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مهندسی عمران مدرس - سال هجدهم شماره 2 (خرداد و تیر 1397)

نشریه مهندسی عمران مدرس
سال هجدهم شماره 2 (خرداد و تیر 1397)

  • تاریخ انتشار: 1397/04/25
  • تعداد عناوین: 22
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  • امیررضا ممدوحی *، فاطمه احمدی پور صفحات 1-12
    ایجاد سفر اولین مرحله از رویکرد چهار مرحله ای کلاسیک است که در آن تعداد سفرهای تولید/ جذب شده به هر ناحیه ترافیکی برآورد می شود. استفاده از مدل رگرسیون خطی در این مرحله بسیار رایج است، هرچند عدم ارائه ی نظریه رفتاری و ماهیت صحیح و غیرمنفی سفرها از محدودیت های این مدل به شمار می رود. جهت رفع این محدودیت ها، مدل های سانسورشده مانند توبیت برای جلوگیری از ایجاد مقادیر منفی، مدل های با داده های شمارشی مانند پواسون و دوجمله ای منفی برای جلوگیری از ایجاد مقادیر پیوسته و منفی و مدل های انتخاب گسسته مانند لوجیت و پروبیت رتبه ای جهت ارائه نظریه رفتاری مسافر و جلوگیری از ایجاد مقادیر پیوسته و منفی پیشنهاد شده است. هدف از این مقاله یک تحلیل ساختاری از مدل های مختلف تولید سفر شامل رگرسیون خطی، توبیت، پواسون و لوجیت رتبه ای و مقایسه ی عملکرد آن ها است. داده های حاصل از پرسشگری نمونه‏ای از ساکنین شهر قزوین، شامل ویژگی های اقتصادی- اجتماعی و سفر تحصیلی 4734 خانوار به عنوان مطالعه موردی انتخاب شده است. جهت پرداخت مدل ها از 85 درصد داده ها و جهت ارزیابی آن ها از مابقی داده ها استفاده می گردد. به منظور مقایسه مدلها از معیارهای کمی میانگین خطای مطلق، رگرسیون خطی برآورد- مشاهده و نمودار مربوط به مقایسه سهم مشاهده و پیش بینی شده همفزون سفرها استفاده می شود. نتایج نشان می دهد از نظر معیار میانگین خطای مطلق، مدل های لوجیت رتبه ای و رگرسیون خطی؛ میزان برازش رگرسیون خطی برآورد- مشاهده، مدل توبیت؛ ضریب تعیین رگرسیون خطی برآورد- مشاهده و مقایسه سهم پیش بینی و مشاهده شده همفزون سفرها، مدل لوجیت رتبه ای دارای عملکرد بهتری نسبت به سایر مدل ها است.
    کلیدواژگان: تولید سفر، رگرسیون خطی، توبیت، پواسون، لوجیت رتبه ای
  • جمشید اسماعیلی *، سید نیرم آهوقلندری صفحات 13-24
    پیش ساختگی رویکردی مفید برای ساخت سازه هایی به تعداد زیاد در مدتی اندک و یا طرح گونه ای خاص از بنا می باشد. سازه های پیش ساخته به دلیل طرح و ساخت گسسته اعضا نسبت به سازه های درجا ماهیت متفاوتی دارند.محدودیت های ساخت و چینش اعضا در این سازه ها به طرح تیرهایی با اتصالاتی ساده و ضعیف انجامیده است. در بسیاری از موارد برای دستیابی به اتصالی مقاوم از لحاظ خمشی نیازمند تراکم آرماتوری بالا برای انتقال لنگر در تیرها و به ویژه ناحیه اتصال آنها هستیم.از طرف دیگر کاربرد بتن درجا در تیر به منظور تامین مقاومت لازم برای آن با رویکرد و هدف پیش ساخته سازی سازه های بتنی در تناقض است. در این مطالعه سعی بر آن است با ارائه تیری پیش ساخته علاوه بر تامین ظرفیت مناسب در برابر تلاش های وارده از ایجاد تراکم آرماتور در تیر و ناحیه اتصال جلوگیری به عمل آورده و قابی بدون تکیه بر بتن ریزی درجا درپای کار ارائه داد. برای این منظور گره میانی یک سازه چهار طبقه دارای سیستم قاب خمشی متوسط در دو سازه پیش ساخته و درجا با استفاده از آنالیز اجزای محدود با هم مقایسه شدند. نتایج نشان می دهد که تیر و اتصال ارائه شده در مقایسه با گره درجای معادل خود عملکرد مطلوبی تحت تلاش های وارده در زمینه مقاومت، جذب انرژی و شکل پذیری نشان می دهد.
    کلیدواژگان: اتصال تیر به ستون، قاب پیش ساخته، آنالیز اجزای محدود، اتصال پیش ساخته، تیر مختلط
  • بابک امیدوار *، صنم مقیمی، سعید کاکایی صفحات 25-35
    یکی از مهم ترین مسائلی که در تصمیم گیری های کلان مطرح است، اولویت بندی و تخصیص بودجه مقاوم سازی لرزه ای شریان های حیاتی است. هنگامی که استراتژی بهینه انتخاب گردد و تخصیص بودجه با اولویت بندی صحیح انجام شود، انتظار می رود که بیشترین کاهش خسارت حاصل گردد. در حالتی که منابع مالی محدود باشد، اولویت بندی مذکور از درجه اهمیت بالاتری برخوردار است. در این تحقیق با استفاده از مدل عدم عملکرد دینامیکی داده-ستانده، استراتژی بهینه مقاوم سازی شریان های حیاتی آب، حمل و نقل، برق، گاز و مخابرات در برابر زلزله از دیدگاه خسارات اقتصادی غیر مستقیم و حساسیت انتخاب شده است. بدین منظور از شاخص های کاهش خسارت اقتصادی نسبت به هزینه استراتژی و کاهش حساسیت نسبت به هزینه استراتژی و همچنین روش پارتو استفاده شده است. نتایج تحقیق نشان می دهد که افزایش 25 درصدی عملکرد لرزه ای شریان ها نسبت به وضعیت موجود استراتژی بهینه مقاوم سازی از دیدگاه اقتصادی است. در این استراتژی شاخص های کاهش خسارت اقتصادی نسبت به هزینه اجرای استراتژی و کاهش حساسیت نسبت به هزینه اجرای استراتژی به ترتیب برابر 3996/0 و 66/3 می باشد. شایان ذکر است که در تمامی محاسبات اندرکنش اقتصادی میان شریان ها مدنظر قرار گرفته شده است.
    کلیدواژگان: شریان های حیاتی، زلزله، مقاوم سازی، مدل داده، ستانده دینامیکی، اولویت بندی استراتژی مقاوم سازی
  • محمد تمنایی *، محمدحسین ولی صفحات 37-48
    یکی از راهکارهای مناسب جهت رفع گلوگاه های ظرفیتی شبکه ریلی، برقی سازی است. با این حال، برقی سازی یک محور به صورت مجزا و بدون فراهم نمودن ظرفیت کافی و زیرساخت های لازم در نقاط مختلف شبکه، ممکن است نتواند جذب تقاضای ریلی شبکه را به نحو قابل قبول افزایش دهد. در این صورت، پروژه برقی سازی از نظر اقتصادی توجیه پذیر نخواهد بود. هدف از پژوهش حاضر، ارائه الگوریتمی است که مشخص نماید اصلاحات ظرفیتی در کدام نقاط شبکه ریلی بایستی انجام شود تا برقی-سازی یک محور ریلی از نظر اقتصادی توجیه پذیر باشد. محور ریلی مورد نظر در این پژوهش جهت برقی سازی، محور ریلی ناحیه شمال ایران است. این محور، دارای پتانسیل بالا در جذب بار ریلی می باشد. در این پژوهش، سناریوهای مختلفی در نظر گرفته شده اند و میزان افزایش جذب بار ریلی شبکه و نیز تحلیل اقتصادی هزینه-فایده، به عنوان مهمترین معیارهای مقایسه سناریوها لحاظ شده اند. نتایج حاکی است که برقی سازی محور ریلی مذکور، به تنهایی و بدون رفع گلوگاه های ظرفیتی موجود در سایر نواحی شبکه، از نظر اقتصادی توجیه پذیر نیست و قادر به جذب بار ریلی قابل توجهی نمی باشد. در حالی که با رفع برخی گلوگاه های شبکه همزمان با برقی سازی این محور ریلی می توان میزان جذب بار ناحیه شمال را تا حدود 4 میلیون تن افزایش داد. الگوریتم پیشنهادی در پژوهش حاضر، می تواند در تصمیم گیری پیرامون بایسته های اثربخشی پروژه های برقی سازی محورها، مورد استفاده کارشناسان و مدیران راه آهن قرار گیرد.
    کلیدواژگان: شبکه ریلی، برقی سازی، گلوگاه های ظرفیتی، تقاضای بار، تخصیص
  • حسن امینی راد *، عطیه جبلی صفحات 49-59
    شیرابه ی تولید شده در لندفیل بدلیل ساختار پیچیده و آلودگی بالا نیازمند روش های تصفیه ی فیزیکی و شیمیایی و بیولوژیکی پیشرفته ای می باشد.یکی از روش های تصفیه ی شیرابه که اخیرا بسیار مورد توجه قرار گرفته است ، تصفیه ی شیرابه توسط گرانولهای هوازی در راکتور SBAR می باشد.در این آزمایش ساخت گرانولها و تصفیه ی شیرابه در دو فاز مجزا انجام شده است: ساخت گرانول در راکتور SBAR به مدت 28 روز با افزایش بارگذاری تا 6000 میلی گرم در لیتر و تصفیه شیرابه در همین راکتور به مدت 24 روز تا بارگذاری 6000 میلی گرم در لیتر انجام شده است.باتوجه به تغییر فاضلاب ورودی و جایگزینی شیرابه بجای فاضلاب مصنوعی ، در برخی گرانول ها فروپاشی اتفاق افتاده است.نتایج نشان می دهد بعد از خو گرفتن گرانولها به شیرابه ورودی به راکتور ، افزایش فعالیت باکتریایی منجر به بهبود راندمان تصفیه شیرابه در سیستم شده و راندمان حذف COD در راکتور به 90% رسیده است.
    کلیدواژگان: گرانول های هوازی، فاضلاب مصنوعی، تصفیه ی شیرابه، حذف COD
  • کمیل خاکپور *، علی کمک پناه صفحات 61-73
    در اغلب اوقات آزمایش بارگذاری شمع در فاصله زمانی کوتاه پس از اجرای آن انجام می شود. نتایج حاصله بعنوان ظرفیت باربری نهایی شمع در طراحی لحاظ می شود. کوبش شمع سبب تغییر شکل زیاد خاک اطراف شمع و بوجود آمدن اضافه فشار آب حفره ای در پیرامون آن می شود این امر سبب کاهش مقاومت برشی و ظرفیت باربری شمع می گردد. آزمایش استاتیک و دینامیک شمع بیانگر ظرفیت باربری شمع در زمان آزمایش می باشد برای بررسی تاثیر گیرش در ظرفیت باربری شمع، آزمایش ها باید در زمان های مختلف انجام شود که این امر زمان بر و غیراقتصادی می باشد. بنابراین باید راه حل های عددی و تجربی توسعه یابد تا بتوان با توجه به تعداد محدودی آزمایش های استاتیکی و دینامیکی تاثیر زمان در ظرفیت باربری شمع را بررسی کرد. محاسبه ظرفیت باربری شمع با زمان سبب کاهش قطر، طول و تعداد شمع و کاهش اندازه تجهیزات کوبش می شود که این موضوع از دیدگاه اقتصادی قابل توجه است. هدف از این تحقیق بررسی ظرفیت باربری شمع های کوبشی در خاک رسی نرم در زمان های مختلف پس از کوبش می باشد. آزمایش ها برای ارزیابی افزایش ظرفیت بابری شمع کوبشی در خاک رس نرم شمال ایران در نظر گرفته شده است. چندین آزمایش بارگذاری بر روی شمع های آلومینیومی کوبشی در خاک زسی نرم انجام شد. نتایج نشان می دهد 14روز پس از کوبش، ظرفیت باربری شمع نسب به زمان پایان کوبش تقریبا 80% افزایش داشته است. بخش عمده از افزایش ظزفیت باربری در سه روز پس از کوبش می باشد و پس از آن نرخ افزایش ظرفیت باربری شمع کاهش می یابد.
    کلیدواژگان: شمع کوبشی، گیرش خاک، مدلسازی فیزیکی
  • فاطمه خسروی، صلاح الدین حمیدی، سید مهدی حسینی *، سید مرتضی مرندی صفحات 75-87
    آلاینده های فلز سنگین علاوه بر ایجاد مشکلات ژئوتکنیکی، می تواند سبب به خطر انداختن سلامت محیط زیست و انسان شود. با افزایش جمعیت، پیشرفت تکنولوژی و به تبع آن افزایش آلاینده های فلز سنگین و نیز قرارگرفتن یک چهارم سطح زمین در مناطق سردسیر و لزوم طراحی و احداث بنا بر روی این خاک ها، مطالعه ی تاثیر ذوب و یخبندان بر روی خاک های رسی تثبیت شده در معرض ذوب و یخبندان ضروری به نظر می رسد. برای تثبیت و جامدسازی خاک های آلوده افزودنی های مختلفی به کار رفته است که در این میان سیمان بواسطه سازگار بودن با مواد آلاینده و کارایی زیاد، دسترسی آسان و ارزان بودن مصالح، کاربردی تر می باشد. در پژوهش حاضر از سیمان برای تثبیت خاک آلوده به آلاینده فلز سنگین سرب در سیکل های مختلف ذوب و یخبندان استفاده شد. با توجه به اهمیت نشست در خاک های رسی بر روی نمونه های مورد آزمایش، آزمایش تحکیم انجام شد. همچنین با توجه به کاربرد فراوان بنتونیت در سایت های آلوده از نمونه ی رسی بنتونیت برای انجام مطالعات آزمایشگاهی استفاده شد. نتایج مطالعات انجام شده نشان می دهد که در اغلب مواقع سیکل بحرانی سیکل 7 می باشد. همچنین تثبیت با سیمان در شرایط مختلف پارامترهای مقاومتی از جمله تنش پیش تحکیمی خاک را 2 تا 8 برابر بهبود می بخشد. علاوه بر آن مقدار بهینه سیمان در نمونه های آلوده و غیرآلوده در سیکل های مختلف ذوب و یخبندان متغیر بوده، اما در اغلب نمونه ها حدود 5% تا 10% بوده است. در ادامه، بررسی بازدهی تثبیت و مطالعه تشکیل ترکیبات هیدراته سیمان و خاک رس با استفاده از آزمایش شیمیایی pH انجام شد.
    کلیدواژگان: خاک آلوده، سیمان، سیکل های ذوب و یخبندان، بنتونیت، تحکیم
  • مهرداد رزاقیان قادیکلایی، اصغر حبیب نژاد کورایم *، مهیار غرقی، علیرضا شریف صفحات 89-100
    در دهه های اخیر مطالعات زیادی در زمینه تاثیر نانو ذرات رس بر خصوصیات کامپوزیت های سیمانی انجام شده است. بااین وجود، برخلاف خواص مطلوب نانوذرات هالوسیت از جمله سطح ویژه بالا، خاصیت پوزولانی، نسبت طول به قطر قابل ملاحظه که می تواند تاثیر قابل ملاحظه ای بر دوام بتن داشته باشد تحقیقات اندکی در رابطه با تاثیر این نانوذرات به عنوان زیر شاخه ای از نانو ذرات رس بر خصوصیات کامپوزیت های سیمانی انجام شده است. لذا در این تحقیق تاثیر نانو ذرات هالوسیت بر عملکرد ملات سیمانی ارزیابی شده و کارایی و نفوذپذیری نمونه های ملات حاوی 3 درصد نانولوله هالوسیت مورد بررسی قرارگرفته است. نتایج این پژوهش حاکی از افزایش 28 درصدی مقاومت الکتریکی، کاهش تقریبی 26 درصد نرخ جذب آب، کاهش حدودی 23 درصد در نرخ دفع آب و همچنین کاهش کارایی و افزایش سرعت هیدراتاسیون ملات حاوی 3 درصد نانولوله هالوسیت در مقایسه با نمونه ملات شاهد بوده است. این نتایج بیانگر آن است که نانو لوله هالوسیت می تواند به عنوان یک نانو ذره مناسب برای بهبود خواص بتن مورداستفاده قرار گیرد. نتایج این تحقیق می تواند به کاربرد نانوذرات در ماتریس های سیمانی کمک نموده و زمینه استفاده از سیمان های کاراتر را فراهم نماید.
    کلیدواژگان: نانولوله هالوسیت، کارایی، نفوذپذیری، ملات
  • محمد هادی رضایی، ناصر خاجی * صفحات 101-112
    هم زمان با پیشرفت نیاز جوامع به سازه های پیچیده تر، نیاز به شناخت بیشتر بارهای وارده برسازه به ویژه بارهای لرزه ای نیز گسترش می یابد. داشتن تخمینی قابل اطمینان از حرکات قوی زمین در یک ساختگاه مشخص، بدون داشتن شناخت صحیح از مکانیزم تولید امواج لرزه ای، عوامل ساختاری اثرگذار بر این امواج در مسیر انتشار، و شناخت شرایط فیزیکی محل ساخته شدن سازه ها میسر نخواهد بود. در این میان، مدل موانع ویژه که از مشهورترین روش های سینماتیکی شبیه سازی گسل زلزله می باشد، گسل را به عنوان مجموعه از ترک های دایره ای در نظر می گیرد. گسیختگی به صورت افت تنش های موضعی در این ترک ها فرض می شود، و توقف و شروع های مکرر گسیختگی، عامل اصلی تولید امواج فرکانس بالا در این مدل است. در این مطالعه سعی شده است با استفاده از مدل موانع ویژه به شبیه سازی چشمه گسل مولد زلزله لاکوئیلا در کشور ایتالیا اقدام شود، همچنین در سوی دیگر با استفاده از روابط کاهندگی مناسب منطقه تاثیرات مسیر انتشار امواج در مدل سازی لحاظ شود. در انتها نیز به کمک ضرب توابع انتقال لایه های سطحی خاک تاثیرات ساختگاه بر نتایج اعمال گشته و نتایج را قابل مقایسه با نتایج به دست آمده از زلزله مذکور ساخته است.
    کلیدواژگان: روش های سینماتیکی، مدل سازی گسل، مدل موانع ویژه، طیف چشمه زلزله، زلزله لاکوئیلا
  • مجتبی شابدین، نادر خواجه احمد عطاری *، مژده زرگران صفحات 113-126
    هدف از تحقیق حاضر بررسی رفتار دیوارهای بنایی غیرمسلح استفاده شده در ساختمان های بنایی موجود در کشور به عنوان عضو اصلی باربر جانبی، می باشد. در حالت کلی دیوارهای موجود در ساختمان های بنایی کشور دارای مشخصات مصالح متفاوت می باشند. ارزیابی رفتار دیوارهای ساخته شده با کیفیت مصالح متفاوت به منظور انتخاب مناسب ترین راهکار مقاوم سازی، حائز اهمیت می باشد. برای این منظور یک مطالعه آزمایشگاهی بر روی 2 نمونه با مقیاس واقعی انجام پذیرفت. تغییر در مشخصات ملات مورد استفاده برای آجرچینی دیوار به عنوان مشخصه اصلی تحقیق درنظر گرفته شده است. برای ساخت نمونه ها از آجرها و سیستم آجرچینی مشابه اما مشخصات ملات های متفاوت استفاده شده است. براساس نتایج آزمایشات، استفاده از ملات با کیفیت مناسب تر، در کنار افزایش 20 درصدی در مقاومت، ظرفیت تغییرشکل نمونه را در حدود 70 درصد افزایش داد که این موضوع به خصوص در مناطق لرزه خیز بسیار مطلوب می باشد. همچنین کیفیت مناسب تر ملات موجب افزایش قابل توجه در جذب انرژی گردید.
    کلیدواژگان: دیوار بنایی غیرمسلح، آزمایش رفت و برگشتی، مود شکست، مشخصات ملات، ساختمان مدارس
  • داریوش شریفی اسدی، علیرضا اردکانی *، قاسمعلی گروسی صفحات 127-138
    یکی از روش های متداول بهسازی خاک، استفاده از افزودنی ها به منظور بهبود خصوصیات مقاومتی و نفوذپذیری خاک است. اغلب از سیمان یا مواد شیمیایی به عنوان عامل چسبنده ذرات خاک استفاده می شود که باعث افزایش مقاومت برشی خاک و کاهش هدایت هیدرولیکی آن می شود. در این پژوهش با استفاده از آخرین فناوری زیستی میکروبی، نوع جدیدی از مصالح ساختمانی، یعنی سیمان زیستی، به عنوان جایگزینی برای سیمان و یا مواد شیمیایی ایجاد شده است. سمنتاسیون زیستی یا فرآیند رسوب میکروبی کربنات کلسیم (MICP)، بهبود مقاومت و سختی خاک و سنگ با استفاده از فعالیت های میکروبی و فرآورده های آن هاست. در این پژوهش از خاک ماسه ای با درصد متفاوت سیلت %0، %5،%10، %15 و %20 و در دو حالت سست (Dr=40%) و متراکم (Dr=100%) و از باکتری Sporosarcina Pasteurii به دلیل فعالیت اوره آزی بالا و غیر بیماری زا بودن در فرآیند MICP استفاده شد. به منظور در نظر گرفتن شرایط خاک بر عملکرد این نوع روش بهسازی، پارامترهای آزمایش تک محوری و میزان رسوب کربنات کلسیم موردبررسی قرار گرفت. با توجه به نتایج، افزایش درصد ریزدانه از 0 تا 20 درصد منجر به کاهش %40 و %46 در میزان رسوب کربنات کلسیم، افزایش %57 و %41 در مقاومت تک محوری و افزایش %79 و %71 در مدول الاستیسیته نمونه ها به ترتیب در دو حالت سست و متراکم گردید. بنظر می رسد این تغییرات ناشی از کم شدن فضای خالی و افزایش سطح تماس بین ذرات خاک بوده است.
    کلیدواژگان: بهسازی زیستی، رسوب میکروبی کربنات کلسیم، مقاومت تک محوری، خاک ماسه ای، سیلت غیرخمیری
  • عیسی شوش پاشا *، آریا شریفی صفحات 139-148
    یکی از کاربردهای مهم پی های عمیق و به خصوص شمع ها تحمل بارهای کششی اعمال شده بر سازه است. ظرفیت کششی در این پی ها غالبا از طریق اصطکاک سطح تماس آنها با خاک ایجاد می شود. تعیین ظرفیت کششی شمع های لوله ای فولادی که با تکنیک جک زنی در ماسه های نواحی ساحلی نصب می شوند از جمله مواردی است که روش-های مذکور تا کنون به طور جدی به آن نپرداخته اند و اطلاعات کافی برای طرح این نوع از شمع ها در اختیار نمی گذارند. با توجه به اینکه تکنیک جک زنی در راستای دست یابی بهتر به مقاومت خاک و رفع نقایص در سایر روش های نصب، پیشنهاد شده است، لذا بررسی اثر آن در رفتار شمع ضروری است. در این روش، پس از نصب شمع ها با استفاده از جک های هیدرولیکی، مطابق استاندارد، ظرفیت کششی آنها تعیین می شود (ASTM D-3689). پس از ثبت نتایج، با استفاده از معیارهای تعیین ظرفیت کششی، ظرفیت نهایی کششی شمع ها تعیین و سپس با ظرفیت کششی تحلیلی مورد مقایسه قرار گرفت. نتایج ضمن آشکار ساختن تکرارپذیری آزمایشات انجام شده، نشان دادند که ظرفیت کششی بدست آمده بزرگتر از ظرفیت کششی تحلیلی می باشد و جابجایی خاک و تراکم آن در اثر نصب شمع می تواند مقاومت اصطکاک جداره را افزایش دهد. همچنین مشاهده شد که در اکثر شمع ها معیار خطوط مماسی تعیین کننده ی ظرفیت کششی نهایی می باشد.
    کلیدواژگان: آزمایش کشش، جک زنی، ظرفیت کششی نهایی، شمع لوله ای، ماسه ساحلی
  • طاهره صالحی شهرابی *، وحید صابری، مسعود احمدوند، حمید صابری صفحات 149-158
    طبقه نرم بیشتر در طبقه ی همکف به دلیل فضای باز برای احداث مغازه، پارکینگ و یا حتی در مدارس به وجود می آید. در این مقاله به بررسی اثر زلزله های نزدیک و دور از گسل بر روی دو مجموعه قاب خمشی فولادی میان مرتبه و کوتاه مرتبه پرداخته شده است. در هر دو مجموعه، یک قاب منظم با ارتفاع طبقات 3.2 متر و دو قاب نامنظم با طبقه نرم همکف به ارتفاع 4.5 و 5.5 متر ارزیابی شده است. در تحلیل IDA پارامتر شدت IM متناظر با ماکزیمم نسبت دریفت بین طبقه ای و پارامتر پاسخ DM متناظر با شتاب طیفی مود اول لحاظ گردید و سطح عملکرد جلوگیری از فروپاشی CP مورد بررسی قرار گرفت. نتایج حاصله از منحنی های شکنندگی در حالت حدی (CP) برای سازه های میان مرتبه بیانگر این مطلب است که با افزایش ارتفاع طبقه نرم و متعاقبا نرمتر شدن آن، احتمال خرابی ده درصد سازه در رکوردهای نزدیک نسبت به دور از گسل کاهش بیشتری داشت. لیکن در سازه های کوتاه مرتبه در رکوردهای دور از گسل کاهش بیشتری خواهد داشت
    کلیدواژگان: سازه نامنظم، طبقه نرم، منحنی شکنندگی، نزدیک و دور از گسل، قاب خمشی ویژه فولادی
  • امیر طریقت *، یاقوت مدرس، میلاد محمدی صفحات 159-168
    حمله سولفاتی مجموعه ای از واکنش های شیمیایی و فیزیکی است که بین خمیر سیمان سخت شده و یون های سولفات رخ می دهد. نفوذ یون های سولفات به داخل مواد سیمانی منجر به تشکیل فازهایی همچون گچ و اترینگایت می شود که انبساط و خرابی بتن را به دنبال دارند. در این تحقیق از شبیه سازی ترمودینامیکی بر اساس روش به حداقل رساندن انرژی آزاد گیبس، برای درک بهتر حمله سولفات خارجی و رفتار خمیر سیمان سخت شده در نمونه های ساخته شده از سیمان پرتلند معمولی و سیمان های آمیخته با خاکستر پوسته برنج، استفاده شده است. با کمک این روش علاوه بر بررسی غلظت محلول منفذی و نوع و حجم فازهای تشکیل شده طی حمله سولفاتی، عوامل دیگری ازجمله تاثیر خاکستر پوسته برنج، درصد بهینه جایگزینی آن و غلظت های مختلف محلول سولفات سدیم موردمطالعه قرارگرفته اند. شبیه سازی خمیر سیمان سخت شده در محلول سولفات سدیم با غلظت های 4 و 44 گرم بر لیتر انجام شده و جایگزینی 10 و 15 درصد خاکستر پوسته برنج در نظر گرفته شده است. نتایج ارائه شده به وضوح نشان می دهد که غلظت محلول سولفاتی در نوع و حجم فازهای تشکیل شده، به ویژه گچ و اترینگایت، تاثیرگذار است؛ در غلظت های پایین، 4 گرم بر لیتر، تشکیل گچ مشاهده نشده است. خاکستر پوسته برنج در 15 درصد جایگزینی، آب آهک را به طور کامل مصرف و بیشترین حجم ژل سیلیکاتی را تولید می کند و از این درصد به بالا دیگر تاثیر قابل توجهی در ژل سیلیکاتی که عمده مقاومت خمیر سیمان را تامین می-کند، ندارد. به طور کلی نتایج شبیه سازی با مطالعات و نتایج آزمایشگاهی که ریزساختار را بررسی نموده اند، تطابق خوبی دارد.
    کلیدواژگان: حمله سولفاتی، شبیه سازی، ترمودینامیک، سیمان پرتلند، خاکستر پوسته برنج
  • هاجر قاسمیان گرجی، بهناز دهرآزما * صفحات 169-178
    مقدار قابل توجهی پساب آلوده به مشتقات نفتی توسط پالایشگاه های نفت تولید می شود که مستلزم تصفیه قبل از ورود به محیط زیست می باشد. در این تحقیق حذف بخش محلول گازوئیل از محیط آبی با استفاده از جاذب گل قرمز پودری مورد بررسی قرار گرفت. میزان حذف مشتقات نفتی حاصل از انحلال گازوئیل در آب با اندازه گیری میزان COD در بخش گازوئیل حل شده در آب قبل و پس از استفاده از جاذب اندازه گیری و محاسبه گردید. تاثیر فاکتورهای مختلف شامل pH، زمان تماس، دوز جاذب و غلظت اولیه آلاینده بر فرایند جذب و مقدار پارامتر COD محلول مطالعه گردید. بیشینه کاهش در COD محلول در بهترین نتایج در حالات بررسی شده، pH معادل 7، زمان تماس 15 دقیقه، دوز جاذب 10 گرم بر لیتر و غلظت اولیه آلاینده 1%، برابر 100% محاسبه گردید. نتایج به دست آمده از فرآیند جذب بیش ترین انطباق را با مدل ایزوترم لانگمویر و سینتیک شبه مرتبه دوم به ترتیب با ضرایب همبستگی 98/0 و 99/0 داشته است. با توجه به نتایج حاصل از آزمایشات، جاذب مورد استفاده در این تحقیق، دارای بازده مناسب جهت کاهش COD ناشی از انحلال هیدرو کربن های گازوئیل در آب می باشد.
    کلیدواژگان: جذب، گازوئیل، گل قرمز، محلول آبی
  • مرتضی قالیشویان، احمد شوشتری *، ماهر عبدالغنی صفحات 183-193
    شناسایی پارامترهای مدال سازه ها اهمیت فراوانی را در بسیاری از حوزه های مهندسی عمران و مکانیک داراست. امروزه روش های شناسایی مبتنی بر پاسخ سازه محبوبیت روز افزونی یافته است. در این روش ها، که اصطلاحا آنالیز مدال عملیاتی نام دارند، پارامترهای دینامیکی سازه (فرکانس های طبیعی، شکل های مدی و نسبت های میرایی) تنها با در دست داشتن پاسخ خروجی سازه قابل تخمین است. در این خصوص، با فرض آنکه نیروی ورودی به سازه دارای ماهیتی تصادفی و پهن باند باشد، نیازی به اندازه گیری نیروی ورودی وجود ندارد. یکی از توانمندترین روش های آنالیز مدال عملکردی در حوزه ی فرکانس، روش تجزیه ی حوزه ی فرکانسی بهبودیافته نام دارد. فرآیند شناسایی در این روش بر مبنای تجزیه ی مقادیر تکین ماتریس چگالی طیف توان پاسخ سازه قرار دارد. علی رغم توانمندی بالا، این روش در تخمین میرایی سازه ها عملکرد چندان قابل قبولی ندارد. در این مقاله ابتدا روش تجزیه ی حوزه ی فرکانسی بهبودیافته تشریح و ویژگی های آن، به ویژه در حوزه ی تخمین میرایی، مورد بررسی قرار میگیرد. سپس، به منظور بهبود عملکرد آن در تخمین میرایی، استفاده از راه کار تخصیص مدال عملکردی پیشنهاد میشود. ایده ی اصلی روش پیشنهادی بر آن اساس استوار است که تابع خودهمبستگی پاسخ خروجی یک سیستم ارتعاشی تحت اثر نویز سفید، با تابع پاسخ ضربه آن سیستم و البته با یک اختلاف فاز مشخص برابر می باشد. با استفاده از 70 مرتبه شبیه سازی یک سازه ی چهارطبقه ی برشی، توانمندی تخمین میرایی روش پیشنهادی در کنار راهکار تجزیه ی حوزه-ی فرکانسی ارزیابی و نتایج با یکدیگر مقایسه می گردد. نتایج حاصل شده، کاهش قابل توجه خطای نسبی و واریانس تخمین میرایی را نشان می دهد.
    کلیدواژگان: تخمین میرایی بر مبنای فقط، خروجی، روش تجزیه ی حوزه ی فرکانسی بهبودیافته، روش تخصیص مدال عملکردی
  • حسین عاشق، علی اکبر شیرزادی جاوید *، پرویز قدوسی، اصغر حبیب نژاد کورایم، محمدعلی اورعی صفحات 193-202
    بطور کلی وظیفه حفاظت سطحی در بتن جلوگیری از آسیب های ناشی از عوامل مهاجم از جمله جلوگیری یا تاخیر در خوردگی آرماتور یا ایجاد حفاظت در برابر نفوذ یون می باشد. در این تحقیق عملکرد سه ماده حفاظت سطحی بتن بر روی دو نوع بتن خودتراکم با نسبتهای آب به سیمان متفاوت و یک نوع بتن معمولی، مورد ارزیابی قرار گرفت. آزمایش های نفوذپذیری بخار آب، اختلاف پتانسیل نیم پیل، شدت خوردگی و زاویه تماس آب و تصاویر SEM برای ارزیابی عملکرد این مواد انجام شد. نتایج نشان داد که استفاده از مواد حفاظت سطحی تاثیر بسزایی در کاهش نفوذپذیری، اختلاف پتانسیل نیم پیل و شدت خوردگی و در مجموع افزایش دوام بتن خواهد داشت به طوری که نمونه های حفاظت شده به غیر از یک مورد تا هفته 49 وارد فاز فعال خوردگی نشدند. افزایش نسبت آب به سیمان بتن پایه موجب تضعیف عملکرد مواد حفاظت سطحی خواهد شد. همچنین نتایج گویای این مطلب بوده است که مواد حفاظتی که اجازه تبخیر آب محبوس را به اندازه کافی نمی دهند نسبت به موادی که اجازه عبور بخارآب می دهند تاثیر کمتری در کاهش خوردگی دارند. نمونه حفاظت شده با سیلان- سیلوکسان و نمونه حفاظت شده با اپوکسی به ترتیب 92% و 35% نسبت به بتن شاهد اجازه عبور بخار آب را می دهند و نمونه EP-SCC2 در همان هفته های ابتدایی وارد فاز فعال خوردگی شده است و اختلاف پتانسیل بیش از 270- نشان داده است.
    کلیدواژگان: حفاظت سطحی بتن، دوام بتن، خوردگی بتن، تنفس بتن
  • بنیامین گنجه خسروی *، سید حسین قاسم زاده موسوی نژاد، جواد رزاقی لنگرودی صفحات 203-212
    در این مطالعه آزمایش نیمه مخرب break-off برای ارزیابی مقاومت بتن حاوی الیاف فولادی در محل مورد بررسی قرار گرفته است. بتن حاوی الیاف فولادی بدلیل مزایای آن در افزایش چقرمگی و مقاومت بتن بویژه کششی و خمشی، در این مطالعه انتخاب شده است. به منظور فراهم کردن یک پایگاه آماری کامل و جامع، 24 طرح اختلاط با مقادیر مختلف عیار سیمان 400، 450 و 500 کیلوگرم بر متر مکعب با نسبت آب به سیمان ثابت 0/4، حداکثر اندازه سنگدانه 12/5 و 25 میلیمتر و الیاف فولادی با نسبت های حجمی 0، 0/33، 0/67 و 1 درصد در سنین مختلف 14، 28 و 90 روز انتخاب گردید. سپس، عوامل تاثیرگذار بر خصوصیات بتن حاوی الیاف فولادی و همچنین نتایج آزمایش Break-off مورد ارزیابی قرار گرفت. بررسی ها نشان می دهد علاوه بر مشخصات آزمایش، درصد و مشخصات الیاف فولادی تاثیر بسزایی بر خواص بتن و نتایج آزمایش Break-off دارد. نتایج حاکی از آن است که ارزیابی مقاومت با روش فوق دارای قابلیت اعتماد مناسب می باشد، هر چند تخمین مقاومت بتن براساس یک منحنی کالیبراسیون کلی ممکن نیست. از اینرو منحنی های کالیبراسیون مستقل برای هر بتن با درصدهای متفاوت الیاف به منظور تفسیر واقع گرایانه نتایج ارائه گردیده است.
    کلیدواژگان: آزمایش break، off، مقاومت بتن، الیاف فولادی، آزمایش نیمه مخرب
  • موسی محمودی صاحبی *، علیرضا شیرپور، آرش زارع زاده مهریزی صفحات 213-222
    سازه ها در برابر زلزله های شدید به دلیل تغییر شکل های بزرگ در معرض آسیب های شدید قرار می گیرند. استفاده از مهاربند ضربدری نقش تعیین کننده ای در پایداری سازه ها در مقابل بارهای جانبی ناشی از زلزله و باد دارد. بدیهی است اتصالات در ایفای نقش فوق بسیار حائز اهمیت هستند. هدف این مقاله ارزیابی عملکرد لرزه ای اتصالات فلنجی و همچنین پانل برشی شکل پذیر به عنوان اتصالات میانی در مهاربندهای ضربدری است. برای این منظور با تحلیل عددی در محیط نرم افزار Abaqus، رفتار کمانشی، پس کمانشی و غیرخطی مهاربندهای ضربدری با اتصالات فوق مورد بررسی قرار گرفت و با نتایج حاصل از اتصالات رایج مقایسه شد. نتایج نشان می دهد استفاده از پانل برشی شکل پذیر جاری شونده در اتصال میانی باعث اتلاف انرژی بیشتر توسط مهاربند ضربدری و عدم کمانش اعضای مهاربندی می شود، همچنین استفاده از مهاربند ضربدری با اتصال میانی فلنجی باعث هماهنگی کمانش اعضای مهاربندی و به تبعیت از آن باعث بهبود عملکرد فشاری مهاربند ضربدری می شود.
    کلیدواژگان: مهاربند ضربدری، ضریب طول موثر، کمانش و پس کمانش، اتصال فلنجی، پانل برشی شکل پذیر
  • فرزاد ملک احمدی، محمدصادق بیرژندی * صفحات 223-232
    روش ضرایب بار و مقاومت (حالت حدی) که چند سالی است در مبحث نهم مقررات ملی ساختمان (آیین نامه طراحی سازه های فولادی) به عنوان روش اصلی شناخته می شود، با ویرایش چهارم آیین نامه 2800 به لحاظ ماهیت هماهنگ است. هدف از این پژوهش، ارزیابی احتمالاتی ضوابط قاب های خمشی فولادی با شکل پذیری متوسط و ویژه، طراحی شده به روش حالت حدی آیین نامه ایران (مبحث دهم) و مقایسه آن با قاب های طراحی شده به روش تنش مجاز در مناطق حوزه نزدیک به گسل با استفاده از تحلیل دینامیکی افزاینده (IDA) و منحنی های شکنندگی است. از بهترین و جدیدترین روش های ارزیابی عملکرد لرزه ای ساختمان ها، استفاده از تحلیل دینامیکی افزاینده (IDA) و استخراج منحنی های شکنندگی است که رفتار جامعی از سازه را در محدوده خطی تا غیرخطی نمایش می دهد. نتایج حاصل از تحلیل ها حاکی از این است که سازه های طراحی شده به روش حدی در ناحیه خطی دارای شیب بیشتری هستند که نشان دهنده رفتار سخت و تردتر آن ها می باشد. مقایسه مقادیر میانه توابع شکنندگی سازه های طراحی شده به دو روش نشان می دهد که در همه سازه ها در هیچ یک از سطوح عملکرد، روش حالت حدی وضعیت بهتری ندارد. به طور خلاصه، روش تنش مجاز منجر به افزایش (بهبود) میانه تابع شکنندگی تا 11% برای سازه های مختلف در سطوح عملکرد مختلف شده است.
    کلیدواژگان: تحلیل دینامیکی افزاینده (IDA)، منحنی های شکنندگی، طراحی به روش حالت حدی، قاب خمشی فولادی، زلزله نزدیک به گسل
  • امین منشی زاده نایین، سید احسان سیدیحسینی نیا * صفحات 233-244
    چکیده- خطوط لوله مدفون به واسطه طول زیاد خود ناگزیر از عبور از گسل هایی هستند که حرکات بزرگ آن ها می تواند باعث بروز شکست و گسیختگی در لوله های مدفون شود. این حرکات بزرگ ممکن است در یک زمین لرزه رخ دهد و یا اینکه بر اثر حرکت خزنده گسل که در طول عمر بهره برداری خط لوله اتفاق می افتد، بوجود آید. بنابراین ضروری است رفتار لوله های مدفون در برابر حرکات گسل مورد مطالعه قرار گیرد. در ادبیات فنی موجود، تمرکز بیشتر بر مطالعه رفتار خطوط لوله در گذر از گسل های نرمال و امتداد لغز بوده است. در مطالعه حاضر، رفتار لوله های مدفون گذرنده از گسل معکوس با کمک نرم افزار آباکوس مطالعه شده است. ابتدا نحوه و روند شبیه سازی های انجام شده با نتایج آزمایشگاهی و عددی دیگر مقایسه شده است که نشان از صحت نتایج دارد. سپس مطالعه حساسیت بر روی تاثیر نوع خاک و پارامتر های ژئوتکنیکی آن و همچنین اثر نسبت عمق دفن به قطر لوله انجام گرفته است. مطالعات عددی انجام شده نشان می دهد که کرنش های فشاری علت اصلی وقوع گسیختگی لوله ها در گسلش معکوس هستند و استفاده از خاک های نرم و با تراکم کم و هم چنین کاهش عمق دفن لوله سبب کاهش مقادیر کرنش های فشاری و کششی ایجاد شده در لوله می شوند. این در حالی است که تغییر مدول الاستیسیته خاک تاثیر چندانی بر مقادیر کرنش های ایجاد شده در لوله ندارد. همچنین، افزایش زاویه اتساع خاک در جابه جایی های بزرگ گسل سبب افزایش مقادیر کرنش های ایجاد شده در لوله می شود.
    کلیدواژگان: لوله مدفون، گسل معکوس، مدل عددی، نرم افزار ABAQUS، اندرکنش خاک و لوله
  • محمد واقفی *، ندا صفری پور، الهام زارعی، امین محمودی، سید شاکر هاشمی صفحات 245-255
    در این مقاله کاربرد صفحات مستغرق و تاثیر آن بر تغییرات توپوگرافی بستر قوس علی الخصوص اطراف پایه ی پل مورد بررسی قرار گرفته است. برای انجام آزمایش ها از یک پایه ی استوانه ایی از جنس PVCبه قطر5 سانتی متر مستقر در یک فلوم آزمایشگاهی با قوس 180 درجه ی تند با انحنای نسبی2 با ارتفاع 90 سانتی متر و عرض 100 سانتی متر استفاده گردید. طول مسیر مستقیم بالادست قوس 5/6 متر و طول مسیر مستقیم پایین دست 1/5 متر می باشد. در شرایط آب زلال با 97/0u_*/u_(*c) = آزمایشات انجام شد. جهت مدلسازی صفحات مستغرق از صفحاتی از جنس پلکسی گلاس با آرایش های مختلف با ضخامت معادل 20 درصد قطر پایه و طولی برابر 5/1 برابر قطر پایه با استغراق 75 درصد استفاده گردید. موقعیت قرارگیری مرکز صفحات به فاصله ی 7 برابر قطر پایه ازمرکز آن می باشد. آزمایشات برای صفحات مستغرق موازی با همپوشانی متفاوت به سمت ساحل داخلی و خارجی انجام گرفت. نتایج حاصله نشان می دهد که صفحاتی که به صورت موازی، با هم پوشانی 50 درصد و با زاویه ی 25 درجه پادساعتگرد با افق در جهت جریان، بهترین عملکرد در کنترل آبشستگی پایه پل داشته اند.
    کلیدواژگان: آبشستگی، پایه پل، صفحات مستغرق، آرایش صفحات، قوس 180 درجه
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  • Amir Reza Mamdoohi *, Fatemeh Ahmadipour Pages 1-12
    Trip generation is the first stage of the conventional four-step travel forecasting framework that estimates the number of trips to and from a traffic analysis zone. Using linear regression model is common in this step and generates an acceptable level of performance from the perspective of transport planning, however this model does not incorporate traveler behavior, integer and non-negative nature of trips. To overcome these limitation, several models have been suggested: censored model such as Tobit for deleting negative values; count data models such as negative binomial and Poisson for deleting continuous and negative values; and discrete choice models such as ordered logit and probit for incorporating traveler behavior and preventing continuous and negative values. Given the importance of trip generation stage and lack of sufficient and quantitive attention to various trip production models, this paper develops alternative trip production models. The purpose of this paper is a structural analysis for various trip production models and comparison of their performance in prediction. Four representative models (regression, Tobit, Poisson and ordered logit) are applied to the educational trips in Qazvin city. The modeling unit employed in this study is the household. Sample is included econometric- social attributes 4734 houshols. 85% of the data used for estimation and the rest to validation. The models are assessed by how closely they are able to replicate trips ,made by each household in the estimation and validation dataset. in order to compare the performance of models in prediction, each of the models is developed on estimation dataset, and the models are used to predict the trips made by each household in validation and estimation dataset. Measures assessing how well the predicted number of trips made daily by each houshold by each of the models compared to the observed number of trip made by the houshold are evaluated and compared. The four measure for assessing performance are the mean absolute error, regression of the predicted number of household- trips against the observed number of household trip in term of goodness of fit and coefficient of determination, and compare plot of observed and predicted aggregate trip shares. In order to modeling is used stata software. The result show that, In every four models, number of school students, number of university students, and household car ownership have been statistically significant. The performance of each of the models are different in term of various measures (mean absolute error, regression of the predicted number of household- trips against the observed number of household trip in term of goodness of fit and coefficient of determination, and compare plot of observed and predicted aggregate trip shares).From mean absolute error perspective, ordered Logit and linear regression models have the best performance, but from goodness of fit regression of the predicted number of household- trips against the observed number of household trip, Tobit models have the best performance. Ordered Logit models have the best performance in terms of coefficient of determination of the predicted number of household- trips against the observed number of household trip and comparision of predicted share of every trip rate level with observed share. The performance of each of the models are similar in prediction of validation and estimation dataset.
    Keywords: trip production, linear regression, Tobit, Poisson, ordered Logit
  • J. Esmaili *, S. N. Ahooghalandary Pages 13-24
    Precasting is a useful approach for building structures in large numbers over a short period of time or for a specific type of them. Precast structures due to the discrete design and construction of the members have different nature than in-situ structures. The constraints on the construction and arrangement of members in these structures have led to beams with simple and poor connection design. In many cases, resistant moment connectionrequires a high reinforcement bar density for getting moment capacity in the beams, and particularly in the joint area. On the other hand, the use of in-situ concrete at the beam to provide the necessary resistance is in conflict with the precastapproach. To solving these problems, the interiorjoint of a structure with an intermediate moment frame system was compared in two precast and in-situ structures by linear dynamic analysis. Considered structure had 4 stories with 3.2 m height and 4 bays in 6 m length. The case study was symmetrical. Applied load cases includes dead, live and earthquake loads. This structure was designed for residential applications and Earthquake design of it was based on Iranian code of practice for seismic resistant design of buildings, Standard 2800. Design of mentioned joints in precast and in-situ cases was based on ACI318-08 and PCI 2004 codes. Moment and shear capacity of beams and columns, splice length of reinforcements, moment axial interaction of columns, joint shear, intermediate moment concrete and steel frame specifications, possible plastic hinge region in beams and design order in connection segments were considered in design process. A finite element based software, ATENA 3D, used for structural analysis of joints. Nonlinear behavior of concrete, longitudinal and transverse reinforcements and strain concentration of concrete hinge were investigated through this software at this research paper. To study the performance of connection joints through nonlinear finite element analysis, the accurate and idealized definition of applied materials is so essential. therefore various material models are used in software. For instance CEB-FIP model is used to investigate the stress-strain curves and also the concrete-reinforcement bonding, Von Mises plasticity theory is used for post yielding behavior of steel connection segments and Interface model is used according to Mohr-Coulomb theory. To study the behavior of connection joints the Force-Drift curves, Crack opening schemeand measured strain of reinforcements and steel segment are investigated. At this paper, we tried to present a moment resistant connection which is simple in production, transportation and assembling. The results show that the introducing beam and its connection, in comparison with equivalent in-situ connection, performs satisfactorily under the efforts of resistance, energy dissipation and ductility. Also plastic hinges formation at proposed beams is due to longitudinal reinforcements yielding just like as in-situ beams, but the position of plastic hinges is in distance with the connection area. In addition to mentioned capabilities, proposed connection can lead to a reduction in reinforcement concentration in beam and also in-situ concrete placing can be eliminated in construction assembling stages. It has been found that, the proposed precast connection can be presented as a good alternative for currently used moment resistant precast connections.
    Keywords: Beam to column connection, Precast structure, Finite element analysis, Precast connection, Composite beam
  • Babak Omidvar *, Sanam Moghimi, Saeed Kakaiee Pages 25-35
    Natural disasters and their impacts on human’s life are one of the most important concerns of our societies. Infrastructures such as power systems, water distribution systems, transportations, communication systems and gas networks are among the main components of urban environment. There are interdependencies among infrastructures and their subsectors. Infrastructures performance in disasters have significant role in reaching to a disaster resilient society. The uncertainty in vulnerability assessment of these lifelines in one hand and the lack of proper planning for recovery and selection of optimized strategies for different sectors on the other hand, may result in a great losses. Iran is located in a seismic active zone and has always been faced with devastating earthquakes. Tehran, the capital of Iran, is at seismic risk, since it sits on major active faults and suffers from techtonic activities. However, poor construction practices, and having large population, makes Tehran more vulnerable to earthquakes. Accordingly, it becomes necessary to have proper recovery plan beforehand based on accurate seismic performance modeling of interconnected infrastructures. Optimal financial resource allocation to the seismic retrofitting of the infrastructures and specifying their priority are considered as prominent issues in the macro scale decision making process. As the optimum strategy is adopted and the budget allocation is performed with the appropriate priority, it is expected that a significant loss reduction is achieved. When the financial resources are limited, allocating based on the proper priority seems to be more vital. The study tries to find out the economic effect of infrastructures’ interdependencies using Leontief Input-Output Model based on the matrix of value of commodity flow among different sectors. Tehran is chosen as a case study. In this work, the optimum strategy for retrofitting the infrastructure networks as the water, transportation, communication, gas, and power infrastructures is investigated using Uncertainty Dynamic Inoperability Input-Output Model (U-DIIM). This optimum strategy is adopted against the earthquake impacts in terms of the indirect economic losses, sensitivity to the parameters of the commodity flow matrix and cost of retrofitting strategy. Therefore, the indices employed in this research include reducing the economic losses and also the sensitivity with respect to the costs associated with the conduction of the strategy. By minimizing the total economic loss, sensitivity to economic loss parameters and cost of implementation of strategies, the best optimal scenario is selected for retrofitting strategy. The strategy selection is based on initial inoperability, recovery time and demand perturbation after earthquake. The Pareto method is also used in this work to select the optimal retrofitting strategy. The results reveal that increasing the seismic performance of the infrastructures by 25% is the optimum retrofitting strategy from the economic point of view. Following this strategy, the ratio of economic loss reduction to the strategy implementation costs and also the ratio of the sensitivity reduction to the strategy implementation costs are 0.3996 and 3.66, respectively. It is worthwhile to note that all economic interactions between the infrastructures are taken into account in the research. The proposed methodology may be used for the optimal selection of the other set of infrastructures in an uncertain situation.
    Keywords: Infrastructure, Earthquake, Retrofitting, U, DIIM, Prioritizing retrofitting strategy
  • Mohammad Tamannaei *, Mohammad Hossein Vali Pages 37-48
    Electrification is one of the appropriate solutions to increase the railway network capacity. However, use of this solution without provision of the sufficient capacity and required infrastructure through the whole of the network, may not acceptably increase the attracted railway demand. In such cases, the electrification project may be uneconomical. This research aims to propose an algorithm to identify which bottlenecks of the network must be removed, in order to justify the electrification of a specific railway corridor. We investigated the electrification of the railway corridor at north of Iran. This corridor has a substantial capability for absorption of the freight transportation demand. The railway freight demand related to all of the origin-destination pairs of Iranian railway network, along with the capacities of all block sections of the network are considered as inputs of the problem. for freight assignment in the railway network, FARS (Freight Assignment in Railway System) software was used. This Iranian software is developed by transportation research center of Isfahan University of Technology (IUT), in 2013. The assignment method used in this software is based on Incremental assignment. Different scenarios are considered and two main criteria are employed to compare the scenarios: tonnage of increase in railway freight demand, and economic index of benefit to cost called Net Present Value. According to the results, the electrification of the railway corridor at north of Iran, with no resolution of the bottlenecks in other locations of the network, cannot absorb a remarkable demand. The individual electrification of the mentioned corridor can only increase the absorbed freight demand from 1.65 million tons to 1.95 million tons, which is not considered an impressive progress. In this scenario, the Net Present Value (NPV) index and Net Uniform Annual (NUA) index are negative, which implies that the execution of this scenario is uneconomical. The low increase of the demand absorption is due to the existence of the capacity bottlenecks in other parts of the railway network. The existence of these bottlenecks prevents the complete usage of the added capacity potential emerged from the electrification. Consequently, the possibility of handling the transportation demand at north of Iran would be limited. By using the algorithm proposed in the present study, the main bottlenecks which prevent the load flow through the network, were identified. Then, by execution of the capacity increase scenarios for the identified bottlenecks, the absorption of the railway freight demand was increased to 3.97 million tons, with positive values for both NPV and NUA indices, which imply the economic justification of the railway electrification at north of Iran, simultaneously with improvements for capacity bottlenecks at other parts of the railway network. In other words, to achieve the absorption of the freight demand of the railway corridor in north part of Iran, it is not adequate to merely increase the capacity of this corridor itself. The railway electrification project in a specified part of the network is preferred to be performed simultaneously by the capacity improvement projects in other parts of the network. The proposed algorithm can be used in decision making for justifying the railway electrification projects.
    Keywords: Railway, Electrification, Capacity Bottlenecks, Freight Demand, Assignment
  • Hasan Amini Rad *, Atiyeh Jebelli Pages 49-59
    Leachate generated in the landfill due to the complex structure and high pollution requires developed physical and chemical and biological treatment methods. Aerobic granular sludge is one of the newest technology of immobilized microbes that has the potential to improve the biological wastewater treatment technology. One of the leachate treatment method which have been highly regarded recently is the leachate treatment by aerobic granules in the SBAR reactor. This study has been done for the purpose of treatment of leachate with aerobic granular. In order to optimize the formation of the granules and use it in the leachate treatment of this experiment, the construction of granules and leachate treatment has been done in two distinct phases: granules production has been done in the SBAR reactor for 28 days with increase loading to 6000 mg per liter and leachate treatment has been done in the same reactor in 24 days to loading 6000 mg per liter. The reactor used in this test is made of Plexiglas and has the dimensions 75 *20*20 cm3 and the volume of 28 liter. To link the upper and lower part of the reactor as well as effective mixing in the reactor an airlift PVC pipe has been used with the height of 50 and diameter of 20 cm. Some holes with the diameter of 2 cm has been created at the bottom of the airlift pipe and aeration is in the middle of airlift pipe and the bottom of reactor to led to rotation confusion and the oxygen transfer well done. For granules cultivation the synthetic wastewater containing glucose has been used as the carbon source, the ammonium chloride as the nitrogen source, the potassium dihydrogen phosphate as the phosphorus source as well as the micronutrients such as magnesium sulfate, ferrous sulfate, calcium chloride, potassium dihydrogen phosphate. At first the granules are made with synthetic wastewater in 6-hour cycles containing 30 minutes feeding, 270 minutes’ aeration, 30 minutes settling, 30 minutes’ wastewater discharge. In this experiment, the temperature has been controlled in the range of 20-23 C and DO in the range of 6-8 ppm and PH in the range of 7.5-8.3. In the next stage, the feasibility of using these granules in the leachate treatment has been tested. The results of the MLSS, SVI, VELOCITY, DIAMETER, COD REMOVAL tests show that the granules produced from synthetic glucose wastewater will be able to purify leachate. Synthetic sewages loading in the 6-hour cycles and the organic loading increases have been done till the formation of granules in 28 days. After each cycle, the parameters mentioned above were examined and the sludge morphology. With the entering of synthetic sewage to the reactor, at first the suspended solids increased and the granule's seeds production reduced. With the consolidation of granules and its sustainability, the leachate is injected to the reactor and is replaced by the artificial sewage. With the arrival of leachate to the reactor, the granules start to disintegrate and thus lead to an increase in the suspended solids of the system. Due to the change of the raw sewage and replacement of leachate instead of synthetic sewage, in some granules collapse happened. The results show that when granules are accustomed to the leachate entering the reactor, increase of bacterial activity lead to the improvement of efficiency of leachate treatment in the system and the efficiency of COD removal reached 90%.
    Keywords: aerobic granules, synthetic wastewater, leachate treatment, COD removal
  • Komeil Khakpour *, Ali Komakpanah Pages 61-73
    Determination of ultimate pile capacity is important for proper design and construction of pile foundations. Most of the time, the pile load test is carried out shortly after the installation of pile. The pile capacity obtained from the load test is often assumed to be the ultimate pile capacity in most of design methods. However, during pile installation, the soil around the pile experiences large deformations and changes in excess pore water pressure, which in turn reduces the shear strength and pile bearing capacity. After the completion of pile driving, the pile capacity increases as the strength of the surrounding soil increases mainly by reconsolidation, manifested by the dissipation of excess pore pressure at the soil-pile interface zone. the ultimate pile capacity could be underestimated if pile load test was carried out while excess pore water pressure still remains, which may lead to a conservative pile design. It should be noted that a pile static load test (SLT) and a dynamic load test (DLT) only measure the pile load–displacement relation and ultimate load at the time of testing; they do not provide any information on pile capacity variations over time. Pile load tests must be repeated at different times to evaluate any set-up effects, which can be time-consuming and costly during pile construction. Therefore, it is essential to develop empirical and numerical solutions to enable analyzing and estimating long-term pile set-up effects on the basis of limited numbers of SLT and DLT tests. Accurate estimation of pile setup, rather than measuring directly in the field, may reduce the cost of piling and still provide the required performance for the pile. Prediction of pile capacity gain with time after driving would certainly be advantageous from an economic standpoint. Incorporating the effects of setup into pile design is expected to reduce the general cost of piling project by reducing pile diameter, pile length, size of driving equipment, and subsequently piling duration. The major reasons for set-up can be categorised into the following two groups: (1) the generation of excessive pore water pressure during pile driving and subsequent dissipationover time, leading to soil consolidation, and (2) the aging process. The purpose of this research is to conduct experimental research aimed at developing an understanding of pile capacity in soft clays and to develop relationship between the pile capacity and elapsed time after the end of initial driving for cohesive soils. An experimental program was developed to study the evolution of pile capacity increase with time for piles driven into a type of soft clay in northern Iran. results of a series of pile load tests conducted on small-scale Aluminum pile foundations driven into soft clay. The piles were tested instantly after driving to measure their initial bearing capacities, and were tested repeatedly over different elapsed times to study the evolution of pile capacity over time. Results show pile capacity increases approximately 80% of initial value, 14 days after initial pile driving. A large proportion of this pile capacity increase over time, also known as setup, was generated within the three days due to fast excess pore water pressure dissipation, and afterward, the pile capacity increased at a lower rate.
    Keywords: Driven pile, Soil set, up, Physical modeling
  • Fatemeh Khosravi, Salaheddin Hamidi, Seyed Mehdi Hosseini *, Seyed Morteza Marandi Pages 75-87
    Heavy metals are elements that exhibit metallic properties such as ductility, malleability, conductivity, cation stability, and ligand specificity. They are characterized by relatively high density and high relative atomic weight with an atomic number greater than 20. Clay and other soils may become contaminated by the accumulation of heavy metals and metalloids through emissions from the rapidly expanding industrial areas, mine tailings, disposal of high metal wastes, leaded gasoline and paints, land application of fertilizers, animal manures, sewage sludge, pesticides, wastewater irrigation, coal combustion residues, spillage of petrochemicals, and atmospheric deposition. Heavy metal contaminants in addition to geotechnical problems creation and change in the soil strength parameters especially in clay soils, can cause environmental and human health risks due to penetrate through the groundwater. Most commonly heavy metal found at contaminated sites are lead (Pb), chromium (Cr), arsenic (As), zinc (Zn), cadmium (Cd), copper (Cu), mercury (Hg), and nickel (Ni). Also, freezing and thawing cycles have a significant effects on the behavior of stabilized clay soils specially on the heavy metal contaminated clay soils stabilized by cement od other additives. So, by population increasing, advancement of technology and consequently increase in heavy metals emissions, as well as being a quarter of the earth surface in the cold regions and the necessity of building design and construction on these soils, it seems necessary to study the impact of the freezing and thawing cycles on the stabilized clay soils. Different additives such as cement, lime, gypsum, fly ash and other additives were used for stabilization and solidification of heavy metal and oily contaminated soils, the cement is more practical among the stabilizer additives, because of its compatibility with pollutants and high efficiency, low cost and easy access. In this research used cement for stabilization of the lead heavy metal contaminated soil exposed to freezing and thawing cycles. According to the importance of the soil settlement in the clay soils, one dimensional consolidation test was conducted on the experimental samples. Also, due to extensive use of bentonite clay soil in contaminated sites, bentonite clay sample was used for experimental studies. The results of this research indicate that in most cases the critical cycle is a cycle 7. Also, The soil strength parameters such as over-consolidation stress increased about 2 to 8 times in different conditions by cement stabilization. Also, stabilization of heavy metal contaminated by cement clay soils that exposed to freezing and thawing cycles reduce the Cc and Cs coefficients of bentonite clay samples about 50 to 80 percent depending on number of freezing and thawing cycles and heavy metal concentration in bentonite clay sample and also causing preconsolidation in soft clay soils or normally consolidated soils throug the pozzolanic reactions of soil and cement at a low time. Furthermore, the optimum content of cement in contaminated and uncontaminated samples in different freezing and thawing cycles is variable, but in most cases is about 5% to 10% depending on number of freezing and thawing cycles and heavy metal concentration in bentonite clay sample. In continence, stabilization efficacy and the formation of hydrated compounds of cement and clay soil was investigated by using pH chemical test.
    Keywords: Contaminated soil, cement, freezing, thawing cycles, bentonite, consolidation
  • Mehrdad Razzaghian Ghadikolaee, Asghar Habibnejad Korayem *, Mahyar Ghoroqi, Alireza Sharif Pages 89-100
    In the last decades, the development of nanotechnology has been rising and nanomaterials have been widely used in combination with many traditional materials. The prominent chemical and physical properties of nanomaterials enable them to play an important role in various applications such as modifying the structure of materials, improving the properties of composites, and manufacturing new multifunctional products. The building industry has not been exempted from this rule. Many studies have been carried out on the effect of nanoparticles on concrete performance and most of them demonstrated the improvement of concrete properties. There are a lot of studies on the effect of nanoclay on cement composites. However, there are little researches on the halloysite nanotube (HNT) effect, as subcategories of nanoclay, on the properties of cement composites. Halloysites are a kind of mineral clay which are often produced by air-induced erosion or by thermal transformation of ultramafic rocks, volcanic glasses, and pumice. They are chemically similar to kaolinite but, unit layers in halloysites are separated by a monolayer of water molecules. In general, halloysites have different shapes and exist in the plate, spherical, and tubular forms. The tubular structure is the dominant form of halloysite in nature. Chemically, the outer surface of the HNTs has properties similar to SiO2 while the inner cylinder core is related to Al2O3. Due to the tubular geometry, HNTs like carbon nanotubes could be classified as one-dimensional nanoparticles. Halloysite can grow into long multi-walled tubules, which morphologically resemble to multi-walled carbon nanotubes. In terms of dimensional characteristics, HNTs have an external diameter of about 30 to 190 nm, an inner diameter of about 10 to 100 nm and a length between 3 to 30 µm. Halloysite characteristics could be sum up as high length to diameter (L/D) ratio, high specific surface, large pore volume, low density in surface, and pozzolanic properties. Mechanical properties of HNTs could make them an ideal reinforcing additive to improve the mechanical properties of cement composites. In addition, due to the nano scale size of HNTs, they can play the role of filler and make a denser and stronger microstructure. Therefore, in this research, the effect of HNTs on the performance of cement mortar was evaluated and the workability and permeability of mortar samples containing 3% halloysite nanotubes were presented. The results indicated an increase of more than 28% of electrical resistance, a decrease of approximately 26% of water absorption rate, 23% reduction in water repellent, a decrease in the workability, and an increment in the rate of hydration of cement mortar due to the incorporation of 3% halloysite nanotube. These results indicate that halloysite nanotubes can be used as an appropriate nanoparticle to improve the properties of cementitious composites. The pozzolanic properties of HNTs enable them to decrease the permeability of cementitious matrices. Silicate of HNTs react with calcium ions of hydrated cement and increase the calcium silicate hydrate gel. This could lead to an enhancement in the durability of cementitious matrices. This paper can provide more insights on the application of nanoparticles with cementitious composites.
    Keywords: Halloysite nanotubes, Workability, Permeability, Cement mortar
  • Mohammad Hadi Rezaei, Naser Khaji * Pages 101-112
    Earthquakes are one of the most Terrible danger that are likely to cause heavy human losses and destroy entire civilization on scale of minutes. The more recent damaging events in Mexico City (1985 Mexico) in bam (2003 Iran) or Tohoku (2011 Japan) recall that so far little is known about earthquake physics that could prevent people from their deadly effects. To reduce casualties Decades of research involving numerous laboratories worldwide aim at investigating this large scale phenomenon and trying to understand how it triggers, propagates, and stops. A trusty physical modeling of strong ground motion requires to examine three crucial parameters of seismic source specifications, wave propagation path, and seismic site effects. A reliable physical modeling of strong ground motion requires to examine three crucial parameters of seismic source specifications, wave propagation path, and seismic site effects. Among various seismic source specifications, a more physically realistic source model is the specific barrier model or (SBM) for short. The SBM is specifically more suitable for regions with poor seismological data bank and/or ground motions from large earthquakes with large recurrence intervals. In order to simulate seismic ground motions from a specific earthquake source model in an efficient way, the stochastic modeling method has been widely used. An essential part of the seismological model used in this method is the quantitative description of the far-field spectrum of seismic waves emitted from the seismic source. Since shear (S) wave is primarily the main factor of earthquake damages, the application of stochastic approach of the SBM has almost been focused on the far-field S wave spectrum, in which two corner frequencies of observed earthquake are represented. The ‘two-corner-frequency’ shows two considerable length-scales of an earthquake source: a length-scale that quantifies the overall size of the fault that ruptures (e.g., the length L of a strike-slip fault) and another length-scale that measures the size of the subevents. Associated with these length-scales are two corresponding time scales: (1) the overall duration of rupture, and (2) the rise time. The SBM has a few main source parameters which have been calibrated to earthquakes of different tectonic regions. In this paper, it has been tried to simulate source, path and site of entire earthquake and compare the results of simulation with real earthquake. To this end SBM with uniform PDF for arrival time but different types of PDFs of subevent size used to simulate source. To investigate effect of PDFs of subevent size on the source spectra as well as earthquake spectra as result of simulation, uniform and fractal distribution along with classic distribution for subevent size are considered. In order to take into account, the effects of path of propagation, Geometric and inelastic Attenuation Compatible with center of Italy (L’Aquila region) have been used. Finally, to considering effect of the layers of soil (sediments) near surface on amplitude, period, duration and other characteristic of seismic waves, transfer function for linear wave propagation has been computed with the Thomson-Haskell matrix method. Transfer function in this method illustrate how a soil column with different layers attenuates and amplifies seismic waves as a function of frequency.
    Keywords: Kinematic methods, Fault modeling, Specific barrier model, Seismic source spectrum, Laquila earthquake
  • Mojtaba Shabdin, Nader K.A. Attari *, Mojdeh Zargaran Pages 113-126
    This paper presents the results of cyclic tests investigating the in-plane behavior of URM walls as the main lateral resistant members in school buildings. Generally, URM walls of existing building in the country contain different material properties with different strengths. Therefore, considering the effect of changing in material properties on their failure modes is required. A hypothetical two-story URM building was defined as the prototype structure of the presented cyclic in-plane research study. This prototype structure was selected to be a proper representative of existing URM school buildings in Iran. First story walls of this building with a loading bay equal to five meter were selected as the test specimens. Some properties of specimens were assumed and considered stationary to make the global response of the specimen match with the real condition of existing URM buildings in Iran. For this purpose, the thickness and the height of the walls were considered 0.35 and 3 m, respectively. The experimental study was carried out on two full-scale specimens. A special height-to-length aspect ratio of the wall was selected to generate enough lateral strength to ensure the bed-joint sliding failure of the URM wall during in-plane cyclic experiment. Lateral strength, Q, of considering URM walls was considered the lesser of the lateral strength based on bed-joint sliding, rocking, diagonal tension or toe crushing strengths. Changing in material properties of walls was considered as the major parameters in the investigation. The specimens were constructed in the structural laboratory of Building and Housing Research Center (B.H.R.C) and subjected to a sequence of cyclic loads. In the construction of walls, similar brick with different mortar and then different strengths were used. According to the results, the behavior of specimens revealed that they could be able to maintain a significant amount of their resistance after cracking without considerable strength degradation especially for the wall with proper mortar strength. Therefore, URM walls can resist lateral load after formation of the first crack with little lose of strength. According to this ductile behavior of walls and partnership of other elements in lateral load capacity of URM building, the estimation of system strength could be more than limited strength by the first crack of the wall. Changing in material properties of wall affected the failure mode, lateral resistant, displacement capacity, and energy dissipation. The specimen with proper mortar strength experienced bed-joint sliding failure mode, while the specimen with weaker mortar strength experienced mixed sliding-diagonal failure mode. The relationships presented in the standards can present relatively proper prediction for shear sliding capacity of the specimens, while the predicted capacity of them for diagonal capacity is overestimated. Test results showed that the improving the material properties of URM wall improved the lateral strengths of specimens. The wall constructed with the mortar with more appropriate properties revealed more lateral resistant and could experience more deformations. This wall could dissipate much more energy. The experimental m-factors were higher than current code values for both specimens and improving the material properties resulted in a considerable increment in m-factor.
    Keywords: Unreinforced Masonry Walls, cyclic test, failure mode, mortar properties, school building
  • D. Sharifi Asadi, A. Ardakani *, G. Garoosi Pages 127-138
    One of the most common methods of soil improvement is to use additives in order to improve strength properties and permeability of the soil. Cements or chemicals are usually used as binders for soil particles, which lead to increase the soil shear strength and reduce its hydraulic conductivity (i.e. permeability). Nevertheless, these materials are not suitable for soil improvement in the long term because they require significant natural resources. The use of cement and chemicals for soil improvement is expensive and time-consuming. Management of renewable natural resources (microorganisms and their products) could lead to solve geotechnical and environmental problems and achieve great economic benefits in the building industry. In addition, the application of microbial biotechnology in the building industry make easier some of the existing methods of construction. Using the latest microbial biotechnology, a new type of building materials, namely biocement, has been produced as an alternative to cement or chemicals. Biocementation is the improvement of strength and stiffness of rock and soil by using microbial activity and their products. The process of the formation of precipitates or biocement in the presence of microorganisms is called microbialy induced calcium precipitation (MICP). Biocement can be used in solid and liquid states. In the liquid state, biogrout can flow like water with very low viscosity. Therefore, compared to cement and chemicals, it will be transmitted into the soil, more easily. Naturally, biocement is formed in the presence of microorganisms in ambient temperature and thus, it requires less energy. Because of the abundance of microorganisms in the nature and easy to reproduce with low cost, this type of cement is sustainable. The Microorganisms that are suitable for the production of biocement are usually non-pathogenic and environment friendly. In addition, unlike cement, soil can be improved without disturbance of ground and the environment; since microorganisms can penetrate into the soil and grow in it. This dissertation aims to realize the effect of ground condition on the MICP process in non-cohesive soils. Since this method is still in the laboratory stage, for being used in practical projects, it is required to carry out laboratory experiments, including relative density and particle size distribution, to evaluate the performance of this method in different ground conditions. For this purpose, it was used from Sandy soil with different silt contents of 0%, 5%, 10%, 15% and 20% in two states of Loose (Dr = 40%) and dense (Dr = 100%) conditions in this research. The high urease activity and non-pathogenic bacteria S. Pasteurii was also used in the MICP process. In order to consider the soil conditions on the efficiency of this type of improvement method, uniaxial compressive test parameters and precipitated calcium carbonate content were investigated. According to the results, increasing of silt content from 0% to 20%, leads to reductions of 40% and 46% in precipitated calcium carbonate content, increases of 57% and 41% in the uniaxial strength and increases of 79% and 71% in the elasticity modulus of the samples in two loose and dense conditions, respectively. It seems that these changes were resulted from shrinking of the empty space and increasing of the contact area between the soil particles.
    Keywords: Biological Improvement, Microbial Induced calcium carbonate Precipitation (MICP), Unconfined compressive strength, Sandy soil, Non, plastic Silt
  • Issa Shoosh Pasha *, Aria Sharifi Pages 139-148
    Pile foundations often used to transfer structural loads into deeper layers. On granular soils shaft resistance is an important factor bearing capacity of axially loaded, especially when the pile is subjected to tensile loading. Tensile forces apply on the pile holding the position of ship repair, basements, pumping stations, waterworks structures which are under water. In addition, transmission lines towers, tall chimneys, submerged platforms, masts, and other similar structures that are built on piles, in exposed disturbing moments resulting from wind, earthquakes and sea waves. In such structures, disturbing moments transferred, in some piles for pressure and other piles for tensile load. So, study the behavior of these piles and also effective parameters on the tensile capacity of is very important. Bearing the applied tensile loads on structures is one of the important applications of deep foundations, especially piles. Tensile capacity of these foundations is often produced by the frictional resistance in soil-pile interface. Piles are deep foundations which have considerable acceptance because of multi-applications. Understanding the behavior of piles and prediction of their tensile capacity is so important. In the last three decades various theories have been created regarding the behavior of piles under different loading conditions. The validity of these theories is evaluated by comparing the test results on models or structures piles with the predictions of theoretical. The field tests are Perfect scale and highly desirable, but often costly and difficult. For this reason, laboratory experiments are used to study the behavior of piles under tensile load. But to consider real conditions of the area, especially coastal sites, can be installed the piles in the soil that have been used to study the tensile behavior of piles. The reliability of tension test results in the homogeneous soils and the impact of surface layers of sand in providing friction force are special cases that have not been tested in real conditions of the site. Different methods are developed to achieve safe, constructible and economic design, such as analytical, experimental and in-situ methods, but in some cases they are still subjected to limitations. These methods can’t neither determine tensile capacity of pipe piles in coastal sand nor examine behavior of them. Since jacking technique is recommended for achieving improved soil properties and eliminating the deficiencies of other installation methods, so investigation of its effect is important. In this method, after jacking the piles with hydraulic jacks, the piles are arbitrarily tested under compressive loading to determine their compressive bearing capacity and then their tensile capacity is determined based on ASTM D-3689 procedure. After reading test data, the ultimate tensile capacity of piles were determined using tensile capacity criteria and then compared with analytical results. Tensile behaviors of piles at large displacements are also investigated and required force for larger pull out displacements were measured. The results showed that determined uplift capacities are more than analytical results and sand compaction due to pile installation can increase frictional resistance. It also revealed that the tangential criterion is determinant to obtain ultimate tensile capacity in most piles.
    Keywords: tensile test, jacking, ultimate tensile capacity, pipe pile, coastal sand
  • Tahere Salehi Shahrabi *, Vahid Saberi, Masoud Ahmadvand, Hamid Saberi Pages 149-158
    Soft story in the ground floor is established due to the open space for establishing shops, parking lots or even schools. The 2008 regulation suffices to only define the soft story. That is, when the lateral rigidity of each story is less than 70% of the lateral rigidity of the higher story or is less than 80% of the average lateral rigidity of the three stories above them, this story is called the soft story. The previous earthquakes such as those of Chichi in 1921, Koobeh in 1995, Bam in 2003 and Keshmir in 2005 had destructive effects on structures with soft stories and even caused them to collapse. Through conducting further studies on the destructive effects of the earthquakes near to and far from the fault on the regular and irregular structures, conducting precise analyses such as the IDA increasing dynamic analysis, and drawing fragility curves obtained from the statistical relationships, we can study the performance of the structures with soft stories which are of great significance such as schools, etc. so that we can better know the performance of these kinds of structures under the earthquakes near to and far from a fault to be able to strengthen these structures to be less vulnerable against the future earthquakes. In This paper aims to study the effect of near and far fault earthquakes on two series of nine-story steel bending frames, one with 3.2 meters and another with disordered in ground story with the height of 4.5 and 5.5 meters constituting soft story. The IDA increasing dynamic analysis is utilized for the estimation of the different performance level of buildings. It means that the structural models are modeled under one or more earthquake records with different intensities and one or several reply curve (s) is (are) produced due to the quake’s severity level. The severity of the records applied on the structure, which is increased during the analyses, and the analyses’ output, which is the structure’s reply, are presented by IM and DM parameters, respectively. The IDA curves are in fact the outline of the relationship between the structure’s reply (DM) and the severity change (IM) of the records. The selected parameters for IM and DM should well indicate the impact of the earthquake and the behavior of the structure. In this paper the parameter of IM corresponding to the maximum of inter-story drift and the parameter of DM corresponding to the spectral acceleration of the first mode (T1, 5%) Sa were considered. In addition, the collapse-preventing performance level of CP was analyzed. The results obtained from the fragility curves in the mode of CP indicate that with the height increase of soft story and consequently becoming softer, the collapse possibility of 10% of structure was greater in near fault records than the far fault ones. Also, the destruction probability of 10% of the regular and irregular structures under the records near to the fault is almost the same, whereas the destruction probability of the regular structure under the records far from the fault is averagely 15.35% more than other structures under the records near to and far from the fault, which indicates that the regular structure under the records far from the fault is more subject to destruction. Also through increasing the height of the soft story from 4.5 m to 5.5 m, the destruction probability of 10% under the records far from the fault compared to the regular structure, underwent a more reduction.
    Keywords: Irregular Structures, Soft Story, Fragility Curve, Near, Far Fault, Steel moment resistance frames
  • Amir Tarighat *, Yaghout Modarres, Milad Mohamadi Pages 159-168
    Sulfate attack is a series of physico-chemical reactions between hardened cement paste and sulfate ions. Sulfate ion penetration into the cement results in the formation of voluminous and deleterious phases such as gypsum and ettringite which are believed to cause deterioration and expansion of concrete; However, there is no direct relationship between Ettringite or solids formation during the sulfate attack and the amount of expansion. Concrete deterioration due to sulfate attack depends on multiple elements, however, in experimental studies, the implementation of the elements and obtaining the results in a short time are very difficult. Therefore, the significance of theoretical and software modelling along with in experimental studies, reducing the time and cost, increases so much as to achieve reliable results. Thermodynamic simulations, in this research, are employed according to the method of minimizing Gibbs free energy in order to better understand the external sulfate attack and the behaviour of mortar samples made of ordinary Portland cement and blended cements.GEM software helps in studying the microstructure of cement, volume and type of phases formed in sulfate solutions under different conditions. With this software, a virtual laboratory of materials could be created, which simulates natural processes such as hydration, sulfate attack, and factors that affect them with less time and cost. This modeling type could be utilized for cement systems in order to calculate sets of stable phases. A system achieves thermodynamic equilibrium when there is no more spontaneous tendency for change. GEM software which is able to calculate the stable phase as a function of reactants, temperature and pressure is employed. In this software chemical interactions involving solids, solid solutions, metls, gas/fluid mixture, aqueous electrolyte, (non-)electrostatic surface complexation, and ion exchange can be considered simultaneously in the chemical elemental stoichiometry ( electrical charge) of the system, i.e. without any mass balance constraints for ligands or surface sites. GEMS simulates various mass-transfer processes and reaction paths, such as mixing; But this software cannot replace our knowledge of physical chemistry. Type and volume of phases formed during the sulfate attack and factors affecting that such as cement chemistry, rice husk ash and sulfate solution with different concentrations were studied With the help of this method. Simulation of mortar samples was performed in sodium sulfate with concentrations of 4 and 44 g per liter and 10 and 15 percent rice husk ash substitution. Mortar samples at 20 ° C and water-cement ratio of 0.5 is assumed. Rice husk ash substitution has an effective role in microstructures improvement, reduced impermeability, and volume of forming products. Sodium sulfate is more dangerous and destructive compared to other sulfates like calcium sulfate or potassium sulfate and forms phases with higher volumes. The results clearly indicate that rice husk ash, consumed portlandite completely and produced maximum volume of calcium silicate hydrate(C-S-H) by 15 percent replacement and also there is not a simple relationship between the increase of formed phases by the penetration of sulfate ions and the observed expansion. Generally, the results correspond to the studies and in experimental results which have examined micro structure.
    Keywords: Sulfate attack, Simulation, Thermodynamic, Portland cement, Rice husk ash
  • H. Ghasemia Gorji, B. Dahrazma * Pages 169-178
    Contamination of water resources with petroleum products is an environmental problem in the recent decades. There are many different methods for remediation of aquatic environments. Adsorption is considered one of the most effective water remediation techniques. The availability and cost of absorbent is very important factor in the absorption process. In recent years, a wide range of materials were used as adsorbent for remediation of contaminated water. This study was performed to investigate the use of raw red mud as an adsorbent to remove COD from the soluble fraction of gasoline in aqueous solutions. The effects of different parameters including pH, contact time, adsorbent dose and initial concentration of gasoline on the removal process were investigated. It should be noted that all tests were repeated three times. The results showed that increasing pH, from 3 up to 11, increases the efficiency of COD reduction by the sorbent. According to the results, pH of 7 was selected as the optimal pH. The efficiency of COD reduction in contact times of 2.5, 5, 10, 15, 20, 25, 30, 60 and 120 minutes were studied. The COD reduction by raw red mud occurred quickly at the first step, then proceeds at a slower rate until equilibrium achieved within 15 minutes. Therefore, 15 minutes was considered as the optimum contact time. The effect of adsorbent dosage on the removal of COD of the solution for the values of 1, 2, 5, 10, 15, 20, 50 and 100 g/L was studied. The results showed that with the increasing of adsorbent dosage, the removal rate was increased. Based on the results, the optimal dosage of 10 g/L of raw red mud adsorbent was selected. The COD removal experiments were performed for the initial concentrations of 1%, 2%, 5%, 10% and 20% of gasoline. Removal of COD at low concentrations (1%) was close to 100%. Increasing the initial concentration of pollutant in the aqueous solution decreased the removal rate. Maximum removal of COD (%100) was occurred at the optimum conditions of pH = 7, contact time = 15 min, adsorbent dose = 10 g/L, and initial concentration of pollutant = %1. In order to determine the mechanism of adsorption of pollutants to the surface of raw red mud adsorbent, Langmuir, Freundlich and D-R isotherm models were evaluated. Results of the isotherm studies showed a high consistency (R2 = 0.98) with Langmuir isotherm model. It means that adsorption of gasoline on the surface of raw red mud is occurred as single layer, on the homogeneous surface of adsorbent and limited number of adsorbent active sites. Zero order, Pseudo first order and Pseudo second order kinetic models were investigated to determine the rate of the gasoline adsorption on the adsorbent surface. The kinetics of adsorption process was followed a pseudo-second-order model with a correlation coefficient of 0.99. Parameters such as short contact time, appropriate range for pH, acceptable absorption capacity, low cost and easy accessibility of the absorbent were the advantages of using red mud as an adsorbent to remove COD from soluble fraction of gasoline.
    Keywords: Adsorption, Gasoline, Red mud, Aqueous solution
  • M. Ghalishooyan, A. Shooshtari *, M. Abdelghani Pages 183-193
    Modal parameter identification of structures is of significant importance in many fields of civil and mechanical engineering. Output-only modal identification methods have gained great attention of civil engineers community in recent years. The algorithms estimating the dynamic parameters (natural frequencies, mode shape vectors and modal damping ratios) of structures just based on the output responses, became popular as operational modal analysis (OMA) or output-only modal analysis or ambient vibration analysis. In the context of OMA, the force acting on the structure should be stochastic, smooth and broadband and there is no need to measure it. Therefore, these methods are appropriate for identification of huge and complex civil structures. One of the most well-established and popular methods of OMA is frequency domain decomposition (FDD) proposed by Brincker et al. Estimation procedure of FDD is based on singular value decomposition of power spectral density matrix of structure responses. Then, the single degree of freedom spectral bell is obtained using modal assurance criteria (MAC) and transformed to correlation function of corresponded degree of freedom by inverse Fourier transform. Later, Brincker et al. presented the enhanced frequency domain decomposition (EFDD) method to estimate not only modal frequencies (with higher accuracy in the comparison with FDD) and mode shapes, but also modal damping ratios. Despite the high capability of EFDD in frequency and mode shape estimation, it still suffers from some limitations in identifying modal damping ratio. This paper first aims to investigate the modal parameters identification by EFDD and explains its merits and demerits and then proposes in-operation modal appropriation (INOPMA) algorithm for use with EFDD to improve the modal damping estimation. The key idea of INOPMA is to realize that the correlation sequence of the system output (subjected to random input) is the sum of decaying sinusoids with a certain phase shift and therefore it may be considered as an impulse response. The convolution of this correlation sequence with a pure sine wave allows the isolation of the mode at a characteristic frequency which depends on the modal damping ratio. By using a force in quadrature of phase with a sine wave, it is possible to estimate the damping ratio which in turn allows the estimation of the undamped natural frequency. In fact, modal damping ratios are first estimated by INOPMA and natural frequencies are then identified based on damping ratio values. By 70 times simulation of a four-story shear frame, capability of proposed method is validated for damping estimation through EFDD analysis. The results are then compared with the ones derived from the typical EFDD method. Regarding randomness of input force, different results are obtained by each new simulation run. So, the comparison process should be performed based on several numbers of simulations. The number of simulation was adopted in a way that the mean or variance of estimated modal damping ratios converges to a constant value. The relative error (the exact value minus the estimated value over the exact value) and variance of the set of the estimated modal dampings are regarded as comparison indexes. Finally, it is shown that by proposed method, the damping ratios are estimated with much less variance and error.
    Keywords: Output, only modal damping estimation, Enhanced frequency domain decomposition method, In, operation modal appropriation algorithm
  • Hossein Ashegh, Ali Akbar Shirzadi Javid *, Parviz Ghoddousi, Asghar Habibnejad Korayem, Mohammad Ali Oraie Pages 193-202
    The surface protection materials have effective results to prevent concretes from corrosion. Reinforced concrete structures have the potential to be very durable and capable of withstanding a variety of adverse environmental conditions. However, failure in the structures does still occur as a result of premature reinforcement corrosion. There are corrosion protection systems and methods to extend the long-term durability of steel reinforced concrete. For example, application of zinc rich or cement based protective primers to reinforcement, surface protection systems of concrete, Cathodic protection using sacrificial zinc anodes, and conductive anode overlays within an impressed current cathodic protection system. In general, the main duty of surface protection is controlling both physical and chemical damages to concrete in order of preventing or reducing from steel bar corrosion and creating a coat of safekeeping against penetration of chloride ion, carbon dioxide, oxygen, and most importantly water. According to European Norm, three types of protection materials are existed based on function mechanism. Coating, hydrophobic impregnation, and impregnation materials are these systems, and two types of them used in this study. In this study, two materials of surface protection have used on the surface of three types of concrete. Two types of self compacting concrete with different w/c ratio and one ordinary concrete with similar mixture design to one of those SCC were used for estimating of durability of concrete. Epoxy resin and silane-siloxane were two types of surface treatment materials used in this study. SEM analysis and water contact angle test were done to study the function mechanism of surface protection material. The other tests are water vapor permeability, corrosion potential, and corrosion intensity. Some of the results of this study is that using this materials have effective impact on declining of corrosion potential, decreasing of corrosion intensity, and after all increasing durability of concrete. As shown in this paper, all of the protected samples except one, until 49th week did not have a sign of corrosion active phase. Increasing in ratio of W/C in the substrate makes weakness in function of this materials. In the other hand, results of half-cell potential of unprotected samples show SCC2 with 0.55 w/c ratio and NC with 0.45 w/c ratio shift from passive to active state in first days and SCC1 with 0.45 w/c ratio attained its active state in 5 weeks. However once corrosion has started in SCC2-EP in 8 weeks, corrosion rate was lower than unprotected samples. In the presence of surface protection systems, due to their ability to reduce water ingress in concrete, the corrosion intensity in all samples were lower than 0.23 µA/ cm^2. The results of water vapor permeability test showed that epoxy can decrease the water vapor permeability up to 65% instead of unprotected concrete. In the meantime, silane-siloxane doesnt have effective results in concrete breathability and have a similar performance to unprotected concrete. The results show using SCC dont have much different effect on quality of the materials function instead of ordinary concrete. Another important result is that protection materials which dont let to enough evaporate, are cause of much corrosion in compare of those that let concrete to breath.
    Keywords: Surface protection, Durability of concrete, Corrosion, Concrete breathability
  • Benyamin Ganjeh Khosravi *, Hoseyn Ghasem Zadeh, Javad Razzaghi Pages 203-212
    Here, the efficiency of the non-destructive Break-Off (BO) test was investigated for assessing the in-place compressive strength of steel fiber reinforced concrete (SFRC). SFRC was studied due to its advantages in increasing toughness and tensile and flexural strength in particular. To provide a through and comprehensive database, 24 mix designs were selected with cement contents of 400, 450 and 500 kg/m3 with constant water/cement ratio of 0.4 for all mixes, two maximum aggregate sizes of 12.5 and 25 mm along with steel fiber volume fractions of 0%, 0.33%, 0.67% and 1% for ages of 14, 28 and 90 days. A total of 360 BO tests and 216 standard cube tests were carried out in this investigation.Then, effective parameters of SFRC and BO test results were evaluated. In the BO method, the force required to break off an in-place concrete cylinder of 55 mm in diameter and 70 mm long, is related to the compressive strength of the concrete from a predetermined calibration curve developed for concrete mix.The studies showed that volumetric percentage and features of steel fibers had a significant influence on concrete properties as well as BO test results. According to the experimental results it could be generally concluded that the influencing factors, namely, SFRC properties due to presence of steel fibers and BO test significantly affect the results as follows: Generally, for a constant W/C ratio, it can be concluded that raising the cement content increase the mean values of BO strength. It can be stated that the maximum aggregate size within the range of 12.5–25 mm has a negligible effect on the BO test results for SFRC with 1% steel fiber volume fractions as the average value of BO strength for 25 mm aggregate concrete was significantly more than the corresponding value for 12.5 mm aggregate size for plain concrete. Moreover, the improving trend the BO strength with age is observed to be similar for all different concretes. Furthermore, increase of BO strength of SFR concretes respect to corresponding plain value is observed as concrete grows older. In addition, results showed that strength estimation based on a single general calibration curve is not feasible. Therefore, a specific calibration curve for each SFRC should be represented for a realistic assessment and interpretation of results. The coefficient of variation of the BO strength was in range of 4– 11%. The higher values are for concretes with higher amounts of fibers, especially at early ages. The reliability of the method seems to be good in which the coefficient of variation for each group of BO tests are below 11%. It should be noted that even under ideal conditions with a specific calibration it is unlikely that 95% confidence limits of better than ±15% can be achieved for an absolute prediction of concrete compressive strength. The findings show that higher values are not only due to the lack of precision of the test procedure, but also due to the intrinsic heterogeneity of granular materials like concrete, particularly in presence of higher amounts of fibers.
    Keywords: Break, off test, strength, Steel Fiber, partially, destructive
  • M. Mahmoudi Sahebi *, A. Shirpour, A. Zarezadeh Mehrizi Pages 213-222
    Braces systems have been commonly used as load-bearing systems in steel structures due to their easy and rapid construction and erection, reduced amount of materials used for the lateral load-bearing system (as compared to the shear wall system), and higher conformity with structural deformations at upper stories Buildings in seismic regions are prone to severe damage due to large deformations and low capacity to absorb energy. X-bracing is effectively employed in maintaining the structure stability when earthquakes occur or extreme lateral loads act on the structure. The widespread use of X-bracing systems in steel structures reveals the importance of understanding mid-connections in this kind of braces. When applying a lateral force on X-braces, one structural member comes under tension while the second one is under stress. Buckling occurs to the member subjected to stress and when effective length factor reduces, the member handles a more critical load. X-brace effective length factor is not only influenced by end connection forces but it also depends on mid-connection and its implementation. If the stiffness of tensile bracing is considerable enough, the mid-connection can provide the interaction between the two braces. In fact, should the mid-connection have enough bond, stress brace buckling will be in the second mode. In this state, when the mid-connection slightly changes into a lateral sway, it stops and the stress bracing deforms as double-curved. Nevertheless, in its ideal state, the mid-connection lateral displacement is considered zero. This study aims to design based on Abaqus 3D software the two new mid-connections, flanged joint, and yielding ductile shear panel. Their buckling and post-buckling were also analyzed using nonlinear geometry and materials. In flanged joint, one member is bonded and two other ones are connected to this bonded member. Interior stiffener is used to prevent this bonded member from crushing. Furthermore, in new X-bracing systems instead of mid-connection sheets a yielding ductile shear panel is used. This sample was examined in two modes with and without stiffener. The results indicate that flanged joint increases the critical load and consequently decreases X-bracing effective length factor. This joint also leads to brace buckling coordinate or as it is known as X-bracing second mode buckling. This kind of buckling increases the ultimate strength and decreases displacement outside of bracing member sheet compared to that of the common joint. Furthermore, yielding ductile shear panel connection increases the X-bracing critical load as well as decreases X-brace effective length factor. The using of stiffener in this kind of connection improves loading and reduces X-brace effective length factor. The connection along with the stiffener comes with a 32 percent increase of the X-bracing ultimate strength due to the yielding of the shear panel and the lack of brace buckling. Also, this connection brings about a 23 percent increase in energy adoption by bracing frame. It is important to note that both connections increase the X-bracing behavior factor compared to the common connection. Yielding ductile shear panel connection not only shows the best stress performance among the connections but also with the lowest costs the X-brace can be repaired by changing mid-connection after the earthquake.
    Keywords: X, Brace, Effective length factor, Buckling, Post, Buckling, Flanged joint, BDSP
  • F.Malekahmadi, M.S.Birzhandi * Pages 223-232
    Recently, the Iranian code is established for the LRFD design of steel structures that consistent with the Iranian seismic design code (2800-4). This study is aimed to compare the performance of steel moment frames (SMF and IMF) in the Near-faults earthquakes designed with the Allowable Stress Design (ASD) and Load and Resistance Factor Design (LRFD) in a probabilistic framework. After the Static Push over (SPO), new Performance based earthquake engineering (PBEE) approach is incremental dynamic analysis (IDA) that can lead to the probabilistic judgment using fragility curves of the structure under the different types of ground motions at different levels of intensity. For the incremental dynamic analysis a large number of nonlinear time history analysis must be carried out. The evaluated steel moment frames are 4-story and 8-story frames. The nonlinear models of structures are constructed in the Perform-3D software to perform the nonlinear time history analysis. For the nonlinear modelling of beam element, the chord Rotation Model is used that proposed by FEMA and available in the Perform-3D software for the beam elements. This model predict the nonlinear behavior of element in the two end region that plastic hinge may be caused duo to the seismic load of earthquake. For the column elements, the fiber element method was employed. In this method, the cross-section of column element is subdivided into some spring elements. Each spring is subjected to axial load, given by the combination of axial force and bending moment acting on the section. This model sometimes is called multi-axial spring model (MS model). The fiber model represents a section at the structural member-end. This modelling can represent the axial-flexural interaction in the column element that their properties of nonlinear flexural bearing depends on its axial load in each time step. Near-field events due to their pulse-like effect are in the spotlight in the last decay. To evaluate their effects on the steel structures that located in the seismic areas of Iran, a number of near-field earthquakes are used in the probabilistic assessment. In the IDA curves, the roof drift is used as Damage Measure (DM) and the Spectral Pseudo-Acceleration of the first mode of the structure with 5% modal damping ( ) is used as Intensity Measure (IM). Also in the probabilistic fragility curves, the direct method is used. It means that the IM is used directly in the fragility curve. To predict the probabilistic function for the different level of performance of structures, the lognormal distribution was used. The study results show that the structures designed by the ASD method have a better seismic performance than the LRFD frames specially in the performance level of Life Safety (LS) and Collapse Prevention (CP). It can be concluded from comparison of the median of collapse functions. For example for the special moment frame (8-story structure), the use of ASD design (instead of LRFD design) leads to a 11% increase in the median of fragility function in the Life Safety (LS) level and 10% increase in the Collapse Prevention (CP) level.
    Keywords: Incremental Dynamic Analysis, Fragility Curves, Steel Moment Frame, LRFD for steel structures, Near Field Earthquakes
  • Amin Monshizadeh Naiin, Ehsan Seyedi Hosseininia * Pages 233-244
    Pipelines are considered as lifelines, because they are used for transportation of different fluids such as natural gas, oil and water, which the human life depends on their existence. The damages to the pipelines are usually associated with human fatalities, financial losses and also environmental pollution. Earthquake wave propagation and permanent ground displacement (PGD) caused by surface faulting are potentially devastating natural events which threaten buried pipelines. Although small regions within the pipeline network are affected by faulting hazards, the rate of the damage is very high since fault movement imposes large deformation on pipelines. On the contrary, the whole of pipeline network is influenced by the wave propagation hazards, but the damage rates is lower which leads to lower pipe breaks and leaks per unit length of the pipe. On the other hand, buried pipelines due to their long length, have to pass through active faults which their large movements may lead to failure and rupture of the buried pipes. It is, therefore, essential to investigate the behavior of buried pipelines against fault displacements in order to mitigate the losses caused by these natural events and to try to keep them in service under various situations. Over the years, many researchers have attempted to analyze pipeline behavior via numerical, analytical an experimental modeling, but most of these works were designed to assess pipe response to strike-slip faulting and some were implemented to recognize the behavior of pipelines under normal faulting with right deformation angles. In the present study, In order to understand the behavior of the pipelines under reverse fault movements, the effects of different geotechnical and geometric conditions on the response of the pipes is examined. Numerical simulations have been conducted using the software ABAQUS based on finite element method. In most of the previous studies, a simplified beam-spring model was used to simulate the behavior of the pipes, but in this study a 3-D continuum model is employed to simulate the behavior of the buried pipes against reverse fault movements. In order to increase the accuracy of the analysis, it is tried to use the elements that best match with reality of the nature of soil and pipe behavior and the interaction between them. The results of the numerical study confirmed that the compressive strains in pipe caused by reverse faulting are larger than the tensile strains, thus compressive strains are considered as the main cause of the failure of the buried pipes in the reverse fault motions. Investigating the pipes behavior in different soil types demonstrated that the buried pipelines in loose and soft soils experience less amount of strain in comparison with those which are bureid in other types of the soils. This is due to the fact that the displacement of the pipeline in loose and soft soils is easier and there are less soil resistance forces against pipe displacement. The assessment of effect of soil dilatation angle illustrated that in large fault displacements, the amounts of pipe strain decline with the reduction of the dilation angle, while changing the modulus of elasticity of the soil has no impact on the response of the pipes. The results also showed that by reducing the burial depth, the level of strain induced in the buried pipes decreases.
    Keywords: Buried Pipe, Reverse Fault, Numerical Model, ABAQUS Software, Pipe, Soil, Interaction
  • M. Vaghefi *, N. Safaripour, E. Zarei, A. Mahmoudi, Sh.Hashemi Pages 245-255
    Submerged vanes are simple structures that can be used to control the sediment and redistribute the flow and sediment in open channels. Submerged vanes are low aspect ratio flow-training structures mounted vertically on the riverbed at an angle to the prevailing flow. The technique of submerged vanes is a new and efficient sediment management method in rivers. Odegard and et al (1991) are the creators of the idea of using vanes, they have chosen the angle of the vanes between 15 to 25 degrees and found that the vortex created by the vanes causes a change in the amount and direction of shear stress and dispersion velocity and depth,is resulting in sediment transport. When a submerged vane is installed in the river bed with a small angle to the flow direction, due to the pressure difference on either side of the vane, vortex and induced circulation is created around the vane. as a result of this vortex, at the downstream of vane, sediment are taken from the suction side of the vane and are deposited on the pressure side of the vane. So by installing a row of vanes on the riverbed, sediment can be distributed over a larger surface. In river meandering, when flow passes through a bend, reduction of flow velocity and rising hydrostatic pressure cause super elevation phenomena at outer side and reduction of water surface at inner-side of the bend. A helical motion results, causing erosion of the outer side of the bend. Installation of submerged vanes on the stream bed can reduce erosion of the outer bank significantly. Most of previous studies in this regard have been tasted in a rectangular flume cross section. In this research use of submerged vane and its influence on the bed topography changes, especially around the bridge pier is studied. Experiments were conducted in the laboratory flume with a 180 degree bend with rational curvature of 2 , height of 90 cm, width of 100 cm and a length of straight direction upstream and downstream of the bend respectively 6.5 m and 5 m, material with specific gravity of 1.5 and a cylindrical pier of 5 cm diameter, With clear water conditions u_*/u_(*c) =0.97 ,the water discharge of 70 liters per second, with a depth of 18 cm was tested. The vane was made of 10 mm thick plaxi glass. The height of the vane above the streambed level was 4.5 cm, 75% of the flow depth. and its length is 7.5 cm (1.5 D, D= pier`s diameter). Dissimilar arrays of vanes with same angles (25 degree) to main flow direction were employed. Five experiments were carried out considering various positions of the submerged vanes and one experiment was done without the presence of vanes, only with a bridge pier located at 90 degrees. The performance and efficiency of a submerged vane is related to its position. The results illustrate that the experiment with vanes in parallel, by overlapping of 50%, under angle of 25 degrees counterclockwise with the horizon in the direction of flow, has the best performance in control of pier scour protection.
    Keywords: Scouring, Bridge pier, Submerged vanes, 180 Degree bend