames of 4-, 8-, 12-, 16-, and -20 stories were examined. Nonlinear time-history analyses were performed utilizing software. The results showed that considering the rotational component of earthquake can increase structural responses. In this regard, the maximum acceleration, inter-story drift, moment, shear force, roof drift and maximum tendon stress ratio were increased up to 24.6, 9.3, 10.4, 9.6, 623 and 11%, respectively.Furthermore, the results suggested that as the height of the structure increases, the response values of maximum roof drifts and maximum stress ratio increase. In SC base-rocking wall systems studied, the maximum residual roof drift was equal to 0.01 %.
    Keywords: Self-centering systems, Rocking Wall, Near-fault, Rotational component, Nonlinear dynamic analysis
  • Saeid Gheshlaghi, Fariborz Nateghi Elahi * Pages 57-76
    One of the main aims of structural seismic design is to control structural damage due to severe earthquakes. A feasible solution to control and deplete earthquake energy is to use a bracing system. When the bracing is in the process of cyclic deformation or seismic load, the plastic deformation of the compressive and tensile cycles will occur in the restrained parts of the core plates, which will create a suitable energy absorption capacity in the brace. Among them, Buckling-Restrained Brace (BRBs) are widely used due to their stable hysteresis behavior. BRB braces usually have two main parts: a core that withstands the axial force, and a lateral restraint shell to prevent the core from buckling under compressive force. In the event of a severe earthquake, the core surrenders, but still reduces structural damage by absorbing seismic energy. However, due to the fact that the stiffness after the surrender of the brace is relatively low and it is not able to return to the conditions before the surrender, the structural frame faces damage and deformation of the residue after severe earthquakes. In this regard, the buckling brace with the ability to return to the original position known as Self-Centering Buckling-Restrained Brace (SC-BRB) has recently been considered by researchers. In this type of braces, the return phase is provided by polymer tendons. Since the numerical study of SC-BRB behavior measurement has not been done so far, so the present study tries to evaluate the behavior of this type of brace and compare it with steel bending frame and braced frame. For this purpose, Abaqus software has been used.In the present study, the results of the laboratory study of Zhou et al. (2015) in the analysis of the self-returning buckling system reinforced by SC-BRB basalt fibers have been used to validate the finite element model and the specifications of the brace to the steel frames of the case. The discussion in this study is generalized. The development of numerical model has been based on laboratory study. Then, a single-story, single-span frame in four different modes, simple bending frame, frame with simple bracing, frame with non-buckling brace, and frame with self-returning buckling brace was subjected to hysteresis and the results were compared. Then, design in ETABS software and seismic analysis in Finite element Abaqus software for 5-story structures with and without bracing against far and near Landers and Northridge earthquake faults.Comparisons were also made between the performance of a simple bending frame, a braced frame, a buckle with a buckling brace, and a braced frame with the SC-BRB system. Finally, the seismic performance of the frame was performed with SC-BRB bracing. The general results obtained from this study are as follows: Using appropriate behavioral models of materials, very accurate answers in the analysis of non-buckling irreversible buckling by basalt polymer fibers by finite element modeling using Abaqus. A very good approximation of the results obtained from the numerical model with the research model of Zhou et al. has been able to prove the accuracy of the results of the present numerical model. The results generally indicate the very good behavior of SC-BRB braces, the use of which in the structure has significantly increased the load-bearing capacity and ductility of the structure. The application of SC-BRB bracing in the bending frame increased the lateral bearing capacity of a single-story single-span frame from 1248 kN with a 2.8-fold increase to 3576 kN. Also, the strength of the five-story structure using SC-BRB braces installed in the two modes of middle openings and side openings was 21% and 38% higher than the simple bending frame, respectively.
    Keywords: BRB, SC-BRB, Hysteresis analysis, Seismic Analysis, FEM
  • Zahra Toorang *, Omid Bahar Pages 77-94
    Damage in structural elements causes obvious changes in their physical properties such as stiffness and damping. These changes affect the stiffness and damping matrices of whole building so its mode shapes change. Therefore, mode shapes of existing building are widely used in damage detection methods. Since vibration test can only provide translational components of mode shapes, previous methods mostly worked with this type of data. This paper focused on considering the importance of using some rotational/translational components of the mode shapes to detect damages in structural frames. In order to analyze the frames and update them, an automatic iterative model updating program is developed in MATLAB software that works with OpenSees for conducting finite element analysis. The iterative program evaluates a set of objective functions in each step and tries to optimize them by means of nonlinear least square method. Objective functions are defined based on the combination of two criteria of these four items: comparison between frequencies and/or mode shapes of two situations, the modal assurance criteria (MAC), and the modal flexibility matrices. In each step of the analysis, based on optimization results, a new frame will be modeled in OpenSees software that its elements stiffness is changed according to new sets of data, then finite element analysis will be done and new modal data will be extracted and optimization process will be repeated by new data. To verify the effectiveness of the developed program, two three-dimensional steel structures are modeled and evaluated, one of them is a five-story moment resisting frame and the other one is a three-story brace frame. It has been considered that these frames suffered damages which are defined by three different scenarios for each of them. Damage scenarios consist of minor, severe and both minor and severe damages. Actually, in this study, damages are defined by reduction in elements’ stiffness. In fact, damage is a percentage of reduction of stiffness in damaged element in comparison with its healthy condition. Mode shape components and natural frequencies of damaged structures are the only needed input data for the program. To investigate the influence of rotational components in model updating, frames have been analyzed with three types of data in each scenario, all translational or rotational components, and all components of mode shapes. Extensive analyses show that among employed objective function, the one which compares mode shapes is the most successful one in damage detection, also modal flexibility can be effective when it works by only rotational components of mode shapes. The findings indicated that the translational components of mode shapes are not capable of detecting damages accurately. Results of model updating by use of only translational components of mode shapes indicate that not only the damages’ location and their intensities could not be predicted, but also several false damages are reported in undamaged elements. It can be concluded that using rotational data leads to more precise results in determining both damages’ locations and their intensities. Besides, the number of false damage detection has been decreased by use of rotational components. It means, when the rotational components are employed, the methods report no damage in healthy elements or the amount of detected damage is very small that can be ignored. Real data extracted from existing building are always polluted by noises due to human or machine faults or sometimes errors in numerical methods lead to inexact input data. Since the data employed in this study are exact numerical data, to consider the effects of these errors, analytical modal data has been polluted by some noises. These noises are generated by use of random function in MATLAB software. Surprisingly, the results show that even with noisy data, the proposed method can detect damages precisely.
    Keywords: Model Updating Method, Iterative Optimization Method, Damage Detection Method, Rotational DOFs, Translational DOFs
  • Masoud Mahmoudabadi *, Seyed MohammadReza Hasani, Babak Taqavi Pages 95-109

    Usually, by modeling the structures using the finite element method, their undamped free vibration frequencies are calculated analytically. In addition, the issue of accurate calculation of natural frequencies and the shape of vibration modes corresponding to them for bending systems that have distributed mass and elasticity and possibly a combination of several bending beams, sometimes requires solving complex mathematical equations and requires a relatively heavy mathematical work demands. Bending beams are beams whose axial deformations is insignificant compared to their bending deformations, and as a result, these members are assumed to be axially rigid. By using the conventional finite element method, the natural vibration frequencies of these beams can be obtained approximately. By increasing the number of finite elements used in the model, the calculation error of natural frequencies of vibration decreases. When the consistent-mass matrix is used, the frequency values obtained from the finite element method converge to the exact frequency values with larger values, while if the lumped-mass matrix is used, the frequency values obtained from the finite element method converge to the exact frequency values with smaller values. It should be noted that the consistent-mass matrix is non-diagonal, but the lumped-mass matrix is diagonal. The interpolation functions (shape functions) used for bending finite elements (beam elements) are polynomial functions of the 3rd degree. This bending finite element has two nodes, each node has one translational degree of freedom and one rotational degree of freedom. The new idea that came to the authors of this article is that instead of using polynomial functions, trigonometric and exponential interpolation functions are used to calculate the stiffness matrix and mass matrix of the finite element. In fact, these trigonometric and exponential functions are the solutions of the differential equation governing the free vibration of bending beams with distributed mass and elasticity. The argument of these trigonometric and exponential functions includes a parameter called beta, which is proportional to the square root of angular frequency of the bending beam. By changing this parameter in a suitable range and with a certain step, it is possible to plot the changes in the frequencies of the different modes of the studied prismatic beam in terms of beta. In this paper, three models were studied, which included a uniform cantilever beam, a uniform beam clamped at left side and simply supported at right side, and a uniform beam free at both ends. Using the conventional finite element method and using the consistent-mass matrix, these three models were analyzed and the approximate frequencies of the first few modes of these beams were calculated, which were greater than their corresponding exact values. In the innovative method presented in this article, a uniform beam was modeled with a finite element model with one translational degree of freedom and one rotational degree of freedom. The stiffness matrix and the mass matrix of this beam were calculated for different betas and having these two matrices, the first and second frequency values of this model were calculated for different beta values and its graph was drawn for different betas. The values of the maximum frequency of the first frequency are the same as the values of the minimum frequency of the second for certain betas, and by specifying these betas, the frequencies of different vibration modes can be accurately determined. The detected frequencies of different modes with this method had a very good match with their exact corresponding frequencies. For the second model investigated in this paper, one rotational degree of freedom was considered. Considering that this beam had only one rotational degree of freedom, therefore, by plotting the first frequency of this model for different betas and finding its minimum, the frequency values of different modes of this beam were obtained, which matched the exact values like the previous model very well. The third model was the same as the previous two models. The diagram of the first to fourth natural frequencies of this model was drawn for different betas. By having the approximate values of the frequencies of different modes obtained from the conventional finite element method and these diagrams, the frequencies of different modes of the model were identified, which were in good agreement with their corresponding exact values.

    Keywords: Natural frequencies, distributed systems, Finite element, interpolation functions
  • Soroush Nodehi, Seyed Mehdi Zahrai * Pages 111-130
    Statistical collection of existing buildings, especially in Tehran, and their classification can be a great help in identifying crisis management in order to reduce earthquake damage. Modern architecture is widely used due to its economical and practical benefits. In this architecture, the infills on the ground floor are generally removed. In Iran, most infills are constructed in such a way that they are connected to the corner of the frame by bricks, mortar, and other elements. For this reason, they are considered structural elements and will affect the lateral stiffness and lateral strength of the structure. Many studies have been conducted on buildings with this style of architecture designed based on gravity loads, which show their poor performance due to the formation of the soft story. In this study, first, statistical information is collected from recently built buildings in regions No. 9 and 11 of Tehran that are designed and constructed based on seismic criteria and are classified based on the reasons for the formation of the soft stories. Most of the buildings in these regions are RC moment-frame structures and have 6-8 stories and 2-3 bays in each direction. The first story in these buildings is used as parking. Therefore, assuming the correct constructions, the factor of removing the infills on the ground floor can cause the formation of a soft story in these structures.Next, a six-story concrete building with similar architecture in accordance with the results of statistical studies, is modeled in a three-dimensional mode in the OpenSees to evaluate the seismic behavior of the structure in different scenarios of infills arrangement on the ground floor and earthquake at different angles. To better cover all angles and reduce analysis costs, through the LHS sampling method, the selected angle for analysis is determined. Due to the lack of laboratory studies in three-dimensional mode and the importance of the axial-flexural interaction in the column in this research, structural modeling in this study was considered through the fiber model. The model of two compression struts placed diagonally in the panel is used to model the infills, and the numerical modeling is verified with experimental research.In this research, the probable formation of the soft story is evaluated based on three criteria: the ratio of the lateral linear stiffness of the stories, mode shapes, and distribution of the nonlinear lateral drift of the stories. The linear analysis results show that because these infills have high initial linear stiffness, the mode shape and lateral linear stiffness of these buildings are like soft-story buildings. However, the results of the nonlinear dynamic analysis show that since these structures are designed based on seismic criteria and the height of the ground floor is smaller than others, the infills have low ductility. Therefore, the removal of infills in this story does not necessarily lead to a soft story and instead can improve the performance of the structure by uniformly distributing damage across all floors. On the other hand, in the case that infills are evenly distributed in all floors, the behavior of the structure is similar to the moment frame and the damage is concentrated in the middle stories. This type of infill distribution increases the lateral stiffness and reduces the capacity of the structure. Therefore, it has even poor performance in comparison with building without infills in the first story. Also, different scenarios of infill arrangements on the ground floor change the behavior of the structure. Applying earthquakes at different angles indicates the building will experience varied behavior at each angle so that for some angles the building even collapses while for others not. Therefore, according to the numerical results, this modeling and analysis method will help show the actual behavior of the structure during an earthquake to prepare capacity curves for design.
    Keywords: Statistical Studies, Soft Story, Infill, OpenSees, Three-Dimensional Nonlinear Analysis
  • Mohsen Rostami *, Zeinab Valipouri, Fatemeh Gorji Sinaki, Abdolreza S.Moghadam Pages 131-140
    Earthquake damage in concretre structures has led to the development of new methods for the design and construction of earhquake resistant concrete structures. However, recent earthquakes have shown that concrete structures are damaged by earthquakes, making them very difficult and even impossible to repair. For this reason, after relatively severe earthquakes, these buildings have been damaged and destroyed, and in order to reuse the structure, it is necessary to spend a lot of time and money due to the extent of damage to the structure, and this issue creates a new idea to limit damage to specific points of the structure. In this way, buildings can be exploited more quickly by replacing damaged elements. One of the new methods to improve the seismic performance of concrete buildings is the use of systems that limit damage to the structure. Among these methods, we can mention systems with rocking motion. In these systems, the main building behaves elastically so that the energy absorption and the nonlinear performance occur only in certain parts of the building that have been predicted. Therefore, in this study, a new system has been developed that transmits damage to fuses by using Rocking shearwall system, and make the concrete structure safe during and after the earthquake by making a very easy repair. Details of connections and design of this system are done in ABAQUS software and nonlinear analysis of the structure equipped with rocking shear wall has been performed in SAP2000 software under seven seismic near field records. The solid element was used to model the rocking system in Abaqus and concrete damage palsticity model was used for modeling the concrete, which is used to model the nonlinear behavior of concrete. The contact between the steel bolts and the concrete shear wall is simulated using contact element. The concrete shear wall in this method remains in the elastic range, but the dampers connected to the shear wall due to the elevation of the shear wall absorb most of the seismic force. The results shown that the use of rocking shear wall compared to the concrete structure without it has effectively reduced the damage to the structure due to seismic records and the concrete structure equipped with it has remained intact. Also, the functional levels of the structure equipped with rocking shear wall has remain in immidiate occupancy but in the concrete structure without it, plastic hinges have even entered the collapse area. Improving the seismic behavior of a structure equipped with rocking shear wall about 30 percent more than a sismilar structure without it. The use of a controlled rocking motion system significantly reduces axial force in structural members by about 25 percent and post-tensioned cables in the cradle drive system have a more than 70% effect in reducing the deformation of the structure and then the yielding damper is placed. The amount of vertical displacement on the sides of rocking concrete shear walls should be less than 5 cm. The use of a new repairable shear wall with rocking motion has caused the vibration mode to dominate the structure of the first vibration mode and the distance between the torsion mode and the first and the second modes are very large.
    Keywords: Low Damage Building, Concrete Reparable building, Rocking Shear Wall
  • Akbar Vasseghi *, Mehdi Pournadaf Haghi Pages 141-152
    Multi-span concrete girder bridges with simple supports are the most common highway bridges in Iran. In these bridges, expansion joints are usually installed at each end of simple spans to provide for deck longitudinal movement due to temperature, shrinkage, and creep. The presence of expansion joints causes many problems with regard to bridge maintenance. These problems include filling of the joint with debris, vertical misalignment of the deck, and loss of concrete cover and corrosion of cap beam reinforcement caused by water leakage through the joint. These damages in many multi-span bridges of the country are mainly due to improper maintenance. Elimination of expansion joints at the interior bents has been the subject of recent studies. These studies have led to development of a design concept for jointless bridges. In this approach, the bridge girders are simply supported but the expansion joints are replaced by constructing continuous slabs over the interior bends. The continuous portion of the slab is called the "link slab" and its presence changes the dynamic characteristics and seismic behavior of the bridge. In this paper, the results of seismic analyses of four-span and seven-span concrete girder bridges with and without the link slabs are presented. The analytical study was performed by spectral analysis in both longitudinal and transverse directions of the bridges. Seismic behavior of the bridges was investigated by comparing seismic demands in bridge substructures for various configurations and layout of link slab and expansion joint. The results of this study show that link slabs significantly affect the seismic behavior of the bridges. The total length of the bridge and the arrangement of expansion joints and link slabs on the bridge deck are the dominating parameters affecting the seismic behavior of the bridge and the distribution of the base shear to the substructure elements.
    Keywords: bridge, structure, Concrete, Earthquake, Link Slab
  • Shahrokh Pourbeyranvand * Pages 153-163

    There are many applications for stress field information today. Reservoir identification and management, the stability of mines, tunnels, boreholes and landfills, calibration of geomechanical-numerical models, four-dimensional hydrothermomechanical simulations and seismic hazard assessment using fault slip and failure potential analysis are examples of these applications. Considering the current projects in earthquake risk analysis in the study area with the approach of landslide rate and distributed deformation studies, the importance of using the stress database in an improved and comprehensive manner has been increased. Due to the many applications that exist today for stress field information, as well as current projects in related fields that are closely related to the subject of tectonic crustal stress, the use of an updated database of stress information has become increasingly important. This study has attempted to complete the study area's stress databases as much as possible using various data sources. One of the sources that provide extensive information in this field for free is the World Stress Map Project. In this study, an attempt has been made to add the existing knowledge about the stress field in the Makran region, including data on the focal mechanism of earthquakes and their inversion, etc., to the current database available in the World Stress Map Project. Data on the focal mechanism of earthquakes in the study area have been obtained from various sources. It can be seen that WSM databases in Makran, especially in the central parts, do not contain much information and the available information is not of high quality. Since most World Stress Map database records consist of single focal mechanisms of earthquakes, focal mechanisms extracted from international research centers can be added to this database. In calculating the stress direction of a single focal mechanism, the relationship between the type of focal mechanism and the axis corresponding to the maximum stress direction must be considered. As we know, the principal stress directions are different for various fault mechanisms. In the present study, the information obtained from single focal mechanisms has been compared with the stress inversion results. The current stress database is the most complete one in the area regarding the available data and the ground for improving the relevant studies is provided. According to the present study results, the stress field in the Makran region has significant spatial changes. These changes indicate opposite stress directions in Eastern, Central and Western Makran. In this study, it was shown that single focal mechanism data obtained from the ISC database and other sources are suitable for adding data to the World Stress Map. Also, comparing the results of stress inversion using the focal mechanism of earthquakes in the study area with the results of the present study showed that the individual focal mechanism data of earthquakes generally have a relatively good agreement with the actual directions of stress in the region and can be used as a preliminary estimate of these directions. In this study, using GPS velocity vectors and tectonic plate motion vectors, surface locking was observed in central Makran. However, according to the evidence in the northern parts of central Makran, the deformation continues at great depths aseismically. Also, comparing the results with the geological structures in the area showed good agreement. Depth separation of the focal mechanism of earthquakes showed that the stress data calculated in this study are mainly related to the upper 40 km. Further investigations in this area by installing and operating temporary seismic networks and enhancing permanent facilities are encouraged.

    Keywords: Tectonic Stress, Focal mechanism, Earthquake, World Stress Map, Makran