ORIGINAL_ARTICLE بررسی الگوی جریان اطراف آبشکن با دیواره‌ی شیب‌دار در این مقاله به مطالعه¬ی آزمایشگاهی ساختار جریان پیرامون آبشکن با دیواره¬ی شیب¬دار پرداخته شده است. بدین منظور، هیدرودینامیک سه بعدی اطراف تک آبشکن مستقیم با دیواره¬ی شیب¬دار 75 درجه، بصورت آزمایشگاهی و در یک کانال مستقیم با بستر صلب مورد مطالعه قرار گرفت. مشخصات جریان با برداشت پارامترهای آشفتگی اطراف آبشکن به وسیله سرعت¬سنج نقطه¬ای سه بعدی ADV، مورد بررسی قرار گرفت. در پشت آبشکن با کاهش سرعت جریان که منجر به تشکیل ناحیه¬ی سکون می شود، سرعت جریان در نواحی میانی افزایش می¬یابد. به همین علت جریان به دو قسمت تقسیم شده و قسمتی از جریان به سمت بالا و قسمتی از جریان به سمت پایین که فشار کمتر است، حرکت می‌کند. جریان پایین رونده عامل تشکیل گردابه¬ی نعل اسبی می¬باشد. دو ناحیه¬ی تشدید سرعت، که اولی مربوط به تشدید سرعت در هسته¬ی اصلی جریان و ناشی از کاهش عرض عبوری جریان بوده و ناحیه¬ی پرسرعت دیگر که مربوط به تشدید موضعی سرعت در پایین¬دست آبشکن و در ناحیه¬ی بیرونی لایه¬ی برشی می¬باشد، تشکیل می¬شد و حداکثر مقدار مؤلفه¬ی تنش -ρ(u^' v^' ) ̅در امتداد لایه¬ی برشی رخ می¬دهد. با توجه به مقادیر منفی تنش¬های رینولدز (-ρ(v^' w^' ) ̅) و (-ρ(u^' w^' ) ̅)، تجمع رسوبات در ناحیه¬ی چرخشی پشت آبشکن اتفاق می افتد. http://mcej.modares.ac.ir/article-1-4199-fa.pdf 2016-03-20 1 11 آبشکن مستقیم دیواره ی شیب دار پارامترهای آشفتگی Experimental study of flow around spur dike with side slope Experimental study on effect of single spur dike side slope on flow structure carried out. In the study, 3D flow dynamics around the single spur dike with side slope of 75 degree has been studied experimentally in straight fixed bed channel. In order to analysis of flow characteristics, turbulence parameters flow around the scour have been measured using Acoustic Doppler Velocimeter (ADV). In behind of the spur dike, due to reduction of flow velocity that leads to formation of stationary zone, flow velocity will be increased in central zones. Therefore, a part of the flow is conducted upward and another part will be directed downward, where the pressure is lower. Downward flow is the cause of horseshoe vortex formation. Two velocity intensifier zones is formed, one is located in the main core of flow which is caused by reduction of flow width and the other one is a high velocity zone that is related to local velocity intensifying in outer layer of shear zone in the downstream of the spur dike. This is stemmed from increase in velocity of flow caused by reduction in flow width and leads to scour initiation from this zone. The maximum amount of “-ρ(u^' v^' ) ̅” stress element in shearing layer direction is occurred. Regarding to negative amounts of “-ρ(v^' w^' ) ̅” and “-ρ(u^' w^' ) ̅” stress elements, accumulation of deposits is happened in circular zone behind the spur dikes. Increases in both the speed, a core area to increase the speed of the flow and reduce the width of the high-speed flow and other areas related to the intensification of local rapidly down the breakwater and in the area the outer layer the shear is formed. The maximum mean flow velocity at the bottom of the breakwater 55/1 is the mean flow velocity is approaching. In the upstream region of the breakwater a rotating flow in the leg is shaped breakwater. It has small dimensions and rotational flow near the breakwater body rotation power was concentrated in the can be high. Upstream of the nose, the lines of the horseshoe vortex, the rotation around the nose, the hands move downward and adjacent layers come to be intertwined with the shear. The average flow field, the maximum kinetic energy in the central part of the channel and away from the shear layer form is the maximum kinetic energy of turbulence along the shear layer will occur. Increase in kinetic energy along the shear layer plays an important role in the sediment bed holds it down, so that the kinetic energy due to the formation of vortex turbulence the total flow depth have been developed. In behind of the spur dike, due to reduction of flow velocity that leads to formation of stationary zone, flow velocity will be increased in central zones. Therefore, a part of the flow is conducted upward and another part will be directed downward, where the pressure is lower. http://mcej.modares.ac.ir/article-1-4199-en.pdf 2016-03-20 1 11 Side angle Spur dike Turbulence parameters 1 AUTHOR 2 AUTHOR 3 AUTHOR
ORIGINAL_ARTICLE ارزیابی ریزساختاری میزان مصرف آهک و پیشرفت واکنش‌های پوزولانی خاک‌ واگرای تثبیت‌شده با آهک وجود خاک‌های واگرا در محل اجرای سازه‌های مهندسی به‌عنوان یکی از مشکلات ژئوتکنیکی شناخته شده‌است. هدف اصلی این تحقیق، تعیین نرخ رشد و پیشرفت واکنش‌های پوزولانی خاک واگرا و آهک در کوتاه‌مدت و بلندمدت از منظر ریزساختاری و درشت ساختاری و همچنین تعیین میزان آهک مصرفی در طی زمان و تأثیر آن بر پارامترهای مکانیکی بوده‌است. در این راستا آزمایش‌ها با درصدهای مختلف آهک هیدراته (0 تا 10 درصد) انجام شد. از مهم‌ترین نتایج این پژوهش می‌توان به ارائه یک معیار ساده برای شروع واکنش‌های پوزولانی و تعیین میزان آهک مصرف‌شده در طی واکنش‌های پوزولانی بر اساس pH و ضریب هدایت الکتریکی (EC) اشاره نمود. بر اساس نتایج آزمایش‌های pH و ضریب هدایت الکتریکی (EC)، پراش پرتو ایکس (XRD) و مقاومت فشاری محدود نشده (UCS) در مقادیر mS/cm 4 ≤ EC واکنش‌های پوزولانی صورت می‌پذیرد و تشکیل ترکیبات جدیدی مانند ساختار هیدرات سیلیکات کلسیم (CSH) و هیدرات آلومینات کلسیم (CAH) موجب افزایش خصوصیات مقاومتی خاک می‌شود. در طی زمان با کاهش mS/cm 4 ≥ EC و 12.4 ≥ pH نرخ واکنش‌های پوزولانی و افزایش مقاومت خاک محدود می‌شود. در خاک واگرای مورد مطالعه حدود 3 تا 4% آهک برای واکنش کوتاه‌مدت که شامل تبادل کاتیونی است، کافی است. بر اساس نتایج، افزایش 6% آهک در طی 14 روز اول (mS/cm 4 ≤ EC و pH ≥ 12) مقاومت فشاری نمونه تثبیت‌شده را حدود 10 برابر افزایش می‌دهد این در حالی است که پس از 14 روز (mS/cm 4 ≥ EC و pH ≥ 12) افزایش مقاومت تنها حدود 5% است. http://mcej.modares.ac.ir/article-1-8622-fa.pdf 2016-03-20 11 22 ضریب هدایت الکتریکی (EC) پراش پرتو ایکس (XRD) آهک خاک واگرا Microstructural Assessment of Lime Consumption Rate and Pozzolanic Reaction Progress of a Lime-Stabilized Dispersive Soil The existence of soft clay and dispersive soft clay at the site of engineering structures is regarded as one of the geotechnical problems. This study is performed on silty soft clay that according to the experimental results showed 100% dispersivity potential. Due to the low bearing capacity of this type of soil in the site, the slaked lime was used to stabilize the soil geotechnical properties, to increase its strength, to decrease plasticity behaviour of soil, and to overcome its dispersive properties. The main goal of the present study is to determine the growth rate and progress of lime-soil pozzolanic reactions in short and long terms from micro- and macro- structural point of view, as well as the measurement of the consumed lime rate over the time and its effect on mechanical parameters of the stabilized soil. The results of this study allow determining the minimum percentage of the lime that is necessary to react with clay minerals for making an acceptable change in long-term properties of stabilized soil. In this regard, a number of tests carried out with different percentages (0 to 10 percent) of hydrated lime. The pH, electric conductivity (EC), unconfined compressive strength, and lime consumption rate determination by X-ray diffraction analysis were the tests used in this study to observe the progress of lime reaction with clay. In order to determine the microstructural and mineralogical changes, and reaction products formed in the modified soil, X-ray diffraction (XRD) evaluation and scanning electron microscopy images have been used. Among the most important results of the present study, this paper propose a simple criterion for the onset of pozzolanic reactions and determination of the consumed lime rate during the pozzolanic reaction process based on pH and electric conductivity measurements. Based on the results from pH, EC, XRD, and unconfined compressive strength (UCS) tests, the pozzolanic reaction occurs at EC ≥ 4 mS/cm. Following that, the formation of new components such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH) causes an increase in soil strength. Over the time, with the reduction of EC ≤ 4 mS/cm and pH ≤ 12.4, the progress rate of pozzolanic reaction and the progress rate in soil strength suspend. The results show that for the dispersive soil around 3-4% lime is sufficient for its short-term reaction, which includes cation exchange. Based on the achieved results, the use of 6% lime for stabilization of sample gives EC ≥ 4.0 mS/cm and pH ≥ 12 after the first 14 days period. The unconfined compressive strength of the stabilized sample increased around 10 times in the same period, while only 5% increase in strength observed after 14 days (EC ≤ 4.0 mS/cm and pH ≤ 12). http://mcej.modares.ac.ir/article-1-8622-en.pdf 2016-03-20 11 22 pH Electric Conductivity (EC) XRD pH lime Dispersive Soil Vahid Ouhadi 1 Bu-Ali Sina University, Faculty of Eng., Civil Eng. Department, Iran AUTHOR 2 AUTHOR 3 AUTHOR
ORIGINAL_ARTICLE شبیه سازی عددی شکل گیری جت حاصل از خرج گود و نفوذ آن در اهداف بتن مسلح خرج گودها، موادمنفجره با قابلیت نفوذ بالا هستند وبرای اهداف نظامی وغیر نظامی استفاده می شود. در کاربردهای غیر نظامی خرج گود در کارهای تخریب، حفاری نفت و معدن استفاده می شود. در کاربردهای نظامی، خرج گودها در برابر انواع مختلف زره و همچنین سازه¬های امن استفاده می شود. تحلیل مسائل شکل گیری و نفوذ پرتابه¬های حاصل از خرج گود دارای پیچیدگی¬های زیادی است که انفجار خرج، انتشار موج شوک درون خرج و اصابت موج به لاینر، تغییر فرم لاینر، شکل گیری پرتابه و در نهایت اصابت آن به سطح هدف و نفوذ در آن تا توقف کامل را شامل می¬شود. با توجه به پیچیدگی رفتار هدف بتنی درهنگام نفوذ جت، به مدل¬هایی نیاز است که بتواند اثر تغییر شکل¬های بزرگ، فشار هیدرواستاتیک ونرخ کرنش بالا وگسیختگی را مدلسازی نماید. اگرچه مراجعی درمورد شبیه سازی نفوذ برخی خرج گودها در اهداف فولادی منتشر شده است ولی در خصوص نفوذ خرج گود در اهداف بتنی، مرجع کاملی یافت نشد. هدف اول از این تحقیق ارائه یک روش شبیه سازی عددی مطمئن به وسیله نرم افزارهای موجودبر روی نفوذ خرج گود RPG-7 در اهداف بتنی می¬باشد. بدین منظور در سه مرحله نتایج شبیه سازی¬ها با نتایج آزمایشگاهی موجود مورد مقایسه قرار گرفت که شامل تشکیل جت، نفوذ جت در اهداف فولادی و رفتار هدف بتنی در مقابل نفوذ می¬یاشد. هدف دوم تحقیق، تعیین ضخامت ایمن هدف، از جنس بتن معمولی در مقابل نفوذ RPG-7 وبررسی رفتار این نوع بتن به لحاظ عمق نفوذ، شعاع حفره وگسیختگی دروجوه جلویی و پشتی هدف می¬باشد. http://mcej.modares.ac.ir/article-1-8005-fa.pdf 2016-03-20 23 34 خرج گود تشکیل جت نفوذ هدف بتنی Numerical simulation of shaped charge Jet formation and penetration in the reinforced concrete targets Shaped charges are explosive devices with a high penetration capability and are used for both civilian and military purposes. In civilian applications shaped charge devices are used in demolition works, oil drilling and mining. In the military applications, shaped charges are used against different kinds of armors and Protective Structures. Analysis of forming and penetration of shaped charge projectiles issue is so complex that include explosion of charge, propagation of the shock wave in the charge, hitting the shock wave to the liner, liner deformation, projectile formation and finally striking projectile to target until it stops. According to the complexity of Behavior of the concrete during the Penetration of the Jet, the material models shoude be able to model the effect to large deformation, high hydrostatic pressure, high strain rate and failure. Although there are many references about Numerical simulation of shaped charge Jet in the armor targets, however it was not found any comprehensive sources about penetration of shaped charge in the reinforced concrete targets. Experimental results suggest that both kinetic energetic projectile and shaped charge are capable of destroying concrete targets, but the magnitudes of damage due to them are different. Compared with a kinetic energy projectile, a shaped charge has more significant effect of penetration into the target, and causes very large spalling area. In this paper, AUTODYN software was used to numerical simulation of shaped charge jet formation and target penetration. Different solver and modeling alternatives of AUTODYN were evaluated for jet formation and penetration problems. Euler solver of the AUTODYN was used to jet formation simulations and Lagrange solver was used for penetration simulations and both models were 2D axisymmetric. To simulate the penetration performance of the RPG – 7 charge, both the jet and the target were modeled by Lagrangian elements. The results of jet formation simulations, performed by the Euler solver were used to determine the properties of the jet. Penetration simulations were performed for a fixed 2 CD standoff distance. The jet material distribution obtained by the Euler solution at 2 CD standoff distance was mapped onto the Lagrange solver. The quality of this Euler-to-Lagrange mapping was limited to the mesh resolution of the Lagrangian jet part. The first goal of this research is presentation of a reliable method to numerical simulation of Penetration of shaped charge of RPG – 7 into the concrete targets by use of available software tools. Therefore, simulation results were compared to the experimental results in three stages that Include the jet formation, jet Penetration in armor targets and behavior of concrete target against Penetration. The second goal is determination of the safe thickness of conventional concrete targets against the Penetration of RPG – 7 weapen and investigation of the behavior of this concrete type of target in terms of penetration depth, hole diameter and failure of the front and rear surfaces of the target. http://mcej.modares.ac.ir/article-1-8005-en.pdf 2016-03-20 23 34 shaped charge jet formation penetration concrete target ahmad heidarian khorzoughi 1 AUTHOR ghasem Dehghani Ashkzari 2 AUTHOR
ORIGINAL_ARTICLE بررسی رفتار لرزه‌ای لوله‌های مدفون فولادی تحت اثر گسلش‌نرمال با توجه به توسعه شهرنشینی و نیاز مردم به انرژی و آب، صنعت خطوط لوله نفت، گاز، آب و فاضلاب نیز پیشرفت کرده است. با توجه به احتمال عبور خطوط لوله از محل گسل‌ها در طول مسیر مطالعات ویژه جهت بررسی پاسخ خطوط لوله عبوری از گسل‌ها احساس می‌شود. مطالعه عددی حاضر پاسخ خطوط لوله فولادی مدفون تحت گسلش نرمال را مورد مطالعه قرار داده است. گسل عمود بر خط لوله بوده و در جهت قائم تغییر مکان می‌دهد که سبب ایجاد تنش‌ها و کرنش‌هایی در دیواره خط لوله می‌شود. مدل‌سازی سیستم خاک – لوله به طور دقیق با استفاده از المان‌های محدود که کرنش‌‌ها و تغییر مکان‌های بزرگ و رفتار غیر خطی مصالح را در نظر می‌گرفتند، انجام شده است. هدف از این مطالعه تعیین تغییر مکانی از گسل بود که لوله درآن دچار خرابی می‌شد و از آن می توان در طراحی خطوط لوله استفاده کرد. نتایج برای نسبت‌های مختلف قطر به ضخامت لوله در نموداری که کرنش بحرانی و تغییر مکان بحرانی گسل را نشان داده‌اند، نمایش داده شده است. http://mcej.modares.ac.ir/article-1-10459-fa.pdf 2016-03-20 35 44 گسلش نرمال خطوط لوله فولادی مدفون طراحی بر اساس عملکرد Seismic response of buried pipelines subjected to normal faulting Buried pipelines, commonly used to transport water, gas and oil, are critical elements of the infrastructure of today’s modern cities and usually pass through large geographical distances. They are classified as lifelines as they carry materials that are essential to support human life. Due to the importance of maintaining the operability of these lifelines, it is of primary importance to study the effect of different hazards on their behavior in order to be able to mitigate any possible damages. Therefore, they could be subjected to different types of natural hazards such as earthquakes in the form of permanent ground displacement and/or wave propagation. Seismic waves could pose great threats to above ground facilities and perhaps to a lesser content to buried pipelines. Permanent ground displacement is often caused by surface faulting, landslides, or liquefaction. Over the past years, many researchers have attempted to study the behavior of buried pipelines crossing active faults. Many reconnaissance reports show that significant damages are observed in buried steel pipelines crossing active faults. The corresponding ground deformations are applied in a quasi-static manner, and are not necessarily associated with high seismic intensity. During the ground deformation, the pipeline may undergo severe deformation, well beyond the elastic range of pipe material and may cause pipeline failure, i.e. high tensile stresses may result in tensile fracture of the pipe wall, specifically at welds, whereas compressive stresses may cause local buckling or wrinkling of the pipe wall. In case of moderate buckling, deformation of the pipe cross-section can lead to flow restriction and high friction losses, and eventually require line replacement; while for severe buckling high localized strains can lead to pipe rupture, loss of contents, and possible pollution of surrounding soil. The present study investigates the mechanical behavior of buried steel pipelines, crossing normal faults of right angle in loose clay. The pipe is assumed to be normal to the fault plane. The interacting soil–pipeline system is modeled through three-dimensional finite element method, which accounts for large strains and displacements, nonlinear material behavior, friction and gap forming on the soil–pipe interface. The analysis is conducted through an incremental application of fault displacement. Considering steel pipelines of various diameter-to-thickness ratios, and typical steel material for pipeline applications , the present study concentrates on identifying the fault offset at which the pipeline fails considering different performance criteria and to use them for performance-based design purposes. The results are presented in the form of diagram showing the critical fault displacement, and the corresponding critical strain versus the pipe diameter-to-thickness ratio. Results show that for pipelines buried in loose clay, the governing failure mode is local buckling of the pipe wall, which occurs at two locations along the length of the pipeline. The distance between the two locations at which local buckling occurs increases with decreasing pipe diameter-to-thickness ratio. It is shown that with increasing pipe diameter-to-wall thickness ratio, longitudinal compressive strains in the pipe wall increases and consequently the capacity of the pipeline to accommodate the ground deformation decreases significantly. http://mcej.modares.ac.ir/article-1-10459-en.pdf 2016-03-20 35 44 Buried steel pipelines Normal faulting performance-based design nader K.A. Attari 1 Dept. of Structural Eng., Road, Housing and Urban Development Research Center AUTHOR mohamad Deljavan Anvari 2 Earthquake Eng. department, Road, Housing and Urban Development Research Center AUTHOR himan hojat jalali 3 Dept. of Civil Eng., Sharif University of Technology AUTHOR mehdi Momeni 4 Retrofit expert, Tehran Gas Company AUTHOR
ORIGINAL_ARTICLE تحلیل و ارزیابی پارامترهای موثر بر فرونشست زمین پدیده فرونشست سطح زمین ناشی از عوامل طبیعی و فعالیت‌های انسانی در نقاط مختلف دنیا و در طی سال‌های اخیر در کشور ایران به خصوص استان فارس به علت برداشت بی رویه از آب‌های زیرزمینی، خشکسالی و عوامل دیگر پدیدار شده است و سبب آسیب‌های جدی به زمین‌های کشاورزی، ساختمان‌های مسکونی، جاده‌ها و دیگر سازندها و بروز خسارت‌های زیست محیطی، اقتصادی و اجتماعی شده است. در این مقاله با انجام یک پژوهش موردی در دشت مرودشت به بررسی عوامل و پارامترهای موثر و ارزیابی میزان تأثیر هر کدام بر نشست سطح زمین پرداخته شده است. در این خصوص نحوه تعیین و تحلیل پارامترهای موثر همچون میزان افت سطح آب، جنس و ضخامت لایه های خاک به خصوص لایه های ریزدانه، خصوصیات ژئوتکنیکی خاک مورد بررسی قرار گرفته است و نتایج حاکی از ان است که جهت انجام محاسبات فرونشست خاک، داده ها و اطلاعات مورد نیاز تا حد امکان باید به صورت دقیق و جامع تهیه شوند و ویژگی‌ها و شرایط متفاوت هر پارامتر در نظر گرفته شود. به عنوان مثال نشست ناشی از افت یکسان آب و یا ضخامت یکسان لایه ریزدانه در اعماق مختلف متفاوت می‌باشد. http://mcej.modares.ac.ir/article-1-8483-fa.pdf 2016-03-20 45 54 "فرونشست زمین" "لایه ریزدانه" "افت آب" "مرودشت" "برداشت بی رویه" Analysis and evaluate the effective parameters on land subsidence Land subsidence phenomenon caused by natural factors and human activities in different parts of the world. This phenomenon in recent years is appeared in Iran, especially in Fars province due to indiscriminate withdrawal of groundwater, drought and other factors. Land subsidence caused lots of damages to agricultural lands, residential buildings, roads, and other structures and generally created environmental, social and economicAL problems. In this research a case study was performed on the villages of Marvdasht plain in order to study the effective factors and parameters and evaluate the influence of each one on land subsidence. And also was examined how to determine and evaluate the main effective parameters such as water levels falling, material and thickness of soil layers especially fine-grained, geotechnical properties of soil layers. Results showed to perform of subsidence calculations the data and requirement information should be prepared accurate and complete as much as possible. It should be noted that the characteristics and different statues of each parameter must be considered. For example, the amount of settlement is different in Various depth due to same water falling or same thickness of layers. Land subsidence phenomenon caused by natural factors and human activities in different parts of the world. This phenomenon in recent years is appeared in Iran, especially in Fars province due to indiscriminate withdrawal of groundwater, drought and other factors. Land subsidence caused lots of damages to agricultural lands, residential buildings, roads, and other structures and generally created environmental, social and economicAL problems. In this research a case study was performed on the villages of Marvdasht plain in order to study the effective factors and parameters and evaluate the influence of each one on land subsidence. And also was examined how to determine and evaluate the main effective parameters such as water levels falling, material and thickness of soil layers especially fine-grained, geotechnical properties of soil layers. Results showed to perform of subsidence calculations the data and requirement information should be prepared accurate and complete as much as possible. It should be noted that the characteristics and different statues of each parameter must be considered. For example, the amount of settlement is different in Various depth due to same water falling or same thickness of layers. Land subsidence phenomenon caused by natural factors and human activities in different parts of the world. This phenomenon in recent years is appeared in Iran, especially in Fars province due to indiscriminate withdrawal of groundwater, drought and other factors. Land subsidence caused lots of damages to agricultural lands, residential buildings, roads, and other structures and generally created environmental, social and economicAL problems. In this research a case study was performed on the villages of Marvdasht plain in order to study the effective factors and parameters and evaluate the influence of each one on land subsidence. And also was examined how to determine and evaluate the main effective parameters such as water levels falling, material and thickness of soil layers especially fine-grained, geotechnical properties of soil layers.this part have a problem http://mcej.modares.ac.ir/article-1-8483-en.pdf 2016-03-20 45 54 "Water Falling" "Land Subsidence" "Irregular Withdrawals" "fine graine" sohrab mirassi 1 Shiraz university of technology AUTHOR HOSSEIN RAHNEMA 2 shiraz university of technology AUTHOR
ORIGINAL_ARTICLE ارزیابی عملکرد دیوار حائل خاک مسلح با تسلیح‌کننده‌های مورب، رویه شیب‌دار و مهار تسلیح‌کننده‌ها طی سه دهه گذشته با توجه به مزایای دیوارهای حائل خاک مسلح، استفاده از این دیوارها در طرح‌های عمرانی افزایش قابل توجهی یافته است. از بزرگترین مزایای دیوارهای خاک مسلح انعطاف‌پذیری این دیوارها و توانایی آن‌ها برای جذب تغییرشکل‌ها به علت شرایط ضعیف خاک شالوده‌ها می‌باشد. در این تحقیق با بررسی مطالعات گذشته سعی شده تا تاثیر شیبداری رویه دیوار، تسلیح‌کننده‌های مورب و مهار تسلیح‌کننده‌ها بر عملکرد دیوار به صورت تجربی مورد بررسی قرار گیرد. در این راستا در مجموع 14 مدل دیوار در مقیاس آزمایشگاهی ساخته شده و عملکرد آن‌ها تحت بارگذاری مناسب مورد ارزیابی قرار گرفت. نتایج حاصل از بررسی‌های تجربی نشان داد که با کاهش شیب رویه دیوار، تغییرشکل رویه کاهش می‌یابد. همچنین با افزایش شیب لایه‌های تسلیح، تغییرشکل افقی رویه دیوار کاهش یافته بود. از این رو با توجه به نتایج به دست آمده، دیوار با شیب لایه‌های تسلیح 10 درجه و شیب رویه 80 درجه باعث بهبود قابل توجهی در عملکرد دیوار می‌گردد به نحوی که حداکثر تغییرشکل افقی رویه تا 20% کاهش می‌یابد. http://mcej.modares.ac.ir/article-1-10815-fa.pdf 2016-03-20 55 68 خاک مسلح تسلیح‌کننده‌های مورب رویه شیب‌دار مهار تسلیح‌کننده‌ها Evaluation of Performance Reinforced Soil Retaining Wall with Oblique Reinforcements, Slope Facing and Reinforcements Anchor Due to the advantages of reinforced soil retaining walls, the using of type of the walls has increased in civil projects over the past three decades. One of the reinforced soil applications is the construction reinforced soil retaining walls. The major advantages of the reinforced soil walls are their flexibility and absorbency of deformations. Regarding experiences derived from previous studies, it attempted to investigate the effect of facing slope, oblique reinforcements and reinforcements anchoring on the performance retaining wall by experimental. In this study, 14 models of the walls were constructed. Results of the study provide evidence that horizontal deformation of the wall facing decreased with decreasing of the facing slope. Moreover, with increasing of the reinforcements slope the horizontal deformation reduced. Results showed that reinforced soil wall with oblique reinforcements of 10 degree and facing slope of 80 degree reduce the maximum horizontal deformation of the facing by 20%.Due to the advantages of reinforced soil retaining walls, the using of type of the walls has increased in civil projects over the past three decades. One of the reinforced soil applications is the construction reinforced soil retaining walls. Regarding experiences derived from previous studies, it attempted to investigate the effect of facing slope, oblique reinforcements and reinforcements anchoring on the performance retaining wall by experimental. In this study, 14 models of the walls were constructed. Results of the study provide evidence that horizontal deformation of the wall facing decreased with decreasing of the facing slope. Moreover, with increasing of the reinforcements slope the horizontal deformation reduced. Results showed that reinforced soil wall with oblique reinforcements of 10 degree and facing slope of 80 degree reduce the maximum horizontal deformation of the facing by 20%.Due to the advantages of reinforced soil retaining walls, the using of type of the walls has increased in civil projects over the past three decades. One of the reinforced soil applications is the construction reinforced soil retaining walls. The major advantages of the reinforced soil walls are their flexibility and absorbency of deformations. Regarding experiences derived from previous studies, it attempted to investigate the effect of facing slope, oblique reinforcements and reinforcements anchoring on the performance retaining wall by experimental. In this study, 14 models of the walls were constructed. Results of the study provide evidence that horizontal deformation of the wall facing decreased with decreasing of the facing slope.Due to the advantages of reinforced soil retaining walls, the using of type of the walls has increased in civil projects over the past three decades. One of the reinforced soil applications is the construction reinforced soil retaining walls. Results of the study provide evidence that horizontal deformation of the wall facing decreased with decreasing of the facing slope. Moreover, with increasing of the reinforcements slope the horizontal deformation reduced. Results showed that reinforced soil wall with oblique reinforcements of 10 degree and facing slope of 80 degree reduce the maximum horizontal deformation of the facing by 20% http://mcej.modares.ac.ir/article-1-10815-en.pdf 2016-03-20 55 68 Reinforced soil Oblique reinforcements Slope facing Reinforcements anchor mohammad shabani rameneti 1 AUTHOR
ORIGINAL_ARTICLE مطالعه آزمایشگاهی ساختار جریان آشفته در میدان دو آبشکن با روشPIV در این تحقیق میدان جریان بین دو آبشکن مستقیم واقع در جریان کم عمق یک کانال عریض با استفاده از روش سرعت سنجی تصویری ذرات سطحی اندازه گیری شده است. بدین منظور آبشکن های مستقیم به طول 25 سانتیمتر در دو فاصله نسبی 1 و 2 در ناحیه جریان توسعه یافته کانالی به عرض 8/1 قرار داده شده و اندازه گیری میدان جریان، به منظور مطالعه الگوی جریانهای چرخشی افقی، ساختار لایه اختلاطی و ناحیه چرخشی پایین دست انجام شده است. برای پردازش تصاویر از نرم افزار GPIV استفاده شده و از روش های وستِرویل و الگوریتم تکراری برِویس برای فیلتراسیون میدان‌های سرعت استفاده شده است. نتایج بصورت توزیع مقادیر متوسط سرعت، شدت‌های آشفتگی و تنش‌های رینولدز ارائه شده است. بر اساس نتایج حاصله، بواسطه کم عمق بودن میدان، بخش عمده‌ای از ساختارهای آشفتگی حالت دوبعدی داشته وشکل گیری یک جریان برگشتی از ناحیه پایین دست به داخل میدان آبشکن باعث پیچیدگی ساختار لایه اختلاطی و در نتیجه پروسه تبادل جرم بین ناحیه چرخشی میدان آبشکن و جریان آزاد می‌شود. http://mcej.modares.ac.ir/article-1-2333-fa.pdf 2016-03-20 69 80 میدان آبشکن جریان آشفته لایه اختلاطی سرعت سنجی تصویری ذرات جریان برگشتی Experimental Study of Turbulent Flow Structures in Two Groyne Field using PIV Method In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. http://mcej.modares.ac.ir/article-1-2333-en.pdf 2016-03-20 69 80 Groyne Field Turbulent Flow mixing layer PIV back flow Zolfaghar Safarzadeh 1 AUTHOR a صفرزاده 2 AUTHOR
ORIGINAL_ARTICLE بهینه‌سازی حداکثر تراز تانک با در نظر گرفتن قابلیت اطمینان هیدرولیکی و کیفی شبکه‌های توزیع آب با استفاده از الگوریتم جامعه مورچگان تانک‌ها در شبکه توزیع آب وظیفه ذخیره آب به منظور استفاده در شرایط اضطراری، مصرف آتش‌نشانی و کنترل نوسانات مصرف را به عهده دارند. هزینه ساخت تانکها زیاد بوده و بنابراین در زمان بهره‌برداری استفاده بهینه از کل حجم ضروری می‌باشد. در صورتی که حجم تانک از حجم مورد نیاز در طول دوران بهره‌برداری کمتر و یا بیشتر باشد، قابلیت اطمینان بهره‌برداری از آن کمتر خواهد بود.براین اساس، رابطه جدیدی برای قابلیت اطمینان تانک با توجه به تغییر تراز آب در تانک تعریف شده است. به علاوه، با توجه به اینکه تغییر تراز آب می‌تواند روی فشار و سن آب در گره‌ها تاثیرگذار باشد، این تاثیر با درنظر گرفتن قابلیت اطمینان هیدرولیکی و کیفی بررسی شده است. همچنین برای بررسی تاثیر همزمان تغییر تراز آب برروی قابلیت اطمینان هیدرولیکی و کیفی، رابطه‌ای برای قابلیت اطمینان تلفیقی نیز تعریف شده است. در این مقاله با معطوف شدن به فاز بهره‌برداری، سعی می‌شود بهینه‌سازی چندهدفه عملکرد شبکه‌های آبرسانی بررسی شود که هدف اول حداقل ساختن هزینه ساخت تانک است و هدف دوم حداکثر نمودن قابلیت اطمینان هیدرولیکی، کیفی و تلفیقی می‌باشد. به منظور بهینه‌سازی عملکردی شبکه توزیع آب به علت کارایی بالا و سادگی پیاده‌سازی الگوریتم جامعه مورچگان، الگوریتم NA-ACO-CD در محیط Visual C++ تدوین شده است. کارایی الگوریتم تدوین شده با بهینه‌سازی توابع ریاضی آزمایش، اثبات شده و قابل اجرا بر شبکه‌های توزیع آب می‌باشد. منحنی پاره‌تو حاصل از بهینه‌سازی چندهدفه به تصمیم‌گیرنده این امکان را خواهد داد تا با توجه به شرایط موجود گزینه برتر را انتخاب نماید. http://mcej.modares.ac.ir/article-1-5766-fa.pdf 2016-03-20 81 92 بهینه‌سازی چندهدفه الگوریتم جامعه مورچگان تانک قابلیت اطمینان سن آب Ant Colony Optimization of Tank Maximum Level Considering Hydraulic and Quality Reliability of Water Distribution Networks Tanks in water distribution networks are used to store water for emergency conditions, fire flow demand and demand oscillations controll. Construction of tanks spends a lot of money and therefore using whole volume of tanks is essential while operation. Otherwise, if tank volume will be more or less than what is required during operation, tank reliability is reduced. Accordingly, in this paper, a new relationship for tank reliability according to water level variation in tanks is defined. Therefore, maximum water level in tanks is defined as the decision variable. The definition of tank reliability is as follows. At first, the values of maximum level for each tank is computed such a way that optimal use is provided from balancing volume of tanks. In fact, for these maximum level values, maximum reliability is acheived for each tank. Now if during optimization process, a value lower than these computed maximum level is selected for decision variables, tank reliability is reduced. To compute the value of tank reliability, the values of tank water level for the selected decision variables is devided by the values of tank water level for maximum tank reliability. Also, because water level variation can effect on pressure and water age in demand nodes, this effect is investigated by considering hydraulic and quality reliability. In fact, variation of water level in tanks changes node demand pressures and in result actual node demands. Also, variation of water level or on the other hand variation of storage volume affects on water age in demand nodes. Besides, in order to investigate the simultaneous effect of water level variation on hydraulic and quality reliability, a relationship is also defined for integrated reliability. Definition of integrated reliability is to investigate whether there is optimum maximum tank level values that both hydraulic and quality reliability is improved simultaneusly while tank construction costs is minimum. Optimal management of tanks in water distribution networks to provide required water of consumers with desired quality is of high importance. To acheive this, optimization is defined as a powerful tool. In this paper, by focusing on operation phase, multiobjective optimization of water distribution performance is performed in which tank costs is considered as the first objective and tank reliability, node hydraulic reliability, node water age reliability and integrated reliability is considered as the second objective. Ant colony algorithm is codified in Microsoft Visual C++ for optimization due to its simplicity and high performance. The validity of the edited algorithm is tested on mathematical functions and proved to be applicable on water distribution networks. The created trade-off curve from multiobjective optimization helps the decision makers to select the top choice based on the importance of their own criterion whether it is hydraulic or quality. http://mcej.modares.ac.ir/article-1-5766-en.pdf 2016-03-20 81 92 Multiobjective Optimization Ant colony algorithm Tank Reliability Water Age mahmood Fotuhi 1 AUTHOR 2 AUTHOR
ORIGINAL_ARTICLE توسعه میراگر شکافدار در محل اتصال تیر به ستون با ایجاد شکاف‌های بیضی میراگر شکافدار فولادی یک ورق یا پروفیل استاندارد فولادی با تعدادی شکاف بریده شده در جان آن است. نوارهای باقیمانده در جان میراگر، با جذب تغییر شکل های غیر الاستیک، انرژی لرزه ای را مستهلک کرده و مانع از انتقال آن به اعضای سازه‌ای اصلی می شوند. میراگرهای شکافدار فولادی با عرض نوار یکنواخت، به منظور جلوگیری از شکست ترد اتصالات و خرابی اعضای سازه ای اصلی، در محل اتصال تیر به ستون استفاده شده اند. طبق تحلیل‌های صورت گرفته در نرم‌افزار المان محدود آباکوس، استفاده از میراگرهای شکافدار با عرض نوار یکنواخت در تحقیقات آزمایشگاهی قبلی، موجب تمرکز تنش در قسمت های انتهایی نوارها، توزیع نامتوازن تنش های فون میسز در طول نوارها و عدم مشارکت قسمت های میانی نوارهای میراگر شکافدار در استهلاک انرژی شده است. بنابراین، به منظور رفع این مشکل و افزایش سطح جاذب انرژی در قسمت های انتهایی نوارها، میراگر شکافدار با شکاف های بیضی پیشنهاد شده و با میراگر شکافدار ارائه شده در مقالات قبلی، مورد مقایسه قرار گرفته است. نتایج تحلیل اتصالات تحت بارگذاری تناوبی، نشان داده است که استفاده از میراگر شکافدار پیشنهادی با شکاف های بیضی، موجب توزیع بهتر تنش ها در طول نوارهای میراگر، عملکرد هیسترزیس بهتر و افزایش میزان جذب انرژی در اتصال شده است. نتایج نشان داده است که میزان استهلاک انرژی و حداکثر دوران پلاستیک تجمعی تحمل شده توسط اتصال مجهز به میراگر شکافدار پیشنهادی با شکاف های بیضی نسبت به میراگر شکافدار با عرض شکاف ثابت، به ترتیب، 6/99 و 8/26 درصد افزایش یافته است. http://mcej.modares.ac.ir/article-1-2005-fa.pdf 2016-03-20 93 102 "زلزله" "اتصال تیر به ستون" "میراگر شکافدار فولادی" "شکاف بیضی" Application of Elliptic Slits for Development of Slit Damper in Beam-to-Column Connection The rigid steel connections were suffered severe damage because of low rotational capacity during earthquakes. Hence many investigations have been performed on the connections of steel structures. In order to prevent brittle failure of connections and damage of main structural members, steel slit dampers with uniform strip width are used in the beam-to-column connections. Slit damper is a plate or a standard section with a number of slits in the web. The remaining strips in the web of damper, dissipate the seismic energy with inelastic deformation absorption and also prevent seismic energy transmission to the main structural members. No special fabrication technique was involved in the slit dampers, thus the device can be easily used in practice. To verify the accuracy of finite element modeling, the obtained results of ABAQUS finite element software were compared with an experimental study done by Oh et al (2009). The analytical results have a good agreement with experimental ones and the average error is about 2%. According to the analyses performed in the ABAQUS, using steel slit dampers with uniform strip width is resulted in stress concentration at the ends of the damper strips, unbalanced distribution of Von-Mises stresses along the strips length and low participation of middle parts of slit damper strips in the energy dissipation. Therefore, to resolve these problems and energy-absorbing area rise in the end parts of strips, elliptic slit damper is proposed and compared with the previous investigated slit damper. Slits dimensions of elliptic slit damper are calculated as such that both of present and previous slit dampers have the same weight. The objective of this paper is to improve the seismic performance of steel slit dampers. Nonlinear analyses are carried out in the beam-to-column connections equipped with slit dampers. Effects of geometrical and material nonlinearity are considered in the analyses. Nonlinear characteristics of steels are defined with stress-strain curves. Bilinear stress-strain curves are used for all steel parts except the slit damper which is defined with completed stress-strain curve. Plasticity behavior of steel materials is based on the Von-Mises yielding criteria. Loading protocol recommended by FEMA-350 is used for cyclic analyses. All parts of connection are modeled using shell elements except the split-T plates and the upper plate of slit dampers which are modeled using solid elements. The results of connections analysis under cyclic loading show that the proposed elliptic slit damper causes better distribution of stresses along the damper strips, better hysteresis performance and increase the amount of energy dissipation in the beam-to-column connection. Also elliptic slit damper leads to strength and ductility increment in the connection. Additionally, it is concluded that in the proposed elliptic slit damper compared to the slit damper with uniform strip width, the energy dissipation and the maximum plastic rotation of connection increase about 99.6 and 26.8%, respectively. http://mcej.modares.ac.ir/article-1-2005-en.pdf 2016-03-20 93 102 "Earthquake" "Beam-to-column connection" "Steel slit damper" "Elliptic slit" Saeed Farahi Shahri 1 University of Sistan and Baluchestan AUTHOR Seyed Roohollah Mousavi 2 Assistant Professor, University of Sistan and Baluchestan AUTHOR
ORIGINAL_ARTICLE بررسی اثرات مؤلفه قائم زلزله‌های نزدیک ودور از گسل بر پل سه دهانه راه آهن اندازه گیریهای حرکات زمین در طول زمین لرزه های گذشته نشان می دهد که شتاب قائم زلزله می تواند به بزرگی شتاب های زمین لرزه در جهت افقی برسد ویاحتی ممکن است در بعضی موارد از این شتاب ها نیز تجاوز نماید. مقاله حاضر اثر مؤلفه قائم زلزله را روی پل های راه آهن جعبه ای شکل سه دهانه مورد بررسی قرار داده است. نتایج تحلیلها روی پل‌ها، یکبار با در نظر گرفتن اثر مؤلفه قائم و بار دیگر بدون در نظر گرفتن اثر مؤلفه قائم انجام شد و نتایج تحلیلهای در دو حالت مقایسه شدند. نتایج نشان می دهد تغییر میزان تقاضای نیروی محوری ستون، تقاضای گشتاور موجود در وسط عرشه و تقاضای گشتاور در محل اتصال عرشه به ستون را به طور قابل ملاحظهای به وسیله حرکات قائم زلزله تشدید می شوند. همچنین در تحلیل‌های خطی ملاحظه گردید که اثر مؤلفه قائم زلزله روی سازه را می توان به صورت جدا ومستقل از اثر مؤلفه‌های افقی در نظر گرفت. نتایج بدست آمده، باضوابط SDC-2006 که برای منظور کردن اثر شتاب قائم زلزله ضریب از بار مرده بر سازه اعمال شود، مقایسه شده است. در نهایت برای در نظر گرفتن اثر مؤلفه قائم زلزله ، اعمال ضرایبی روی بارمرده در طراحی پل پیشنهاد شده است. http://mcej.modares.ac.ir/article-1-8257-fa.pdf 2016-03-20 103 116 پل راه آهن مؤلفه قائم زلزله تحلیل دینامیکی رکورد نزدیک گسل رکورد دور از گسل Effects of Near-Fault and Far -Fault Vertical Ground Motions on three span railway bridges The Study on the Accelerometers of the past earthquake indicates that the vertical acceleration can reach values comparable to (and sometimes even higher than) the horizontal accelerations. This study investigates the effect of vertical component of earthquakes on the railway bridges with box girders cross section. Results of bridge analyses when vertical motions of earthquake are included in earthquake effects are compared to the case when vertical motions are excluded. Comparison of the results show that the vertical components of ground motions cause significant amplification in the axial force demand in the columns and moment demands in the box girder at both the midspan and at the face of the joints to column. Another finding from the linear analytical study is the fact that the effect of vertical component is completely uncoupled to the horizontal effects. With the results obtained, the comparison of the results with SDC-2006 suggestions shows that a unit multiplier of the dead load effect for compensation of vertical effect of earthquake. Finally, for considering the effect of an earthquake's vertical component, Dead Load Multipliers have been suggested; they are used in designing bridges. http://mcej.modares.ac.ir/article-1-8257-en.pdf 2016-03-20 103 116 Railway Bridge vertical component of earthquake dynamic analyses near-fault record far-fault record Modar Feddah 1 AUTHOR hamid Moharrami 2 Director of Structural Eng. group, Tarbiat Modares University AUTHOR Farhad Daneshjoo 3 Tarbiat Modarres University AUTHOR
ORIGINAL_ARTICLE بررسی قابلیت سیستم الکتروفنتون با استفاده از الکترود گرافیت با پوشش نانو لوله کربن در حذف رنگزای اسید اورانژ 7 در این تحقیق فرایند الکتروفنتون با استفاده از کاتدی از جنس گرافیت با پوشش نانو لوله کربنی و آندی از جنس فولاد زنگ نزن برای حذف رنگ از فاضلاب سنتزی انجام شد. نتایج بر روی فاضلاب سنتزی نشان داد که فرایند الکتروفنتون تحت شرایط بهینه غلظت اولیه رنگزا 100 میلی گرم بر لیتر، چگالی جریان 1 میلی آمپر بر سانتی متر مربع، بدون هوادهی، pH معادل با 5/6، سطح الکترود 90 سانتی متر مربع، غلظت الکترولیت 01/0 مولار و با مصرف انرژی 13/0 کیلووات ساعت به ازای هر ppm رنگزای حذف شده پس از 360 دقیقه به ترتیب به راندمان حذف 98 و 95 درصد برای رنگزا و COD رسید. در این تحقیق نشان داده شد که سیستم الکتروفنتون با استفاده از الکترودهای گرافیت با پوشش نانو لوله کربنی و فولاد زنگ نزن در عین کاهش هزینه‌های اجرایی از کارایی بالایی در حذف رنگزای اسید اورانژ 7 برخوردار می‌باشد. بر اساس نتایج بدست آمده، فرایند الکتروفنتون برای تجزیه فاضلاب حاوی رنگزا و آلاینده‌های مقاوم می‌تواند به عنوان پیش تصفیه مورد استفاده قرار گیرد. این تکنولوژی قابل اجراء موجب بهبود قابلیت تصفیه پذیری زیستی فاضلاب نساجی می‌گردد. http://mcej.modares.ac.ir/article-1-1702-fa.pdf 2016-03-20 117 126 الکتروشیمی سطح الکترود شدت جریان انرژی مصرفی Analysis of degradation of Acid Orange 7 by Electro-Fenton process with graphite cathode coated by carbon nanotubes Azo dyes constitute the largest class of dyes and contains one or various azo groups conjugated with aromatic systems such as acid azo dyes which have sulfonic groups causing strong attachment to the cationic groups of fibers. The characteristics of these materials are high color intensity and visibility in very low concentrations, complex chemical structures, and light resistance and hard to biodegradability, variability in pH range and above of these they have high carcinogenic and mutagenic potential. Generally, the physical, chemical and biological methods are considered as textile wastewater treatment techniques such as electrocoagulation, absorption, advanced oxidation, Fenton, photo-Fenton, photoelectrochemical and photoelectrocatalytic. Electro-Fenton is an indirect oxidation process and is based on in situ electrochemical generation of peroxide hydrogen due to electrochemical reduction of dissolved oxygen next to graphite cathode. In this process hydroxide radicals are generated by reaction of hydrogen peroxide and iron ions in acidic condition. Hydroxide radicals are the most powerful radicals with high oxidation potential lead to degrade organic matters into simple compounds like water and carbon dioxide. Recently carbonic material like carbon felt, graphite, activated carbon fibers, carbon nanotubes, carbonic sponge and graphite-PTFE are used to improve electro-Fenton process. Enhancement of surface area, reaction rate and electron transfer are the main reasons which Carbon nanotubes are used to improve electrochemical production of hydrogen peroxide in electro-Fenton process. Dye removal increased at initial reaction time by increasing current intensity, aeration rate and electrode surface due to enhancing electro-Fenton regents, meanwhile it decreased with increasing pH and electrolyte concentration. Reduction in dye degradation is usually caused by scavenging role of hydrogen peroxide and iron ions due to reaction of these compounds with hydroxyl radicals which decreased its concentration in reactor. Dye degradation increase by enhancement of Initial dye concentration from 35 to 100 mg/L but when initial dye concentration increased further to 200 mg/L, degradation rate was reduced. On the other hand energy consumption reduced by decreasing current intensity from 2 to 1 mA/cm2 and enhancing electrode surface from 30 to 90 cm2. It has been shown that carbon nanotubes coated on graphite cathode could enhance dye removal rate by increasing hydrogen peroxide concentration due to increase electrode surface area, electron transfer and reaction rate. The results showed that dye and COD removal efficiency was obtained 98% and 95% after 180 and 360 minutes respectively at the optimal condition of effective parameters such as current density of 1 mA/cm2, pH of 6.5, no aeration, initial dye concentration of 100 mg/L, electrode surface of 90 cm2, electrolyte concentration of 0.01 M, temperature of 25 ◦C and energy consumption of 0.13 KWh/ppm. Electro-Fenton process seems to be an economic and environmental friendly process to remove the toxicity of the persistent organic pollutants from water due to generation of hydrogen peroxide and hydroxyl radicals. It has been demonstrated that electro-Fenton process with the use of stainless steel anode and graphite cathode coated with carbon nanotube is a very effective and operative method to degrade Acid Orange 7. http://mcej.modares.ac.ir/article-1-1702-en.pdf 2016-03-20 117 126 pH electrochemical pH electrode surface current intensity energy consumption Bita Ayati 1 P.O.Box 14155-4838 AUTHOR 2 AUTHOR
ORIGINAL_ARTICLE محاسبه‌ی ضریب شکل‌پذیری معادل با در نظر گرفتن اثرات خستگی کم‌چرخه در اثر زیان‌های تجمعی ناشی از بارهای رفت و برگشتی (پدیده خستگی کم‌چرخه)، نیاز شکل‌پذیری سازه‌ها در برابر زلزله‌های شدید افزایش می‌یابد. به همین دلیل، در طراحی سازه‌ها، ظرفیت شکل‌پذیری سازه‌ها، کمتر از حالت معمول در نظر گرفته ‌می‌شود. در این تحقیق، تاثیر خستگی کم‌چرخه بر ظرفیت شکل‌پذیری سازه‌ها، مورد بررسی قرار گرفت. برای این منظور هفت شتاب‌نگاشت مربوط به حرکت افقی زمین در خاک نوع 2 انتخاب شد. این شتاب‌نگاشت‌ها، به سیستم یک درجه آزادی با مدل‌های مختلف بار-تغییرشکل، اعمال شد و نیازهای شکل‌پذیری در برابر آن‌ها تعیین شد. برای بررسی تاثیر خستگی کم‌چرخه، مدل‌های مختلف آسیب برای پدیده خستگی در نظر گرفته شد و ضریب شکل‌پذیری متناسب با آن‌ها تعیین شد. این مدل‌ها بر پایه تغییرمکان ماکزیمم، اتلاف انرژی ماکزیمم و ترکیب تغییرمکان ماکزیمم و اتلاف انرژی ماکزیمم استوار می‌باشند. تغییرات ضریب شکل‌پذیری بر حسب پارامتر که تابعی از انرژی چرخه‌ای، تغییرمکان ماکزیمم و فرکانس طبیعی است بیان گردید و رابطه‌ای برای آن ارائه شد. نتایج نشان می‌دهد که پارامتر در تمام طول بازه‌ی زمان تناوب، نسبتا پایدار و تقریبا برابر 9/0 است. http://mcej.modares.ac.ir/article-1-4649-fa.pdf 2016-03-20 127 136 ضریب شکل‌پذیری معادل خرابی تجمعی خستگی کم‌چرخه طیف طراحی The Effect of Low-Cycle Fatigue on Ductility Demand Factor Ductility demands of structures are increased during strong ground motion as a consequence of the dissipation of hysteretic energy caused by cyclic load reversals. In other word, the cumulative damage of the structures due to cyclic loading reduces the ductility capacity of the structures. This phenomenon is called Low-cycle fatigue. If the real force-deflection model of members is used to nonlinear analysis; the effect of cumulative damage will be concluded in design automatically. But the monotonic ductility capacity could not take into account Low-cycle fatigue. Hence this ductility capacity should be reduced in design procedures (equivalent ductility factor) and should be used instead of the conventional monotonic ductility supply in design procedures. The equivalent ductility factor is applied for determination of force reduction factor. In this study, the effect of low-cycle fatigue on ductility capacity factor is examined. For this reason the replies of a single degree of freedom system was evaluated using nonlinear dynamic analysis. Seven records related to soil type II from strong ground database are extracted. Also in order to assess the effect of low-cycle fatigue on ductility factor, various models of damage have been selected. Three models have been proposed to determine the equivalent ductility factor taking into account cumulative damage. The first two models based on the maximum displacement and maximum dissipation energy are the upper and lower values. The third one model is Park-Ang model. According to the Park-Ang model, the damage is related to hysteretic energy and concluded of maximum displacement and maximum dissipation energy. The parameter γ controls the hysteretic energy and depends on maximum displacement and natural frequency of the system. In order to obtain the quantity of the parameter γ, a parametric study of the inelastic response of SDOF systems was carried out. In the parametric study, input ground motion, as well as the initial stiffness (period), strength, ductility, hysteretic behavior and damping of SDOF systems, was varied. In this paper the variation of this parameter was considered and the effect of the ductility factor, force reduction factor, time history acceleration and damping ratio was evaluated. The results show that the reduction of the ductility factor due to low-cycle fatigue (controlled by parameter γ) is significant. It is proved that the parameter is relatively stable during all length of periods. If approximate values for γ are used, the determination of equivalent ductility is very simple, and thus appropriate for design purpose. The formulae for equivalent ductility factors include damage indices. In design procedures only life safety limit states are considered and the other purposes such as serviceability, immediate occupancy and collapse prevention limit states do not. A more rational design procedure should permit the designer to choose rational limit state. This idea has been realized by including damage indices into the formula for equivalent ductility factors. The parameter γ varies from 0.6 to 1.2. For practice peruses it is assumed that the value of γ is 0.9. Using this assumption it is possible to determine equivalent ductility factor taking into account low cycle fatigue. http://mcej.modares.ac.ir/article-1-4649-en.pdf 2016-03-20 127 136 Equivalent Ductility Factor Cumulative Damage Design spectra Low-cycle fatigue Mussa Mahmoudi 1 Lavizan, Shahid Rajaee Teacher Trainig University AUTHOR 2 AUTHOR
ORIGINAL_ARTICLE تعیین منحنی عملکرد روسازی با استفاده از مطالعه موردی به منظور آگاهی از شرایط روسازی در طول سال‌های متمادی برای قطعه‌های متفاوت شبکه راه، ضروری است نرخ تغییر کیفیت روسازی در اثر عواملی همچون عبور ترافیک، شرایط جوی، نوع روسازی و ضخامت آن، بر اساس شاخص‌های بیان کننده وضعیت روسازی تخمین زده شود. مطالعات زیادی در کشورهای توسعه یافته انجام شده است که نتایج آن‌ها معمولاً به صورت منحنی‌های عملکرد ارائه می‌شود. در این منحنی‌ها تغییرات شاخص بیان‌کننده وضعیت روسازی راه در اثر گذشت زمان رسم می‌شود. منحنی عملکرد به طور قابل توجهی به تصمیم گیرندگان برنامه‌های تعمیر و نگهداری راه‌ها جهت کاهش هزینه‌ها با تعیین زمان صحیح انجام عملیات تعمیر و نگهداری، عمر باقی‌مانده روسازی و در نهایت بهبود کیفیت روسازی شبکه را‌ه‌ها کمک خواهد کرد. در این مقاله اطلاعات خرابی به صورت چشمی از چند قطعه راه دارای شرایط مشابه در شهر تهران و سبزوار جمع‌آوری شد. آنگاه کیفیت روسازی آسفالتی بر اساس اطلاعات جمع‌آوری شده و با محاسبه شاخص وضعیت روسازی برای این دو شهر، تعیین شد. در نهایت منحنی عملکرد که نشان‌دهنده تغییرات کیفیت روسازی راه در طول عمر آن بود، با بکارگیری چندین تابع برازش متداول ترسیم شد. منحنی چندجمله‌ای درجه یک برای منحنی عملکرد شهر تهران و شهر سبزوار بر اساس دو پارامتر مجموع مربعات باقی‌مانده اصلاح شده و مجذور متوسط مربعات خطا، مناسب تشخیص داده شد. نتایج نشان می‌دهد اگر حداقل سطح مطلوب شاخص وضعیت روسازی برابر 40 فرض شود، عمر مفید روسازی‌های منطقه یک تهران و سبزوار به ترتیب 6/7 و 5/11 سال خواهد بود. http://mcej.modares.ac.ir/article-1-8234-fa.pdf 2016-03-20 137 146 مدل رفتار روسازی منحنی عملکرد شاخص وضعیت روسازی Determining Pavement Performance Diagram Using Case Study To determine the future condition of pavements in a pavement network, the deterioration rate of pavement condition should be estimated with accordance to traffic volume, environmental condition, pavement type and its thickness. The pavement condition index (PCI) can be used to estimate the pavement condition. PCI is a practical index widely used in Pavement Management System (PMS) and ranges between 0 to 100. The severity and quantity of pavement disteresses increase as it gets older. As the result of it, PCI decrease by the pavement age increase. PCI can be predicted in future by applying different models. These models consist of deterministic and probalistic models. Deterministic models yields a single value of future pavement condition while the probalistic ones yields a probability for any value of the future pavement condition. Empirical, mechanistic and imperical mechanistic models can be used for pavement condition calculation. Among them empirical models are more practical because of its simpilisity in development and application. In this paper, empirical deterministic model is used to predict the future pavement condition. A lot of research has been done on this subject in the developed country and its result is presented by performance diagrams. In such diagrams, pavement condition changes within the years are shown. Performance diagrams can significantly contribute to the road authorities to reduce their costs by right time selection for maintenance and rehabilitation actions, remaining life determination and pavement condition improvement in the road network. In this paper, type, severity and quantity of distresses is collected by visual inspection in Tehran NO.1 district and Sabzevar city. There are up to 5 years old pavements in Tehran district NO.1 which are all rehabilitated pavements. In contrast, Sabzevar’s mainly initial pavements reaches the age 15 years and consequently more deteriorated condition with lower PCI. The least PCI for Tehran NO.1 district is 61 percent and for Sabzevar city is 11 percent. Pavement condition index as an indicator of pavement condition is then calculated according to the collected data and Performance diagram, which is the pavement condition change during pavement life, is interpolated using different typical functions including exponentioal, linear and multi polynomial equations up to 3th order on. 1th order polynomial diagrams is best descriptive diagrams for Tehran and Sabzevar which are selected based on Adjusted R square and Root mean square error parameters. All the plotting performance diagram, Adjusted R Square and Root Mean Square Error calculation is done by SPSS. Adjusted R square equal to 1 and Root Mean Square Error of 0 are the ideal conditions which means the interpolated diagram passes through the scattered points. To obtain more precise estimation of scattered data both parameters should be considered as it is done in this paper. The results indicate that if the minimum desirable level of pavement condition index is assumed 40, then the useful life of the pavement in the Tehran NO.1 district and Sabzevar city will be 7.6 and 11.5 years. http://mcej.modares.ac.ir/article-1-8234-en.pdf 2016-03-20 137 146 Pavement behavior models Perfarmance diagram Pavement Condition Index 1 AUTHOR 2 AUTHOR Reza Imaninasab 3 AUTHOR
ORIGINAL_ARTICLE بررسی آزمایشگاهی پرش هیدرولیکی در حوضچه آرامش با آستانه پلکانی پرش هیدرولیکی جریان متغیر سریعی است که طی آن جریان فوق بحرانی به جریان زیر بحرانی تبدیل می‌شود. حوضچه‌های آرامش معمولاً در پایین دست سازه‌های نظیر شوتها و دریچه‌ها، برای کنترل پرش هیدرولیکی استفاده می‌شود. بلوکهای میانی، پله های مثبت و منفی و آستانه انتهایی تجهیزاتی هستند که معمولاً برای استقرار پرش هیدرولیکی درون حوضچه آرامش استفاده می‌شوند. در تحقیق حاضر تشکیل پرش هیدرولیکی درون نوع جدیدی از حوضچه آرامش با آستانه پلکانی مورد بررسی قرار گرفته است. آزمایشات درون کانالی با عرض 60 سانتی متر، ارتفاع 1 متر و طول 12 متر انجام شده است. در این آزمایشات تاثیر آستانه بر خصوصیات پرش هیدرولیکی مورد بررسی قرار گرفته است. اثر پارمترهای مهمی چون عمق پایاب، هندسه آستانه و موقعیت قرار گیری آن مورد ارزیابی قرار گرفته است. پرش‌های شکل گرفته در حوضچه با آستانه پلکانی به پنج نوع A، B، B کمینه، C و C کمینه تقسیم بندی شده است که پرش‌ها در تبدیل از نوع A به B و نهایتاً C کمینه، بتدریج از حوضچه خارج می‌شوند. نتایج نشان می‌دهد با وجود اثر مثبت پله‌ای کردن آستانه شیبدار، در شرایط ثابت جریان (عمق پایاب و عدد فرود اولیه)، افزایش تعداد پله‌های آستانه از 2 به 3 اثر منفی بر حفظ پرش در قبل از آستانه (درون حوضچه) دارد. در انتهای کار با توجه به نتایج حاصله، روابطی برای محاسبه میزان خروج پرش از حوضچه ارائه گردیده است. http://mcej.modares.ac.ir/article-1-8009-fa.pdf 2016-03-20 146 156 "پرش هیدرولیکی"؛ "وطالعه آزمایشگاهی"؛ "آستانه پلکانی" Experimental Investigation of Hydraulic Jump in stilling basin with Stepped Sill Hydraulic jump is a rapid and sudden transition from a high-velocity supercritical flow to a subcritical flow in an open channel flow. Stilling basins are used to control the hydraulic jump at the downstream of chutes, sluice gates,… End Sills, baffle blocks and negative steps are often used to control hydraulic jumps in stilling basins. The present study focuses on the formation of hydraulic jump in the new type of stilling basins with stepped sills. Extensive experiments were conducted in a rectangular flume 0.6 m wide, 12.0 m long and 1.0 m deep, with various discharges from 30 to 120 l/s. Water was pumped from an underground sump into a head tank and the discharge was measured with a ultrasonic flowmeter. At the downstream end of the head tank there was a sluice gate into the flume. The edge of the sluice gate has a streamlined lip in the shape of a half-cylinder of diameter 20 cm to minimize flow contraction and provide a uniform supercritical flow. A point gauge with an accuracy of 0.1 mm was used to measure water depths. In order to visualize the flow field, the dye-injection method and a high speed camera were employed. A tailgate located at the downstream end of the flume was used to control the tailwater depth. The effects of stepped end sills on hydraulic jumps were investigated experimentally. Firstly, dimentionless parameters affecting the hydraulic jump on stepped sill introduced using Buckingham π theorem. The effect of important parameters such as approach Froude number (Fr1), relative tailwater depth (〖y_t/y〗_2^*) and the end sill geometry (shape and relative height of sill (s/y1)) on hydraulic jump were investigated. The hydraulic jumps over stepped end sills were classified into A-jump, B-jump, minimum B-jump, C-jump and minimum C-jump. By changing the type of flow from A-jump to minimum C-jump, the jump is going to sweepout from basin. A-jump is entirely formed in the basin and at the upstream of sill. In the case of minimum C-jump, most of the surface roller of jump formed at the downstream of sill. The flow types are presented in the form of 6 different diagrams as functions of the relative step height s/y1. By increasing the tailwater depth, sill height, the probability of occurance of hydraulic jump in the stilling basin increased. It was found that the sill with 2 steps have better performance in stabilizing the jump in the stilling basin as compare to sill with 3 steps. By increasing the approach Froude number, the jump began to sweep away from basin. By knowing the initial condition like upstream velocity and upstream froude number, tailwater depth, sill height and its number of steps the toe distance from sill can be found out with desirable accuracy. http://mcej.modares.ac.ir/article-1-8009-en.pdf 2016-03-20 146 156 "Hydraulic jump"؛ "Experimental Study"؛ "stepped sill" afshar minaei gigloo 1 student of tarbiat modares university AUTHOR masoud ghodsian 2 AUTHOR mojtaba mehraein 3 AUTHOR
ORIGINAL_ARTICLE مطالعه آزمایشگاهی تاثیر رفتار هیسترسیس هیدرولیکی بر روی ظرفیت باربری کالیفرنیا یک مخلوط ماسه رسی تراکم پذیر غیراشباع در این تحقیق به بررسی آزمایشگاهی تاثیر پارامترهای نسبت تخلخل اولیه، درصد رطوبت، مکش بافتی، درجه اشباع و هیسترسیس هیدرولیکی بر روی ظرفیت باربری کالیفرنیا یک مصالح روسازی پرداخته شده است. برای این منظور، مقدار سی بی آر یک خاک مخلوط ماسه رسی در بازه ای از مقادیر نسبت تخلخل اولیه بر روی بازه های تر و خشک شدگی منحنی مشخصه آب – خاک اندازه گیری شده است. آزمایش های تر شدگی سی بی آر بر روی نمونه های خاک متراکم و تر شده در بازه ای از مقادیر نسبت تخلخل و درصد رطوبت اولیه انجام پذیرفت. نمونه های خاک مورد استفاده در آزمایش های خشک شدگی نیز ابتدا مطابق با روند و پارامترهای نمونه های مورد استفاده در آزمایش های تر شدگی ساخته شده و بعد از خشک نمودن یکنواخت آن ها با استفاده از تکنیک هوادهی مقادیر سی بی آر آن ها اندازه گیری شده است. بر پایه نتایج آزمایشگاهی، ظرفیت باربری کالیفرنیا خاک مورد مطالعه با افزایش مقادیر تراکم اولیه و مکش بافتی خاک افزایش یافته است. لیکن نتایج آزمایشگاهی حاکی از کاهش مقدار سی بی آر خاک مفروض با افزایش درجه اشباع خاک می باشد. با عنایت به مشاهدات آزمایشگاهی در یک مکش بافتی مفروض، ظرفیت باربری خاک مورد مطالعه دارای مقادیر کمتری بر روی بازه های خشک شدگی نسبت به بازه های تر شدگی بوده است. این روند هیسترتیک مشاهده شده در تغییرات سی بی آر، با توجه به رفتار هیسترسیس هیدرولیکی منحنی مشخصه آب – خاک بیان شده است. http://mcej.modares.ac.ir/article-1-9769-fa.pdf 2016-03-20 157 166 خاک های غیراشباع مخلوط ماسه رس دار سی بی آر هیسترسیس هیدرولیکی منحنی مشخصه آب – خاک Experimental investigation on the influence of hydraulic hysteresis on the California Bearing Ratio of an unsaturated deformable clayey sand Many of the past experimental research on the design of road pavement layers was confined to the behavior of saturated pavements materials. Among the experimental studies to determine the road layers properties, California bearing ratio (CBR) has been one of the most common and applicable parameter for determination of the resistance of roads subgrade in both design and practical purposes. An extensive amount of research exist in the literature that explains the behavior of California bearing ratio of saturated soils. However, any change in the degree of saturation of subgrade materials and in particular different hydraulic response in wetting and drying paths can affect the CBR value of a pavement material. In compare to the extensive previous studies on the California bearing ratio of soils, this phenomenon is rarely concerned in the previous studies. The goal of this laboratory research is to examine the influence of the initial compaction void ratio, moisture content, degree of saturation, matrix suction and hydraulic hysteresis on the California bearing ratio of a pavement material. To this end, California bearing ratio of sand-kaolin mixture was measured in a range of initial void ratios and initial water contents along drying and wetting portions of the soil-water characteristic curve. The CBR tests along wetting paths was performed on the soil samples that were dynamically compacted and wetted in a range of initial void ratios and initial water contents. The CBR tests for drying paths was also carried out on the soil samples that were compacted identically to the samples used in wetting tests, but they were air dried for seven days before CBR measurements. The air drying process was achieved from the both ends of soil samples as to maintain a homogenous moisture distribution thorough the soil. This was experimentally verified by measuring the moisture contents of top, middle, and bottom portions of the specimens. The CBR values of soil samples were measured within the loading speed of 1.2 mm/min both for wetting and drying paths. According to the laboratory results, it is observed that the CBR value is increased within the increment of initial soil compaction and matrix suction. Based on the results, it is also observed that the value of California bearing ratio of the understudying soil is decreased within increment of the degree of saturation and initial moisture content of the soil. The experimental data also revealed that the California bearing ratio of the pavement material along the drying and wetting paths are not identical, and for a given suction, the CBR values for drying paths possess lower values than the wetting paths. This hysteretic trend for the change of CBR along drying and wetting paths is explained with regard to the hysteretic behavior of the soil-water characteristic curve. http://mcej.modares.ac.ir/article-1-9769-en.pdf 2016-03-20 157 166 Unsaturated Soils Sand-Kaolin Mixture CBR Hydraulic Hystersis Soil-Water Characteristic Curve Meghdad Negahban 1 M.Sc. of Highway and Transportation Engineering, Department of Civil Engineering., Isfahan (khorasgan) Branch, Islamic Azad University, Isfahan, Iran AUTHOR Ali Mirzaii 2 Assistant Professor, Department of Civil Engineering, Faculty of Engineering, University of Kashan AUTHOR
ORIGINAL_ARTICLE مدل‌سازی تیرهای بتن‌مسلح تحت پیچش با مدل خسارت - خمیری از بین چهار حالت بارگذاری اصلی یعنی نیروی محوری، نیروی برشی، لنگر خمشی و لنگر پیچشی، فقط پیچش است که یک میدان تنش سه‌‌محوری به وجود می‌آورد. از طرف دیگر، ضعف مقاومت پیچشی می‌تواند یکپارچگی کل سازه را به مخاطره بیاندازد.لذا اهمیت بررسی مسائل پیچش در اعضای بتنی از اهمیت بالایی برخوردار است.در این مقاله، تیرهای بتنی مسلحتحت اثر لنگر پیچشی خالص با استفاده از روش اجزای محدود غیرخطی مدل‌سازی شده است. بدین منظور، رفتار بتن با استفاده از مدل خسارت – خمیری همسانگرد موجود در نرم‌افزار آباکوس شبیه‌سازی شده، اما به منظور در نظرگیریعدم قطعیت‌های موجود در مدل‌سازی، فرضیات مدل‌سازی با تحلیل حساسیت مورد ارزیابی قرار گرفته و متغیرهای مدل خسارت – خمیری با توجه به مفهوم فیزیکی هر کدام، کالیبره شده است.انطباق بالای منحنی‌های پاسخ لنگر پیچشی– زاویه پیچش، الگوهای ترک‌خوردگی و سازوکارهای خرابی حاصل از مدل اجزای محدود غیرخطی، نشان دهنده فرضیات صحیح مدل‌سازی می‌باشد ه ه . http://mcej.modares.ac.ir/article-1-9966-fa.pdf 2016-03-20 167 178 بتن مسلح پیچش اجزای محدود غیرخطی مدل رفتاری Plastic – Damage Modeling of RC Beams under Torsion Among four basic load-bearing mechanisms of reinforced concrete structural elements, namely, axial, flexure, shear and torsion, only the latter is truly a three-dimensional problem. Consequently, studies of pure torsion serve to verify three-dimensional modeling as a pre-requisite for general solutions of combined loads. To our best knowledge, however, few studies have been conducted on torsional behavior of concrete beams which most of them are experimental investigations or simplified analytical models based on early and modified version of Compression Field Theory (M-CFT). Previous researchers focused on the torsional behavior of plain and reinforced concrete beams as well as FRP strengthened RC beams. However, the focus of this study is to find a rational set of constitutive laws of materials to simulate a three-dimensional reinforced concrete element. From the viewpoint of constitutive modeling of RC elements, there are two approaches; discrete crack and continuum level models. The major disadvantage that adheres to discrete crack models is the fact that these models focus on a local crack behavior and seeking to detect the crack paths, requiring a high computational cost. By contrast, continuum level models taking advantage of the spatially averaged macroscopic models to predict the structural behavior of the entire member (i.e. columns, beams etc.). In this method, the control volume of simulation is a finite domain between two primary transverse cracks which contains several secondary bond cracks, leading to relatively low computational cost along with acceptable accuracy. Furthermore, there are two major approaches for simulation of RC elements in continuum level; smeared cracks models and the models based on classical theory of plasticity. Smeared cracks models originally have been developed as a solution for 2D problems. Nevertheless, most of plasticity based models originally have been developed for 3D problems. The downside of plasticity based models however, is the uncertainty in calibration of material constant because most of these models are phenomenological models, not a physical consistent rule. Taking advantage of classical theory of plasticity along with damage mechanics, Lubliner et. al. (1989), proposed an isotropic Damage Plasticity Model for simulating the plain concrete. However, variety of researchs have been conducted on reinforced concrete members based on damage plasticity model. This model, includes material parameters such as dilation angle, yield surface factors etc,. which should be calibrated for each problem. The aim of this study is to investigate the effect of each parameter on the numerical response of the beam. Hence, solid RC beams under pure torsion have been simulated using nonlinear finite elements. Concrete material is simulated using isotropic plastic-damage model integrated in ABAQUS software. The constitutive laws of materials is modified using present methods to take into account for anisotropic behaviour of RC elements under torsion. The torque – twist curves, crack patterns and detected failure modes obtained from the proposed nonlinear finite element analysis are in good agreement with experimental results. http://mcej.modares.ac.ir/article-1-9966-en.pdf 2016-03-20 167 178 reinforced concrete Torsion nonlinear finite elements constitutive law 1 1 1 1 AUTHOR 2 AUTHOR 3 AUTHOR
ORIGINAL_ARTICLE عملکرد بتن الیافی سازگار با محیط زیست در روسازی بتنی امروزه استفاده از مصالح بازیافتی در صنعت در حال افزایش می‌باشد. نمونه‌ای از آن تولید بتن سبز و سازگار با محیط زیست‌ است. تاکنون تحقیقات گوناگونی در دنیا در مورد استفاده از خرده بتن‌های ناشی از تخریب سازه های بتنی به عنوان سنگدانه در بتن انجام شده است. با بررسی انجام شده مشخص گردید علاوه بر بتن، مواد دیگری همچون خرده آجر، خرده سرامیک خرده سنگ‌های ساختمانی و دیگر مواد در نخاله های ساختمانی کشور وجود دارد. تحقیق کنونی به بررسی استفاده از مصالح بازیافتی ناشی از نخاله‌های ساختمانی به عنوان سنگدانه در بتن پرداخته است. جهت تقویت این نوع بتن و بتن معمولی از الیاف فلزی بازیافتی از لاستیک خودروهای فرسوده استفاده شده است. نمونه‌های بتنی با درصدهای مختلف الیاف و سنگدانه‌های بازیافتی ساخته شده و تحت آزمون‌های مقاومت فشاری، مقاومت کششی، مقاومت خمشی وطاقت خمشی قرار گرفتند. نتایج آزمون‌ها نشان داد که استفاده از این نوع بتن الیافی به عنوان بتن سازه‌ای قابل قبول می‌باشد. در بررسی نقش الیاف فلزی بازیافتی و سنگدانه‌های بازیافتی در طراحی ضخامت دال روسازی بتنی از تئوری خطوط تسلیم استفاده شد. نتایج حاکی از آن است که افزودن الیاف فلزی بازیافتی به بتن باعث کاهش تقریبی ضخامت دال به میزان %20 می‌گردد. http://mcej.modares.ac.ir/article-1-11831-fa.pdf 2016-03-20 179 188 نخاله‌های ساختمانی بتن الیاف فلزی بازیافتی performance of environmentally friendly fiber concrete in concrete pavement Nowadays the use of recycled materials in the industry is increasing. An example of this is production of environmentally friendly green concrete. So far, various studies regarding the use of concrete debris from demolished concrete as aggregate in concrete have been utilized. The study showed that in addition of crushed concrete, brick and other materials such as, small ceramic rubble and other debris are present. The current study investigates the use of recycled materials resulting from construction debris as aggregate in concrete. Steel fibers recycled from old car tires are used to reinforce concrete and ordinary concrete. Samples with different percentages of recycled fibers and aggregates were made and tests such as compressive strength, tensile strength, flexural bending strength were adopted. Test results showed that the use of this type of fiber concrete as a structural concrete is acceptable. Yield line theory was used to investigate the role of steel recycled fiber and recycled aggregate concrete in slab design thickness. The design method showed that the addition of steel recycled fibers in the concrete reduces the thickness of slabs approximately by 20%. Nowadays the use of recycled materials in the industry is increasing. An example of this is production of environmentally friendly green concrete. So far, various studies regarding the use of concrete debris from demolished concrete as aggregate in concrete have been utilized. The study showed that in addition of crushed concrete, brick and other materials such as, small ceramic rubble and other debris are present. The current study investigates the use of recycled materials resulting from construction debris as aggregate in concrete. Steel fibers recycled from old car tires are used to reinforce concrete and ordinary concrete. Samples with different percentages of recycled fibers and aggregates were made and tests such as compressive strength, tensile strength, flexural bending strength were adopted. Test results showed that the use of this type of fiber concrete as a structural concrete is acceptable. Yield line theory was used to investigate the role of steel recycled fiber and recycled aggregate concrete in slab design thickness. The design method showed that the addition of steel recycled fibers in the concrete reduces the thickness of slabs approximately by 20%. Nowadays the use of recycled materials in the industry is increasing. An example of this is production of environmentally friendly green concrete. So far, various studies regarding the use of concrete debris from demolished concrete as aggregate in concrete have been utilized. The study showed that in addition of crushed concrete, brick and other materials such as, small ceramic rubble and other debris are present. The current study investigates the use of recycled materials resulting from construction debris as aggregate in concrete. Steel fibers recycled from old car tires are used to reinforce concrete and ordinary concrete. Samples with different percentages of recycled fibers and aggregates were made and tests such as compressive strength, tensile strength, flexural bending strength were adopted. http://mcej.modares.ac.ir/article-1-11831-en.pdf 2016-03-20 179 188 construction debris concrete steel recycled fiber mohsen ahmadi 1 AUTHOR abolfazl hassani 2 AUTHOR 3 AUTHOR 4 AUTHOR
ORIGINAL_ARTICLE ارائه ی روشی جدید جهت تعیین جابجایی و نیروی وارد بر شمع های نصب شده در شیب های خاکی پایداری شیبهای خاکی در اثر عوامل مختلف مانند نیروهای زلزله، تغییر تراز سطح آب زیر زمینی، خاکریزی در بالادست شیب و یا خاکبرداری از پایین دست شیب، تهدید می گردد. با افزایش نیروهای محرک از مقاومت خاک کاسته شده و در نهایت خاک به مرحله تسلیم می رسد. با افزایش نقاط تسلیم، سطح گسیختگی در شیب ایجاد می شود و در نهایت باعث ناپایداری شیب خاکی می گردد. بکی از راهکارهای پایدارسازی شیب های خاکی نصب یک ردیف شمع در دامنه شیب می باشد. در این مقاله تلاش شده است بر مبنای سطح گسیختگی اولیه ی ایجاد شده در شیب و نیروی های جانبی ناشی از وزن گوه گسیختگی و با در نظر گرفتن مشخصات مقاومتی خاک، روشی جدید جهت محاسبه ی نیروی وارد بر شمع ارائه شود. سپس جابجایی سر شمع با استفاده از حل معادلات دیفرانسیلِ مربوطه محاسبه می گردد و در نهایت، نتایج حاصل از روش تحلیلیِ پیشنهاد شده با مقادیر حاصل از روش اجزای محدود مقایسه می شود. در این مقاله دو رابطه ی تحلیلی جدید پیشنهاد شده است که یکی برای محاسبه نیروی وارد بر شمع و دیگری برای محاسبه جابجایی نوک شمع است که در نوع خود کاری جدید و نو است. نتایج حاصل از تحقیق حاضر با نتایج دیگر محققین صحت سنجی شده است که تطابق خوبی با یکدیگر دارند. http://mcej.modares.ac.ir/article-1-7848-fa.pdf 2016-03-20 189 198 شیب خاکی نیروی وارد بر شمع جابجایی شمع پایدارسازی A New Method for Estimating of displacement and Lateral Force Acting on Stabilizing Piles in Earth Slope What should be considered at the beginning of any stabilization process besides slope safety is the minimization of expenses. Therefore, excavation on slope upstream and/or filling slope downstream and/or moderating slope angle are the primary and effective stabilization methods. If these methods cannot provide the desirable factor of safety it would be necessary to put effort in other methods such as increasing soil strength parameters, draining surface water and sub-surface (ground) water at embankments, and installing retaining walls and piles. Implementation of these solutions is usually costly and sometimes in order to achieve a desirable factor of safety it is necessary to combine one or several methods. Anyway, the aforementioned solutions are aimed at mitigating the driving force behind ruptures and/or increasing resistive forces. Slopes stabilization methods can be studied as empirical, analytical, and numerical methods. This classification has been so far used by researchers and has undergone numerous studies. One of the methods used for improving resistive forces is the installation of piles in earth slopes. Installing piles for stabilizing susceptible earth slope is an effective way of preventing the imbalance of force and instability. Stabilizing effect by using pile is provided by the passive resistance of the pile below the slip surface and load transfer from the sliding mass to the underlying stationary soil or rock formation through the piles due to soil arching mechanism. Moreover, slope stability and optimizing pile location by installing a row of piles have been studied by many researchers. The piles are embedded in the stable soil by the length 5D (D=pile diameter), because the zone of influence of each pile has been demonstrated not to exceed 5D and the length of the pile is restricted to 10D. In this paper a new method is presented for estimating of displacement and lateral force acting on stabilizing piles in earth slopes. The growth mechanism of lateral force acting on stabilizing piles in a row due to the surrounding ground undergoing plastic deformation is discussed, and its theoretical analysis is carried out considering the interval between the piles (Ito and Matsui, 1975). Several methods have been proposed to determine the force exerted on the pile in addition to having the merits, defects such as lack of accuracy required in a particular interval between the piles. In this paper with regarded to initial slip surface and acting force due to weight of failed soil is proposed lateral force acting on piles. 1. The assumptions are considered in this paper are, 2. The suitable location for installing of piles is middle of slope. 3. The pile behavior is considered as elastic. 4. The soil behavior is considered as elastoplastic. 5. The pile tip is embedded in the stable soil by the length 5D. http://mcej.modares.ac.ir/article-1-7848-en.pdf 2016-03-20 189 198 Earth Slope Lateral force on pile Pile displacement Stabilization 1 AUTHOR A. Reza Mazaheri 2 Ph.D Student AUTHOR
ORIGINAL_ARTICLE تحلیل رفتار اتصالات لوله ای T شکل تقویت شده به وسیله موادکامپوزیتی (FRP) تحت بار محوری فشاری سازه‌های دریایی بخصوص سکوهای دریایی به علت آسیب‌دیدگی و یا ضرورت‌های دیگر ممکن است نیاز به تعمیر و تقویت داشته باشند. به دنبال نتایج مثبت به دست آمده ازکاربرد FRP در سازه‌های خشکی، اخیرا توجه ویژه‌ای به استفاده از این مواد برای انجام تعمیرات سازه‌های فراساحل معطوف شده است. به این منظور مطالعه ای با هدف بررسی رفتار اتصالات T-‌ شکل تقویت‌شده با مصالح FRP تحت بار محوری فشاری انجام شده است تا میزان کارآمدی این مصالح در بهبود این اتصالات مورد ارزیابی قرار گیرد. در این راستا و به منظور بررسی اثر متغیرهای مختلف، مدل‌هایی با استفاده از نرم‌افزار اجزای محدود غیر خطی ساخته شد و با تحلیل عددی آن‌ها، پارامترهای موثر در رفتار نمونه‌ها، مورد ارزیابی قرار گرفتند. در این ارزیابی اثر تعداد لایه های FRP و جهت الیاف بر ظرفیت نهایی اتصالات لوله‌ای تقویت شده مورد بررسی قرار گرفت. نتایج بدست آمده از تحلیل عددی، بهبود در ظرفیت نهایی اتصالات تقویت شده را نشان داد که با افزایش تعداد لایه‌ها این میزان بهبود افزایش یافت. با مقایسه بار شروع گسیختگی FRP با بار نهایی اتصال روشن شد که کامپوزیت می تواند مقدار قابل توجهی از بار نهایی اتصال را بدون گسیختگی تحمل کند. همچنین با مقایسه تنش فون- میسس و تغییر‌مکان قائم و افقی (بیضی‌شدگی) عضو اصلی اتصالات تقویت شده و اتصالات بدون FRP مشاهده شد که این روش تقویت، با کاهش قابل توجه این مقادیر باعث به تاخیر انداختن تسلیم فولاد و افزایش سختی اتصال و بهبود رفتار اتصالات می‌گردد. http://mcej.modares.ac.ir/article-1-12245-fa.pdf 2016-03-20 199 208 اتصالات T- شکل بار فشاری اجزای محدود غیر خطی ظرفیت نهایی اتصالات Analysis of the Behavior of Tubular T Joints Strengthened by FRP under Compressive axial Load In recent decades, significant progress has been made on the use of Fiber Reinforced Polymers (FRP) in civil infrastructures. These materials have been used widely for the repair of concrete members, but their application to steel structures has been so far limited. Offshore structures, especially offshore platforms are very important and expensive ones, due to rising demand of energy. These structures may require repair and strengthening due to damages they may suffer in service. Searching for methods which are faster, more reliable, and less expensive led to application of FRP in repairing of offshore structures. Durability and high resistance against fatigue as well as high ratio of strength to weight enable these material superior to other conventional materials for this purpose. In addition high resistance of these materials against corrosion is an advantage for their use in marine environment. Composite materials are being increasingly used for the strengthening and repair of offshore structures. More recently, carbon fiber reinforced laminates have been used to upgrade fire walls in Mobil's Beryl Bravo platform to enable them to withstand blast loading. Also a number of corroded conductors and caissons have been repaired by composites on several Gulf of Mexico and North Sea platforms. In current research, the behavior of T-shaped tubular joints reinforced with FRP material under compressive axial load is studied to evaluate the efficiency of these materials in strengthening the connections. For this purpose and in order to examine the effect of different variables, a numerical study was carried out using the non-linear finite element program. An elastic-perfectly plastic stress-strain curve was used for steel and glass/epoxy composite was used as the FRP. A four-node quadrilateral shell element was used to model the tubular members and composite. A perfect bond between steel and composite was considered. For considering different modes of FRP failure the criteria proposed by Hashin is used. The numerical model was verified using the data available for a T- joint which was tested earlier. The model showed acceptable accuracy especially up to the level of maximum strength of the joint. Using the verified model a number of joints with different strengthening scheme ware analysed under a monotonically increasing axial compression loads. Material and geometric nonlinearities were considered in the analyses. The analysis method was modified RIKS algorithm. The effect of number of FRP layers and the fibers direction on the ultimate capacity of reinforced tubular joints was studied. The results of numerical analysis showed improvements in the capacity of reinforced joints which were further enhanced by increasing the number of layers. Comparing FRP failure initiation load with ultimate capacity of joint, it was found FRP can bear a considerable amount of ultimate load without breaking. In addition, by comparing the Von-Misses stress and the vertical and horizontal displacement (ovalization) of chord in reinforced joints were observed that a substantial reduction in mentioned factors led to hindering the yielding of steel and increased the stiffness and ultimately the strength of connections. http://mcej.modares.ac.ir/article-1-12245-en.pdf 2016-03-20 199 208 FRP FRP T-shaped joints Compressive axial load Nonlinear finite element ultimate capacity m حسین نژاد 1 AUTHOR a آقاکوچک 2 AUTHOR
ORIGINAL_ARTICLE بررسی آزمایشگاهی پیوستگی بین خمیر سیمان و سنگدانه در بتن پیوستگی بین سنگدانه‌ و خمیر سیمان از پارامترهای مهمی است که بر مقاومت بتن تاثیر می‌گذارد. نحوه اتصال سنگدانه به خمیر سیمان متاثر از نوع و خواص سنگدانه است که بررسی آن از اهداف این تحقیق می‌باشد. در این تحقیق به منظور بررسی پیوستگی بین خمیر سیمان و سنگدانه، آزمایشی ساده‌ای طراحی و مقاومت پیوستگی بین خمیر سیمان و سنگدانه برای چند نوع سنگدانه تعیین شده است. سنگدانه‌ها‌ی انتخاب شده با خواص فیزیکی و مکانیکی متفاوت بوده که از معادن قرضه مختلف گردآوری شده و جهت ساخت بتن مورد استفاده قرار گرفته است. در ادامه نیز خواص این سنگدانه‌ها تعیین و پس از خرد کردن و تبدیل به شن و ماسه، بر اساس استاندارد‌های موجود بتن تهیه شده و مقاومت بتن ساخته شده با پارامتر‌های مقاومت فصل مشترک مقایسه شده است. نتایج بررسی نشان داد که خواص مقاومتی بتن ساخته شده از سنگدانه‌ها، ارتباط نزدیکی با مقاومت پیوستگی فصل مشترک که با روش پیشنهادی اندازه‌گیری شده است، دارد. همچنین نتایج نشان داد که سنگدانه دولومیتی بیشترین مقاومت سطح اتصال و سنگدانه دیوریت و لوماشل کمترین مقاومت ناحیه اتصال دارند، که این مهم به طور زیادی توسط کانی‌شناسی، شکل و خواص سطحی سنگدانه‌ها و همچنین خواص سیمان کنترل می‌شود. همچنین نتایج نشان داد که مقاومت سنگدانه‌ها نقش زیادی در مقاومت سطح اتصال دارند که این نقش در سن بالای بتن مشهودتر می‌باشد. http://mcej.modares.ac.ir/article-1-11223-fa.pdf 2016-03-20 209 218 بتن مقاومت پیوستگی بین سنگدانه و خمیر سیمان سنگدانه خمیر سیمان Study of Interfacial Bond between Aggregate and Cement paste in Concrete Mechanical and durability properties of concrete depend on paste composition, paste volume, the physical characteristics of aggregate, and the nature of the interfacial transition zone (ITZ). The ITZ is usually regarded as the weakest region in concrete, influencing both mechanical properties and durability, and is the reason why the stress deformation behavior of concrete differs from that of its individual components, i.e., hydrated cement paste and aggregate. The processes responsible for the formation of the ITZ are not well understood. Indirect evidence of the bonding mechanisms due to mechanical interlocking aided by the aggregate surface texture has been established by comparing the bond strength of fractured rock surfaces with that of polished rock surfaces. Due to the importance of interfacial transition zone on the mechanical properties of concrete and the lack of a simple and accurate method of measurement, it is necessary to develop a test for measurement of aggregate-cement paste interface. For this purpose, an apparatus was designed, based on the direct shear test and aggregate-cement paste interface strength of different concrete aggregates was measured. For this purpose, test specimens were preparing in based of direct shear test. Due to the difficulties involved in studying ITZ in normal concrete, laboratory specimens were prepared by casting cement paste on aggregate specimen. The aggregates were sawed into cylinder with height and diameter of 60 mm. A thin layer of cement with the same diameter was applied over aggregate in cylinder mould, and then layer of concrete apply over it. Therefore upper aggregate part was sawed aggregate and the other part consists of concrete and cement paste interlayer. The later procedure was used to prepare all specimens. Based on above discussions, 90 samples were made by ten aggregate types for three curing time. To measure the interfacial force, the shear box was positioned inside the servo-controlled direct shear machine and the specimens after 7, 14 and 28 days of curing in surface saturated-dry condition. The test was carried out using shear box with 30×30 cm2 dimensions. After carrying out test, The test results of ITZ strength showed values between 1 and 18 MPa at 7, 14 and 28 days. The highest ITZ strength of 15.64 Mpa at 28 curing days was measured in the concrete specimens prepared with the dolomite aggregates while the lowest ITZ strength was in diorite and lumashele aggregates. The result show that, ITZ strength of concrete is strongly influenced by the aggregate properties such as mineralogical source, compressive strength, porosity, water adsorption, shape, and surface texture. Mineralogical source of aggregate caused high degree of hydration in concrete at all ages, but is more appreciable in old age. Shape and surface texture porosity and water adsorption controls ITZ strength of concrete in all ages. Therefore surface texture porosity of aggregate has important in physical interlocking of aggregate with cement paste. Also, mechanical properties of aggregate are important in ITZ strength in all ages, this effect is visible in late age. In order to prepare high-strength concrete, the aggregate with high ITZ strength could be used. Therefore, in high-strength concrete, the aggregate-cement paste interface plays an important role in the strength. http://mcej.modares.ac.ir/article-1-11223-en.pdf 2016-03-20 209 218 concrete Interfacial Transition Zone (ITZ) strength Aggregate Cement paste 1 AUTHOR 2 AUTHOR 3 AUTHOR
ORIGINAL_ARTICLE ارزیابی رفتار لرزه ای قاب خمشی فولادی با مهاربند هم مرکز دارای لقی اولیه مهاربندهای هم مرکز با وجود سختی بالا شکل پذیری پایینی داشته و تحت بارهای جانبی و نیروهای فشاری عملکرد ضعیفی از خود نشان می دهند و هنگامیکه در قابهای خمشی جهت مقاوم سازی بکار می روند به علت کمانش ناگهانی شکل پذیری سازه را کاهش می دهند. برای اصلاح عملکرد این مهاربندها به ویژه افزایش استهلاک انرژی، روشهای متعدد و مختلفی ارائه گردیده است که از جمله آنها استفاده از اتصالات با عملکرد ویژه نظیر اتصالات با لقی اولیه در اعضای مهاربندی جانبی می باشد. هدف اصلی این مقاله در کنار بررسی مطالعات تحلیلی صورت گرفته بر روی قاب های خمشی فولادی با مهاربند هم مرکز دارای اتصال لقی بدون اصطکاک، مقایسه رفتار لرزه ای این نوع قاب ها با قاب های خمشی مهاربندی شده هم مرکز معمولی و انتخاب لقی بهینه می باشد. برای این منظور قابهای مهاربندی شده با و بدون لقی مدل سازی شده و تحت تحلیلهای تاریخچه زمانی و استاتیکی غیر خطی قرار گرفته اند. همچنین در ادامه اقدام به محاسبه ضریب رفتار این نوع قابها شده است. نتایج بدست آمده نشان می دهد که استفاده از اتصال لقی در کنار کاهش پیچیدگیهای اجرایی مربوط به استفاده از میراگرهای اصطکاکی، باعث بهبود عملکرد لرزه ای و افزایش استهلاک انرژی در قابهای مورد مطالعه شده است. همچنین مقدار ضریب رفتار بدست آمده از این مطالعات برای این نوع قابها بزرگتر از ضریب رفتار مهاربند هم مرکز می باشد. http://mcej.modares.ac.ir/article-1-263-fa.pdf 2016-03-20 219 226 اتصال لقی ضریب رفتار تحلیل تاریخچه زمانی غیرخطی مهاربند هم مرکز Evaluation of steel moment frame seismic behavior With concentric brace associated by initial looseness Although, concentric braces have proper stiffness, but ductility and energy absorption of these are low and under pressure and lateral forces exhibit poor performance and also structural ductility will reduce due to buckling when these braces are used for retrofitting of structural frames.Several methods have been proposed for improving of concentric braces performance, especially increasing energy dissipation capacity. The uses of connections with especially performance such as connections with the initial loosening at the end of concentric braces are among these methods.The main objectives of this paper are comparison of the seismic behavior of concentric brace frames with and without initial looseness and calculation of optimal looseness besides the review of analytical studies conducted on no friction brace looseness.For this purpose, the braced frames with and without initial looseness have been modeled and studied using nonlinear static and time history analysis and then the behavior coefficient was calculated.The studied models in this research are concentric moment frames with and without initial looseness. As briefly, the method which is used in this research based on the principle that the moment frames resist against the seismic lateral load at first and then (if it is necessary) braces are activated for carrying lateral load when the lateral displacement is increased and exceeded from the certain level. To achieve this goal, at the junction of the moment frame and brace initial looseness with a certain amount is applied.After reaching to the desired displacement in frame, the bolts at the junction of the moment frame and brace reached to the end of slotted joint and brace will participate with moment frame in bearing lateral forces. In this case the amount of lateral force that can be tolerated by the concentric moment frame with initial looseness is significantly more than the brace without loosening.Based on the results obtained in this investigation the use of loosening in concentric brace frame connection, in addition to reduction of operational complexity of friction dampers, improves seismic performance and also increases seismic energy dissipation capacity of frames which were studied. Also behavior coefficient obtained for this type of frames is greater than behavior coefficient of conventional concentric brace frames.The study of desired frames in this paper indicated that the optimal value of looseness (L_b) should be in the range of 3/4 L≤L_(b )≤L to achieve maximum flexural capacity of moment frame and maximum axial resistance of brace simultaneously. Also, if the ratio of concentric brace stiffness to the stiffness of moment resistance frame is about 1.0, in the concentric moment frame with initial looseness, energy absorption and dissipation capacity is more than the other axial to moment stiffness ratios. In this state the value of load resistance and also behavior coefficient increase although the coefficient of ductility and reduction coefficient due to ductility don't follow any particular trend and are almost constant.It has been observed also that at the all studied models in this research, frames with looseness connection caused an average 17% energy dissipation more than frames without looseness connection. http://mcej.modares.ac.ir/article-1-263-en.pdf 2016-03-20 219 226 Looseness Behavior coefficient Nonlinear time history analysis Concentric brace hesam azizi 1 AUTHOR jamal ahmadi 2 AUTHOR
ORIGINAL_ARTICLE بررسی تأثیر میراگر اصطکاکی سیلندری بر پاسخ لرزه ای سازه های فلزی در این مقاله ، پاسخ لرزه ای سازه های فولادی با استفاده از میراگر اصطکاکی سیلندری (CFD) مطالعه شده است. میراگر اصطکاکی سیلندری شامل دو عنصر اصلی، شفت(استوانه توپر) و سیلندر(استوانه توخالی) است. این دو عنصر به طور کامل درون هم قرار می گیرند. اگر نیروی محوری میراگر بیش از نیروی اصطکاک بین شفت و سیلندر شود ، شفت داخل سیلندر حرکت می کند که منجر به جذب قابل توجه انرژی خواهدشد . برای ارزیابی اثر بخشی میراگر اصطکاکی سیلندری، قاب های فولادی مختلف مورد تجزیه و تحلیل قرار گرفته است. قاب ها تحت تحلیل غیر خطی تاریخچه زمانی و تحلیل غیر افزایشی دینامیکی (IDA)قرار گرفته اند که پاسخ های قاب فلزی دارای میراگر اصطکاکی سیلندری و بدون آن ، تاکید بر اثربخشی میراگر اصطکاکی سیلندری در بهبود پاسخ لرزه ای دارد.نتایج نشان می دهد میراگر اصطکاکی سیلندری به شکل قابل توجهی پاسخ های لرزه ای را کاهش می دهد. http://mcej.modares.ac.ir/article-1-342-fa.pdf 2016-03-20 227 236 میراگر اصطکاکی سیلندری کنترل غیر فعال سازه تحلیل دینامیکی افزایشی بار لغزش بهینه پاسخ لرزه ای Effect of Cylindrical Frictional Dampers on Seismic Response of Steel Structures In this investigation, seismic response of steel structures utilizing Cylindrical Frictional Dampers (CFD) is studied. CFD is an innovative frictional damper which comprises two principal elements, the shaft and the hollow cylinder. These two elements are assembled such that one is shrink-fitted inside the other. If the damper’s axial force overcomes the static friction load, the shaft inside the cylinder will move and results in considerable mechanical energy absorption. To assess the efficacy of CFD, various steel frames are constructed and analyzed . Nonlinear time history analyses and Incremental Dynamic Analysis (IDA) are applied to the frames and clear distinction has been drawn between the frames comprising CFD and the counterparts without CFD to emphasize the effectiveness of CFD in altering seismic responses. The results show that CFD extremely improves the seismic response of the structure. Frictional devices dissipate energy through friction caused by two solid bodies sliding relative to each other. The idea of using frictional dampers was first proposed by Pall (1979). Pall and Marsh (1982) proposed frictional dampers installed at the crossing joint of the X-brace. Tension in one of the braces forces the joint to slip thus activating four links, which in turn force the joint in the other brace to slip. This device is usually called the Pall frictional damper (PFD). B. Wu et al. (2005) introduced improved Pall frictional damper (IPFD) which replicates the mechanical properties of the PFD, but offers some advantages in terms of ease of manufacture and assembly. Sumitomo friction damper (1990) utilizes a more complicated design. The pre-compressed internal spring exert a force that is converted through the action of inner and outer wedges into a normal force on the friction pads. Fluor Daniel Inc., has developed and tested other type of friction device which is called Energy Dissipating Restraint (EDR) (1994). The design of this friction damper is similar to Sumitomo friction damper since this device also includes an internal spring and wedges encased in a steel cylinder. The EDR utilizes steel and bronze friction wedges to convert the axial spring force into normal pressure on the cylinder. Constantine et al. (1990) proposed frictional dampers composed of a sliding steel shaft and two frictional pads clamped by high strength bolts. Grigorian et al. (1998) studied the energy dissipation effect of a joint with slotted holes both analytically and experimentally. Mualla and Belev (2002) proposed a friction damping device and carried out tests for assessing the friction pad material. Cho and Kwon (2004) proposed a wall-type friction damper in order to improve the seismic performance of the reinforced concrete structures. Recently Mirtaheri et.al. (2011) proposed an innovative type of frictional damper called cylindrical friction damper (CFD). In contrast with other frictional dampers the CFDs do not use high-strength bolts to induce friction between contact surfaces. This reduces construction costs, simplifies design computations and increase reliability in comparison with other types of frictional dampers. http://mcej.modares.ac.ir/article-1-342-en.pdf 2016-03-20 227 236 passive control Cylindrical Frictional Damper Incremental dynamic analysis Seismic response optimum slip load hamid mirzaeeafrd 1 AUTHOR m میرطاهری 2 AUTHOR h رحمانی سامانی 3 AUTHOR