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مهندسی عمران مدرس - سال هفدهم شماره 2 (خرداد و تی ر 1396)

نشریه مهندسی عمران مدرس
سال هفدهم شماره 2 (خرداد و تی ر 1396)

  • تاریخ انتشار: 1396/05/08
  • تعداد عناوین: 22
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  • مقاله اصلی
  • مصطفی آدرسی، ابوالفضل حسنی *، محمدرضا سلیمانی کرمانی، علی یزدیان ورجانی صفحات 1-9
    تکنولوژی نظارت و کنترل سلامت ساخته های مهندسی (SHM ) با تامین راهی جهت ارزیابی ایمنی و دوام رویه بتنی در طول عمر آن، این امکان را به وجود می آورد تا بتوان از میزان سلامت، رویه بتنی درهرحال باخبر بود. به منظور عملیاتی نمودن سیستم SHM لازم است که زیرساخت آن از قبیل ایجاد حسگر در نقاط مختلف رویه بتنی به منظور برداشت لحظه به لحظه اطلاعات مربوطه عملیاتی گردد.

    یکی از مهم ترین و اقتصادی ترین حسگرها، حسگرهایی از جنس خود رویه بتنی راه می باشند که از اختلاط نانولوله کربن با بتن تولید می شوند. هدف از این تحقیق، تشریح چگونگی ساخت حسگرهای بتنی از جنس رویه بتنی راه به گونه ای که خواص مکانیکی (مقاومت فشاری و خمشی) حسگر تولیدشده نزدیک به رویه بتنی راه باشد. در این راستا تعیین مقدار بهینه و کیفیت پخش نانولوله های کربنی با توجه به تاثیر مواد فعال کننده سطحی مختلف به عنوان اصلی ترین پارامتر تاثیرگذار در خواص حسگر موردبررسی قرار گرفت. برای این منظور از دو نوع ماده فعال کننده سطحی و مقادیر متفاوت نانولوله کربن برای ساخت حسگرهای مختلف بتنی استفاده شد. برای سنجش خصوصیات مکانیکی حسگر بتنی، دو آزمایش مقاومت فشاری و خمشی مورداستفاده قرار گرفت و همچنین به منظور ارزیابی الکتریکی پاسخ حسگر نیز دو معیار حساسیت حسگر و انحراف معیار از خطای پیش بینی مورداستفاده قرار گرفت. نتایج نشان دادند که حسگر ساخته شده با نانولوله کربن به مقدار 0.15% وزنی سیمان، به همراه فعال کننده سطحی ترکیبی فوق روان کننده و SDS دارای خواص مکانیکی سازگار با رویه بتنی راه و پاسخ الکتریکی مناسبی است.
    کلیدواژگان: حسگر بتنی، نانولوله کربن، خواص مکانیکی، خواص الکتریکی، بتن
  • حمید امیری، بیتا آیتی *، حسین گنجی دوست صفحات 11-20
    صنایع نساجی بدلیل تنوع رنگزاهای مصرفی و روش های تولید، پساب هایی با کمیت و کیفیت شیمیائی متفاوت تولید می کنند. بعضی از این رنگ ها بدلیل داشتن ساختار شیمیایی پیچیده، نیازمند روش های کارا و دارای راندمان تصفیه، نظیر روش های اکسیداسیون پیشرفته هستند. در این تحقیق به منظور افزایش کارائی فرایند فتوکاتالیستی در تصفیه پساب حاوی Reactive Yellow (RY81)، از یک راکتور دیسکی آبشاری تثبیت شده با نانوذرات اکسیدروی استفاده شد.
    در این راکتور به منظور غلبه بر محدودیت های انتقال جرم در راکتورهای با بستر تثبیتی، سطح دیسک ها بوسیله زبری مصنوعی پوشش داده شد، همچنین به دلیل وجود جریان آبشاری، علاوه بر ایجاد اختلاط، هوادهی فاضلاب بصورت خودبخودی انجام می شد. تاثیر پارامترهای غلظت اولیه رنگزا، pH، میزان کاتالیست پوشش داده شده و دبی جریان بر حذف رنگزا مورد بررسی قرار گرفت و میزان بهینه پارامترها، به ترتیب mg/L50، 8، gr/m240 و cc/s80 بدست آمد. نتایج مدلسازی سینتیکی نشان داد که مدل لانگمایر- هینشلوود با میزان k_(L-H) و K_ads، به ترتیب mg L-1 hr-1 17/7 و mg-1 L 122/0 توانایی زیادی در پیش بینی نرخ واکنش دارد. در انتها به منظور پیش بینی ثابت واکنش شبه درجه اول، رابطه رگرسیون غیرخطی پیشنهاد شد که با دقت بالایی (R2=0.95) تحت شرایط بهره برداری مختلف توانایی پیش بینی نرخ واکنش را دارد.
    کلیدواژگان: راکتور دیسکی آبشاری، رگرسیون غیرخطی، مدل لانگمایر، هینشلوود، زبری مصنوعی
  • مجید امین افشار* صفحات 21-33
    در این مقاله الگوریتم اصلاح شده کنترل گر بهینه خطی گوسی برای کنترل موثرتر پاسخ لرزه ای سازه های قابی پیشنهاد می گردد. بارهای محیطی (نظیر زمین لرزه) در همان لحظه محاسبه و اعمال نیروی کنترل بر سازه، قابل اندازه گیری نیستند. از اینرو، این بارها در الگوریتم-های کنترل متداول از جمله تنظیم گر درجه دوم خطی و کنترل گر بهینه خطی گوسی، لحاظ نمی شوند. بنابراین فرمان کنترل گر بهینه LQG، صرفا متناسب با حالت تقریبی سازه در لحظه اعمال نیروی کنترل است. در الگوریتم کنترل پیشنهادی، با بهره مندی از یک متغیر جدید، شتاب زلزله، در معادله تخمین گر فیلتر کالمن و تنظیم گر بهینه درنظر گرفته می شود. بر اساس روش پیشنهادی، دو نوع استراتژی کنترل ارائه می گردد. فرمان کنترلی اول شامل نیروی کنترل، ضریبی از حالت تقریبی سیستم و خروجی سنجش حسگرها، در گام زمانی پیشین، است. این حالت تقریبی سیستم در فرمان کنترل اول توسط الگوریتم فیلتر کالمن متداول و شناخته شده محاسبه می گردد. در حالی که در استراتژی کنترلی دوم، نخست تخمین گر فیلتر کالمن بر اساس معادلات فضای حالت جدید اصلاح شده، و سپس از مقادیر حالت تقریبی سازه بدست آمده از آن، در محاسبه فرمان کنترل بهره گرفته می شود. تحلیل عددی کنترل فعال سازه هفت طبقه، جهت ارزیابی تاثیر دو کنترل گر پیشنهادی در کاهش پاسخ لرزه ای سازه تحت زلزله های نزدیک و دور از گسل و مقایسه آنها با پاسخ سازه بدون کنترل و با کنترل گر متداول LQG، انجام گرفته است.
    کلیدواژگان: کنترل بهینه LQG، فیلتر کالمن، کنترل فعال سازه، دینامیک سازه، زلزله
  • حسین بخشی *، مهرالله رخشانی مهر، محمد رامشینی صفحات 33-45
    پیشرفت دانش مهندسی روش ها و تکنیکهای جدید در صنعت ساخت، امکان احداث سازه هایی که به نحو قابل ملاحظه ای سبک، مرتفع و انعطاف پذیرباشند را فراهم کرده است. حساسیت چنین سازه هایی در برابر نیروی باد بیشتر از سازه های سنتی و کم ارتفاع می باشد. اصولا نیروی باد نقش مهم و تعیین کننده ای در طراحی سازه های بلند دارد و لازم است در طراحی آن ها اثر باد و نیروهای حاصل از آن با دقت بیشتری بررسی شود. یکی از پارامترهای مهم و تاثیرگذار در رفتار تعادلی سازه و احساس آرامش افراد مستقر در سازه، میزان ارتعاش سازه است که با درصد توربولانس معرفی می شود. به دلیل وجود تراکم بیشتر پوششهای گیاهی و سازه های پیرامونی در نقاط نزدیک به زمین، میزان درصد توربولانس در ارتفاعات پایین بیشتر می باشد. در این تحقیق با استفاده از مطالعات قبلی در خصوص شبیه سازی لایه مرزی اتمسفریک هوا در تونل باد، مدلسازی نرم افزاری پروفیل سرعت باد ایجادشده در اطراف دو ساختمان در حین ساخت- در مراحل مختلف تکمیل دیوارهای جانبی- با شکلهای متفاوت در پلان، انجام و درصد توربولانس تولیدشده در اطراف هر دو ساختمان بررسی می شود. درنهایت مشخص می شود سازه هایی که در پلان از خاصیت آئرودینامیک بیشتری برخوردارند رفتار بهتری در برابر نیروی باد از خود نشان می دهند.
    کلیدواژگان: مدلسازی لایه مرزی اتمسفریک، تونل باد، درصد توربولانس، آئرودینامیک در پلان
  • محسن خطیبی نیا *، جاسم بنی اسد، حمیدرضا ناصری صفحات 45-55
    در قاب خمشی بتن آرمه، نیروی برشی قابل توجهی در اتصالات آن تحت بار جانبی ایجاد می شود که با تغییرشکل های زیادی همراه است. لذا از مهم ترین عوامل موثر بر رفتار قاب خمشی تحت بار جانبی، عملکرد صحیح اتصالات می باشد. در این تحقیق، 6 الگوی تقویت اتصال تیر-ستون بتن مسلح تقویت شده با استفاده از ورق های الیاف کربنی (CFRP) پیشنهاد شده و عملکرد لرزه ای اتصال بررسی شده است. برای رسیدن به این هدف، ابتدا مدل سازی اتصال تیر-ستون تقویت شده با استفاده از نرم افزار اجزائ محدود آباکوس انجام شده است. در این مدل، مدل سازی بتن با استفاده از مدل الاستوپلاستیک آسیب دیده و ورق های CFRP به صورت الاستیک و ارتوتروپیک مدل شده اند. سپس با استفاده از نتایج تحلیل، انتخاب بهترین الگوی تقویت اتصال تیر-ستون با ورق های CFRP بر پایه ی بهبود عملکرد لرزه ای اتصالات از لحاظ میزان باربری، جذب انرژی، سختی اولیه و تغییر مکانیزم شکست اتصال تعیین شده است. نتایج نشان می دهد که چیدمان مناسب ورقهای CFRP، می تواند باعث افزایش میزان باربری، بار ترک خوردگی، سختی اولیه، استهلاک انرژی و جذب انرژی اتصال شود. همچنین الگو های تقویتی پیشنهادی باعث انتقال شکست از بر ستون به تیر در اتصال می شود.
    کلیدواژگان: اتصال تیر- ستون، تقویت اتصال، ورق های الیافی کربنی، بهبود عملکرد لرزه ای
  • محمد شاکرخطیبی*، علی بهنامی، رضا دهقانزاده، سیاوش درفشی، میرمحمد چاوشباشی، زهرا اکبری، اسماعیل فاتحی فر صفحات 55-67
    این مطالعه با هدف ارزیابی عملکرد سیستم لجن فعال هوادهی گسترده مورد استفاده برای تصفیه فاضلاب مجتمع پتروشیمی تبریز انجام شده است. سیستم تصفیه شامل آشغالگیر، API، متعادل سازی، انعقاد و لخته سازی، سیستم DAF، حوض هوادهی، زلال ساز اولیه و ثانویه و فیلتراسیون می باشد. این تصفیه خانه جهت تصفیه فاضلاب صنعتی تولیدی از واحدهای مختلف مجتمع و با هدف استفاده مجدد از پساب تصفیه شده، طراحی شده است. جهت ارزیابی عملکرد تصفیه خانه، نمونه های ترکیبی 12 ساعته متناسب با دبی در 4 نوبت در طی 6 ماه برداشته شده و پارامترهای COD، BOD5، TDS، TSS، فنل، سیانید، روغن، آمونیاک و TKN مطابق با روش های استاندارد اندازه گیری شده اند. همچنین ساختار جمعیت میکروبی سیستم بیولوژیکی نیز مورد بررسی قرار گرفته است. ارزیابی عملکرد تصفیه خانه به صورت کلی و واحد به واحد انجام شده و بر اساس نتایج، مقادیر COD، BOD5 و TSS در ورودی و خروجی تصفیه خانه به ترتیب 230±1319، 491±967 و 174±227 میلی گرم بر لیتر و 6/19±6/73، 9/25±6/33 و 9/5±4/6 میلی گرم در لیتر بوده است. همچنین، در مقادیر بار آلی kg/m3.d 15/0±48/0 در حوض بیولوژیکی، راندمان حذف COD و BOD5 به طور میانگین به ترتیب 37 و 46 درصد محاسبه شده است. نتایج آنالیز میکروبی نشان داد که از میان باکتری های جداسازی شده، جنس های Alcaligenes، Pseudomonas، Bacillus، Moraxella و Veillonella به عنوان باکتری های نیتریفایر هتروتروف غالب در سیستم می باشند.
    کلیدواژگان: ارزیابی عملکرد، پتروشیمی، لجن فعال، تصفیه فاضلاب، آنالیز میکروبی
  • حسین تحقیقی*، محمد مهدی حاج نوروزی صفحات 67-80
    خطوط لوله موسوم به شریان های حیاتی در مقایسه با سایر ابنیه متعارف از اهمیت ویژه ای در خدمت رسانی به طیف وسیعی از جامعه برخوردار هستند. با مروری بر خرابی های ایجاد شده در زلزله های گذشته، جابه جایی ناشی از حرکت گسل یکی از مخاطرات اصلی برای لوله های مدفون قلمداد می شود. با توجه به محدودیت روش های تحلیلی، انجام مطالعات شبیه سازی عددی و ارزیابی دقیق تر بازتاب لوله های مدفون ضروری به نظر می رسد. در این تحقیق، اثر جابه جایی قابل انتظار گسل های معکوس بر روی پاسخ خطوط لوله فولادی پیوسته مدفون با استفاده از روش اجزاء محدود سه بعدی تحلیل می شود. در این بررسی، تاثیر عوامل مختلف از جمله زاویه تقاطع لوله با گسل، زاویه شیب گسل، مشخصات خاک پیرامون لوله، عمق دفن و خصوصیات سطح خارجی لوله مطالعه شده است. تحلیل رفتار لوله به روش استاتیکی غیرخطی و با لحاظ نمودن اثر اندرکنش لوله و خاک صورت می گیرد. در ادامه، راهکارهای متعددی برای کنترل و یا کاهش میزان خرابی در خط لوله ناشی از اثر گسلش ارائه می گردد.
    کلیدواژگان: اندرکنش خاک - لوله، گسل معکوس، روش اجزاء محدود، عملکرد لوله، تحلیل غیرخطی
  • کیوان توکلی، حسین منتصری* صفحات 81-92
    در این تحقیق با استفاده از نرم افزار فلوئنت به ارزیابی مدل های دوفازی اویلری و فاز گسسته لاگرانژی در مدل سازی پدیده انتقال رسوب و مکانیسم های ورود رسوبات به آبگیر جانبی واقع در موقعیت 115 درجه از یک کانال قوسی 180 درجه با روش تزریق رسوب پرداخته شده است. برای بررسی عملکرد مدل های دوفازی، روند حرکت رسوبات در زمان های مختلف از شروع تزریق درمدل های عددی با مدل آزمایشگاهی مقایسه گردیده اند. نتایج نشان دهنده عملکرد مناسب هر دو مدل در تعیین مسیر حرکت ذرات بستر در زمان های مختلف در کف کانال و مکانیسم ورود رسوبات به داخل آبگیر می باشد اما مدل اویلری از عملکرد بهتری برخوردار است. در شبیه سازی توپوگرافی بستر نیز عملکرد روش اویلری بسیار بهتر از مدل فاز گسسته بوده است. در عوض روش فاز گسسته توانایی تعیین درصد ذرات منحرف شده به داخل آبگیر را دارا می باشد. در این تحقیق اثر زاویه انحراف آبگیر و درصد دبی آبگیری بر مکانیسم شکل گیری توپوگرافی بستر، مکانیسم ورود رسوبات به آبگیر و درصد رسوب انحرافی مورد مطالعه قرار گرفته است. مکانیسم ورود رسوبات به ابگیر در دبی های آبگیری مختلف متفاوت است اما همواره دو پشته رسوبی در مجاورت قوس داخلی در نیمه اول و دوم قوس ایجاد می شود. افزایش دبی آبگیری باعث کاهش نسبی ابعاد پشته های رسوبی می گردد. مکانیسم ورود رسوبات به آبگیر تحت تاثیر زاویه انحراف آبگیر نیز میباشد. در زاویه آبگیری 50 درجه کمترین مقدار رسوب در کلیه دبی های آبگیری وارد آبگیر می گردد.
    کلیدواژگان: مدل دوفازی اویلرین، مدل دو فازی فاز گسسته، توپوگرافی بستر، مکانیسم انتقال رسوب، فلوئنت
  • محمد مهدی خلوصی*، علی رئیسی استبرق، جمال عبدالهی صفحات 93-106
    در این پژوهش، رفتار یک خاک رسی آلوده به ماده هیدروکربنی آنتراسن و امکان بهسازی آن جهت بهبود خواص فیزیکی و مکانیکی، با افزودن سیمان، مورد مطالعه قرار گرفت. بدین منظور، نمونه های خاک طبیعی، خاک آلوده به آنتراسن، خاک-سیمان و خاک آلوده اختلاط یافته با سیمان در مقادیر (5، 10، 15و 20 درصد) سیمان تهیه شدند و بر روی آنها آزمایش مقاومت فشاری محصور نشده (USC) و حدود اتربرگ انجام شد. جهت انجام آزمایش مقاومت، از روش تراکم استاتیکی اقدام به ساخت نمونه ها شد و آزمایش روی نمونه های حاوی سیمان در زمان عمل آوری (3، 7، 14 و 28 روزه) صورت پذیرفت. نتایج نشان داد که افرودن آنتراسن، سبب افزایش حدود اتربرگ در خاک آلوده نسبت به خاک طبیعی می گردد. افزودن سیمان به خاک طبیعی و خاک آلوده به طور کلی حدود اتربرگ در نمونه-ها را کاهش می دهد. همچنین نتایج نشان داد آلودگی خاک به آنتراسن، کاهش مقاومت خاک آلوده نسبت به خاک طبیعی را در پی دارد. با افزودن سیمان به خاک آلوده، مقاومت آن افزایش می یابد؛ این افزایش مقاومت تابعی از درصد سیمان بکار رفته و زمان عمل آوری است. از طرف دیگر نتایج بدست آمده از مدول الاستیسیته خاک حاکی از افزایش شکنندگی خاک آلوده اختلاط یافته با سیمان است که با افزایش درصد سیمان بکار رفته و یا زمان عمل آوری، این شکنندگی بیشتر می گردد.
    کلیدواژگان: حدود اتربرگ، زمان عمل آوری، فلوکولاسیون، مدول الاستیسیته خاک
  • سیدعلی اصغر حسین زاده*، ایوب کامرانی نژاد صفحه 105
    تحقیق حاضر با استفاده از روش المان محدود به بررسی کمی و کیفی تاثیر نسبت لاغری و شرایط تکیه گاهی در خصوصیات رفتار غیرخطی و جذب انرژی پانل های برشی فولادی و آلومینیومی می پردازد. صفحات لاغر، بسته به میزان لاغری، تا لحظه وقوع کمانش ظرفیت نسبتا محدودی در ناحیه رفتار خطی دارند و عمده باربری آن ها در ناحیه پس از کمانش صورت می گیرد. در این محدوده از لاغری، ظرفیت باربری می تواند به میزان قابل توجهی کوچکتر از ظرفیت اسمی تسلیم برشی باشد و ورق کمی بعد از وقوع اولین تسلیم به پایان باربری خود می رسد. در صفحات با لاغری متوسط، عمده باربری در محدوده رفتار خطی صورت می گیرد. کمانش و تسلیم تقریبا به طور همزمان اتفاق می افتد و پس از آن، ورق تا حدی به باربری در ناحیه غیرخطی ادامه می دهد. در این محدوده از لاغری، ظرفیت نهایی تا حدی کوچکتر از ظرفیت اسمی تسلیم برشی است. در صفحات با لاغری کم نیز عمده باربری در ناحیه رفتار خطی تا قبل از وقوع اولین تسلیم در ورق صورت می گیرد، لیکن تقریبا همزمان با وقوع کمانش در ورق (در صورت وقوع) سیستم به پایان باربری خود می رسد. در این محدوده از لاغری، ظرفیت نهایی ورق تقریبا با ظرفیت اسمی تسلیم برشی آن برابر است. همچنین در شرایط یکسان بارگذاری، افزایش ضخامت و مدول االاستسیته مصالح بیشترین تاثیر را در افزایش جذب انرژی صفحات دارد، درحالیکه تاثیر تنش تسلیم مصالح و شرایط گیرداری به مراتب کمتر ارزیابی می شود.
    کلیدواژگان: پانل برشی، صفحات، رفتار چرخه ای، روش اجزاء محدود، تحلیل غیرخطی
  • احسان دهقانی*، محمدکاظم بحرانی، وحیدرضا افخمی صفحات 107-120
    یکی از مسائلی که مهندسین سازه در طراحی سازه های فولادی بوسیله نرم افزار های تجاری از قبیل SAP یا ETABS با آن مواجهند، نحوه در نظر گرفتن اثرات ناحیه همپوشانی المانها (طول ناحیه صلب انتهایی) در چشمه اتصال است. در این نرم افزارها امکان در نظر گرفتن این ناحیه بصورت کاملا صلب یا نیمه صلب وجود دارد، در حالی که اتخاذ هر یک از این گزینه ها منجر به تفاوت قابل ملاحظه ای در نتایج و محاسبات خواهد شد. در این تحقیق با معرفی دو مدل تحلیلی متعارف در مدلسازی چشمه اتصال و تمرکز روی اتصال با ورق انتهایی، به بررسی دقیقتر تاثیر میزان طول ناحیه صلب انتهایی در نتایج مدلسازی قابهای فولادی پرداخته شده است. برای این منظور نتایج بدست آمده از تحلیل به روش مرسوم با نتایج بدست آمده از تحلیل دقیقتر بر اساس روش پیشنهادی آیین نامه یوروکد مقایسه شده اند. در نهایت پیشنهاداتی برای در نظر گرفتن میزان صلبیت ناحیه انتهایی المانها به منظور دستیابی به نتایج دقیقتر سختی و مقاومت قاب فولادی ارائه گردیده است.
    کلیدواژگان: چشمه اتصال، طول ناحیه صلب انتهایی، اتصال با ورق انتهایی
  • مجید رضایی، احمد جمشیدی زنجانی* صفحات 120-130
    سالانه میلیون ها تن پسماند در سراسر دنیا تولید می شود که مدیریت صحیح آنها از مهم ترین دغدغه های جوامع بشری است. مکان یابی محل دفن پسماندهای شهری فرآیندی پیچیده است که نیاز به معیارهای متعدد زیست محیطی و فنی دارد. در این پژوهش، مکان یابی محل دفن پسماندهای شهری شهرستان اراک با روش تصمیم گیری چند معیاره در GIS انجام شده است. نخست پس از تبدیل داده های وکتوری به لایه های رستر و تهیه نقشه های رستری لایه های اطلاعاتی، استانداردسازی لایه ها بر اساس نوع توابع عضویت فازی (صعودی یا نزولی) بین صفر و یک انجام شد. برای تعیین وزن نهایی لایه ها از روش فرآیند تحلیل سلسله مراتبی (AHP) استفاده شد. در مرحله بعد روش ترکیب خطی وزن دار برای تلفیق لایه های اطلاعاتی مورد استفاده قرار گرفت. در نهایت 5 طبقه با تناسب های مکانی بسیار پایین، پایین، متوسط، بالا و بسیار بالا برای دفن پسماندهای شهری شهرستان اراک حاصل شد و بالاترین تناسب مکانی در طبقه فازی 69/0 تا 87/0 به دست آمد. بیشترین مساحت برای انتخاب مکان دفن پسماندهای شهری شهرستان اراک مربوط به مناطق با تناسب مکانی بالا با وسعت 44/1212 کیلومتر مربع و کمترین مساحت مربوط به مناطق با تناسب مکانی بسیار پایین با وسعتی حدود 73/270 کیلومتر مربع محاسبه شد.
    کلیدواژگان: مکان یابی، منطق فازی، تصمیم گیری چند معیاره، لندفیل، سیستم اطلاعات جغرافیایی
  • فاطمه رضایی*، غلامرضا موسوی، علیرضا ریاحی بختیاری، یدالله یمینی صفحات 131-142
    مهمترین پارامتر برای حذف آلاینده های آلی در روش ازن زنی کاتالیستی بکارگیری کاتالیست مناسب است. در این تحقیق کارائی کاتالیست های MnO/GAC و MgO/GAC برای حذف تولوئن از هوا در حضور ازن در مقیاس آزمایشگاهی مورد مطالعه قرار گرفت.
    کاتالیست های MnO/GAC و MgO/GAC با روش سل-ژل تولید و با آنالیزهای BET، XRD و SEM تعیین مشخصات شدند. متغیرهای زمان ماند (5/0، 1، 5/1، 2و Sec 4)، غلظت تولوئن (100، 200، 300 و ppmv 400) و دمای هوای ورودی (25، 50، 75 و ̊C100) بعنوان پارامترهای عملکردی موثر در فرایند ازن زنی کاتالیستی مورد مطالعه قرار گرفتند. دوز ازن ورودی معادل g/h 1/0 در کلیه آزمایشات ازن زنی کاتالیستی ثابت نگه داشته شد. کارائی کاتالیست های MgO/GAC و MnO/GAC در حذف تولوئن در حضور ازن بر اساس زمان نقطه شکست و ظرفیت حذف تعیین و از نظر آماری مقایسه شدند.
    نتایج نشان داد افزایش زمان ماند از 5/0 به Sec4 زمان شکست ستون MgO/GAC و MnO/GAC را به ترتیب 3/11 و 9/13 برابر افزایش داد. افزایش غلظت تولوئن (ppmv 100-400) باعث کاهش زمان نقطه شکست و افزایش ظرفیت حذف به ترتیب به میزان 65% و 1/39% برای MgO/GAC و 2/62% و 4/50% برای MnO/GAC شد. کارائی کاتالیستMgO/GAC و MnO/GAC با افزایش دما از 25 به ̊C100 به ترتیب 3/78% و 5/31% افزایش یافت.
    یافته های تحقیق نشان داد کاتالیست های MgO/GAC و MnO/GAC پتانسیل بالایی برای حذف ترکیبات آلی فرار از جریان هوا در حضور ازن دارند. کاتالیست MgO/GAC نسبت به MnO/GAC پتانسیل بالاتری در حذف تولوئن از جریان هوا در حضور ازن داشت (05/0P ≤).
    کلیدواژگان: ازن زنی، تصفیه هوا، کاتالیست، اکسید منگنز، اکسید منیزیم
  • رزا رهبری، عباسعلی تسنیمی* صفحات 143-156
    در این مقاله به بررسی ضوابط طراحی براساس استاندارد 2800 و متناسب نمودن طراحی با سطح عملکرد انتخابی پرداخته شده است. برای انجام این بررسی 6 قاب خمشی بتن مسلح سه دهانه با شکل پذیری متوسط و تعداد طبقات 4، 5، 6، 8، 10 و 12 در نرم افزار IDARC مدلسازی و تحلیل استاتیکی غیرخطی و دینامیکی غیرخطی با استفاده از 7 شتابنگاشت بر روی آنها انجام شده است. نسبت نیاز به ظرفیت خمشی هریک از ستونها و سطح عملکرد سازه محاسبه شده و سپس با استفاده از نتایج حاصل شده معیار کنترل تغییرمکان نسبی و همچنین ضریب بزرگنمایی تغییرمکان نسبی در ویرایش سوم و چهارم استاندارد 2800 مورد نقد و بررسی قرار گرفته است. بدین منظور نسبت تغییرمکان غیرارتجاعی حاصل از تحلیلهای غیرخطی به تغییرمکان ارتجاعی تعیین و ضریب (Cd) برای هریک از قابها محاسبه شد. سپس نتایج حاصل با ضریب بزرگنمایی استاندارد 2800 (R7/0) مقایسه و به مقدار R5/0 اصلاح گردید. در نهایت نظر به اینکه ویرایش چهارم استاندارد 2800 در حال ابلاغ میباشد، به منظور بررسی تغییرات ایجاد شده، یک نمونه از قابها با ضوابط پیش نویس نهایی استاندارد 2800 و همچنین با استفاده از ضریب بزرگنمایی کاهش یافته (R5/0) مجددا طراحی و تغییرات ایجاد شده در پاسخ سازه مورد مطالعه قرار گرفت. نتایج بدست آمده حاکی از آن است که کاهش محدودیت تغییرمکان نسبی موجب کاهش ابعاد مقاطع، کاهش تمرکز آسیب در طبقه ای خاص از سازه، طراحی واقع بینانه تر سازه و در نهایت نزدیک شدن سطح عملکرد سازه به هدف عملکردی استاندارد 2800 میشود.
    کلیدواژگان: نسبت نیاز به ظرفیت خمشی، ضریب بزرگنمایی تغییر مکان، ستون بتن مسلح، سطوح عملکرد
  • طرح پژوهشی
  • سید محمد علی زمردیان، مرتضی عرب، مسیح ذوالقدر صفحات 157-166
    مهمترین دلیل نگرانی، در خصوص پایداری پل ها، وقوع آبشستگی موضعی در اطراف آن هاست.مساله آبشستگی موضعی در اطراف پایه و تکیه گاه پل در سال های اخیر به طور گسترده توسط محققین مختلف مورد بررسی قرار گرفته است که نتیجه آن ارائه روش های مختلفی برای کنترل و کاهش آبشستگی بوده است. یکی از این روش ها تراکم خاک بستر می باشد. تراکم بستر رسوبی اطراف فونداسیون پل، مقاومت آن را در مقابل آبشستگی افزایش داده، موجب کاهش آبشستگی و به تاخیر افتادن پیشرفت آن می شود. در تحقیق حاضر به منظور کاهش آبشستگی در اطراف پایه و تکیه گاه پل 5%، 10% و 15% رس به بستر غیر چسبنده اضافه و سپس متراکم گردید. با توجه به نتایج آزمایشات مشاهده شد هنگامی که 15% رس به رسوبات غیر چسبنده اضافه شود، در شرایط اشباع بستر و تراکم 70%، بعد از گذشت 24 ساعت از شروع آزمایش، آبشستگی پیرامون پایه به طو کامل حذف می گردد.
    کلیدواژگان: آبشستگی، تکیه گاه پل، پایه پل، تراکم، کاهش آبشستگی
  • مقاله اصلی
  • صالح شریف طهرانی*، سید حسین حسینی لواسانی، بهروز شیرگیر صفحات 167-176
    روسازی راه از مهمترین سرمایه های هر کشوری می باشند و سالانه هزینه های قابل توجهی صرف تعمیر و نگهداری آنها می شود. با توجه به کاهش مقاومت لغزشی راه ها در هنگام وجود برف و یخ، مقادیر زیادی ماده یخ زدا برای آب نمودن برف و یخ راه ها استفاده می شود. مواد یخ زدا، باعث ذوب برف و یخ شده و آب حاصل که حاوی ماده یخ زدا می باشد تحت شیب بر سطح راه جریان می یابد. حضور مواد یخ زدا اثرات مخرب زیادی بر روسازی دارد و توجه بسیاری از محققین را به خود جلب نموده است. اما آنچه به خوبی بررسی نشده است، اثرات جریان آب حاوی ماده یخ زدا می باشد. لذا این تحقیق به بررسی اثرات توامان جریان آب و مواد یخ زدا در سیکل های یخ زدن و ذوب شدن بر خرابی های بتن آسفالتی پرداخته است. در این راستا نمونه های آسفالتی ساخته شده تحت اثر پنج حالت مختلف از سیکل های یخبندان و دو ماده یخ زدا شامل نمک یخ زدا و استات کلسیم قرار داده شدند. همچنین به منظور بررسی دوام بتن آسفالتی، یک دستگاه سایش طراحی گردید تا نمونه های آسفالتی را تحت بارگذاری عمودی و اصطکاکی قرار دهد. میزان درصد افت وزن و مقاومت مارشال نمونه ها به عنوان شاخص های خرابی بتن آسفالتی در نظر گرفته شدند. نتایج این آزمایشات نشان می دهد که جریان محلول های یخ زدا در دوره یخبندان باعث افزایش شدت خرابی آسفالت می شود. به علاوه استفاده از نمک یخ زدا تاثیر به مراتب مخرب تری نسبت به استات کلسیم از خود نشان می دهد.
    کلیدواژگان: یخ زدایی، جریان مواد یخ زدا، آسفالت روسازی، خرابی، استات کلسیم
  • شهیر*، میثم شایان صفحات 179-191
    کاهش مقاومت و سختی خاک در اثر روانگرایی باعث ایجاد لنگرهای خمشی و تغییرشکل های جانبی زیادی در شمع های واقع در خاک روانگرا می شود. در این تحقیق برای بررسی رفتار شمع در محیط روانگرا از آنالیز دینامیکی همبسته اندرکنش خاک-شمع-سازه (SPSI) استفاده شده است. اندرکنش شمع-خاک با استفاده از روش فنر غیرخطی دینامیکی p-y شبیه سازی شده است. تاثیرات روانگرایی با استفاده از یک ضریب کاهنده به مقاومت جانبی شمع اعمال می گردد. رفتار خاک روانگرا با استفاده از مدل چند تسلیمی وابسته به فشار مدلسازی می شود. برای شبیه سازی اندرکنش فازهای جامد و سیال خاک اشباع بر مبنای تئوری محیط متخلخل اشباع از فرمولاسیون همبسته u-p استفاده شده است. به منظور تایید صحت مدل عددی، نتایج مدل عددی با داده های دو آزمایش سانتریفیوژ مقایسه شده است. پس از صحت سنجی مدل عددی، برای بررسی تاثیر پارامترهای مختلف بر پاسخ دینامیکی شمع و فشار جانبی وارد بر شمع، آنالیز پارامتریک انجام شده است. پارامترهای مورد بررسی شامل ضخامت لایه روانگرا، فرکانس تحریک ورودی، گیرداری سر شمع، سختی شمع، شتاب ماکزیمم ورودی و دانسیته نسبی خاک روانگرا می باشند. نتایج مطالعه پارامتریک نشان داد که فشار جانبی وارد بر شمع تقریبا در عمق لایه روانگرا شده ثایت بوده و حدود 7 الی 10 درصد فشار سربار کل در پایه لایه روانگرا می باشد.
    کلیدواژگان: خاک روانگرا، شمع، اندرکنش، فنر غیرخطی، آنالیز همبسته
  • علی شیخ ابوالحسنی، محمد واقفی*، علیرضا فیوض صفحات 193-201
    در این تحقیق به بررسی آزمایشگاهی تاثیر مواد آب بند کننده بر مقاومت بتن و بتن الیافی پرداخته شده است. بدین منظور برای بتن بدون الیاف و نیز بتن الیافی با الیاف فولادی، پلی پروپیلین و شیشه، پارامتر های مقاومتی فشاری و خمشی با اضافه نمودن مواد آب بند رایج با درصدهای مختلف مورد بررسی قرار گرفته است. آزمایشات مقاومت فشاری و خمشی در سنین 7، 28 و90 روزه بر روی آزمونه های منشوری انجام گرفته است. آزمایشات در 34 طرح اختلاط به تعداد 408 نمونه و با تکرار صورت گرفت. در ساخت بتن الیافی از ترکیب مواد آب بند کننده شامل ماده آب بند کننده پودری با خاصیت اسیدی خنثی و مایع با خصوصیت قلیایی و الیاف شامل فولادی، پلی پروپیلن و شیشه ای استفاده شده است. نتایج آزمایشات بیانگر این است که حضور مواد آب بند کننده ی با خاصیت اسیدی خنثی در بتن بدون الیاف باعث افزایش مقاومت فشاری و خمشی بتن می گردد. همچنین از مهمترین نتایج این تحقیق این است که افزودن 1 درصد ماده آب بند کننده bc40 (با خاصیت اسیدی خنثی) به بتن الیافی شکل گرفته با 2 درصد الیاف فولادی باعث افزایش 27% مقاومت فشاری نسبت به نمونه شاهد با الیافی فولادی و بدون ماده آب بند در مقاومت 90 روزه شده است در حالیکه در مقاومت خمشی این ترکیب تغییر محسوسی ملاحظه نگردیده است. بحث و تجزیه و تحلیل پیرامون نتایج در حالات مختلف از دیگر نکات مطرح شده در این مقاله می باشد.
    کلیدواژگان: مواد آب بند کننده، بتن الیافی، مقاومت فشاری، مقاومت خمشی، طرح اختلاط
  • فرزین نصیری صالح*، مرتضی علوی نیا، حسین اسدی صفحات 203-213
    انتقال رسوب ناشی از بارندگی یکی از اصلی ترین بخش های فرسایش بین شیاری خاک در طبیعت است. در طی رگبارهای طبیعی شدت بارندگی در نوسان است. نوسانات شدت بارندگی در طی رگبار را می توان پروفیل رگبار نامید. در این تحقیق با شبیه سازی چهار رگبار با پروفیل های متفاوت و انرژی جنبشی یکسان بر روی دو نوع خاک متفاوت، اثر پروفیل رگبار بر رواناب و رسوب ناشی از فرسایش بین شیاری مورد بررسی قرار گرفت. نتایج این تحقیق نشان داد اگرچه در هر دو نوع خاک حجم رواناب ناشی از رگبارهایی با پروفیل های مختلف تفاوت معنی داری ندارند اما اثر پذیری حداکثر نرخ رواناب از پروفیل رگبار به نوع خاک بستگی دارد. نتایج مربوط به رسوب نیز نشان داد معنی دار بودن اثر پروفیل رگبار بر تولید رسوب به نوع خاک بستگی دارد. علاوه بر این یافته های این تحقیق نشان می دهد در رگبارهای شدت متغیر استفاده از مدل هایی که فرسایش بین شیاری را با استفاده از شدت بارندگی برآورد می کنند کارایی ندارد. از این رو توسعه استفاده از شبیه سازی رگبارهای شدت متغیر در مطالعات فرسایش خاک و انتقال رسوب می تواند باعث شناخت دقیق مکانیسم های موثر حاکم بر تولید رواناب و رسوب در فرسایش بین شیاری گردد.
    کلیدواژگان: پروفیل بارندگی، رواناب، رسوب، شبیه سازی باران، فرسایش بین شیاری
  • سعید فرزین، خسرو حسینی، حجت کرمی، سید فرهاد موسوی* صفحات 213-223
    مولفه های هیدرولوژیک دریاچه ها نقش اساسی در مدیریت کمی و کیفی آنها دارند. بررسی آشوبناکی و تصادفی بودن سری زمانی بارش در دریاچه ها اهمیت دارد. در این تحقیق، با استفاده از روش بعد همبستگی (CDM)، سری زمانی بارش ماهانه دریاچه ارومیه، طی دوره آماری 40 ساله (1386-1346) تحلیل شد. پس از محاسبه زمان تاخیر، با استفاده از روش میانگین اطلاعات متقابل (AMI)، بعد نهشتن و الگوریتم نزدیکترین همسایگی کاذب (FNN)، فضای حالت بازسازی و بعد همبستگی محاسبه گردید. سپس، با محاسبه شاخص نمای لیاپانوف و طیف توانی فوریه، وجود آشوب بررسی شد. نتایج نشان داد که بعد همبستگی غیرصحیح (56/2)، مقدار مثبت نمای لیاپانوف با حداکثر حدود 5/2 و پهنای وسیع باند طیف فوریه، شواهدی بر وجود آشوب در سری زمانی بارش ماهانه می باشند. بنابراین، سیستم دارای نظم است و جزو فرایند های تصادفی مطرح نمی شود. در چنین سیستمی، نظریه آشوب قابلیت استخراج سری زمانی کوتاه مدت از سری زمانی بلندمدت را دارد.
    کلیدواژگان: بعد همبستگی، بارش ماهانه، دریاچه ارومیه، طیف توان فوریه، نمای لیاپانوف
  • بهروز کشته گر* صفحات 235-246
    خوردگی میلگردها در بتن یک فرایند پیچیده بوده که موجب کاهش سطح مقطع فولاد و زوال مقاومت سازه بتن آرمه می گردد. در این مقاله خواص آماری پارامترهایی مانند ضریب انتشار یون های مخرب، نرخ خوردگی و زمان شروع خوردگی برای خوردگی موضعی آرماتور تیرهای بتن آرمه ارزیابی شده است. از توابع توزیع احتمال مختلف مانند گاما، نرمال، لوگ-نرمال، گامبل و وایبول جهت برازش پارامترهای خوردگی استفاده شده و بهترین تابع توزیع احتمال پارامترهای خوردگی با استفاده از آماره مربع کا انتخاب گردیده است. بر اساس تحلیل آماری پارامترهای خوردگی، اثر خصوصیات آماری متغیرهایی نظیر مقاومت فشاری بتن، پوشش آرماتورها، مقدار ثابت و مورد انتظار یون مخرب بر زمان شروع خوردگی با استفاده از روش شبیه سازی مونت کارلو بررسی شده است. در انتها میزان کاهش آرماتورهای وابسته به زمان در تیرهای بتنی برای چهار قطر مختلف میلگرد ( شماره های 8، 12، 16 و 20) مطالعه شده است. نتایج حاکی از آن است که اکثر پارامترهای خوردگی از تابع توزیع احتمال لوگ-نرمال پیروی می کند و پوشش آرماتورها نقش بسزایی در کاهش خوردگی میلگردها دارد. همچنین خواص آماری سطح مقطع خورده شده به قطر و زمان خوردگی وابسته است بطوریکه افزایش زمان و کاهش قطر موجب کاهش بیشتر سطح مقطع آرماتور می گردد.
    کلیدواژگان: تحلیل آماری، شبیه سازی مونت کارلو، تیرهای بتن آرمه، خوردگی موضعی آرماتور
  • حبیب الله یونسی *_مجتبی هدافوی فر_نادر بهرامی فر. ف مهداد صفحات 247-258
    کمپوست به عنوان یکی از این روش های بازیافت زباله ها به کود می باشد. یکی از مشکلات موجود در این فرایند، مدیریت شیرابه است که اثرات نامطلوبی بر محیط زیست و سلامتی دارد. شیرابه به دلیل داشتن ترکیبات آلی پیچیده که به روش زیستی به سختی تجزیه می شوند، به تصفیه شیمیایی از جمله اکسیداسیون پیشرفته نیاز خواهند داشت. در این مطالعه کارایی فرایند H2O2/UV برای تصفیه شیرابه کمپوست تصفیه شده توسط روش بیولوژیکی در سیستم ناپیوسته مورد بررسی قرار گرفت. هدف از این مطالعه ارزیابی بازده فرایند آب اکسیژنه با تابش UV(H2O2/UV) به منظور حذف اکسیژن خواهی شیمیایی (COD) و رنگ و کدورت با استفاده از روش پاسخ سطحی (RSM) در طرح مرکب مرکزی (CCD) بود. شرایط عملیاتی مختلف شامل pH اولیه، دز آب اکسیژنه و زمان تماس با UV به منظور کاهش آلاینده های شیرابه کمپوست برای بهینه سازی حداکثر حذف آلاینده ها بررسی شد. تعداد 20 تیمار انجام شد. شرایط بهینه درpH اولیه 5/7، دز آب اکسیژنه mL/L 3/2 و زمان تماس با UV در 95 دقیقه حاصل گردید. میزان حذف COD، رنگ و کدورت شیرابه توسط فرایند H2O2/UV در شرایط بهینه حذف با روش پاسخ سطحی به ترتیب %32/12، %83/20 و NTU 68/8 به دست آمد. نتایج نشان داد فرایند H2O2/UV در کاهش کدورت موفق تر بوده است و در حذف COD کارایی چندانی نداشته است.
    کلیدواژگان: شیرابه کمپوست، تصفیه پساب، فرایند اکسیداسیون پیشرفته، H2O2-UV
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  • A. Hassani * Pages 1-9
    Annually, various concrete infrastructures are damaged and may collapse due to the presence of destructive factors. In this regard, the Structural Health Monitoring (SHM) provides a way to evaluate the safety and durability of a structure during its service life in order to ensure the serviceability and sustainability of it. Therefore, the sensor technology is a critical part to operate SHM system for recording of relevant data through its lifespan. Sensor is a device which is capable of identifying the probability or the value of parametric changes and showing them as a relevant output (typically electrical or optical signal. Making materials electrically conductive may be useful in many different ways such as creating piezoresistive sensors with the ability to acquire stress-strain or load-displacement data or creating sensors with the ability to acquire data on the extent of damage to the concrete. The piezoresistive sensor is capable of detecting the applied forces to the structure based on the changes in the electrical resistance. But the damage detection sensor operates based on the contacting conduction of CNTs. This means that by increasing the amount of CNTs in concrete, the three-dimensional contacting network of CNTs is built. When the amount of CNTs exceeds the percolation threshold, the contacting conduction will affect the electrical conduction of nanocomposites. One of the most significant and economical types of the sensor is the damage detection sensor which is provided by mixing conductive fibers (such as carbon nanotubes (CNT)) with concrete. For preparing damage detection sensor, CNTs and surfactants were mixed in the water for 10 minutes using a magnetism stirrer at 5000 rpm. Then, the mix was prepared at one ultrasonic dispersion energy. Then the cement and CNTs were added to high-speed mixer to be uniformly mixed. After adding the aggregate to the mixer, the concrete was placed in pre-oiled molds and by applying appropriate vibration, any air that may have been trapped was released. The specimens were curing for 28 dayes and they were tested under the static loading by Instron-Tech. test equipment. In order to remove the effect of polarization which is due to the movement of free ions in the concrete sensor during the measurement, an alternating current generator with the magnitude was used to nullify this phenomenon. After preparing the sensors, two main factors affecting the performance of concrete sensors are the amount of CNTs and their dispersion quality in the mixture. The goal of this study is to determine the optimum amount of CNTs with regard to the combined effects of the surfactant and the CNTs dispersion quality on the performance of the sensor using various criteria such as sensitivity of the sensor (Se), the standard deviation of the prediction error as electrical criteria and comparison and flexural strength as mechanical critera. The results have demonstrated that the sensor provided by 0.15 wt% CNTs, superplasticizer and SDS as a surfactant has the best performance. Also, The static criteria indicated that the quality of the dispersion (using proper surfactant material) and the amount of CNTs are effective on the sensitivity and the standard deviation of the prediction error, respectively.
    Keywords: Concrete sensor, Carbon nanotubes, Mechanical Properties, Electrical properties, concrete
  • Bita Ayati * Pages 11-20
    The use of different synthetic dyes in textile industries has increased in recent decay, resulting in the release of dye-containing industrial effluents into natural aquatic ecosystem. Since most of dyes are usually very recalcitrant to microbial degradation, therefore dye removal from effluent is a main concern in many studies. Different process was used for the treatment of dye effluent. In the last few years, studies were focused on advanced oxidation process (AOPs) methods such as UV-ZnO, UV-H2O2, UV-O3 and UV-TiO2. Photocatalytic process such as UV-ZnO is an efficient method that treats non-degradable wastewater by active radicals. The photocatalysis needs a photo-reactor that contacts reactant, products and light. In recent years, different types of photo-reactors have been used for wastewater treatment. In some reactors, nano-photocatalysts are utilized in slurry form, and the other particles are coated on bed. In Photocatalytic reactors with fixed bed, nano-photocatalysts are immobilized on bed and do not need the separation unit, but the main disadvantage of this photo-reactors is the low mass transfer rate between wastewater and nano-photocatalysts. Consequently, Different optimal photo-reactors were developed for increasing mass transfer rate. In this study, a novel photocatalytic cascade disc reactor coated with ZnO nano-photocatalysts was applied and in order to increase mass transfer rate artificial roughness were created on the surface of disks. Applying artificial roughness changes mass transfer rate by providing vertical mixing, creating secondary currents and increasing the Reynolds number. This photo-reactor has a number of advantages that include eliminating the need for catalyst separation units as the catalyst is immobilized, creating the flow mixing by non-mechanical method, increasing the transport of oxygen from the gas phase to the photocatalyst surface by providing the flow cascade pattern. The photo-reactor was used in order to remove Reactive Yellow 81 (RY81) dye from textile industry effluent, by means of UV-ZnO process. RY81 is a reactive dye composed of 10 Benzene rings and two –N=N azo bonds. The effect of different operational parameters such as initial Concentration of dye, pH, Catalyst surface loading and flow rate in removal efficiency was investigated, and the optimal value of those parameters were 50 mg/L, 8, 40 gr/m2 and 80 cc/s, respectively. A rate equation for the removal of RY81 was obtained by mathematical kinetic modeling. The Langmuir-Hinshelwood kinetic model is one of the most common kinetic models that are used for studying the kinetics of heterogeneous photo-catalysis. The results of reaction kinetic modeling indicate the conformity of removal kinetics with Langmuir-Hinshelwood model, and the constants kL-H and Kads were obtained 7.17 mg L-1 hr-1, 0.122 mg-1 L, respectively.
    One way of inserting various operational parameters to a rate equation is regression analysis. Therefore, in this study, nonlinear regression model was developed for prediction pseudo- first order rate constant as a function of initial concentration of dye, pH, catalyst surface loading and flow rate. This equation could properly predict (R2=0.95) the removal rate constant of RY81 removal in the photocatalytic cascade disk reactor under different operational conditions and a good consistency was observed between the calculated results and experimental findings.
    Keywords: Reactive Yellow 81, Non-linear regression, Cascade photocatalytic reactor, Langmuir-Hinshelwood
  • Maijd Amin Afshar * Pages 21-33
    In this paper, a modified linear-quadratic-Gaussian (MLQG) optimal control algorithm is proposed for controlling the seismic response of frame structures. Environmental loads (e.g., earthquakes) at the moment of calculation and exertion of control forces to structures, can not be measured. So these loads are not included in the conventional control algorithms, such as linear quadratic regulator and linear-quadratic-Gaussian control. Therefore the command of LQG optimal controller is merely a proportional feedback of estimated state of structure at the moment of exertion. This state approximation is performed by optimal state stimator or Kalman filter. In the proposed control algorithm, using a new variable, including control force andearthquake force, acceleration of gound motion, which is non-measurable duting exertion of control force, is considered in the state space equation of motion and also in both of Kalman Filter estimator and the optimal regulator. According to the proposed control algorithm, two ways are selected. So first command control are sum of the control force and ratios of the estimated state and measurement output of sensors, which are obtained and used in previous time step. The estimated state of system, used in the first command control, is calculated by the conventional and knownKalman Filter. but in second strategy of control, First, the Kalman Filter estimator is modified based on new state space equations, and then the estimated state of structure obtained from it, is used for calculation of command control. Numerical simulation of a seven-storey structure with active control system under several far-fault and near-fault earthquakes are performed to show effectiveness of two proposed controls on mitigation of structural responses and compare to those of a uncontrolled structure and a structure controlled with conventional control. Also sensitivity of some perforemance measures for controllers are investigated against changes of some controlling and perturbation parameters of systems or uncertainties. The alalysis results demonstrate that control performance of the proposed controllers, specially the second one, are better and also stable and robust under variations of uncertainties. So that the greatest reduction in maximum displacement (even up to 80 percent) compared to uncontrolled displacement of structure and meanwhile, very low energy consumption are attained by the second proposed control strategy.but in second strategy of control, First, the Kalman Filter estimator is modified based on new state space equations, and then the estimated state of structure obtained from it, is used for calculation of command control. Numerical simulation of a seven-storey structure with active control system under several far-fault and near-fault earthquakes are performed to show effectiveness of two proposed controls on mitigation of structural responses and compare to those of a uncontrolled structure and a structure controlled with conventional control. Also sensitivity of some perforemance measures for controllers are investigated against changes of some controlling and perturbation parameters of systems or uncertainties. The alalysis results demonstrate that control performance of the proposed controllers, specially the second one, are better and also stable and robust under variations of uncertainties. So that the greatest reduction in maximum displacement (even up to 80 percent) compared to uncontrolled displacement of structure and meanwhile, very low energy consumption are attained by the second proposed control strategy.
    Keywords: LQG optimal control, Kalman filter, Active structural control, Structural dynamics, earthquake
  • Hoseiin Bakhshi * Pages 33-45
    Development in engineering knowledge, methods and techniques in the construction industry has provided the possibility of establishing structures that are significantly light, high and flexible. The sensitivity of high buildings against wind power is more than other ordinary buildings. Basically, wind power has an important role in the design of high buildings. Therefore, it is essential to study more carefully the effects of wind forces in the design of these structures. An important issue that must be considered in all tall building studies in the field of wind engineering is study of atmospheric boundary layer around the structures. Atmospheric boundary layer is a layer of air around the surface of the earth that at a height above the earth surface, friction has not effect on the natural flow of wind. In the present experimental research a wind tunnel was used. It generally consisted of a huge duct in collaboration with a fan in the middle. By switching on the fan, air blows into the duct. Different measurement devices were installed along the wind tunnel which made it possible to consider different test sections in width, height and longitude. In the present research a wind tunnel with 2 meter long, 1.2 meter height and 1 meter width was used with an open wind circulation system. To check every structure in the wind tunnel environment at first the atmospheric boundary in that environment should be simulated. After this stage, any structure can be placed in a wind tunnel and be examined. In this study, two buildings with the same height and cross sectional area but different in plan were examined experimentally. Both Buildings were modeled with scale of 1:600 as a fifteen floors structure with twenty cm height. Buildings had square and circular plans. Speed, pressure and turbulence at any point of the tunnel test section can be measured directly. In this study the rate of percentage of turbulence is provided in different parts of the front and back of the building. In the recent years, numerical models specially finite volume methods have been developed in the fluid sciences. In the present research, all models were simulated in Fluent software numerically. A comparison between numerical and experimental data could help one to see the ability of numerical models. Moreover, by using the numerical model many points which are not accessible in the experimental model can be recorded and analyzed. In different sides of each model the turbulence percent was measured and analyzed. Results showed that by increasing the side walls the percent of turbulence increased. The reason can be more effect of wind impact on the building surface which caused to increase the friction meaningfully. It was also concluded that covering the ground surface around the considered tall building with canopy and trees or other buildings caused more percent of turbulence. It was also observed that from a certain height of building to up, the turbulence percent was went to zero which means non friction along the wind towards the structure. The results of this study helps to provide a better understanding of the effect of plan shape of a tall building in view of wind impact.
    Keywords: wind tunnel, Percent of Turbulence, Tall Building, Canopy, Fluent
  • Mohsen Khatibinia * Pages 45-55
    In the design process of a moment resisting frame (MRF), the principle of weak–beam and strong–column should been considered because the plastic hinge occurs in the beams. This mechanism is caused that the frame has capable of dissipating significant energy and remain stable in the inelastic region. Hence, the stability is defined as the ability of the frame to maintain its elastic level of resistance throughout the entire inelastic range of response. Using this principle, plastic hinges can be develop in the beams adjacent to the connections and usually very close to the column face. This mechanism allow cracks caused by the plastic hinging. The cracks can also propagate into the connection core region, and initiate a brittle failure mechanism. Furthermore, the mechanism has been not established in many existing MRFs designed based on the previous codes. Hence, the methods have been proposed and developed in order to relocate the plastic hinge away from the column face. Fiber Reinforced Polymer (FRP) has been used as a strengthening solution of beam–column connections and successfully reported for retrofitting existing structures. In fact, the use of a web–bonded FRP retrofitting system can control the mechanism of plastic hing and provide the strong–column weak–beam concept. Due to the many advantages, such as high strength, low weight, endurance and convenience, Carbon Fiber–Reinforced Polimers (CFRPs) have been widely used in strengthening concrete structures.
    However, the strength and stiffness of CFRP are severely reduced at elevated temperatures, which will affect the strengthening effect seriously.
    In this study, six schemes of strengthened concrete beam–column connection using CFRP are proposed and the seismic performance of the strengthened connection is investigated. In order to achieve this purpose, seven scaled–down RC exterior joint of a typical ordinary MRF are chosen and modeling this strengthened connection is implemented in the general finite element program, ABAQUS software. In the finite element model of strengthened concrete beam–column connection, the concrete is modeled using the damaged plastic model. The sheets of CFRP are also considered as the elastic and orthotropic model. These schemes of strengthened concrete beam–column connection are tested under moderately monotonic/cyclic loads. In order to verify the finite element model of the connection, the analysis results of this model is compared with the experimental investigation on the external beam–column connection repaired strengthened using CFRP. The results demonstrates the verification of the finite element model. The selection of the best scheme of strengthened concrete beam–column connection using CFRP is based on the improvement of the seismic performance of connection such as the load–carrying capacity, the energy absorption, the initial stiffness and changing failure mechanism of connection. The nonlinear results show that the proper layout of CFRP sheets can increase the load–carrying capacity, the energy absorption and the initial stiffness of connections. Furthermore, the proposed schemes of strengthened concrete beam–column connection are caused that the failure is relocated from the column face and located in beam. Therefore, the proposed best scheme of strengthened concrete beam–column connection using CFRP can be recommended and utilized in the practical projects of concrete structures.
    Keywords: beam–column connection, strengthening connection, Carbon Fiber Reinforced Polimer, Improvement of seismic performance
  • Mohammad Shakerkhatibi * Pages 55-67
    Introduction
    Petrochemical industry is one of the major industries playing significant role in the economy of Iran. In general, petrochemical effluents contain various contaminants including suspended solids, organic matters, oil and grease, metal salts, sulfide, ammonia, hydrocarbons, cyanides, volatile organic compounds (VOCs) and other toxic substances. In most of petrochemical complexes, wastewaters are treated by activated sludge process along with the oil/water separation systems as a pretreatment. Since the performance evaluation of wastewater treatment plant is required to assess the effluent quality, to meet higher treatment requirement and to know the feasibility of handling higher hydraulic and/or organic loadings, this study was conducted to evaluate the performance of a full-scale petrochemical wastewater treatment plant.
    Materials And Methods
    Wastewater treatment system consists of a screening unit, an API, an equalization basin, coagulation and flocculation, DAF system, aeration tanks, primary and secondary clarifier and filtration. The treatment plant was designed to treat the wastewater generated from different units of petrochemical complex with reuse purposes of treated effluent. To evaluate the performance of the treatment plant, 12-h composite flow weighted samples were carried out in 4 days within 6 month and were analyzed for COD, BOD5, TDS, TSS, phenol, cyanide, oil, ammonia and TKN in accordance to standard methods. Microbial structure of activated sludge was also evaluated. Overall performance of the plant and the performance efficiency of each unit were calculated.
    Results
    According to the results, the actual average influent flow was significantly lower than the average design flow based on the long-term data and our measurements. This increases the hydraulic retention time (HRT) in all units in the WWTP. Based on the results, the values of COD, BOD5 and TSS in the influent and effluent were 1319±230, 967±491 and 227±174 mg/l and 73.6±19.6, 33.6±25.9 and 6.4±5.9 mg/l respectively. The ratio of BOD5/COD was calculated about 0.58 indicates a good potential for biodegradability of the wastewater. The results also revealed that 68.5% removal of COD and 81.9% removal of BOD5 have been occurred in preliminary and primary units while; these units are usually designed for the elimination of oil and suspended solids as well as the equalization of quantitative and qualitative parameters of the influent. At an organic loading of 0.48±0.15 kg/m3.d the removal efficiencies for COD and BOD5 in biological unit were calculated about 37 and 46% respectively. The mean value of MLSS within the biological reactor was 1463 mg/l. In addition, the mean plus standard deviation values of MLSS measured in returned activated sludge (RAS) were 2323 ± 1080 mg/l. According to the daily average concentrations of COD in the effluent of the WWTP, in some cases within the study period, the COD values were exceeded from national discharge standards. Microbial analysis showed that among the isolated bacterial strains, the genus belonging to Alcaligenes, Pseudomonas, Bacillus and Moraxella as heterotrophic nitrifying bacteria was identified as predominant strains in biological unit.
    Conclusion
    Based on the results, in 64% of our measurements (135 days from 209 days of study period), the daily average effluent COD values were above national guidelines for surface water discharge (60 mg/l). In 3% of the time during the study period, the daily average values of COD in the effluent were more than 200 mg/l. The results also indicated that the average effluent concentration of oil was significantly higher than the expected design value.
    Keywords: Performance Evaluation, Petrochemical industry, Activated sludge, Wastewater treatment, Microbial analysis
  • Mohammad Mehdi Hajnorouzi, Hoseiin Tahghighi * Pages 67-80
    Response evaluation of buried steel pipelines at active fault crossings is among the top seismic design priorities. This is because the axial and bending strains induced to the pipeline by step-like permanent ground deformation may become fairly large and lead to rupture, either due to tension or due to buckling. Surface faulting has accounted for many pipe breaks during past earthquakes, such as the 1971 San Fernando (USA), the 1995 Kobe (Japan), the 1999 Izmit (Turkey), the 1999 Chi-Chi (Taiwan) events and more recently, the 2004 Mid Niigata earthquake in Japan. Literature review suggests that previous researches in the analysis of pipeline subjected to fault motion have been mainly focused on the case of strike-slip fault. Certainly, a 3D large scale finite element analysis is a powerful method and allows a rigorous solution of the problem with minimizing the number of necessary approximations. The aim of present work is to examine and compare the mechanical response of continuous (welded) buried steel pipelines crossing active reverse faults by three dimensional FEM. General-purpose finite element program ABAQUS is employed to simulate accurately the mechanical behaviour of the steel pipe, the surrounding soil medium and their interaction, considering the non-linear geometry of the soil and the pipe through a large-strain description of the pipeline-soil system and the inelastic material behaviour for both the pipe and the soil. For 3D FEM continuum model, an elongated prismatic model is considered, where the pipeline is embedded in the soil. Four-node reduced-integration shell elements (type S4R) are employed for modeling the pipeline cylinder, whereas eight-node reduced-integration brick elements (C3D8R) are used to simulate the surrounding soil. The analysis is conducted in two steps; gravity loading is applied first and subsequently fault movement is imposed. Seismic fault plane is assumed to be located at the middle cross-section of the pipeline. The steel pipeline was of the API5L-X65 type, with a bi-linear elasto-plastic stress–strain curve given by Ramberg-Osgood model. The mechanical behavior of soil material is described through an elastic–perfectly plastic Drucker-Prager constitutive model. A contact algorithm is considered to simulate rigorously soil–pipeline interaction which accounts for large strains and displacements. The analysis proceeds using a displacement-controlled scheme, which increases gradually the fault displacement. Quasi-static analyses were carried out by applying fault offset components to soil block in the continuum FE models through a smooth loading function of time. Buried steel pipelines have been analyzed for reverse fault motion to study the influence of design parameters viz. crossing angle, backfill properties, burial depth, pipe surface property, pipe material and cross-section properties on maximum compressive strain, and buckling of the pipeline. The following main conclusions were obtained based on the studied response of pipeline subjected to reverse fault motion using the FEM model.
    - For the steel pipeline subjected to reverse fault motion, compressive strain was always found to be more critical than the tensile strain.
    - The capacity of the buried pipeline to accommodate the reverse fault offset could be increased by adopting: a loose granular backfill, a shallower burial depth, near-parallel orientation with respect to the fault line, a smooth and hard surface coating, and increasing pipe-wall thickness.
    - Finally, the obtained information can provide either guidance for developing improved earthquake-resistant design or countermeasures to mitigate damage to pipelines crossing active reverse faults.
    Keywords: Soil-pipe interaction, FEM, Reverse fault, Performance, Non-Linear Analysis
  • Hoseiin Montaseri * Pages 81-92
    A large number of flows encountered in nature and technology are a mixture of phases. Advances in computational fluid mechanics have provided the basis for further insight into the dynamics of multiphase flows. Currently there are two approaches for the numerical calculation of multiphase flows: the Euler-Euler approach and the Euler-Lagrange approach
    In the Euler-Euler approach, the different phases are treated mathematically as interpenetrating continua. In FLUENT, three different Euler-Euler multiphase models are available: the volume of fluid (VOF) model, the mixture model, and the Eulerian model. For sedimentation, we must use the Eulerian model. The Eulerian multiphase model in FLUENT allows for the modeling of multiple separate, yet interacting phases. The phases can be liquids, gases, or solids in nearly any combination. The Lagrangian discrete phase model (DPM) in FLUENT follows the Euler-Lagrange approach. The fluid phase is treated as a continuum by solving the time-averaged Navier-Stokes equations, while the dispersed phase is solved by tracking a large number of particles through the calculated flow field.
    Sediment transport by fluid flow is one of the most important two phase flow in the nature. Due to existence of secondary current in channel bends, the mechanism of flow and sediment transport in these channels is much complex and locationg lateral intake at outer bank of the bens decreases this compelexity.
    In this paper, mechanisms of sediments transport into the intake in a 180 degree bend channel with lateral intake have been simulated whit the Eulerian and Discrete phases models in fluent software. The intake is located at the outer bank of an 180o bend at position 115° with 45° diversion angle. The effect of diversion discharge rate and diversion angle on mechanism of sediment entry to the intake was considered.
    The turbulence model is k-ε model. Model҆s in different time has performed and the result compared with laboratory result.The results show in Qr=40%, the mechanism of sediment entry was consist of continues entrance from downstream edge of intake and periodic entrance from upstream of the intake, however in Qr=25%, the mechanism of sediment entry was only consist of continues entrance from downstream edge of intake. The two models (Eulerian and Discrete phases) have shown good results. The rout mean square errors for outer boundary of the path of the particle at the channel ҆s bed for two discharges (25% and 40%) have measured.
    The number of particle in discrete phases is limited; therefore this model cannot be display the depth of sediment. The Eulerian model displays the bed topography very well. Measuring mean square errors show that the model operation for topography simulation is very well. This model shows the location of intermittent dune and location of sediment accumulation very well. The discrete phase model can be shown the particle trapped place better than the Eulerian model.
    Due to increase in intake discharge, dimension of sediment accumulation is decrease. the mechanism of sediment entry to lateral intake is affected by diversion angle of intake. the minimum sediment is entered to lateral intake at diversion angle equal to 50 degree.
    Keywords: Eulerian model, Discrete Phase Model, Bed topography, sediment transport, Fluent
  • Mohammad Mehdi Kholoosi *, Ali Raeesi Estabragh, Jamal Abdollahi Pages 93-106
    Soil pollution by hydrocarbon is a significant Geo-Environmental problem that can affect the environmental quality of soil, groundwater and air. Soil can be contaminated by organic materials attributable to leakage from underground or aboveground storage tanks and accidental spills. The response of soil to the contaminants not only depends on the local environment but it is also influenced by factors such as particle size, bonding characteristics among particles, and ion exchange capacity. The transport of contaminant components from soil into groundwater can cause serious problems. The use of contaminated soil and its stabilization can be considered in earthworks such as embankments, backfills, and roads if there is no pathway for leaching of contaminants to underground water or if the contaminants pose no risk to the public and the environment. In some areas the native soil is contaminated with hydrocarbon substances. For performing projects in such areas, because of the haulage distance to suitable soil and economic considerations, often the use of local soil is dictated for construction. Thus, the treatment and stabilization of local soil must be considered. On the other hand, in some areas where the soil has been contaminated and the treatment is not economic, for the design of a project in these areas the effect of the contaminating substance on the soil behavior should be evaluated. Therefore, understanding the mechanical behavior of contaminated soils and their treatment is important. Improving the mechanical behavior of clay soils by stabilization is a means of fulfilling geotechnical design criteria.
    An investigation into the behavior of a contaminated clay soil with Anthracene and its treatment was carried out through a program of experimental tests.. Anthracene is a representative of one group of hydrocarbon, which are called PAHs (Poly Aromatic Hydrocarbons). PAHs create due to incomplete combustion of fossil fuels or wastes.
    In order to investigate the effect of cement on the stabilization of clay contaminated soil with Anthracene, the specimens of natural clay soil, contaminated soil with Anthracene, soil-cement and Anthracene-contaminated that is stabilized with different percentage of cement (5, 10, 15 and 20%) in different curing times (3, 7, 14 and 28 days) was prepared by static compaction method at maximum dry density and optimum moisture. Atterberg limits and Unconfined compressive strength (UCS) tests were conducted on the specimens. The results of the experimental work showed that adding Anthracene to clay soil, change the compaction parameters, for example, the dry specific weight of soil is reduced and the optimum water content is increased. Although, adding cement to the Anthracene-contaminated soil, improves the compaction of soil, it increases the dry specific weight and reduced the optimum water content. In addition, adding the Anthracene also is changed the unconfined compressive strength of soil, it reduces strength of soil. Although, adding cement is incresed the strength of the contaminated soil. The amount of increase in the strength is depended on the percent of cement and curing. The results showed that Atterberg limits are increased by adding Anthracene to the clay soil, but are reduced by adding Anthracene or cement or adding Anthracene to soil-cement. The results indicated that adding the Anthracene to the soil, changes its structure to flocculated shape, but the decreasing of friction between soil particles due to adding Anthracene, led the soil particles to move easily together. By the way, the results of this research showed that the cement could stabilize contaminated soil with Antracene.
    Keywords: Atterberg Limits, Curing time, Flocculation, Elastic modulus
  • Seyed Ali Asghar Hosseinzadeh *, Ayub Kamraninejad Page 105
    Thin-walled structures are widely used in different engineering applications. Bridge and building plate girders, box columns and girders, frame bracing systems, liquid and gas containment structures, shelters, offshore structures, ship structures, slabs, hot-rolled W-shape steel profiles, steel plate shear wall systems and many other naval and aeronautical structures are examples of engineering elements that according to their applications use plate of various thicknesses. The knowledge of the actual behavior of plates in such structures can be, of course, helpful in understanding the overall behavior of the structures. In general, plates in thin-walled structures may be under various types of loading, such as shear loading. Material yielding and geometrical buckling of plates are two independent phenomena which may well interact with each other in shear panels. Depending on the material properties, slenderness and aspect ratios, and boundary conditions of perfectly flat plates, yielding may occur before, after or at the same time as buckling. Buckling in slender plates is a local and sudden phenomenon followed by large out-of-plane displacements and loss of stiffness. Slender plates are capable of carrying considerable post-buckling additional loads due to stresses in the inclined tension fields. On the other hand, a plate with low slenderness ratio yields before buckles and thus, no post-buckling capacity is expected. In between, in plates with moderate slenderness ratios, material yielding and geometrical nonlinearity happen almost at the same time. In the present paper, the behavior characteristics of shear panels with simple or clamed boundary conditions and three different materials (carbon steel, stainless steel and aluminum) are studied for various plate slenderness ratios, using finite element method. Results of nonlinear static analyses of different shear panels show that slender plates, depending on the slenderness ratio, carry a relatively small shear load in the elastic stage until the occurrence of shear buckling, but their additional capacity in the post-buckling stage prior to yielding are significantly large. They reach their ultimate shear capacity slightly after yielding. That is, their post-yield capacity is not significant. Note that the ultimate shear strength of slender plates is considerably lower than their nominal shear yield strength. In plates with intermediate slenderness ratios, material yielding and buckling occur concurrently. They carry a relatively large shear load in the elastic stage before yielding/buckling. They have also some post-buckling/post-yield reserves before failure. The ultimate shear strength of moderate plates is somewhat lower than their nominal shear yield strength. In stocky plates, yielding precedes buckling. The shear capacity in the elastic stage before yielding is thus significant. The plates have some post-yield capacity and the ultimate load is coincident with the occurrence of plastic buckling (if happens). The ultimate shear strength of stocky plates is almost equal to their nominal shear yield strength. Moreover, results of quasi-static cyclic analyses of different shear panels show that the energy absorption capability, as expected, is very sensitive to the slenderness ratio of panels and with the decrease of the slenderness ratio (increase of thickness), the absorbed energy by the panels is substantially increased. For a specific slenderness ratio, steel shear panels exhibit higher energy absorption than panels with aluminum materials (although aluminum material has higher yield strength than that of carbon steel and stainless steel materials, here). This, of course, highlights the important role of the modulus of elasticity in the energy dissipation capability of shear panels. However, the material yield strength and panel boundary conditions do not seem to have important role in the amount of energy dissipated by the panels, compared to the material modulus of elasticity.
    Keywords: Shear panel, Plates, Cyclic Behavior, Finite element method, Nonlinear analysis
  • Ehsan Dehghani *, Mohammad Kazem Bahrani, Vahid Reza Afkhami Pages 107-120
    In most steel frame designs the beam to column connections are assumed to be rigid or pinned but in many steel frames we have beam to column connections with semi-rigid behavior. The structures with semi-rigid connections include systems with the connections in joints which are not completely rigid, but allow, usually, some relative movements in directions of generalized displacements.
    Early experimental studies showed the importance of panel shear deformations for stable energy dissipation under cyclic loading. Modeling of the panel is very important for the avoidance of local failure of columns under ultimate limit state.
    A substantial effort has been made in recent years to characterize the behavior of semi rigid connections. Recent studies and modern codes, in especially EC3 and EC4, include methods and formulas to resistance and stiffness of panel zone. EC3 proposes a mechanical model for the semi-rigid joint in which each component is modeled by an equivalent linear spring.In these model we have some components that show with springs. These springs are assembled to form a single bilinear (elastic–plastic) rotational spring that models the connection, and is attached at the intersection between beam and column for the global analysis.
    Both the stiffness and strength of the springs in EC3 and EC4 depend on β factor that definition of this parameter implies an approximation of the internal forces at the joint, and therefore its use requires an iterative process at the time of performing the global analysis of the structure. So E.Bayo proposed a new component-based method (or cruciform element method) to model internal and external semi-rigid connections that revived and modified EC methods. So a cruciform element (a four-node element) is proposed to avoid β factor, and the inherent initial guessing and iterative process that it requires, and includes the finite size and deformation modes of the joint.
    One of main problems that structural engineer deal with is considering End Length Offset in conventional softwares. Extended end plate connection is one of beam-column semi rigid connection that we want to evaluate this behavios by using cruciform connection model and other panel zone models.
    In this paper three 2 dimensional frames with extended end plate connections are modeld in MATLAB using Cruciform element method and these result are compared with SAP2000 results in eight cases that in four cases panel zone are modeld and four cases are without panel zone modeling. In which of this End Length Offset considering are once just for beams and the other for beams and columns (in two case of Rigid Zone Factor : 0.5 and 1). The results show that modeling panel zones according to EC method and considering Rigid Zone Factor equal to 1 in columns and beams are best assumption to analysis of 2D frames with extend end plate connections, but if we don’t model panel zones, we must considering Rigid Zone Factor equal to 0.5 in columns and beams to give nearby actual results.
    Keywords: semi rigid connections, extended end plate, Rigid Zone Factor, End Length Offset
  • Majid Rezaei, Ahmad Jamshidi-Zanjani * Pages 120-130
    The rapid increase of urban population and waste production is one of the most important environmental problems in developed and developing countries. Million of tons of waste material are produced annually in the world, the correct disposal and management of which presents a main concern in the human societies. With the increase in population, and industrialization of societies accompanied by economic growth, the production of waste material has increased throughout the world. It is predicted that the population of the world will increase 2 to 3 Milliard people in the next 30 years. This means that urban waste material production will increase 3 to 4 times. Along with health and environmental adverse effects of the landfill site, emissions of carbon dioxide, the intensification of the process of global warming on a global scale also will follow. Absence appropriate supervision over management and accumulation of these outputs can engender many environmental problems, especially for people who live near the landfill to be followed. Thus, appropriate urban landfill site selection is a main issue related to the stability of cities and human environments. Geographical information systems (GIS) have appeared as useful, computer-based tools for the spatial operations like entry, storage, manipulation, analysis, and display of geographical data. Since GIS can manage a large amount of spatial data, it can serve as an ideal tool in the siting studies. In addition to the use of GIS in the landfill site selection studies, multi-criteria evaluation method to deal with the issues that decision makers and experts face with in landfill site selection is used. Combination of GIS and multi-criterion evaluation method provides a valuable tool for the solution of landfill site selection problems. In this study, fuzzy logic based on Weighted Linear Combination (WLC) were used for urban waste landfill site selection in Arak city in ARC GIS 10.1 software environment with respect to the ecological, and socio-economic parameters.
    In this research, reviewing the international obligations in landfill site selection and using environmental expert views on weighting the effective ecologic, and socio-economic criteria in landfill site selection it was revealed that ecologic sub-criteria, including depth of groundwater resources, distance from surface water resources, and flood potential were of great importance in urban landfill siting. Moreover, among the socio-economic sub-criteria, distance from rural and urban population centers were vital in urban landfill site selection. In the present study, after the production of the final suitability map with fuzzy logic based on WLC, the spatial desirability was divided into 5 classes. The spatial desirability for landfill sites lies in the fuzzy membership degree of between 0.3 and 0.87. Around 11033 polygons with an area of 4146.03 square kilometers were found whose spatial suitability in the fuzzy membership degree of 0.3 to 0.87. The most spatial suitability lie in the fuzzy membership degree between 0.69 to 0.87. The spatial suitability of these areas with their fuzzy membership degree is as follows: very low suitability with the fuzzy membership degree of 0.3 to 0.47, low suitability with the fuzzy membership degree of 0.47 to 0.56, moderate suitability with the fuzzy membership degree of 0.56 to 0.63, high suitability with the fuzzy membership degree of 0.63 to 0.69, and very high suitability with the fuzzy membership degree of 0.69 to 0.87. The area of the existing polygons and their number are as follows: very low suitability polygons with the area of 270.73 km2 and number of 328 polygons, low suitability polygons with the area of 683.48 and number of 1687 polygons km2, moderate suitability polygons with the area of 1187.02 km2 and number of 3006, high suitability polygons with the area of 1212.44 km2 and number of 3954 polygons, very high suitability polygons with the area of 792.36 km2 and number of 2058 polygons.
    Keywords: site selection, Fuzzy Logic, Multi Criteria Decision Making (MCDM), Landfill, GIS
  • Fatemeh Rezaei *, Gholamreza Moussavi, Alireza Riyahi Bakhtiari, Yadollah Yamini Pages 131-142
    Toluene is one of the volatile organic compounds and used extensively in industrial processes. Because of toluene effects on human health and environment, it is necessary to implement methods for toluene removal from contaminated air stream. Catalytic ozonation process (COP) is one of the emergent technologies for removal of volatile compounds from air streams. Catalytic ozonation process is an efficient, cost-effective and easy to operate for elimination of organic compounds. One of the main factors directly affecting the VOC removal efficiency and ozone destruction rate is the type of catalyst. In this study the potential of MnO/GAC and MgO/GAC catalysts was investigated for toluene elimination from air stream in the presence of ozone in a lab scale.
    The MnO/GAC and MgO/GAC catalysts were prepared by Sol-gel method and then characterized by BET, XRD and SEM analysis. Specific concentrations of toluene in the air were produced by using an air pump and a syringe pump. Phocheck was used to measure the concentration of toluene in gas phase. The effect of retention time (0.5-4 Sec), inlet toluene concentration (100-400 ppmv) and air temperature (25-100˚C) were investigated on catalysts efficiency in the presence of ozone. Ozone dosage (0.1 g/h) kept constant in all experiments. The efficiency of MnO/GAC and MgO/GAC were determined from the breakthrough time and removal capacity and the results were compared statistically.
    The BET surface area derived from N2 adsorption- desorption isotherms. From the results the BET surface area of MnO/GAC (1103 m2/g) was greater than that of MgO/GAC catalyst (1082 m2/g). XRD patterns clearly illustrate formation of MgO and MnO crystals on GAC surface. From XRD patterns the peaks at 2θ degrees of 50.3° and 73.8° were related to the MgO crystals. The peaks at 2θ degrees of 42.1°, 51.8° and 70.9° reveal the formation of Mn3O4. The crystallite phase of MgO and MnO was hexagonal and tetragonal respectively. The average size of MgO and MnO crystals was 10 and 12 nm, respectively, calculated using Debby-Scherrer equation. Results of experiments in different retention times showed that breakthrough time of MnO/GAC and MgO/GAC catalysts increased 11.3 and 13.9 times, respectively, by increasing retention time from 0.5 to 4 Sec. When inlet toluene concentration increased from 100 to 400 ppmv, the breakthrough time of MgO/GAC and MnO/GAC columns decreased 65% and 62.2%, respectively. In contrast, removal capacity of MgO/GAC and MnO/GAC was increased 39.1% and 50.4% by increasing inlet toluene concentration from 100 to 400 ppmv, respectively. The efficiency of MgO/GAC and MnO/GAC catalysts was increased 78.3% and 31.5% by increasing air temperature from 25 to 100 ˚C, respectively. These results demonstrates that increase of retention time and bed temperature could positively effect on the performance of MgO/GAC and MnO/GAC catalysts in toluene removal from waste air stream in the presence of ozone.
    It can be concluded that MgO/GAC and MnO/GAC catalysts had high potential in VOCs removal from air stream in the presence of ozone. The difference between the efficiency of MgO/GAC and MnO/GAC catalysts was significant (P ≤ 0.05) and MgO/GAC catalyst had higher efficiency than MnO/GAC for toluene removal from waste air in the presence of ozone.
    Keywords: Ozonation, Air Treatment, Catalyst, Manganese Oxide, Magnesium Oxide
  • Abbasali Tasnimi * Pages 143-156
    Varying the modeling of RC columns in the Updated version of in ASCE41-06 concrete provisions has been resulted in reduction of performance level of structure. This leads to a more conservative safety level in Code 2800. In this study in order to make the design in proportion with the performance level the design itself, the design criteria on code 2800 are investigated. To have a better Proportionality between structure performance level and the Code 2800 performance targets, the parameter of inelastic drift of structure is regulated. In seismic design of structures, estimating maximum inelastic lateral displacement of the structure occurring in the sever earthquake is of great importance. in most seismic design provisions, maximum inelastic displacement of the structure is estimated by amplifying the lateral displacement computed from an elastic analysis with a displacement amplification factor (Cd). Reviewing several seismic design provisions indicates that in most of them Cd is only dependent on the earthquake force resisting system.
    6 RC frames with intermediate ductility and 4.5.6.8.10 and 12 stories are used for this study. For determination of real drift occurring in major earthquake (inelastic drift), nonlinear time history analysis and pushover analysis using IDARC program is performed. For linear analysis, equivalent static procedure is employed using ETABS program. In nonlinear time history analysis, 7 earthquake ground motions consistent with soil type II of Standard no. 2800 are used. These records are scaled according to Standard no. 2800 directions, Also 4 types of lateral loading patterns are used in pushover analysis, and they are triangular distribution, generalized power distribution, uniform distribution and modal distribution. For linear analysis, equivalent static procedure is employed using ETABS program. Performance level of structure elements is obtained based on the mentioned analysis. Bending forces of each of columns are calculated and compared with the strengths calculated based on the ABA. The inelastic displacements which are computed by nonlinear analysis are then divided by elastic displacements and so Cd for each story of 6 frames is determined.
    In most of investigating of frames, the pushover analysis and time history analysis, most of the columns are in the IO performance level and only a small percentage of them have reached the level of performance of LS. The results indicate that lower criteria limitations are needed to control the drifts and its effects on the structure level performance and response are investigated. In this research, Cd is considered as a function of R (structural behavior factor), like most researches and provisions,
    Finally, in order to investigate the changes in 4TH edition of code 2800, the mentioned frame is designed again based on the 4Th edition criteria and then the structure response is investigated. The results indicate that in the frames design by 4TH edition of code 2800, demand capacity ratio of bending in the upper stories of frame increases while in the lower stories There was no significant change. Furthermore the reduction in drift criteria limitations, leads to reduction in section dimensions, damage concentration in a specified story, total structure damage index and also more usage of section capacity. The latter will result in convergence of structure performance level and Code 2800 performance target.
    Keywords: Demand capacity ratio, Magnification factor of drift, RC columns, Performance levels
  • Morteza Arab, Masih Zolghadr, Mohamadali Zomorodiyan * Pages 157-166
    Bridge failures are fortunately rare, but every year a number of bridge collapse that has occurred somewhere in the world. In many cases these collapses could have been avoided by an adequate bridge management regime that included good inspection, assessment and maintenance procedures. One specific type of failure that from time to time causes sudden catastrophic collapse of bridges is the undermining of foundations due to bed scour. Bed scour is the transport of bed material by the flow of water and is present to some degree where the river bed is formed of granular material. Scour increases as flow rates increase and therefore the actual collapse of structures due to scour often occurs during periods of extreme flow due to flooding. Of course, this is exactly the time that direct observation of the foundations of a structure is not possible and therefore a collapse may be put down to an ‘act of God’. A good inspection regime that includes bed measurement and engineering analysis can find indications of developing scour before the situation becomes critical. If this is followed up with well-designed remedial works, undermining of the structure, even in extreme conditions, may be prevented. The formation of scour holes around bridge piers or abutment is one of the main causes of bridge foundation collapse. Local scour at bridge piers and abutment may be defined as a local lowering of the bed elevation. This lowering is mainly caused by the horseshoe vortex combined with the downflow in front of the pier and abutment, the vortex shedding at the back of the pier, abutment and the flow contraction. Bridge failure due to the effects of local scour associated with the structure of the local flow field around piers and abutment involves a considerable interest in scour prediction and scour protection measures. Two basic procedures may reduce the scour depth. The first consists in enhancing the ability of the bed material to withstand erosion. This is generally done by placing an armoring device on the bed, such as riprap. The riprap provides a physical obstacle that resists the erosive power of the flow. The second procedure consists in reducing the downflow in front of the pier and the horseshoe vortex scouring the bed material. The local scour around bridge pier and abutment in recent years has been widely studied by different authors. They proposed different methods to control the scouring depth. The most dominant concern about bridges stability is the occurrence of local scour around foundations. The local scour around bridge piers and abutments has been widely studied by different authors in recent years. They proposed different methods to control the scour depth. In order to reduce scouring around bridge piers and abutments one of the methods is the soil compaction. Compaction rise the relative density and soil resistance which mitigates scour and produce a time delay in scour hole development process. This paper focuses on the effect of clay content percentage and compaction ratio on scour reduction around bridge piers. Hence, 5%, 10%, and 15% clay was added to soil and then compacted. According to the experimental results, when 15% clay was added to non-cohesive sediment materials in saturated bed conditions with a relative density of 70%, the scour process was completely controlled after 24 hours around the bridge pier.
    Keywords: scour, Bridge Abutment, Bridge pier, Compaction, Reduce Scour
  • Saleh Sharif Tehrani *, Seyed Hossein Hosseini Lavassani Pages 167-176
    Roads and pavements are one of the most important assets in any country and considerable amount of money is paid for their rehabilitation or maintenance annually. Pavement surface is the most expensive and susceptible layer as it is in direct contact with traffic and also it experiences different environmental conditions during different seasons. Harsh weather condition and winter maintenance is another parameter that can increase the annual maintenance cost significantly. Winter snow and the resulting ice, can reduce pavement surface friction and therefore, deicing material such as deicing salt or calcium acetate are used to melt the ice and snow. Deicing material decrease the frost temperature and melt the remaining ice and snow and the resulting water flows due to the longitudinal and transverse grade over the pavement surface. The flowing water goes through longer distances in locations were the drainage system is not adequate.
    Although several researchers and scientists have studied the effects of deicing material on asphalt and concrete pavement deterioration, but what has not been fully studied is the simultaneous effects of deicing material and water flow on the rate of pavement deterioration under freeze-thaw cycles. Therefore, the focus of this study is to evaluate the combined effects of flowing water and deicing material on the deterioration of asphalt pavements under freeze-thaw cycles. Two types of asphalt samples were prepared and subjected to five different freeze-thaw exposure conditions. Deicing salt and calcium acetate were used as the deicing material in this study. The samples were also tested in an abrasion test apparatus and subjected to normal and frictional forces. This abrasion test apparatus was built based on the concepts used in Hamburg Wheel-Tracking Device. Marshall strength loss and weight loss of the samples were measured and used as a measure of asphalt deterioration.
    Results showed that the combined effects of water flow and deicers increases the deterioration of asphalt concrete samples under freeze–thaw conditions. Furthermore, deicing salt has more deteriorative effects on asphalt concrete in comparison to calcium acetate. In addition, results indicated the water flow has significant effects on asphalt concrete pavement stripping and strength loss. Water flow slows down the formation of ice during freezing cycles by not allowing or slowing the formation of ice crystals and their agglomeration. In still plain water freeze-thaw chamber, a thin ice layer was formed in zero degrees of centigrade and its depth increased during the freezing cycles but in the flowing plain water freezing condition, where the water flow was present, small ice particles started to form in areas in the chamber where the water flow was in its lowest level. Then, the ice formation gradually expanded to the area with the highest level of water flow. Besides the mentioned effects of water flow, the presence of water flow decreases the freezing temperature of water in the asphalt concrete pores and, consequently, the hydrostatic pressure inside the asphalt concrete increases significantly. Therefore, the asphalt concrete deterioration process becomes faster and more severe when water flow is present in the freeze-thaw cycles.
    Keywords: water flow, de-icing salt, asphalt concrete pavement, Deterioration, freeze–thaw
  • Shahir *, Meysam Shayan Pages 179-191
    Decrease in the strength and stiffness of soil duo to liquefaction may cause large bending moments and lateral deformations in piles located in this type of soils. To reliable design of pile foundations in the liquefaction susceptible soils, it is necessary to have a accurate evaluation of the lateral pressure which will be exerted on the pile if the subsurface layers undergo liquefaction and lateral spreading in the course of earthquake. In this study, a coupled Soil-Pile-Structure Interaction (SPSI) analysis method has been used to investigate the behavior of piles in liquefiable soils. Interaction of soil-pile was simulated by using nonlinear p-y springs. The liquefaction effects were taken into account by introducing a degradation multiplier to the lateral resistance of soil. The degraded lateral resistance of liquefied soil was considered equal to 5% of its initial value for loose sand and 10% for medium sand. Fully coupled dynamic analysis of a soil column in the free-filed condition was performed in the OpenSEES (Open System for Earthquake Engineering Simulation) software. For simulation of the interaction of solid-fluid phases based on the theory of saturated porous medium, u-p formulation has been used. Liquefied soil behavior was modeled using pressure dependent multi yield material model. From the coupled analysis, the time histories of excess pore pressure ratio at the different levels are obtained. The value of excess pore pressure ratio (0.0 to 1.0) is used to interpolate the transient lateral resistance of soil from its initial value in the static condition (excess pore pressure ratio equal to 0.0) to its final degraded value in the fully liquefied condition (excess pore pressure ratio equal to 1.0). In order to verify the numerical model, results of numerical modeling have been compared with two centrifuge experiment's measurements. Both of experiments include two soil layers and the pile is extended into the lower layer. In the first experiment, the loose sand layer is above the medium dense layer and in the second experiment the medium dense sand layer is above the dense layer. After verification of the numerical model, parametric analysis was performed to study the effect of various parameters on the dynamic response of piles and applied lateral pressure from the spreading liquefied soil to pile. Investigated parameters are liquefaction layer thickness, the input excitation frequency, fixity of the pile cap, pile stiffness, maximum input acceleration and the relative density of liquefiable soil. The results of the parametric analysis show that the maximum bending moment in the case of fixed head occurs at the top of pile and in the case of free head at the depth of 1 to 3 meters. The maximum bending moment of pile is also greater in the case of fixed head pile; however, its lateral deformation is lower. Increasing of frequency of input motion and soil relative density or decreasing of liquefied soil thickness lead to decreasing of maximum bending moment and deformation of pile. Regarding the lateral pressure exerted on the pile, the results of analysis indicate that the lateral pressure is relatively constant at the depth of liquefied layer and is equal to 7 to 10 percent of the total vertical pressure at the base of liquefied layer.
    Keywords: Liquefied soil, Pile, Interaction, Non-linear spring, Coupled analysis
  • Ali Sheikh Abolhasani, Mohammad Vaghefi *, Ali Reza Fiouz Pages 193-201
    Concrete is the most widely used building materials. In the our country, Iran, the consumption amount of chemical additives materials than to the average consumption in other countries has been a significant distance and especially ready-mixed concrete industry the significant contribution of concrete production and consumption to be allocated in the country. Ready-mixed concrete industry from the most potential sections that should be pay to the valuable characteristics of the chemical additives and used to it. Therefore it is essential that developed the knowledge and technology use of chemical additives materials over the past in Iran. One of the cases that about concrete structures, especially structures that located in the vicinity of water permanent or non-permanent and chemicals materials, is important, blocked effect performance against leakage, influence, pressure or attack water containing chemical materials, addition to it is well tolerance freight its. In this context, should be made concrete that commonly “waterproof” is called. Also, to prevent cracking, high ductility, supernatural strength and energy absorption capability can be used of fiber in concrete that can be found proportional many application instances for it. Up to now specified that different types of fiber can increase strain capacity, resistance to impact, energy absorption, abrasion resistance and tensile strength of concrete. In this research, the influence of the strength of concrete and fiber concrete sealing substances has been investigated. For this purpose, concrete without fibers and fiber concrete with steel fibers, polypropylene and glass, compressive and flexural strength parameters by adding common waterproof material is studied with different percentages. In this study, by using of materials available in the Khormoj and fiber and waterproof materials, concrete parameters is evaluated of pressure and bending resistive. Carrying out tests crash sand in the province of Bushehr was used. All the stone materials in the concrete mix thoroughly washed before using in the S.S.D state. Dashtestan Cement Type 2 Compliant with ASTM C 150 is used for mixing. Thus, was carried compressive strength tests at ages 7, 28 and 90 days on the cubic test pieces and bending strength tests at ages 7, 28 and 90 days on test pieces of the cubic rectangular. Tests taken in 34 mix design and 408 samples so that in the making concrete is used of waterproof materials composition of inclusive powder sbf-wr201 (acidic neutral) and powder bc40 (acidic neutral) and liquid bc39 (alkaline) and steel, polypropylene glass fiber. In this study, a mix design based on ACI 211 recommendations for concrete without fibers by weight method was prepared. Then fibers (polypropylene, steel and glass and 2% respectively, 2%, and 1% by weight of cement) and the waterproof material (with percentages of 1, 1.5, and 2% by weight of cement) were added separately to the concrete mix design and the mix design was calculated for each compound. The tests of results show that the waterproof materials bc40 and sbf increase the strength and flexural compressive and waterproof material bc39 decreases concrete strength and flexural compressive. The most important result of this study is that to add 1 percent of waterproof materials bc40 to the fiber concrete with steel fiber has been increased 27% compressive strength compared than to control sample fiber for strength 90-day and also in the flexural strength of this combination is not seen a significant change.
    Keywords: Water proof materials, Fiber concrete, compressive strength, Flexural strength
  • Farzin Nasiri *, Morteza Alavinia, Hossein Asadi Pages 203-213
    Soil erosion, as a complicated natural phenomenon, is a global challenge threatening soil and water resources. Therefore, accurate understanding of soil erosion and sediment transport processes and their interactions is necessary for prediction of soil erosion.To distinguish between the dominant processes involved in soil loss, soil erosion has been classified into rill and interrill erosion. Rainfall-induced detachment and transport of sediment have a fundamental contribution to interrill and sheet erosion. Instead of the observation of natural rain showers, simulation of rainfall is widely used for better understanding of processes involved in soil erosion and their interactions. Rainfall intensity is variable during a natural rain showers, such that peak rainfall intensity in an event can exceed the mean event intensity by an order of magnitude. Variations of rainfall intensity during a rainfall event is called ‘event profile’. However, the available information is inadequate to understand its effects on runoff and soil loss processes. Thus, this study was aimed to quantify the effect of event profile on runoff and soil loss in rainfall-induced erosion. The experiments were based on the use of simulated rainfall on disturbed soils in a small laboratory detachment tray. Since kinetic energy controls runoff and soil loss processes, the effects on the soil surface of rainfall events with the same average intensity may be different. Hence to study only the effects of event profile, we used four simulated rainfall events, each with a different profile but all delivering the same total kinetic energy to the soil surface. The study was conducted in the rainfall simulation laboratory, Department of Hydraulic, Faculty of Civil and Environmental Engineering, Tarbiat ModaresUniversity, Iran. For this study, four events with different temporal profiles of rainfall intensity, each with the same kinetic energy, were chosen; (a) constant intensity, (b) increasing intensity, (c) decreasing intensity and (d) increasing - decreasing intensity. The soil samples used in the experiments were a sandy soil (soil A) and a sandy loam soil (soil B). Disturbed soil samples were collected, air dried, crushed to pass a 4.75-mm sieve, and thoroughly mixed. For each experiment soil was packed into a drainable detachment tray to a specific bulk density. The test area of this tray was 15cmwide by 30cmlong and 15cmdeep.Eliminating the effects of soil moisture on results, soil was saturated from the bottom using drainage outlet tube connected to a water reservoir 24hr before each experiment. The tray was setup at a slope of 0.5% and exposed to simulated rainfall events. For each simulation, runoff and sediment were sampled at regular intervals. Our results showed that while the peak runoff was affected by event profile for the two soil types, there was no significant difference in total runoff among rainfall events examined for both soil types. However, our experiments showed that soil type significantly affected the soil loss. In addition our results showed that models that derive interrill soil erosion directly from rainfall intensity can, therefore, be expected to perform poorly in predicting soil erosion from varying intensity rainfall events. It may imply that various and complicated mechanisms might be activated for runoff and erosion under natural rainfall conditions. Our results may indicate that negligence of event profile may lead to inaccurate understanding of mechanisms involved in runoff and soil erosion.
    Keywords: Event Profile, runoff, Sediment, Rainfall Simulation, Interrill Erosion
  • Sayed-Farhad Mousavi * Pages 213-223
    Scientific method for correct recognition and understanding of the hydrologic phenomena is investigation of their simple models. Generally, a model is a simple representation of a complex system. In mathematical models, behavior of the system is described by a series of mathematical equations, along with logical relationships between variables and parameters. Despite the various proposed mathematical models for modeling of the hydrologic phenomena, there is not a unique approach in this respect. This might be due to spatial and temporal variability of hydrologic phenomena and also lack of mathematical tools for extraction of proper structure for these phenomena. These variations are the result of dependability of the phenomena on different components. This problem has caused the past researches on hydrologic modeling to view the situation as random and probabilistic. The performance of most natural phenomena, including hydrologic problems, in short time scales, to be viewed as completely random and without any trend. But, with a change in time scale, and using sophisticated models, a type of interval and order will be observed. Nowadays, researchers believe that hydrologic phenomena, which have dynamic and nonlinear nature, could be better analyzed by nonlinear and deterministic chaotic models. Hydrologic components in lakes have non-linear and dynamic nature. But, since the changes that these components create in the lakes don’t happen suddenly, it is possible to study and predict some of these elements in the hydrologic cycle. Nowadays, with the evolution of computer models, it is believed that analysis, modeling and control of complex natural phenomena, including hydrologic processes, could be better performed with chaotic models than probabilistic models. Studying the hydrologic components in analysis of the water resources systems, such as lakes, is very important in their quantitative and qualitative operation and management. Due to the importance of precipitation in variations of water level in Urmia Lake, located in north-western Iran, the chaos theory could be a powerful approach to analyze and model the complex behavior of such phenomena. Investigation of chaotic or random behavior of rainfall time series in the lake, for the choice of the best suited rainfall simulation approach, is an important and controversial issue that has been dealt with in this research. First, using the correlation dimension method (CDM), the monthly rainfall time series of Urmia Lake was analyzed over a period of 40 years (1967-2007). After calculating the delay time using average mutual information (AMI) and also calculation of the embedding dimension using false nearest neighbor (FNN) algorithm, the phase space was reconstructed and then the correlation dimension was determined. Then, by using Lyapunof exponent and Fourier power spectrum, the existence of chaos was investigated. Results revealed that presence of chaos in the rainfall time series of Urmia Lake is evident with the non-integer CDM of 2.56, positive value of Lyapunof exponent (maximum of about 2.5) and broad band Fourier power spectrum. Consequently, the system behavior is regular; in other words, the system is not considered random. In such a system, chaos theory has the ability to extract short-term time series from long-term records. In addition, the existence of low-dimensional chaos implies the possibility of accurate short-term predictions of precipitation.
    Keywords: Correlation dimension, Urmia Lake, Fourier power spectrum, Lyapunof exponent
  • Behrooz Keshtegar* Pages 235-246
    Corrosion of steel reinforcement has a complex process which leaded the reduction of crass section bars and degradation of concrete structure. the corroded reinforcement bars were the most important issue of the concrete permanence in the marine structures. The important effects of corrosion are in the damages made by corroded concrete structure which include all kinds of structural and non-structural damages. The first one is more important because of the reduction of the safety factor of the structure against the applied external loads. These failures include the reduction of cross-section bars and the changes in the steel mechanical behavior. Corrosion includes two processes: (1) corrosion initiation and corrosion propagation. The initiation time is when the corrosive ions receive on the surface bars and lead to activation of the steel. (2) The propagation time is when the structure loses its capability subject to the loss of the cross-sectional area of reinforcing steel bars, reduction of bond and crack initiation and propagation. The predicative models of life-service of a reinforced concrete structures should be included the two processes of corrosion. Because for new structures, the initiation time of corrosion and insurance from the long-time of corrosion initiation time, and for the existing structures, controlling the corrosion propagation is more important.
    In this paper, statistical characteristics of the chloride diffusion coefficient, corrosion initiation time and corrosion rate including the best probability distribution function and its parameters are investigated based on Mont Carlo simulation of pitting corrosion data. The distribution function parameters of the corrosion variables i.e. the chloride diffusion coefficient, corrosion initiation time and corrosion rate were calculated using the Maximum likelihood method based on mathematical pitting corroded model that corrosion initiation and corrosion propagation processes are considered in this model. the probability density functions such as: Gamma, Gumbel, Lognormal, Normal, and Weibull were used in the statistical analyses of corroded pitting parameters. The best probability distribution function was selected using chi-square statistic. the Lognormal distribution function was obtained the best probability function for the threshold chloride concentration, the corrosion initiation time and the corrosion rate. The corrosion initiation time depend on four basic random variables such as: the concrete compressive resistance, the concrete cover, the threshold chloride concentration and the surface chloride concentration. Thus, their statistical effects of these random variables on corrosion initiation time are parametrically investigated using 10000 Mont Carlo simulations. It is obvious that increasing the concrete resistance leads to increasing the corrosion initiation time and standard deviation of the density function. The concrete physical and mechanical characteristics are effective variables on the corrosion initiation time but the threshold chloride concentration and the surface chloride concentration are insensitive variables on the mean of corrosion time but lead to significant changes in standard deviation of the corrosion time. Finally, Various diameters bars such as: 8, 12, 16 bars and 20 were investigated in time-depended area of the corroded steel of concrete beams. Results illustrated that and the cover depth is important variable in corroded crass section of bars. Also, increasing the bar diameter and decreasing the corrosion time period were leaded to reduce the rate of the crass section bars.
    Keywords: Probabilistic analysis, Mont Carlo simulation, reinforced concrete beams, pitting corrosion
  • Habibollah Younesi * Pages 247-258
    Composting is certainly one of the most natural types of recycling process. One of the problems during this process is the management of leachate that adversely affects human and ecological health in the area. Leachate is a complex organic compound which is difficult to be degraded biologically by conventional methods. Advanced oxidation processes (AOPs) have been widely studied for the degradation of diverse types of industrial wastewaters. The purpose of the study was aimed to evaluate the efficiency of hydrogen peroxide with ultraviolet light (H2O2/UV) for the treatment of high chemical oxygen demand (COD) strength compost leachate, color and turbidity using response surface methodology (RSM) under central composite design (CCD). The various operation conditions such as initial pH, dose of hydrogen peroxide, and UV-contact time was examined in order to optimize the maximum COD and color removal and turbidity of the compost leachate. The total number of 20 experimental runs was set. Optimal condition obtained for H2O2/UV process were initial pH 7.5, dose of hydrogen proxide 2.3 mL/L, and UV-contact time 95 min. In these conditions, the removal of COD and color and turbidity for H2O2/UV process was 12.32%, 20.83%, and 8.68 NTU, respectively. The results indicated that the H2O2/UV process has been successful in reducing turbidity but in COD removal efficiency is not well. Composting is certainly one of the most natural types of recycling process. One of the problems during this process is the management of leachate that adversely affects human and ecological health in the area. Leachate is a complex organic compound which is difficult to be degraded biologically by conventional methods. Advanced oxidation processes (AOPs) have been widely studied for the degradation of diverse types of industrial wastewaters. The purpose of the study was aimed to evaluate the efficiency of hydrogen peroxide with ultraviolet light (H2O2/UV) for the treatment of high chemical oxygen demand (COD) strength compost leachate, color and turbidity using response surface methodology (RSM) under central composite design (CCD). The various operation conditions such as initial pH, dose of hydrogen peroxide, and UV-contact time was examined in order to optimize the maximum COD and color removal and turbidity of the compost leachate. The total number of 20 experimental runs was set. Optimal condition obtained for H2O2/UV process were initial pH 7.5, dose of hydrogen proxide 2.3 mL/L, and UV-contact time 95 min. In these conditions, the removal of COD and color and turbidity for H2O2/UV process was 12.32%, 20.83%, and 8.68 NTU, respectively. The results indicated that the H2O2/UV process has been successful in reducing turbidity but in COD removal efficiency is not well. The results indicated that the H2O2/UV process has been successful in reducing turbidity but in COD removal efficiency is not well.
    Keywords: CompostLeachate, Wastewater treatment, AOPs, H2O2-UV