ORIGINAL_ARTICLE
بررسی عددی تأثیر شعاع زانویی بر شکلگیری کاویتاسیون در زانویی سرریز نیلوفری
سرریز نیلوفری شامل سه بخش اصلی تاج دایرهای، شفت قائم همراه با یک زانویی معروف به گلوگاه و مجرای تقریباً افقی است. در بخش زانویی سرریزهای نیلوفری انتظار میرود بدلیل وجود جریان با سرعت بالا که منجر به جداشدگی و افت فشار ناشی از زبری و انحناء میشود، کاویتاسیون اتفاق بیفتد. این موضوع باعث شده است این سازهها یکی از مستعدترین سرریزها برای وقوع کاویتاسیون باشند. در پژوهش حاضر امکانپذیری وقوع کاویتاسیون در زانویی سرریز نیلوفری با مدلسازی عددی با استفاده از نرمافزار Flow3D مورد بررسی قرار گرفت. مقایسه نتایج مدل عددی با نتایج مدل فیزیکی که در مرکز تحقیقات آب در ایران ساخته شده نشان داد که تطابق مطلوبی بین مدل عددی و مدل فیزیکی وجود دارد. اثر شعاع زانویی بر نتایج فشار در بدنه سرریز نیلوفری در دبیهای مختلف و احتمال وقوع کاویتاسیون با استفاده از شاخص کاویتاسیون در بخش دیگری از این تحقیق مورد بررسی و تحلیل قرار گرفت. نتایج این تحقیق نشان داد تغییر در شعاع زانویی با توجه به تأثیر آن بر انحناءِ خطوط جریان، اثر قابل توجهی بر بهبود یا افزایش خطر کاویتاسیون خواهد گذاشت. نکته قابل توجه این است که تغییر در شعاع زانویی در هر یک از حالتهای رژیم جریان آزاد و رژیم جریان مستغرق دارای رفتارهای متفاوتی است. در رژیم جریان آزاد، افزایش شعاع زانویی خطر کاویتاسیون را تشدید ولی در رژیم جریان مستغرق یا پر بودن مقطع زانویی، افزایش شعاع زانویی خطر کاویتاسیون را کاهش میدهد.
http://mcej.modares.ac.ir/article-1-18732-fa.pdf
2019-05-15
1
13
سرریز نیلوفری
مدلسازی عددی
کاویتاسیون
شعاع زانویی
Flow3D
Investigation of Elbow Radius Effect on Formation of Cavitation in Morning Glory Spillway
Morning glory spillway is one of the most susceptible cases for the occurrence of the cavitation phenomena. In the present study, the flow characteristics included the inlet and outlet discharge and the velocity and pressure close to the elbow walls were calculated for Alborz dam spillway by using of Flow3D software and the results were compared with the experimental data. The comparison of the numerical model results and the experimental data showed the good agreement between them. The results showed, the maximum pressure head in different discharges and for different elbow radius, have been located in median of piezometer in the bottem of elbow. As a result, it is suggested that, if possible, the curvature changes in the entrance area from the vertical shaft to the elbow and also from the elbow to the horizontal tunnel gradually. In different discharge and different radius of the elbow, the cavitation index for bottem of the elbow will increase as a result of dynamic impacts on the bottem of the elbow, but the cavitation index, toward to the end of the curvature, will be lower due to the contraction end of the cross section. The results showed that radius change of the elbow due to considerable effect on the flow field, has the significant effect on the occurrence probability of the cavitation. The radius change of the elbow has the different results for the submerged flow and free surface regimes.
http://mcej.modares.ac.ir/article-1-18732-en.pdf
2019-05-15
1
13
Morning Glory Spillway
Physical Model
Numerical Model
Hydraulic Parameter
Cavitation
Majid
Ehsani
saeed.ehsaninoori@gmail.com
1
Ph.D student- Isfahan University of Technology
AUTHOR
Ehsan
Behnamtalab
e.behnamtalab@hsu.ac.ir
2
Faculty member-Hakim Sabzevari University
AUTHOR
seyed ali akbar
salehi neyshabouri
salehi@modares.ac.ir
3
Faculty member- Tarbiat Modares University of tehran
AUTHOR
ORIGINAL_ARTICLE
بررسی ضریب رفتار قاب خمشی بتن مسلح با شکل پذیری متوسط و ویژه با در نظر گرفتن اثرات نیروی محوری متغیر و برش
امروزه اغلب آییننامههای طراحی لرزهای جهت طراحی سازهها، نیروی جانبی الاستیک وارد بر سازه را توسط ضریب رفتار، کاهش میدهند تا با طراحی سازه بر اساس تحلیل الاستیک، اثرات رفتار غیر الاستیک سازه را اعمال کنند. جهت به دست آوردن ضریب رفتار سازهها انجام یک تحلیل غیرخطی دقیق ضروری میباشد. تحقیقات نشان داده است رفتار غیرخطی اعضای بتن مسلح به عوامل مختلفی چون اثر نیروی محوری متغیر، اثر شکست برشی و همچنین اثر کمانش میلگردهای طولی وابسته است. در این تحقیق ضریب رفتار قابهای بتن مسلح 2، 4 و 8 طبقه با شکلپذیری متوسط و ویژه بر اساس تحلیل غیرخطی دقیق پیشنهادی بررسی شده است. در ابتدا جهت صحت سنجی، مدل تحلیلی غیرخطی پیشنهادی این تحقیق با مدلهای آزمایشگاهی موجود مقایسه شده است. نتایج صحت سنجی نشان میدهد مدل پیشنهادی از دقت بسیار بالایی برخوردار است. جهت به دست آوردن ضریب رفتار قابهای بتن مسلح 2، 4 و 8 طبقه اثر نیروی محوری متغیر، شکست برشی اعضا و همچنین کمانش میلگردهای طولی در تحلیل غیرخطی در نظر گرفته شده است. جهت محاسبه ضریب رفتار، دو معیار برای محاسبه تغییر شکل نهایی قابها در نظر گرفته شده است. معیار اول بر اساس جابجایی قابها متناظر با دوران نهایی و معیار دوم بر اساس جابجایی متناظر با 0.75 دوران نهایی عضو بحرانی در نظر گرفته شدهاند. نتایج نشان میدهد که ضریب رفتار محاسبهشده قابهای خمشی بتن مسلح با شکلپذیری متوسط و ویژه براساس جابجایی متناظر با 0.75 دوران نهایی عضو بحرانی، به ضریب رفتار ارائهشده توسط استاندارد 2800 نزدیکتر میباشد. همچنین در قابهای بتن مسلح با شکلپذیری متوسط مقدار شکلپذیری با افزایش ارتفاع قابها کاهش یافته است که این نتیجه برای قابهای بتن مسلح با شکلپذیری ویژه صادق نیست.
http://mcej.modares.ac.ir/article-1-19330-fa.pdf
2019-05-15
15
25
ضریب رفتار
قاب خمشی بتن مسلح
تحلیل غیرخطی
نیروی محوری متغیر
شکست برشی
شکلپذیری
Investigating the behavior factor of the intermediate and special RC moment resisting frame with considering the effect of variable axial load and shear
Today, most seismic design codes reduce the lateral elastic force by the behavior factor to design structures, so that by designing a structure based on elastic analysis, the effects of non-elastic behavior of the structure are applied. To obtain a behavior factor of structures, a nonlinear analysis is necessary. Research has shown that the nonlinear behavior of RC members depends on factors such as the effect of varying axial load, the effect of shear failure of the members and the effect of the buckling of the longitudinal bars. It is now generally accepted that axial load plays a dominant role in evaluating the seismic behavior of reinforced concrete columns. However columns, especially the exterior ones, can be subjected to varying axial loads depending on the lateral loads. Also the effects of shear on beams and columns are usually neglected in nonlinear analysis, which is carried out based on the flexural behavior of each element. In this research, the behavior factor of 2, 4, and 8 story reinforced concrete frames with intermediate and special ductility based on the proposed nonlinear analysis is considered. Initially, for verification, the proposed nonlinear analysis model was compared with existing experimental models. The verification results show that the proposed model has a very high accuracy. Designing and detailing of the 2, 4 and 8 story reinforced concrete structures are on the basis of the regulation of the Standard 2800 and the National building regulation chapter 9. In order to obtain the behavior of the 2, 4, and 8 story reinforced concrete frames, the effect of varying axial load, shear failure of the members and the buckling of the longitudinal bars are considered in nonlinear analysis. The behavior factor is mostly effected by ductility factor and over strength factor. The ductility factor has dependence with ductility of the reinforced concrete frames. To obtain ductility of reinforced concrete frames, ultimate deformation is needed. To calculate the frames' behavior factor, various criteria are used to calculate the ultimate deformation of frames. One of the criteria is the deformation correspond to the 0.75 percent of ultimate rotation in critical structure member. The other criteria is the deformation correspond to ultimate rotation of critical structure member. The results of the study and comparison of the obtained behavior factor with the proposed behavior factor of the reinforced concrete structures of Standard 2800 with intermediate and special ductility have shown that the calculated behavior factor for 2, 4 and 8 story reinforced concrete frames is bigger than the behavior factor in Standard 2800. Also the results indicate that the calculated behavior factor with the ultimate deformation correspond to the 75 percent of ultimate rotation in critical structure member is close to the proposed value of Standard 2800. In intermediate reinforced concrete frames, the amount of ductility factor and over strength factor decreased when the height of the reinforced concrete frames raised, which is not seen in concrete frames with special ductility.
http://mcej.modares.ac.ir/article-1-19330-en.pdf
2019-05-15
15
25
behavior factor
RC moment resisting frame
nonlinear analysis
varying axial load
shear failure
ductility
Mohammad
Asadi kiadehi
Mohammad.assadikiadehi@stu.umz.ac.ir
1
University of Mazandaran
AUTHOR
Habib
Bengar
h.akbarzadeh@umz.ac.ir
2
University of Mazandaran
AUTHOR
Javad
hayanfar
arch3d.ir@gmail.com
3
University of Mazandaran
AUTHOR
ORIGINAL_ARTICLE
بررسی اثر صفحه گسیختگی بر نحوه توزیع نیروی کششی در طول میخها در پایداری شیبها (مطالعه موردی شیب منتهی به جاده ایلام-صالحآباد)
زمینه و هدف: مطالعات گستردهای پایداری شیروانی را بررسی نمودهاند اما مطالعات محدودی به بررسی اثر صفحه گسیختگی به نحوه توزیع نیروی کششی و نحوه توزیع نیروی کششی در طول میخها بر پایداری شیبهای پرداخته است. بر این اساس هدف این پژوهش بررسی اثر زاویه کوبش و طول میخها بر پایداری شیب با نگرش به نحوه توزیع کرنش برشی است. روش بررسی: در این پژوهش به صورت موردی شیب منتهی به جاده مسیر ایلام-صالحآباد بعد از تونل راهکربلا انتخاب شده است. ابتدا جهت تعیین پارامترهای مکانیکی خاک از محل شیب نمونههایی تهیه شده و در آزمایشگاه بر اساس آیین نامه ASTM مشخصات خاک تعیین شده است. جهت مدلسازی از نرمافزار FLAC2D که نرمافزاری قوی در مدل کردن سازههای ژئوتکنیکی است، استفاده شده است. در ادامه به بررسی اثر زاویه شیب میخها با افق و طول میخها بر روی ضریب اطمینان و نحوه توزیع نیروی کششی میخها پرداخته شده است. بحث و نتیجهگیری: نتایج تحقیق حاضر نشان میدهد که با افزایش شیب میخها با افق از زاویه 0 تا 30 درجه، ضریب اطمینان میخها حدود 23% و بیشینه نیروی کششی حدود 6% افزایش مییابد و پس از آن با افزایش در زاویه شیب میخها ضریب اطمینان کاهش و توزیع نیروی کششی در طول میخها کاهش مییابد. در بررسی اثر طول میخها بر پایداری شیب، مشاهده شد که بیشترین راندمان زمانی حاصل میشود که طول میخها یک متر از اندازه گوه گسیختگی برشی در آن نقطه بیشتر باشد.
http://mcej.modares.ac.ir/article-1-20290-fa.pdf
2019-05-15
27
40
زاویه کوبش
ضریب اطمینان
ابزاردقیق
توزیع نیروی کششی میخها
طول میخ
Effect of Failure Plane on Slope Stability and Tensile Force Distribution along Soil Nails
(Case Study: Slope leading to Ilam-Salehabad Road)
Abstract Background and Purpose: Instability of slopes leading to roads in steep mountainous areas is a major problem in the development of roads worldwide, causing excessive human as well as financial losses. Soil nailing is one way of in-situ soil reinforcement. The behavior of a reinforced soil system depends on different parameters including geometry of the structure, mechanical characteristics of the soil, density of the reinforcing material, and length of the soil reinforcing material as well as the angle it makes with the failure plane. Though much research has been conducted on earth slope stability, few studies have examined the effect on slope stability of the soil nailing angle and tensile force distribution along the nail. In spite of the extensive studies conducted on slope stability, no specific insight has been obtained so far on the effect of the failure plane or soil nailing angle on the tensile force distribution along the nails. In view of these facts, this study aims to examine the effect of nail angle as well as nail length on the nail safety factor with due consideration of the effect of shear strain distribution on slope stability. Selecting the slope leading to Ilam-Salehabad Road in western Iran as our case study, we studied the stability of this slope at different nail lengths and angles. Methodology: The slope leading to Ilam-Saalehabad Road (after the Karbala Road tunnel) was selected as the case study. To determine the mechanical parameters of the soil, we provided soil samples from the slope site and tested them at the laboratory in accordance with ASTM code to obtain the required soil characteristics. The powerful geotechnical software FLAC2 was subsequently used for modeling the slope leading to the road. Upon completion of analysis, we compared the settlement obtained from the software at two points on the earth slope with similar measurements obtained from the instruments, and observed a good agreement between them, with an approximate maximum error of 3%. In the following, the effect of soil nailing angle (with the horizontal line) as well as the length of the nail on the nail safety factor and nail tensile force is discussed. Discussion and Conclusion: Our results showed that increasing the soil nailing angle (i.e., nail driving angle defined as the angle between the soil nail and the horizontal line) from 0 to 30 degrees would increase the nail safety factor by about 23%. Thereafter, increasing the nail driving angle from 30 to 45 would cause a reduction of 2.8% in the safety factor. A further increase of nail angle (with the horizon) caused a corresponding increase in the tensile force induced in the nails, so that the maximum tensile force at 30 degrees increased by about 6%. The maximum nail driving angle efficiency was observed at the points undergoing maximum shear strain: increasing the drive angle to 30 degrees led to a 10-fold increase in the tensile force developed in the nails at points with maximum shear strains. On the other hand, increasing the nail length increased nail safety factor, so that increasing the nail length by 1 meter would increase nail safety factor by 4.3%. However, increasing the nail length beyond 1 meter reduced the rate of increase of the safety factor. Accordingly, the optimum length increase in the nails was taken as 1 meter.
http://mcej.modares.ac.ir/article-1-20290-en.pdf
2019-05-15
27
40
Soil nail angle (soil nail driving angle)
safety factor
instrumentation
tensile force distribution in the nail
nail length
m
amiry
amirii@chmail.ir
1
AUTHOR
samm
saviz
savizsamm.ss@gmail.com
2
AUTHOR
ORIGINAL_ARTICLE
بررسی شدت رهایش گرمای مصالح و مدلسازی حریق در ساختمان پلاسکو
حدود ساعت 8 صبح سیام دی ماه 1395، ساختمان پلاسکو در تهران دچار حریق شد. علت شروع حریق اتصال برق گزارش شده است. دلایل گسترش حریق و چگونگی آن بررسی شد. ساختمان پلاسکو دارای نقاط ضعف زیادی از نظر ایمنی در برابر آتش بود که موارد زیر را باید عنوان نمود: بار حریق بالا به علت مقادیر زیاد پارچه، اشکالات طرح پلکان، ارتباط کامل بین فضاها از طریق سقفهای کاذب و شفت تأسیسات، عدم محافظت سازه فولادی در برابر آتش، عدم وجود جداسازی مقاوم در برابر آتش، عدم وجود سیستمهای کشف، اعلام و اطفای خودکار حریق، عدم تعمیر و نگهداری صحیح از سیستمهای موجود. آزمایش آتش بر روی پارچهها صورت گرفت و نشان داد بار حریق در ساختمان بسیار بالا بوده است. مدلسازی کامپیوتری بر روی چگونگی گسترش حریق در ساختمان پلاسکو صورت گرفت. نتایج مدل نشان داد که حریق توانسته از طریق پنجرهها، فضاهای کاذب، پلکان و شفت آسانسور به فضاهای مجاور و به طبقات بالا گسترش یابد. همچنین افزایش دما در مناطق مختلف ساختمان، به علت آتشسوزی، نشان داده شد. نتایج نشان داد که افزایش دما در ساختمان، بخصوص در طبقات 10 و 11 برای رسیدن سازه به دماهای بحرانی و شکست سازه مستعد بوده است. همچنین مدل حریق نشان داد که مسیر پلکان در همان دقایق ابتدایی، به علت آکنده شدن از دود و تیرگی و نیز افزایش دما، برای افراد معمولی (بدون تجهیزات خاص) غیر قابل استفاده شده است.
http://mcej.modares.ac.ir/article-1-14421-fa.pdf
2019-05-15
41
51
ساختمان پلاسکو
آتشسوزی
مدل سازی
مقررات ساختمانی
شدت رهایش گرما
Heat release rate of materials and fire modelling of Plasco building’s incident
At about 8.00 am of 20th December 2015, a fire started in a shop in Plasco building, located in center of Tehran, which at the end resulted in catastrophic collapse of the building and claimed the lives of 22 fire fighters and other people. According to the findings of the investigations, the main reason of ignition was non-permitted extension of cablings in the shop of the scene; for use of electrical heating devices. Plasco building was constructed before compiling of national building codes of Iran; hence fire safety rules were not properly implemented in the design of the building. This incident took the attention of Iranian society, Engineers and authorities to the need of the improvement of safety of the old buildings, which have been constructed before the establishment of national building code. In the other hand, the national building codes of Iran consists only the requirements for the new buildings and approximately no regulation has been pointed there for existing buildings. The incident was an alarm to the general public and accounted organizations that there might be many other buildings like Plasco in the large cities, which are threatening the safety of the users and the city. Therefore a national committee was appointed to investigate the different aspects of the incident and offers the solutions and measures which should be taken to prevent the similar experiences in the future. One of the subcommittees was accounted to fire engineering studies. The fire safety problems of the building were investigated. Some important shortages were as follows: high fire load in the building, especially because of high content of flammable textiles and clothes, open stairways without a protected shaft, open connection between false ceilings of all shops and corridors in the stories, lack of fire resistant shafts of mechanical installations between floors, lack of fire protection of steel structure, lack of any fire detection and automatic sprinkler in the building. The existing hose-reels didn’t have a regular maintenance and hence they could not be properly used by fire fighting forces. The Plasco was collapsed after about three and half hours of the ignition. Therefore the question was arisen how was the scenario of the fire growth and temperature rise in the building. Different tests were carried out on the sample materials taken from the debris of the building. Heat release rate (HRR) of the sample textiles was measured with cone calorimeter. The place of the building and depot of debris was visited by different special teams. Steel, concrete and other materials, which some of them were molten due to high temperature, was taken for further experimental works. Physical, mechanical, XRD/XRF, petrography and other tests have been carried out, from them only heat release test is discussing in this paper. The results showed high amount of HRR of the burned textile specimen. There were more than 580 mercantile units in Plasco, which most of them were clothing shops or related works. This high content of the textiles and clothing created a high fuel load in the building. Considering the design weaknesses of the building which were pointed out in the above, the fire could rapidly grow in all stories through open connected spaces. A fire modeling was carried out using FDS software and showed how the flames could be raised through windows, shafts and stairways to upper floors. The temperature rise was also investigated by the model. The results showed that the temperature rise, especially in floors 10 and 11 was suit for collapse of structural elements which was widely discussed in report of structure committee. The results also showed that the means of egress was not useable by occupants after only short minutes from the ignition, because of fire and smoke growth in the path.
http://mcej.modares.ac.ir/article-1-14421-en.pdf
2019-05-15
41
51
Plasco building
fire modeling
building regulation
cone calorimeter
heat release rate
Saeed
Bakhtiyari
1
Fire department, Faculty, Road, Housing & Urban Development Research Center, Tehran, Iran
AUTHOR
Masoud
Jamali Ashtiani
2
Fire department, Faculty, Road, Housing & Urban Development Research Center, Tehran, Iran
AUTHOR
ORIGINAL_ARTICLE
بررسی عملکرد لرزه ای سدهای بتنی وزنی با استفاده از تحلیل بار افزون
نیاز روز افزون به منابع آبی وانرژی پاک جوامع بشری را بر آن داشته تا با تحقیقات و مطالعات گسترده فناوری های قدیمی را بهینه سازی کنند تا بیشترین بهره ممکن را از آنها ببرند. یکی از این اختراعات سد ها هستند، سازه هایی که بر روی رودها ایجاد می شود. در گذشته ایجاد سدها عمومآ با هدف تامین آب آشامیدنی و آبیاری مزارع بوده اما امروزه نه تنها تامین کننده مصارف آبی است بلکه در ایجاد انرژی الکتریکی نیز مورد استفاده قرار می گیرند. در بسیاری از مطالعات، برای ارزیابی آسیب پذیری و میزان صدمه دیدن سدها در هنگام وقوع زلزله از تحلیل دینامیکی استفاده می شود. علیرغم دقیق بودن این روش، عدم قطعیت های فراوانی در مراحل تحلیل وجود دارد که باعث هزینه بر بودن و طولانی شدن مطالعات می شود. از این رو محققان با بکار گیری روش تحلیل استاتیکی غیر خطی سرعت تحلیل را بالا برده و هزینه ها را کاهش دادند. هدف تحقیق حاضر، بررسی عملکرد لرزه ای سدهای بتنی وزنی با استفاده از تحلیل استاتیکی غیرخطی (بار افزون) است. بدین منظور الگوهای بار مورد استفاده در تحلیل بار افرون در دو جهت بالادست و پایین دست به سازه سد اعمال می گردد و مشاهدات نشان دهنده آن است که به غیر از الگوی بار مستطیلی تمامی الگوی های بار مورد استفاده در این تحقیق بطور مناسبی می توانند راستای ترک را در بدنه سد به درستی تشخیص دهند.
http://mcej.modares.ac.ir/article-1-16001-fa.pdf
2019-05-15
53
65
سد
عملکرد لرزه ای
تحلیل بار افزون
الگوی بار
Investigation of Seismic Performance of Concrete Gravity Dams using Pushover Analysis
The increasing need for clean water and energy resources for human societies has led them to optimize the old technologies with the best in research and studies to make the most of them. One of these inventions is dams, structures that are created on the rivers. In the past, the creation of dams was generally aimed at providing drinking water and irrigation of farms, but nowadays it is not only a source of water, but also electric energy. In many studies, dynamic analysis is used to assess the vulnerability and damage damages during an earthquake. Despite the precision of this method, there are many uncertainties in the analysis stages that make the study costly and prolonged. Therefore, using nonlinear static analysis method, researchers increased the speed of analysis and reduced costs. The purpose of this study is to investigate the seismic performance of concrete gravity dams using nonlinear static analysis (pushover analysis). For this purpose, load patterns used in the pushover analysis are applied in both directions upstream and downstream of the dam structure. Observations show that, apart from the rectangular load pattern, all load patterns used in this research can adequately correlate Detect the crack in the dam body correctly. The increasing need for clean water and energy resources for human societies has led them to optimize the old technologies with the best in research and studies to make the most of them. One of these inventions is dams, structures that are created on the rivers. In the past, the creation of dams was generally aimed at providing drinking water and irrigation of farms, but nowadays it is not only a source of water, but also electric energy. In many studies, dynamic analysis is used to assess the vulnerability and damage damages during an earthquake. Despite the precision of this method, there are many uncertainties in the analysis stages that make the study costly and prolonged. Therefore, using nonlinear static analysis method, researchers increased the speed of analysis and reduced costs. The purpose of this study is to investigate the seismic performance of concrete gravity dams using nonlinear static analysis (pushover analysis). For this purpose, load patterns used in the pushover analysis are applied in both directions upstream and downstream of the dam structure. Observations show that, apart from the rectangular load pattern, all load patterns used in this research can adequately correlate Detect the crack in the dam body correctly. The increasing need for clean water and energy resources for human societies has led them to optimize the old technologies with the best in research and studies to make the most of them. One of these inventions is dams, structures that are created on the rivers. In the past, the creation of dams was generally aimed at providing drinking water and irrigation of farms, but nowadays it is not only a source of water, but also electric energy. In many studies, dynamic analysis is used to assess the vulnerability and damage damages during an earthquake. Despite the precision of this method, there are many uncertainties in the analysis stages that make the study costly and prolonged. Therefore, using nonlinear static analysis method, researchers increased the speed of analysis and reduced costs. The purpose of this study is to investigate the seismic performance of concrete gravity dams using nonlinear static analysis (pushover analysis). For this purpose, load patterns used in the pushover analysis are applied in both directions upstream and downstream of the dam structure. Observations show that, apart from the rectangular load pattern, all load patterns used in this research can adequately correlate Detect the crack in the dam body correctly.
http://mcej.modares.ac.ir/article-1-16001-en.pdf
2019-05-15
53
65
dam
seismic performance
pushover analysis
load patter
Mohammad
Alembagheri
1
Tarbiat Modares University
AUTHOR
Hossein
Behzadnasab
2
Islamic Azad University
AUTHOR
ORIGINAL_ARTICLE
انواع انرژی در سازه های بلند متصل شده با پل خرپایی کمانش تاب تحت اثر زلزله
متصل نمودن دو برج توسط یک پل میانی می تواند یکی از راهکارهای کنترل جابجایی و هم چنین استهلاک انرژی به حساب آید. این مقاله به بررسی انواع نیازهای انرژی در سازه ساختمان بلند 40 و 60 طبقه می پردازد که در هر کدام از آنها دو هسته بتن مسلح با ارتفاع یکسان توسط یک پل خرپایی به یکدیگر متصل شده اند. خرپای پل از المان های کمانش تاب تشکیل می شود. در ابتدا این سازه با بکارگیری روش تحلیل طیفی طبق آیین نامه های معتبر طراحی می شود و در ادامه با تهیه مدل غیرخطی سازه در نرم افزار PERFORM-3D و انجام تحلیل تاریخچه زمانی تحت اثر زلزله های دور و نزدیک انرژی ورودی، انرژی جنبشی، انرژی میرایی و انرژی غیرالاستیک مورد بررسی قرار می گیرد و مشارکت دیوار و پل در اتلاف انرژی مطالعه می شود. دو رویکرد مفصل یگانه و مفصل گسترده برای هسته در نظر گرفته می شود. در رویکرد مفصل یگانه، فقط در پای هسته بتن مسلح اجازه مفصل پلاستیک داده می شود و بقیه نواحی هسته بتن مسلح به صورت الاستیک مدل می شود و تحلیل تاریخچه زمانی غیرخطی انجام می شود. در رویکرد مفصل گسترده، کل هسته قابلیت گسترش پلاستیسیته را دارد. بطور متوسط در رویکرد مفصل گسترده، سهم هسته ها حدود 48 درصد و سهم پل با اعضای کمانش تاب حدود 52 درصد از انرژی غیرالاستیک تحت کل نگاشت های اعمال شده را شامل می شود و این اعداد در رویکرد مفصل یگانه به ترتیب حدود 34 و 66 درصد است.
http://mcej.modares.ac.ir/article-1-16455-fa.pdf
2019-05-15
67
77
پل
مهاربند کمانش تاب
بتن مسلح
نگارش
تحلیل تاریخچه زمانی غیر خطی
Investigating the types of energy in the connected structures with the buckling resistant bridge
In The efficiency of the RC core system for buildings that are taller than 35 to 40 story is modestly reduced. In these structures, connecting two towers with an intermediate bridge can be considered as one of the solutions for controlling displacement and also energy dissipation. This paper examines the types of energy needs in a high-rise building of 40 and 60 floors, each of which combines two reinforced concrete core of the same height with a truss bridge. The trusses of the bridge are made by buckling resistant elements. Initially, this structure is designed using the spectral analysis method according to the valid regulations. Then, by constructing a non-linear model of the structure in the PERFORM-3D software and performing a time history analysis under the influence of near and far fault ground motions, kinetic energy, inpute energy, damping energy, and non-elastic energy are studied, and the contribution of the wall and bridge is studied in energy dissipation. Single plastic hinge and extended plastic hinge approaches are considered for the core. In a . single plastic hinge approach, only a plastic joint is allowed at the bottom of the RC core, and the rest of the RC core regions are modeled elastically, and nonlinear time histories analysis is done. In an extended plastic hinge approach, the entire core has the ability to expand plasticity. On average, extended plastic hinge approach approach, the core share is about 48%, and the share of the bridge with buckling resistant members is about 52% of non-elastic energy under the total records applied, and these values are 34% and 66% in the single plastic hinge approach. The trusses of the bridge are made by buckling resistant elements. Initially, this structure is designed using the spectral analysis method according to the valid regulations. Then, by constructing a non-linear model of the structure in the PERFORM-3D software and performing a time history analysis under the influence of near and far fault ground motions, kinetic energy, inpute energy, damping energy, and non-elastic energy are studied, and the contribution of the wall and bridge is studied in energy dissipation. Single plastic hinge and extended plastic hinge approaches are considered for the core. In a . single plastic hinge approach, only a plastic joint is allowed at the bottom of the RC core, and the rest of the RC core regions are modeled elastically, and nonlinear time histories analysis is done. In an extended plastic hinge approach, the entire core has the ability to expand plasticity. On average, extended plastic hinge approach approach, the core share is about 48%, and the share of the bridge with buckling resistant members is about 52% of non-elastic energy under the total records applied, and these values are 34% and 66% in the single plastic hinge approach. In an extended plastic hinge approach, the entire core has the ability to expand plasticity. On average, extended plastic hinge approach approach, the core share is about 48%, and the share of the bridge with buckling resistant members is about 52% of non-elastic energy under the total records applied, and these values are 34% and 66% in the single plastic hinge approach.
http://mcej.modares.ac.ir/article-1-16455-en.pdf
2019-05-15
67
77
Bridge
buckling resistant brace
reinforced concrete
non-linear time history analysis.
Hamid
Beiraghi
1
Civil Eng. department, Azad university
AUTHOR
ORIGINAL_ARTICLE
بررسی عددی اثر تغییر منحنی استاندارد سرریزهای سهجانبی در بهبود عملکرد هیدرولیکی آنها
سرریزهای سهجانبی از جمله مجراهای تخلیه کننده سدها بوده که علیرغم محدودیتهای هیدرولیکی، در شرایط خاص توپوگرافی به عنوان بهترین انتخاب مطرح میشوند. سرریزهای سهجانبی دارای برخی شرایط هیدرولیکی نامناسب هستند که بهعنوان نمونه میتوان به تلاطم و آشفتگی جریان، اتلاف انرژی و نیز وارد آمدن ضربات نوسانی شدید آب بر تمامی وجوه سرریز اشاره کرد. در تحقیق حاضر شبیهسازی عددی میدان جریان سهبعدی پیرامون سرریز جانبی U شکل و آبپایه واقع در انتهای کانال جانبی با استفاده از نرم افزار Flow3D مورد توجه قرار گرفته است. در ادامه با پلهای نمودن منحنی استاندارد سرریز اوجی سه جانبی، میزان تغییر در عمق جریان و نوسانات فشار دینامیکی در کانال جانبی مورد ارزیابی قرار گرفته است. برای بررسی کمی نوسانات فشار دینامیکی از عدد بدون بعد پارامتر آشفتگی استفاده شده است. نتایج نشان میدهد پلکانی نمودن منحنی استاندارد این نوع سرریز موجب کاهش برخورد سفرههای ریزشی جریان و افزایش عمق جریان در کانال جانبی میگردد. از سویی دیگر تغییر منحنی استاندارد، کاهش قابل توجه شدت نوسانات فشار در داخل کانال جانبی را به دنبال دارد.
http://mcej.modares.ac.ir/article-1-16951-fa.pdf
2019-05-15
79
90
سرریز سهجانبی
عملکرد هیدرولیکی
منحنی پلکانی
شبیهسازی عددی
Numerical Investigating the Effect of Changing the Ogee Profile of Three-Sided Spillways on Improving their Hydraulic Performance
Three-sided spillways are one of the important dam's outlet works that despite their hydraulic limitations, selected as the best option in storage dam under special topographical conditions. Considerable energy losses, the flow high turbulences, and applying great fluctuations shock on walls and bed of the side channel are the hydraulic conditions that must carefully considered in these spillways. In this study, the three-dimensional flow filed of U-shaped spillway and end-sill of the side channel are simulated using Flow3D and the effect of flow turbulences have been modelled by RNG closure. Comparison of the numerical and experimental results revealed that this model with RNG closure has capable to carefully simulate the turbulence flow field on these structures. The effect of making stepped the ogee profile of the three-sided spillway on flow depth and dynamic pressure fluctuations has been numerically evaluated; the non-dimensional turbulence index has been used to investigate the fluctuations of the dynamic pressure. The results revealed making stepped the ogee profile causes to reduce the encounter of the side overfalls, and to increase the flow depth in the side channel, in which this lead to considerable decrease in pressure fluctuation intensity. Three-sided spillways are one of the important dam's outlet works that despite their hydraulic limitations, selected as the best option in storage dam under special topographical conditions. Considerable energy losses, the flow high turbulences, and applying great fluctuations shock on walls and bed of the side channel are the hydraulic conditions that must carefully considered in these spillways. In this study, the three-dimensional flow filed of U-shaped spillway and end-sill of the side channel are simulated using Flow3D and the effect of flow turbulences have been modelled by RNG closure. Comparison of the numerical and experimental results revealed that this model with RNG closure has capable to carefully simulate the turbulence flow field on these structures. The effect of making stepped the ogee profile of the three-sided spillway on flow depth and dynamic pressure fluctuations has been numerically evaluated; the non-dimensional turbulence index has been used to investigate the fluctuations of the dynamic pressure. The results revealed making stepped the ogee profile causes to reduce the encounter of the side overfalls, and to increase the flow depth in the side channel, in which this lead to considerable decrease in pressure fluctuation intensity. Three-sided spillways are one of the important dam's outlet works that despite their hydraulic limitations, selected as the best option in storage dam under special topographical conditions. Considerable energy losses, the flow high turbulences, and applying great fluctuations shock on walls and bed of the side channel are the hydraulic conditions that must carefully considered in these spillways. In this study, the three-dimensional flow filed of U-shaped spillway and end-sill of the side channel are simulated using Flow3D and the effect of flow turbulences have been modelled by RNG closure. Comparison of the numerical and experimental results revealed that this model with RNG closure has capable to carefully simulate the turbulence flow field on these structures. The effect of making stepped the ogee profile of the three-sided spillway on flow depth and dynamic pressure fluctuations has been numerically evaluated; the non-dimensional turbulence index has been used to investigate the fluctuations of the dynamic pressure. The results revealed making stepped the ogee profile causes to reduce the encounter of the side overfalls, and to increase the flow depth in the side channel, in which this lead to considerable decrease in pressure fluctuation intensity.
http://mcej.modares.ac.ir/article-1-16951-en.pdf
2019-05-15
79
90
Three-sided spillway
Hydraulic performance
Stepped profile
Numerical simulation
H.
Taghizadeh
1
PhD Student of Hydraulic Structure, Faculty of Engineering, Urmia University
AUTHOR
Abolfazl
Arzanlou
2
tehran central azad university
AUTHOR
N.
Kardan
n.kardan@azaruniv.ac.ir
3
Assistant Professor, Department of Civil Engineering, Azarbaijan Shahid Madani University
AUTHOR
ORIGINAL_ARTICLE
روش تقریبی برای تحلیل لرزه ای شبکه های دولایه
پاسخ دینامیکی شبکه های دولایه را میتوان با به کارگیری نرم افزارهای مبتنی بر روش اجزای محدود به دست آورد. از سوی دیگر، به روشهای تقریبی که به آسانی و سرعت تخمین مناسبی از رفتار دینامیکی سازهها و از جمله شبکه های دولایه فراهم آورند، نیز نیاز است. در این مقاله، یک روش تقریبی برای تحلیل لرزهای شبکه های دولایه با طرح مربع روی مربع فضایی و با پلان مربع یا مستطیل و دارای تکیهگاههای ساده در پیرامون سازه، پیشنهاد میشود. این روش توانایی تخمین کوچکترین فرکانس ارتعاش قائم و نیز نیروهای لرزه ای حاصل از شتاب قائم زمین لرزه در شبکه های دولایه را دارا می باشد. برای بررسی توانایی روش پیشنهادی، 21 مدل از شبکههای دولایه با روش دقیق و نیز شیوه تقریبی پیشنهادی تحلیل دینامیکی میگردد و پاسخهای بدست آمده باهم سنجش میشوند. یافته ها نشان دهنده دقت خوب پاسخهای روش تقریبی رابطهسازی شده میباشد.
http://mcej.modares.ac.ir/article-1-14532-fa.pdf
2019-05-15
91
103
شبکه های دولایه
تحلیل لرزه ای
روش تقریبی
فرکانس ارتعاش قائم
Approximate Method for Seismic Analysis of Double-Layer Grids
The dynamic response of the double-layer girds (a kind of space trusses) can be determined by means of the software based on the finite element method. However, it is always needed the approximate techniques by which one can easily and quickly obtain the suitable estimation of the dynamic behavior of the structures. This need may be caused by: 1- providing an appropriate estimation in the first stage of designing the members, and 2- verification of the results of the computer programs.
In this study, an approximate method is suggested for seismic analyses of the double-layer grids with the spatial square on square layout, the square or rectangular plan and simple supports around the structure. The method is on the basis of the simulation of double-layer grid to the equivalent beam and plate. Here, the smallest circular frequency of the vertical vibration is computed by using Rayleigh’s method. In addition, the seismic forces caused by the vertical acceleration of the earthquake are evaluated by employing the equations of the dynamics of the structures and estimating the shape function of the first mode of the vertical vibration. There are the deflections of the structural nodes in the achieved equation for estimating the circular frequency; therefore, an initial estimation for the sizes of the members of the double-layer gird is required. In fact, since the weight of the structure should be considered in evaluating the applied loads, an approximate design must be performed. For this purpose, a step by step technique is suggested based on the AISC Specification to initially design the structure. In addition, the assessment of the deflection of the double-layer girds is done based on the uniformly distributed loads and non-uniformly distributed loads.
Finally, to assess the suggested approximate method, 21 models of the double-layer grids with the spatial square on square layout are considered. These models have the horizontal and diagonal (web) members with the equal lengths. The supports of the double-layer girds are simple. The bays have 30 to 60 m with the step of 5 m and the number of 10, 12 and 14 horizontal members along the span. In order to analyze and design the models, the members are considered to be connected to each other as bending free connections. The spectrum analysis is done to take into account the seismic effects. Also, SAP2000 is used to analyze and design the models in question, and the results achieved by this software are considered as exact outcomes. On the other hand, the models are analyze by the suggested approximate method and the obtained results including frequencies, seismic vertical forces of the members of the models are compared with the exact outcomes in diagrams. The findings show that the proposed method can be evaluated the dynamic properties of the double-layer girds with a suitable precision which prove the robustness of the derived scheme. In fact, the maximum error in estimating the frequency is about 15%, and 12% if it is considered the variation of the weight of the double-layer girds and if it is not considered, respectively. Furthermore, the comparison of the achieved forces of the members between the exact and approximate results is revealed that the maximum error is about 11%, which is a good estimation for an approximate method.
http://mcej.modares.ac.ir/article-1-14532-en.pdf
2019-05-15
91
103
Double-layer grids
seismic analysis
approximate method
vertical frequency of vibration
Hassan
Haji kazemi
1
Civil Engineering Department, Ferdowsi University of Mashhad
AUTHOR
Mehrzad
Sharifian
m.sharifian@qiet.ac.ir
2
Civil Engineering Department, Quchan University of Technology
AUTHOR
Mehrdad
Sharifian
md.sharifian@qiet.ac.ir
3
Civil Engineering Department, Quchan University of Technology
AUTHOR
ORIGINAL_ARTICLE
تحلیل عوامل ترافیکی مؤثر بر وقوع تصادفات در نواحی ورودی تونلهای شهری (مطالعه موردی: تونل رسالت)
. هدف از این تحقیق، استفاده از مدل جمعی تعمیمیافته (GAM) بهعنوان رویکردی ناپارامتری جهت شناسایی عوامل ترافیکی مؤثر بر فراوانی تصادفات در نواحی دسترسی و ورودی تونلهای شهری و مقایسهی نتایج حاصل از آن با مدل خطی تعمیمیافته (GLM) بهعنوان رویکردی پارامتری است. برای این منظور اطلاعات تصادفات رخداده در محدودهی تونل رسالت به همراه دادههای ترافیکی روزانه در طول سه سال متوالی (1389 تا 1391) از مرکز کنترل و مدیریت تونلهای شهری تهران دریافت شد. پس از پردازش اطلاعات، تعداد 1047 تصادف در نواحی دسترسی و ورودی تونل بهعنوان متغیر وابسته و سه متغیر لگاریتم حجم ترافیک، فراوانی وسایلنقلیه سنگین (درصد) و اختلاف سرعت از محدودیت سرعت بزرگراه بهعنوان متغیرهای مستقل نهایی جهت فرآیند مدلسازی انتخاب شدند. بر اساس نتایج مدل خطی تعمیمیافته، اثر خطی متغیرهای لگاریتم حجم روزانه (009/0 p<)، فراوانی وسایلنقلیه سنگین (000/0 p<) و اختلاف میانگین سرعت روزانه وسایلنقلیه عبوری از تونل نسبت به محدودیت سرعت بزرگراه (000/0 p<) در فراوانی تصادفات نواحی دسترسی و ورودی تونل معنیدار گزارش شد.
http://mcej.modares.ac.ir/article-1-16054-fa.pdf
2019-05-15
105
116
تونلهای شهری
فراوانی تصادفات
مدل خطی تعمیمیافته (GLM)
مدل جمعی تعمیمیافته (GAM)
Analysis of Traffic Factors Affecting the Accidents in the Urban Tunnel Entry Areas (Case Study: Resalat Tunnel)
Urban tunnels are one of the major infrastructures in transportation networks of metropolitan cities. Owing to the enclosed space of tunnels, the safety of through passage is essential. Identify factors affecting the frequency of accidents in urban tunnels can be useful in preventing and reducing related casualties. In this research, we try to determine the factors affecting a number of accidents by comparing the generalized linear model and the generalized additive model. The data of Resalat tunnel comes from Tehran's urban tunnels control and management centre, which includes the daily volume variables, the percentage of heavy vehicles, the difference between the average speed of passing vehicles from the tunnel and the speed limit of the highway as independent variables, and the number of accidents per day during the period 2010 to 2012 as dependent variable. In this research, R software programs are used respectively for fitting a generalized linear and generalized additive model. Based on the results of generalized linear and generalized additive models, the percentage of heavy vehicles and the difference between the average speed of passing vehicles from the tunnel and the speed limit of the highway are significantly and positively related to the frequency of accidents in the access and entrance areas of the tunnel. The logarithm of daily traffic volume is not meaningful in the generalized additive model, in contrast to the generalized linear model. Therefore, identifying the factors affecting the frequency of accidents in urban tunnels by using advanced statistical models will greatly help to develop effective measures in improving the safety of tunnels. Urban tunnels are one of the major infrastructures in transportation networks of metropolitan cities. Owing to the enclosed space of tunnels, the safety of through passage is essential. Identify factors affecting the frequency of accidents in urban tunnels can be useful in preventing and reducing related casualties. In this research, we try to determine the factors affecting a number of accidents by comparing the generalized linear model and the generalized additive model. The data of Resalat tunnel comes from Tehran's urban tunnels control and management centre, which includes the daily volume variables, the percentage of heavy vehicles, the difference between the average speed of passing vehicles from the tunnel and the speed limit of the highway as independent variables, and the number of accidents per day during the period 2010 to 2012 as dependent variable. In this research, R software programs are used respectively for fitting a generalized linear and generalized additive model. Based on the results of generalized linear and generalized additive models, the percentage of heavy vehicles and the difference between the average speed of passing vehicles from the tunnel and the speed limit of the highway are significantly and positively related to the frequency of accidents in the access and entrance areas of the tunnel. The logarithm of daily traffic volume is not meaningful in the generalized additive model, in contrast to the generalized linear model. Therefore, identifying the factors affecting the frequency of accidents in urban tunnels by using advanced statistical models will greatly help to develop effective measures in improving the safety of tunnels.
http://mcej.modares.ac.ir/article-1-16054-en.pdf
2019-05-15
105
116
Urban Tunnels
Accident Frequency
Generalized Linear Model
Generalized Additive Model.
B.
shirgir
shirgir@gmail.com
1
AUTHOR
hossein
hassanpour
2
Department of Civil Engineering, kharazmi University, Alborz, Iran
AUTHOR
ORIGINAL_ARTICLE
معرفی و بررسی رفتار یک مهاربند فولادی جدید با قابلیت مرکزگرایی و استهلاک انرژی
سیستم های مقاوم مرسوم در برابر نیروهای لرزه ای، اغلب از طریق تغییرشکل های غیرارتجاعی در برخی از اعضا و اجزای سازه ای، انرژی ورودی زلزله را مستهلک می کنند. در این سیستم ها بعد از وقوع زلزله تغییرمکان ماندگار زیادی مشاهده می شود که هزینه های بازسازی را بالا برده یا تخریب سازه را ایجاب می کند. استفاده از سیستم های مرکزگرا که در ده سال اخیر بسیار مورد توجه مجامع علمی معتبر بوده است، باعث کاهش قابل ملاحظه یا حذف تقریبا کامل تغییرشکل های ماندگار در سازه پس از زلزله می شود. سیستم مرکزگرای بررسی شده در این مقاله، یک مهاربند فولادی جدید است که در آن از کابل های فولادی پیش تنیده به عنوان مکانیزم بازگرداننده برای کاهش تغییرشکل پسماند استفاده شده است. همچنین از میراگرهایی به شکل دندانه-شانه ای که به صورت درون صفحه ای عمل می کنند، برای تامین استهلاک انرژی بهره گرفته شده است. این مهاربند مرکزگرا را می توان به جای مهاربندهای معمول در قاب های فولادی ساده مورد استفاده قرار داد. بررسی معادلات تحلیلی این مهاربند و نیز مدلسازی اجزای محدود نشان می دهد که قابلیت مرکزگرایی و استهلاک انرژی موردنظر می تواند به میزان مطلوبی توسط آن تامین گردد. همچنین تحلیل های غیرخطی تاریخچه زمانی در نمونه هایی از سازه های 6 طبقه برای شتاب نگاشت های مختلفی انجام گرفته که بیانگر رفتار قابل قبول این سازه ها در صورت استفاده از این مهاربند می باشد.
http://mcej.modares.ac.ir/article-1-20196-fa.pdf
2019-05-15
117
129
مهاربند مرکزگرا
کاهش تغییرشکل پسماند
کابل های پیش تنیده
میراگر دندانه-شانه ای
Introduction and Investigation of a New Steel Brace with Self-Centering and Energy Dissipating Capabilities
Current design philosophy for conventional lateral resisting systems is that the frames should not collapse during major earthquakes, however significant structural damage in elements such as beams, braces and sometimes columns may occur. The presence of residual drift due to inelastic deformations may hinder building occupancy or functionality after major earthquakes, and may increase associated repair costs significantly. During last two decades, practicing engineers and researchers have tried to develop seismic resisting systems that can minimize and potentially eliminate residual drift due to earthquakes. Proposed structural systems utilize the so-called “self-centering” systems that can improve the seismic behavior, provide higher resiliency and overcome the significant residual drift of conventional systems. Self-centering (SC) seismic resistant systems, introduced in the literature are developed for both steel and concrete structures. For the steel structures, they may be categorized into three primary groups: SC moment frames, SC rocking systems and SC braced frames. The most important similarity between self-centering systems is that the lateral load resistance of the system has a flag-shaped hysteretic loop. That is the characteristic of systems that self-center after large lateral displacements. Considering the normal practices of construction industry in Iran, it is more feasible and favorable to use metal yielding dampers instead of viscous or friction dampers. Also considering the economic issues, self-centering mechanisms which use pretension tendons are more feasible compared to shape memory alloys. A yielding metallic damper called comb-teeth damper (CTD) provides energy dissipation mechanism. CTD is made of steel plates and includes a number of teeth that dissipate energy through in-plane flexural yielding. The new self centering brace (SCB) can substitute the conventional braces to provide desired seismic performance and to reduce residual deformations and repair costs. The proposed brace can be easily disassembled in the field which provides the possibility of inspection of the core after a large earthquake. Parameters of this system should be selected so that they can provide appropriate stiffness, strength and energy dissipating capacity. In this paper, initially the overall mechanical behavior of the device has been defined in terms of its internal components, based on an analytical approach. The mechanical equations for the SCB were decomposed into two portions, which are the pretension tendons that cause the self-centering behavior and the CTD links that support the energy dissipation mechanism. Also finite element analysis has been conducted to verify the hysteretic responses and mechanics of the proposed SCB. Based on the results, the characteristics of finite element responses have good similarity with the analytical results and show that either of the approaches are reasonable to predict the SCB behavior. Then a parametric finite element analysis has been conducted by varying the mechanical properties of steel elements to optimize the properties of the system. The results show that the desired self centering and energy dissipating capacities would be achieved using the new SCB. Lastly, nonlinear time history analyses have been performed to investigate the characteristics of some 6 story steel buildings equipped with the new SCBs. The results confirm the feasibility of using the new SCBs in braced frame structures.
http://mcej.modares.ac.ir/article-1-20196-en.pdf
2019-05-15
117
129
Self-centering system
Energy dissipating dampers
reducing residual deformations
Comb-teeth damper
Mohsen
Heidari
1
Department of civil and environmental engineering, Tarbiat Modares university, Tehran, Iran
AUTHOR
Aliakbar
Aghakouchak
2
Tarbiat Modares University, Tehran
AUTHOR
ORIGINAL_ARTICLE
تاثیر نامنظمی سختی جانبی بر نیاز زاویه درز انقطاع قاب های خمشی فولادی مجاور تحت زلزله های حوزه نزدیک گسل
به دلیل عدم رعایت درز انقطاع لازم بین ساختمان های مجاور، پدیده برخورد (ضربه) در هنگام وقوع زلزله رخ می دهد. ضربه می تواند منجر به خسارات موضعی به ستون های محل برخورد، خسارات موضعی یا کلی کف ها در تراز برخورد و یا منجر به فروریزش کلی ساختمان شود. از طرفی وجود نامنظمی سختی جانبی(طبقه نرم یا خیلی نرم) به دلیل تغییر در نوع کاربری اولین طبقه ساختمان، از رایج ترین انواع نامنظمی است. این مقاله به تخمین نیاز زاویه درز انقطاع در بالاترین تراز برخورد دو سازه مجاور در ترکیب قاب های خمشی فولادی منظم و دارای نامنظمی سختی جانبی با تغییر در ارتفاع طبقه اول، تحت رکوردهای زلزله حوزه نزدیک گسل می پردازد. بدین منظور قاب های خمشی فولادی 2 تا 20 طبقه 3 دهانه منظم و نامنظم در هفت گروه از ترکیبات دوتایی در مجاورت یکدیگر قرار می گیرند و زاویه درز انقطاع آنها با تحلیل دینامیکی تاریخچه زمانی غیرخطی محاسبه و مقایسه می گردد. نتایج بدست آمده حاکی از آن است که افزایش مقدار نامنظمی سختی جانبی در اولین طبقه سازه، می تواند منجر به افزایش زاویه درز انقطاع در 84 % از ترکیبات همجواری بررسی شده گردد. ضریب میانگین این افزایش در کلیه حالات تحت تاثیر مورد بررسی از ترکیب قاب های منظم و نامنظم با ارتفاع طبقه اول 5/4 و 5/5 متر، به ترتیب 19/1 و 38/1 برابر ترکیبات قاب های منظم است.
http://mcej.modares.ac.ir/article-1-16931-fa.pdf
2019-05-15
131
140
زاویه درز انقطاع
تراز برخورد
نامنظمی سختی جانبی
ساختمان های مجاور
تحلیل تاریخچه زمانی
The Effect of the Irregularity of Lateral Stiffness on the Demand of Separation Gap Angle in Steel Moment Frames Under
Near-Field Earthquakes
In crowded cities, building structures are usually constructed in close proximity to one another because of restricted availability of space. In many cases, every building in a block is in full or partial contact with its neighboring buildings. Because of insufficient separations, their different heights and seismic-resisting systems collision can occur between adjacent buildings during strong ground motions. This collision can make partial or general damages to the structural elements and accelerate their failure by affecting their stiffness. This phenomenon is commonly referred to as structural pounding. Pounding between inadequately separated buildings has been observed in most previous major earthquakes. Each time pounding occurs, building structures will sustain short duration large impact force not specifically considered in conventional designs. The severity of the impact depends on the dynamic characteristics of the adjacent buildings in combination with the earthquake characteristics. options to minimize the effect of pounding have to do with the decreasing of lateral motion by joining adjacent buildings at critical positions so that their motion could be in-phase or by increasing the damping capacity of building pounding by means of energy dissipation, for example, by passive structural control systems. Modern seismic design codes have many pioneering provisions on the non-linear behavior of structures, but amongst others, they do not consider structural pounding, a phenomenon with strong non-linearities, for which codes usually suggest a sufficient separation between adjacent buildings. On the one hand, irregularity in lateral stiffness (a soft or very soft story) due to the different use of the first floor of the building is one of the most common types of irregularity. Aiming to prevent such collisions, these study estimates demand of separation gap angle at the highest level of collision between two adjacent structures in regular steel moment frames with irregularity in the lateral stiffness (with changes in the height of the first floor) under seismic records of a near-field earthquake. Models were considered as two-dimensional, ductile, steel moment frames of 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20-story 3-span buildings. In order to create an irregularity in the lateral stiffness on the first floor, the height of this story was increased from 3.5 m to 4.5 and 5.5 m while the cross-section of the column at the first two stories was kept unchanged. These frames can be placed alongside in seven binary groups considering priority in the arrangement. Each group represents 100 different binary arrangements of the frames. In total, 700 cases of various adjacency were studied. The OPENSEES software was used to analyze the dynamics of the nonlinear history considering 20 perpendicular components to the fault with a progressive orientation of near-field earthquake records of pulse-like faults. The results suggest the increase in the irregularity in the lateral stiffness in the first floor of the building can increase the separation gap angle. On average, the combination of regular and irregular frames with the first-floor height of 4.5 and 5.5 m, is increased 1.19 and 1.38 times, respectively, compared to the combinations of regular frames. Moreover, among various adjacent combinations of regular and irregular frames, in case the taller structure is associated with lateral stiffness (soft floor), the average increase in the separation gap angle is larger than other cases.
http://mcej.modares.ac.ir/article-1-16931-en.pdf
2019-05-15
131
140
Separation Gap Angle
Collision Level
Irregularity of Lateral Stiffness
Adjacent Buildings
Time History Analysis
mostafa
khatami
1
Semnan University
AUTHOR
Mohsen
Gerami
2
Semnan- Semnan university
AUTHOR
Ali
Kheyrodin
3
Semnan University
AUTHOR
ORIGINAL_ARTICLE
شبیهسازی عددی رفتار زهکشینشده خاک دانهای با ذرات چندگوشه به کمک روش اجزای مجزا
در پژوهش حاضر، از روش اجزای مجزا برای شبیهسازی دو بعدی رفتار زهکشینشده در مصالح دانهای چندگوشه استفاده شده است. برای شبیهسازی عددی رفتار زهکشینشده از دو روش حجم ثابت و استوانه استفاده شده و نتایج حاصل از هر دو روش با یکدیگر مقایسه گردید. در روش استوانه فرض میشود که لولهای میان حفرات مجاور وجود دارد و امکان تبادل آب بین مراکز حفرات فراهم میشود. در این روش، قطر استوانه نمایندهای از نفوذپذیری خاک است. در روش حجم ثابت فرض میشود که حجم نمونه طی بارگذاری ثابت میماند. شبیهسازی به کمک هر دو روش برای نمونههایی انجام شده است. این نمونهها تحت تنش همهجانبه 200 کیلوپاسکال قرار گرفته و پس از تحکیم همهجانبه، تحت بارگذاری انحرافی قرار گرفته است. نتایج نشان داد که پاسخهای حاصل از روش استوانه انطباق خوبی با روش حجم ثابت دارد و با افزایش سختی آب، نتایج هر دو روش بهم نزدیکتر میشوند. رفتار زهکشینشده برحسب مقاومت برشی و فشار آب حفرهای متوسط در نمونه ماسهای در تنشهای همهجانبه 800،400،200 و 1600 کیلوپاسکال به کمک روش استوانه مورد بررسی قرار گرفت. نتایج شبیهسازی انطباق خوبی با نتایج آزمایشگاهی دارد، بطوریکه در نمونه تحت تنش همهجانبه بیشتر، مقاومت برشی و فشار آب حفرهای متوسط مثبت بیشتری بوجود میآید، ولی با افزایش فشار همهجانبه، مقدار فشار آب حفرهای متوسط در نمونه کاهش مییابد. در انتها گستردگی توزیع فشار آب حفرهای متوسط در نمونه در کرنشهای 10 و 30 درصد به کمک روش استوانه نشان داده شد و تاثیر تغییرات قطر استوانه در گستردگی توزیع فشار آب مورد بررسی قرار گرفت. بررسی گستردگی توزیع فشار آب حفرهای متوسط در کرنشهای 10 و 30 درصد نشان داد که فشار آب در مرکز نمونه دارای کمترین مقدار است. همچنین با افزایش قطر استوانه، فشار آب در کل حفرات نمونه، بهم نزدیک میشود. در حالیکه هرچه قطر استوانه کمتر باشد، اختلاف فشار آب در حفرات نمونه بیشتر میشود.
http://mcej.modares.ac.ir/article-1-21021-fa.pdf
2019-05-15
141
153
ذرات چندگوشه
روش استوانه
روش اجزای مجزا (DEM)
شبیهسازی عددی
Numerical simulation of undrained behavior of granular materials with polygonal particles by discrete element method (DEM)
In the present study, discrete element method is used to simulate undrained two-dimensional behavior of soil samples containing polygonal particles. Two methods of constant volume and cylinder were used for numerical simulation of undrained behavior and the results from these two methods were compared. In the cylinder method, it is assumed that there are channels among adjacent pores and the possibility of water exchange among the centers of the pores is provided. In this method, the diameter of the cylinder represents the permeability of the soil. In the constant volume method, it is assumed that the sample volume stays constant during loading. The simulations were done by using both methods. The samples were initially subjected to confining pressure of 200 kPa and after consolidation, they were loaded under deviatoric stress. The results showed that the output obtained by the cylinder method are in good agreement with the constant volume method, and by increasing the stiffness of the water, the results of both methods are closer to each other. Then, the undrained behavior was investigated by using cylinder method in terms of shear strength and pore water pressure in a sand sample at the confining pressures of 200, 400, 800 and 1600 kPa. The trend obtained from the simulation results is in good agreement with laboratory results such that with bigger confining pressure, the shear strength and the positive pore pressure are bigger too, but by increasing confining pressure, the amount of pore pressure decreases in the specimen. The pore pressure distribution contour at the strains of 10% and 30% was presented by means of cylinder method and the effect of cylinder diameter changes on the pore pressure distribution contour was investigated. By investigating the pore pressure distribution contour at the strains of 10% and 30%, it was shown that pore pressure in the sample center has the lowest value. In addition, it was seen that by increasing the cylinder diameter, the variation of pore pressure among the voids becomes smaller, which indicates the uniformity of the pore pressure in permeable soils. By reducing the diameter of the cylinder, the variation of pore pressure becomes more through the sample.
http://mcej.modares.ac.ir/article-1-21021-en.pdf
2019-05-15
141
153
Polygonal particles
Cylinder method
Discrete element method (DEM)
Numerical simulation
Masoud
Khabazian
masoud_khabazian@yahoo.com
1
Ferdowsi University of Mashhad
AUTHOR
Ehsan
Seyedi Hosseininia
eseyedi@um.ac.ir
2
Ferdowsi University of Mashhad
AUTHOR
ORIGINAL_ARTICLE
حل عددی معادله حاکم بر فرایند بیوالکتروسینتیک در تصفیه خاک رسی آلوده به نفت خام
روش بیوالکتروسینتیک جهت کاهش محدودیتهای هر یک از فرایندهای بیولوژیکی و الکتروسینتیک تنها در تصفیه آلایندههای آلی از خاکهای ریزدانه، کاربرد دارد. در این روش تلفیقی، فرایند بیولوژیکی در تجزیه آلایندهها و فرایند الکتروسینتیک در تسریع و جهتدهی انتقال آلایندهها و میکروارگانیسمها نقش دارند. هدف از انجام این تحقیق، تعیین معادلات و شرایط حاکم بر فرایند بیوالکتروسینتیک در تصفیه خاک رسی آلوده به نفت خام میباشد. به منظور توسعه و صحت سنجی مدل، ابتدا به راه اندازی سیستم تلفیقی بیوالکتروسینتیک در مقیاس آزمایشگاهی پرداخته شد. آزمایشهای بیوالکتروسینتیک در راکتورهای استوانهای از جنس پلکسی گلاس به طول 55 و قطر 5 سانتیمتر و با استفاده از خاک آلوده به نفت خام و اعمال میدان الکتریکی با شدت مشخص، در حضور سویه Pseudomonas Putida انجام شدند. از سوی دیگر، پس از تعیین و تلفیق معادلات حاکم بر فرایند الکتروسینتیک و سینتیک تجزیه زیستی، با کدنویسی در نرم افزار متلب حل عددی معادله مورد نظر انجام شد. در ادامه، ضمن مقایسه نتایج حاصل از حل عددی مدل پیشنهادی با نتایج آزمایشگاهی، روند یکسانی در تغییرات غلظت نفت خام بین این دو مشاهده گردید. به علت وجود اختلاف بین نتایج مدل و دادههای آزمایشگاهی و به منظور تطابق بیشتر بین این دو، از ضریب اصلاحی مربوط به فاکتور انتقال میکروارگانیسمها تحت میدان الکتریکی استفاده گردید. بدین صورت تطابق بهتری بین نتایج حل عددی و دادههای آزمایشگاهی روش تلفیقی مشاهده شد. طبق نتایج حاصل مدل پیشنهادی توانسته میزان غلظت باقیمانده نفت خام پس از تصفیه به روش بیوالکتروسینتیک را با تطابق خوبی پیشبینی نماید.
http://mcej.modares.ac.ir/article-1-20184-fa.pdf
2019-05-15
155
167
نفت خام
خاک رسی
روش بیوالکتروسینتیک
مدلسازی
حل عددی
Numerical solution of the equation governing on bioelectrokinetic process in remediation of clayey soil contaminated with crude oil
Removal of petroleum hydrocarbons from contaminated soil using electrokinetic method or biological processes has been considered in recent century. The most limiting factors in the electrokinetic process are extreme changes in pH around the electrodes and non-polarity of some pollutants. On the other hand, the key factor of biological treatment is simultaneous presence of microorganisms, pollutants (carbon source of microorganisms), electron acceptors, and essential nutrients for microorganisms’ growth. But in fine-grained soils with low permeability, it is difficult to uniformly distribute bacteria, electron acceptors and nutrients, or making pollutants available for microorganisms. To solve these problems, bioelectrokinetic method is used to eliminate the limitations of both biological and electrokinetic processes in treatment of fine-grained soil contaminated with organic compounds. In this integrative approach, the biological method has a role in biodegradation of pollutants. Whiles, the electrokinetic process can direct and accelerate the transfer of pollutants and microorganisms. The aim of this study is determining the equations and conditions governing on bioelectrokinetic process in removal of crude oil from clayey soil. For this reason, the numerical method of FTCS finite-difference was applied for modeling the pollutant biodegradation and transmission in clayey soil under electric field. In order to develop and validate the model, the first step was to set up a bioelectrokinetic system in a laboratory scale. In this study, each test was conducted in cylindrical cell made of Plexiglas with the length and diameter equal to 55 and 5 cm respectively, for 35 days. They were performed in various conditions of pollution amount and electric field intensity in the presence of Pseudomonas Putida strain. On the other hand, after determining and combining the governing equations on the electrokinetic and biodegradation system, the numerical solution of the equation was coded using Matlab software. In suggested mathematical model, the parameters like initial concentration of crude oil, voltage gradient, time step and spatial step were assumed as variables and parameters related to reactor, soil and pollutant such as the length of reactor, soil porosity and tortuosity, ion mobility, diffusion coefficient and electroosmosis permeability coefficient were considered as constants. In continue, by comparison the result of numerical solution of the suggested model with the experimental results, the same trend was observed in changes in crude oil concentration between the two. Because of differences between the model results and laboratory data and to make more accordance between the two, the modifying factor was used as the factor of microorganism transfer under electric field. In this way, by addition of modifying coefficient in model, a better accordance between them was observed and this difference reduced to minimum. Modeling results showed that electroosmosis, diffusion and electromigration mechanisms, unlike biodegradation, had little impact on the transmission and removal of oil from soil. According to the numerical solution, similar to bioelectrokinetic data, increasing the initial concentration of oil and voltage gradient caused the increase in removal efficiency of oil. In addition, the model has been able to predict the residual crude oil concentration after bioelectrokinetic treatment with a good accordance.
http://mcej.modares.ac.ir/article-1-20184-en.pdf
2019-05-15
155
167
Crude oil
Clayey soil
Bioelectrokinetic method
Modeling
Numerical solution
Behnoosh
Khataei
1
Civil and Environment Eng. Faculty, Tarbiat Modares University
AUTHOR
Nader
Mokhtarani
2
Assistant Professor, Civil & Environmental Engineering faculty, Tarbiat Modares University
AUTHOR
Hossein
Ganjidoust
3
Civil & Environmental Engineering Faculty, Tarbiat Modares University
AUTHOR
ORIGINAL_ARTICLE
تاثیر اندازه نمونه بتن مسلح به الیاف ماکروسینتتیک بر عمر خستگی خمشی
بتن به عنوان یکی از پرکاربردترین مصالح ساختمانی رفتاری شکننده دارد. افزودن الیاف به بتن بر رفتار شکل پذیری مقاومت کششی ، مقاومت خمشی ، مدول الاستیسیته ، مقاومت ضربه و برخی مشخصات مکانیکی دیگر بتن اثر میگذارد. به همین منظور پژوهشی آزمایشگاهی جهت ارائه مدل تجربی عمر خستگی خمشی بتن مسلح به الیاف ماکروسینتتیک با ساخت تیرچه بتنی با سه ضخامت مختلف 80، 100 و 150 میلیمتر انجام شد و مدل های S-N (سطح تنش - بارگذاری) و H-N (ضخامت-بارگذاری ) ارائه شد. نتایج نشان داد که با افزایش ضخامت نمونه های بتنی و افزودن الیاف به مخلوط بتنی مقدار عمر خستگی افزایش می یابد. همچنین اضافه نمودن الیاف به نمونه های بتنی ضخامت نمونه را برای سطح تنش 0.7 تنش نهایی به میزان 12.45-8.24 % ، برای سطح تنش 0.8 تنش نهایی به میزان 22.15-5.45 % و برای سطح تنش 0.9 تنش نهایی به میزان 22.95-10.18 % کاهش می یابد.
http://mcej.modares.ac.ir/article-1-17176-fa.pdf
2019-05-15
169
179
بتن مسلح به الیاف
تاثیر اندازه
عمر خستگی
ضخامت نمونه
the effect of specimen size on Flexural Fatigue Life of macro-synthetic-fiber-reinforced concretes
Concrete is one of the most widely used building materials for fragile behavior. The addition of fiber to concrete affects the behavior of tensile strength, tensile strength, flexural strength, modulus of elasticity, impact resistance and some other mechanical properties of concrete. For this purpose, an experimental research was carried out to provide an experimental model of the flexural fatigue life of reinforced concrete with macrosynthetic fibers by constructing concrete joists with three different thicknesses of 80, 100 and 150 mm. SN models (stress-loading) and HN (thickness-loading) was presented. The results showed that increasing the thickness of concrete samples and adding fibers to concrete mixture increases the fatigue life. Also, the addition of fibers to concrete samples measured the thickness of the sample for the stress level of 0.7 final stresses at 12.45-8.24%, for the stress level of 0.8, the final stress was 22.15-5.45%, and for the stress level of 0.9, the final stress decreased to 22.15% -10.18% Finds. Fiber-reinforced concrete is a type of concrete that is mixed with fiber. Various types of fibers are used to produce fiber-reinforced concrete, which include glass, polymer, carbon and steel. In the present research, macro-synthetic polymer fibers were used. Some of the consequences of applying macro-synthetic fibers in concrete include reduced shrinkage of fresh and hardened concrete, increased ductility, increased strength against fatigue stresses, increased durability and lifetime of concrete, improved concrete mechanical properties (tensile strength, flexural strength, etc.), control of secondary/thermal cracks of concrete, preventing the in-depth propagation of cracks, post-cracking chargeability and reduced permeability against chloride and sulfate ions .In most of the studies, the concrete sample's thickness is increased along with the increase in the beam's length; however, in the present work, only thickness of the beam samples with and without fibers was changed and other dimensions of the samples were kept constant in order to investigate merely the effect of increased thickness. Accordingly, effect of the size of macro-synthetic fiber-reinforced concrete sample at different thicknesses was assessed via fatigue life variations. The intertwisted fibers were added to the concrete mixture by 0.4 vol.%. Then, from each sample, three specimens were made. The obtained results were averaged and, then, recorded in the relevant tables. The following cases were considered as the research objectives: - Effect of sample size on fatigue life of concrete samples - Effect of adding macro-synthetic fibers on fatigue life In order to determine flexural fatigue of the concrete samples with the above-mentioned geometric properties, UTM device was used. The test was performed with constant sinusoidal loading at the frequency of 10 Hz. The input information for the test included loading curve shape, minimum and maximum loading values, loading frequency, and maximum number of loadings, all of which were defined as the input. To measure the values of stress levels in order for measuring the loading values, first, the average of the samples' flexural strength had to be determined; then, the stress levels could be calculated from the obtained results. also A cross sectional analysis of the broken sample showed that most of the sample failure was from aggregate and the mixture design was suitable.
http://mcej.modares.ac.ir/article-1-17176-en.pdf
2019-05-15
169
179
fiber reinforced concrete
size effect
fatigue life
specimen thickness
mohammad
daneshfar
1
دانشجوی دکتری دانشگاه تربیت مدرس
AUTHOR
Abolfazl
Hassani
Hassani@modares.ac.ir
2
Tarbiat Modares University, Jalal Ale Ahmad Highway, P.O.Box: 14115-333, Tehran, Iran
AUTHOR
mohammadreza
mohammadaliha
3
استادیار دانشکده مهندسی صنایع
AUTHOR
ORIGINAL_ARTICLE
بررسی آزمایشگاهی هیدرولیک جریان در سرریزهای اوجی متأثر از تقرب دیوارههای هدایت کننده (مطالعه موردی: سد گرمی چای)
سرریزهای اوجی به دلیل اقتصادی بودن و سهولت طراحی و اجرا به عنوان یکی از سازههای متداول برای تخلیه و اندازهگیری جریان استفاده میشود. در این پژوهش روی طرح اولیه مدل فیزیکی با مقیاس 1:75 سرریز سد گرمی چای که از نوع اوجی و دیوارههای هادی متقارب به سمت پاییندست است انجام گرفت و تأثیر تغییرات زاویه همگرایی دیوارههای هادی سرریز در بازه 0 تا 120 درجه بر پارامترهای هیدرولیکی جریان شامل ضریب دبی، پروفیل سطح آب، عمق و فشار بررسی شد. دلیل استفاده از این نوع سرریز، کاهش عرض سرریز در پنجه نسبت به طول تاج آن به مقدار %78 در طرح اولیه (زاویه 120) بدلیل شرایط خاص منطقهای است. مشاهدات نشان داد تا قبل از استغراق، برای همه زوایا با افزایش بار آبی بالادست، ضریب دبی نیز افزایش مییابد. همچنین تغییر زاویه همگرایی دیوارههای هادی تأثیر قابل ملاحظهای بر ضریب دبی سرریز ندارد اما هنگامی که سرریز در مرحله استغراق قرار میگیرد، هر چه زاویه بزرگتر باشد نرخ کاهشی ضریب دبی بیشتر است. بر این اساس، زاویه صفر درجه غیر مستغرق بالاترین ضریب دبی نسبی با مقدار 07/1 را در بین تمامی زوایای همگرایی به خود اختصاص داد. تنها زوایای صفر و 60 درجه در بین زوایای مذکور توان عبور حداکثر دبی سیلاب محتمل(QPMF) در حداکثر ارتفاع مجاز آب بالادست (Hmax) را دارا بودند که از این بین زاویه 60 درجه با توجه به عرض کمتر در قسمت پنجه، 69 درصد کاهش عرض در این ناحیه نسبت به زاویه صفر درجه، به عنوان زاویه مناسب در بین این زوایا انتخاب شد.
http://mcej.modares.ac.ir/article-1-48885-fa.pdf
2019-05-15
181
193
سرریز اوجی
عملکرد هیدرولیکی
زاویه تقرب
دیوارههای هادی متقارب
Experimental Study of Flow Hydraulics in Ogee Spillways Affected by Converging Training Walls (case study: Germi Chay Dam)
The most typical kind of spillways is the ogee spillway. The advantages of the ogee spillway are its simple design, its steady overflow pattern, and the simplicity to pass flows, in comparison with the other spillways and the closely associated lower prices. In the present study, a 1:75 scale physical model was utilized to assess the impact of converging vertical training walls on the flow quantities in the ogee spillway. In this regard, this structure was tested in varying convergence of training walls ranging from 0 to 120°. The experiments were conducted at the Soil Conservation and Watershed Management Research Institute (SCWMRI) in Tehran, Iran. The results of the experiments indicated that in the converging ogee spillway by increasing total upstream head, the discharge coefficient will go up for each of the convergence angles (θ’s) and before submergence stage for the spillway, the discharge coefficient is independent of converging situations. At a 0ᵒ convergence angle (with ratio of ), having free flow condition for each of the tested discharges, the highest ratio of relative discharge coefficients was 1.07. By contrast, at the submergence stage for the spillway, the difference in the discharge coefficient was observed noticeably. On the other hand, when the spillway was submerged, there is a decrease in the coefficient can be caused by tailwater submergence and it causes the differences in the discharge coefficient for each of the θ’s. For instance, the ratio of coefficient to the discharge coefficient (C/Cd) in 120° convergence, despite went up remarkably to just over 1.0 in H/Hd=1, the mentioned values then significantly dropped in H/Hd>1.8. Also, the data obtained from flow depth and static pressure distribution along the spillway in various convergence angles indicates that as θ increases, the flow depth and static pressure increases at the bottom and the toe of the spillway model. For instance, the flow depth along the convergence angle of 120 ̊ at station 4.3, was nearly 6.2 times greater than the flow depth generated along the 0 ̊ convergence. The range of flow depth changes with any increase in the total upstream head near the walls can be used to estimate the minimum side wall height requirements to decrease overtopping for future site utilizing similar design criteria. It can be inferred from experimental results that 60° convergence with ability to pass the probable maximum flood in the Maximum head allowed can be selected as the most economic convergence angle. This convergence angle was chosen because downstream channel width of it is 69% lesser than that in 0° convergence having capability to pass the probable maximum flood in the Maximum head. This study was aimed to evaluate the impact of converging training walls of the ogee spillway on flow characteristics. Experimental result showed that where the downstream flow is at supercritical stage or where the hydraulic jump occurs, the convergence angles variations has no effect on the discharge coefficient considerably, but when the spillway is submerged, there is a decrease in the coefficient which can be caused by tailwater submergence. In addition 60° convergence having the smallest downstream channel width required to pass the probable maximum flood in the Maximum head allowed can be selected as the most economic convergence angle.
http://mcej.modares.ac.ir/article-1-48885-en.pdf
2019-05-15
181
193
ogee spillway
hydraulic performance
convergence angles
training wall
1
AUTHOR
ORIGINAL_ARTICLE
بررسی اثرات دیوارهای هادی جریان بر عملکرد هیدرولیکی سرریزهای کنگرهای قوسی
استفاده از سرریزهای کنگرهای بعنوان یک راه مؤثر و اقتصادی جهت افزایش ظرفیت آبگذری مطرح میباشد. قرارگیری سیکلهای سرریز کنگرهای بر روی قوسی از یک دایره میتواند بهبود جهتگیری سیکلهای سرریز نسبت به جریان ورودی و نیز افزایش طول تاج بازای یک عرض معین را سبب گردد. این تحقیق به بررسی آزمایشگاهی اثرات دیوارهای هادی جریان بر عملکرد سرریزهای کنگرهای قوسی میپردازد. ضمن بررسی اثرات پارامترهای نسبت بار هیدرولیکی به ارتفاع سرریز (Ho/P)، زاویه دیوار جانبی سرریز (α) و زاویه انحنا (Θ) بر ضریب آبگذری و کارآیی سرریزهای کنگرهای قوسی، اثرات زاویه بین دیوارهای هادی جریان (Θ′) نیز بر این مهم مورد تحقیق قرار گرفته است. نتایج نشان میدهد که قوسیکردن سرریز کنگرهای میتواند بهبود کارآیی آن را سبب گردد. علیایحال با افزایش بار هیدرویکی، کارآیی سرریزهای کنگرهای قوسی کاهش مییابد. در مقادیر پایین زاویه انحنا، انتخاب مناسب زاویه بین دیوارهای هادی جریان میتواند تا حدود 20 درصد کارآیی سرریز را بهبود بخشد. لیکن اثرات این پارامتر در مقادیر بالای زاویه انحنا قابل صرفنظر کردن میباشد.
http://mcej.modares.ac.ir/article-1-19866-fa.pdf
2019-05-15
195
206
ظرفیت آبگذری
دیوارهای هادی جریان
ضریب آبگذری
کارآیی
سرریز کنگرهای قوسی.
Investigation of Effects of Entrance Channel Walls on the Hydraulic Performance of Arced Labyrinth Weirs
Labyrinth weir is one of the approaches to increase the discharge capacity. An arced configuration improves the orientation of the labyrinth weir cycles to the approach flow and increases the weir crest length for a given width. In this study, the effects of the entrance flow conditions on the hydraulic performance of the arced labyrinth weirs is studied experimentally. The effects of the angle between the entrance channel walls (Θ′) on the discharge coefficient and the efficiency are investigated for different values of the headwater ratio (Ho/P), the downstream sidewall angle (α), and the weir arc angle (Θ). Experiments were conducted in a recirculating flume which is 10 m long, 2 m wide, and 0.9 m deep at Tarbiat Modares University. To simulate the reservoir conditions, a specific setup was added to the flume, known as the reservoir simulator. The flume was launched from its two ends by two pipelines. The inflow passes from underneath of the reservoir simulator and enters into it through a semi-circular opening in its horizontal wall. After moving over the horizontal wall, the flow comes up through the gap between the vertical wall. Finally, it flows on the platform and moves towards the downstream channel. All the plates (including the platform and the simulator walls) have a semicircular plan-view with a porosity equal to zero. The weirs were mounted on the platform at the entrance of the downstream channel. Totally 132 experiments were conducted to investigate the effects of the mentioned parameters on hydraulic performance of arced labyrinth weirs. Due to the nappe interference, the local submergence forms in the downstream of the labyrinth weirs. The size of local submergence regions increase by increasing the headwater ratio and the arc angle. However, vice versa trend occurs with the downstream sidewall angle. In addition, for low values of the arc angle, the lateral flow from the side cycles to their adjacent cycles produces the surface turbulences. The results indicate that the discharge coefficient decreases by increasing the headwater ratio and the downstream sidewall angle. For low values of the headwater ratio, the discharge coefficient increases when the arc angle increases. However, a decreasing trend is observed in high head conditions. By increasing the arc angle and decreasing the downstream sidewall angle, the efficiency of a labyrinth weir can be increased. However, the efficiency gains diminish by increasing the headwater ratio. The efficiency of a labyrinth weir can slightly be increased by projecting of the cycles into a reservoir for low values of Ho/P, α, and Θ. However, in the wide range of the research domain, the efficiency decreases when the angle between the entrance channel walls increases. According to the results of this research, the efficiency of a labyrinth weir can be increased up to 20% by channelizing abutments in high head conditions. However, the effect of Θ′ is insignificant for higher values of Θ. In addition, as α decreases, the benefits and the losses of decreasing Θ′ become more severe at higher and lower values of Ho/P, respectively.
http://mcej.modares.ac.ir/article-1-19866-en.pdf
2019-05-15
195
206
Discharge
Entrance channel walls
Discharge coefficient
Efficiency
Arced labyrinth weir
yousef
sangsefidi
yousef.sangsefidi@modares.ac.ir
1
Tarbiat Modares University
AUTHOR
Masoud
Ghodsian
ghods@modares.ac.ir
2
Tarbiat Modares University
AUTHOR
ORIGINAL_ARTICLE
پیش بینی مقاومت فشاری بتن خودتراکم حاوی خاکستر پوسته برنج با استفاده از مدلهای داده مبنا
ساخت و نگهداری روکشهای بتنی از مسائل مهم و پرهزینه در دهه اخیر بوده است. ازاین رو، استفاده از بتن خودتراکم به عنوان بتنی با ویژگی های مقاومتی مطلوب و آلایندگی پایین مورد توجه قرار گرفته است. خواص مقاومتی بتن خودتراکم به فاکتورهای مهمی از نسبتهای اختلاط وابسته بوده که لزوم پژوهش های آزمایشگاهی و آنالیزهای کامپیوتری هوشمند در ساخت آن را نمایان ساخته است. تعیین میزان بهینه مواد تشکیل دهنده بتن به منظور رسیدن به مقاومت مطلوب، صرفه جویی در تعداد دفعات آزمایش و کاهش هزینه های انجام آزمایشها ارائه مدلهای رگرسیونی محاسباتی برای تخمین خواص مقاومتی بتن را مورد توجه قرار داده است. هدف اصلی در این مطالعه ارائه رابطهای محاسباتی برای تخمین مقاومت فشاری بتن خودتراکم حاوی خاکستر پوسته برنج (RHA) با استفاده از رویکرد قدرتمندی به نام برنامه نویسی بیان ژن (GEP) میباشد. برای ارزیابی عملکرد مدل پیشنهادی GEP مطالعهای مقایسهای با استفاده از روشهای کلاسیک مدلسازی داده مبنای شبکه عصبی مصنوعی (ANN) و رگرسیون خطی چندگانه (MLR) نیز انجام شد. مجموعه داده های قابل اطمینان و مناسبی شامل 156 نمونه مقاومت فشاری حاوی RHA از مقالات معتبر جمع آوری و مورد استفاده قرار گرفت. عملکرد مدلهای پیشنهادی ارائه شده با استفاده از شاخصهای خطای ضریب همبستگی (R)، ریشه میانگین مربعات خطا (RMSE) و میانگین خطای مطلق (MAE) محاسبه و ارزیابی گردید .نتایج شاخصهای خطا در ارزیابی عملکرد مدلهای توسعه داده شده نشان داد روش GEPدقت قابل توجه و مقادیر خطای کمتری در محاسبه داشته است. همچنین رابطه محاسباتی براساس عبارات بیان ژنی در روش GEP برای پیش بینی مقاومت فشاری در سنین مختلف ارائه شد که با شاخص همبستگی 0.94 و مقادیر خطای 4-5 مگاپاسکال دقت قابل توجهی را نشان داده است. رابطه ارائه شده به آسانی می تواند برای پیش طراحی نسبتهای اختلاط و همچنین کنترل سریع راه حلهایی قطعی مورد استفاده قرارگیرد .تحلیل حساسیت برای مشخص کردن مقادیر تاثیرگذار در مدل مقاومت فشاری ارائه شده نشان داد، متغیر چسباننده در این مدلسازی نسبتهای اختلاط بیشترین تاثیر عملکردی را ایفا نموده است.
http://mcej.modares.ac.ir/article-1-20432-fa.pdf
2019-05-15
209
221
بتن خودتراکم
برنامه نویسی بیان ژن
شبکه عصبی مصنوعی
رگرسیون خطی چندگانه
مقاومت فشاری
پیش بینی
Prediction of the Compressive Strength of Self-compacting Concrete containing Rice Husk Ash using Data Driven Models
The construction and maintenance of structural pavement was a high-cost problem in last decade. The mechanical properties of self compacting concrete (SCC) required important factors .From its mechanical properties, the compressive strength (CS) is necessary to investigate experimental and computational intelligence analysis in construction materials. Developing models with accurate estimation for this key property caused to saving costs and time and producing an optimal blend. Because of the many advantages, using of SCC in structures is increasing. Construction of precast-prefabricated components, with the use of concrete has also recently been considered. Concrete properties have significant role in precast-prefabricated girders behavior. Exact prediction of these properties is the base of member’s analysis and design. The main purpose of this study is presents new formulation to estimate the compressive strength of self-compacting concrete containing rice husk ash (RHA) using robust variant of genetic programming, namely gene expression programming (GEP) method. To evaluate the performance of the GEP-based proposed model, prediction was also done using classical data driven methods named artificial neural network (ANN) and multiple linear regression (MLR) models. A large and reliable experimental database containing the results of 156 compressive strength of SCC incorporating RHA is collated through an extensive review of the literature. The performance of proposed models of CS is then assessed using the database, and the results of this evaluation are presented using selected performance measures. New expressions for the estimation of CS of SCC are developed based on the database. To evaluate the modeling performances of the proposed GEP models for CS, different statistical metrics were used. Correlation coefficient (R), root mean square error (RMSE), mean absolute error (MAE) were used as the measure of precision. The results showed that the models developed using the aforementioned methods have accuracy over 90 percent in prediction of CS of SCC. The results of testing datasets are compared to experimental results and their comparisons demonstrate that the GEP model (R=0.94, RMSE= 4.308 and MAE=4.916) outperforms ANN (R=0.92, RMSE= 5.136 and MAE=5.624) and MLR (R=0.89, RMSE= 8.212 and MAE=9.472). Proposed models have a strong potential to predict compressive strength of self compacting concrete incorporating rice husk ash with great precision. The importance of different input parameters is also given for predicting the compressive strengths at various ages using gene expression programming. Performed sensitivity analysis to assign effective parameters on compressive strength indicates that cementitious binder content is the most effective variable in the mixture. The assessment results present that the performance of the proposed models are in close agreement with the experimental results. Moreover, the new GEP-based formulation provides improved estimates of the compressive strength of SCC compared to ANN and MLR models. The proposed design equation can readily be used for pre-design purposes or may be used as a fast check on deterministic solutions.
http://mcej.modares.ac.ir/article-1-20432-en.pdf
2019-05-15
209
221
Self-Compacted Concrete
Gene Expression Programming
Artificial Neural Network
Multiple Linear Regression
Compressive Strength
Prediction
MOHAMMAD JAVAD
TAHERI AMIRI
jvd.taheri@gmail.com
1
Babol Noshirvani University of Technology
AUTHOR
Ali
Ashrafian
ali_Ashrafian@yahoo.com
2
Tabari university of Babol
AUTHOR
https://orcid.org/0000-0002-9134-6722
Farshid Reza
Haghighi
haghighi@nit.ac.ir
3
Babol Noshirvani University of Technology
AUTHOR
Maedeh
Javaheri Barforooshi
m.javaheri1392@gmail.com
4
Islamic Azad Unersity, Arak Branch
AUTHOR
ORIGINAL_ARTICLE
بررسی تاثیر پس لرزههای زلزله در ساختمانهای فولادی با نامنظمی هندسی در پلان
گسلها معمولا تمام انرژیهای انباشته خود را زمانی که اولین گسیختگی رخ میدهد، آزاد نمیکنند. بلکه این انرژیها در موقعیتهای مختلف به صورت گسیختگیهای متوالی تا تثبیت گسل ادامه مییابند. این گسیختگیهای متوالی در طول گسل باعث ایجاد زلزلههای متعددی میشوند که عمدتا آنها را به صورت پیشلرزه، لرزهاصلی و پسلرزه تقسیم بندی میکنند. مشاهدات میدانی نشان میدهند که سیستمهای سازهای تحت توالی زلزلهها، مخصوصا سازههایی که به دلیل زمان کم بین دو زلزله بهسازی نشدهاند، دچار خرابی میشوند. در این مقاله به بررسی سازههای نامنظم هندسی در پلان با سیستم قاب خمشی فولادی با شکلپذیری ویژه تحت توالی زلزله پرداخته شده است. هر کدام از این سازهها شامل یک مدل منظم و دو مدل نامنظم با نامنظمی کم و زیاد میباشند، که مطابق آییننامههای ایران طراحی اولیه گردیدند و سپس با انجام تحلیلهای دینامیکی غیرخطی، این سازهها تحت شتابنگاشتهای توالی زلزله واقعی، مورد ارزیابی قرار گرفتند. در نهایت پس از بررسی پارامترهایی چون جابجایی بام، جابجایی نسبی ماندگار طبقات و بیشترین جابجایی نسبی طبقات، افزایش پاسخ سازهها و در نتیجه آن خرابی تحت اثر پسلرزه مشاهده شد. با افزایش میزان نامنظمی در پلان، ناپایداری سازه تحت پسلرزه افزایش پیدا میکند که ممکن است موجب خرابی سازه شود.
http://mcej.modares.ac.ir/article-1-16866-fa.pdf
2019-05-15
223
234
پسلرزه
نامنظمی هندسی در پلان
سازه قاب خمشی فولادی ویژه
تحلیل دینامیکی غیرخطی
The effect of earthquake aftershocks on the steel buildings with irregular plan
Earthquake sequences occur at many regions around the world where complex fault systems exist. These fault systems usually do not relieve all accumulated strains at once when the first rupture takes place. Therefore, high stresses formed at different locations causing sequential ruptures until the fault system is completely stabilized. The sequential ruptures along the fault segment(s) lead to multiple earthquakes which are often hard to distinguish them as fore, main and after-shocks, or a sequence of earthquakes from proximate fault segments. The most recent one sequences occurred are two foreshocks of magnitude 6.2 and 6 followed by a magnitude 7 main shock between 14 and 15 April 2016 caused severe damage and injuries. The event of two earthquakes by magnitude 2.6 and 6, which rocked the cities of Ahar, Varzaghan and Harris in East Azerbaijan in Iran in August 2012, is also a seismic sequence. Field investigations reported failure of structural systems under earthquake sequences, especially where structural retrofitting was not provided due to the short time between the earthquake sequences. In most failure cases the reported damage is mainly due to loss of stiffness and strength of structural elements as a result of material deterioration under earthquake sequences loadings. Buildings may have different configurations depending on the construction location and have different plan dimensions that would lead to irregularity in their planning. Limited research has addressed the seismic behavior of structures subjected to earthquake sequences especially irregular structures. This study investigates the effect of earthquake aftershocks on the steel buildings with irregularity in plan. For this purpose, we studied on structures of 8, 12 and 20 number of stories with special steel frame system under the earthquake sequences. Each of these structures consists of three cases: regular, irregular 1, and irregular 2 models that were designed in accordance to Iranian codes by SAP 2000 software. Geometric irregularities in the plan of the structure created in accordance to Iran's seismic code, a recess should be created in proportion to more than 2% of the total length of the building. In this paper, first irregularity has a recess by 5 meters (one span) and the second irregularity with a recess by 10 meters (two spans), which is 25% and 50% of the length of the building, respectively. The spectral dynamical analysis method has been used to design the structures. For nonlinear analysis, we use Perform-3D software, In Perform-3D, a frame element is used to model beams and columns. Then these structures were evaluated by nonlinear dynamic analysis under actual earthquake sequences. Six sequential earthquake categories that have a major earthquake spacing with corresponding aftershock occurred in less than a week in the area were selected from the PEER (Earthquake Strength Database). Finally, after discussion on parameters such as roof displacement, residual inter story drift and maximum inter story drift, it is observed that aftershock leads to increasing the response of the structures and as a result failure under aftershock. By increasing the irregularity in the plan, the instability of the structure increases under aftershock, which may cause structural failure.
http://mcej.modares.ac.ir/article-1-16866-en.pdf
2019-05-15
223
234
earthquake aftershock
irregularity in plan
steel special moment frame
nonlinear dynamic analysis
Pejman
Kakvan
1
Ms. C Student, Structural Engineering, Islamic Azad University, Branch of Ramsar
AUTHOR
Taha
Bakhshpoori
2
Faculty of Technology and Engineering, Department of Civil Engineering, East of Guilan, University of Guilan, Rudsar-Vajargah, Iran.
AUTHOR
Saeid
Pourzeynali
3
Dept. of Civil Eng., Faculty of Eng., University of Guilan, Rasht, Iran.
AUTHOR
ORIGINAL_ARTICLE
کمانش پوسته های استوانه ای کوتاه قامت فولادی تحت بارگذاری عرضی
مخازن استوانه ای جداره نازک فولادی بدلیل ضخامت کم دیواره، مستعد کمانش تحت بارهای وارده می باشند. بار باد و زلزله از جمله بارهایی هستند که باعث بارگذاری عرضی بر سازه می گردند. در این مطالعه رفتار مخازن دانه ای کوتاه قامت تحت سه توزیع فشار عرضی بررسی شده است. این سه توزیع فشار درنظر دارد، فشار لرزه ای ناشی از محتویات دانه ای بر دیواره سازه را نمایندگی کند. آیین نامه اروپا در زمینه مقاومت و پایداری پوسته ها، از پیشروترین آیین نامه های بین المللی در این حیطه می باشد. روش تحلیل که برگرفته از این آیین نامه است، پایداری استاتیکی این نوع مخازن را با انجام انواع تحلیل های خطی و غیرخطی کمانشی ارزیابی می نماید. تحت بارگذاری انجام شده در این مطالعه، دو مُد کمانشی پای فیل و چین خوردگی مورب برشی در پای سازه، در مخازن کوتاه قامت مشاهده می گردد. پژوهش حاضر ضمن معرفی روش تحلیل آیین نامه اروپا، اطلاعات ارزشمند دیگری نیز در تأثیر وقوع پلاستیسته و وجود نقص یا اعوجاج سازه از هندسه استوانه ای، در مقاومت کمانشی ارائه می نماید.
http://mcej.modares.ac.ir/article-1-20254-fa.pdf
2019-05-15
235
247
پوسته های استوانه ای کوتاه قامت
کمانش
بار عرضی
آیین نامه اروپا
نقص هندسی
Buckling of short cylindrical steel shells under transverse loading
Thin-walled cylindrical shells are extensively used in civil engineering. Due to thin wall thickness, they are vulnerable to stability failure in the form of shell buckling. The European Standard in design of steel structures is considered to be a pioneer in strength and stability assessment of shell structures. Wind pressure and seismic action lead to non-uniform distributed transverse loading on cylindrical shells. It has been shown that non-uniform loading may have a significant and deleterious effect on the structural stability of these structures. The present study deals with buckling behavior of short cylindrical shells under three non-uniform distributed transverse pressures. The loading patterns were adopted in a way to simulate the normal pressures due to ensiled materials in excited situation. It was done with respect to Eurocode design provisions for earthquake resistance of circular silos. Its aim is to produce useful information for the design of cylindrical shells against buckling under general transverse loading. An overview of Eurocode treatments of shell stability using finite element analysis is presented. In addition, the paper explores the effects of different forms of transverse loading on stability response of the structure. The numerical approach was selected to fulfill the stability evaluations. Eurocode has many provisions for the global analysis of shell structures using finite element analysis. Hence, a full suite of computational shell buckling calculations was performed according to this standard. Linear bifurcation analysis was undertaken, firstly. It served as a benchmark for further evaluations. Two different linear bifurcation eigenmodes were observed. The main mode of buckling was diagonal shear wrinkles near the base of silo with partial extension in circumferential direction. The other mode was local axial compression buckle at the foot of the shell. A wide range of imperfection sensitivity studies using these eigenmodes were conducted. The imperfections can take many forms and can have different amplitudes. Some imperfection forms may result in higher strength of the shell. This makes identifying the worst condition very challenging. A sample parametric study on imperfection amplitude in forms of eigenmodes, illustrated this kind of analysis. Additionally, the effect of plasticity was explored through the ideal elastic-plastic model for steel. It was shown that due to loading pattern, the plasticity may cause different amount of reduction in elastic load factor. To establish the actual plastic collapse load, the modified Southwell plots were used. To achieve more realistic evaluation of buckling and post-buckling behavior of thin-walled cylinders, the finite element analyses should include all possible source of strength reduction in stability of the shell structures. To this end the geometrically and materially non-linear analysis with explicit inclusion of imperfections (GMNIA) is considered to be the most advanced form of numerical analysis. The load factors derived from GMNIA analyses showed a stability reduction more than half as compared to linear bifurcation analyses in two load cases. The non-linear incremental buckling modes were also explored. Finally, the general shape of buckled short cylinders under transverse loading was characterized by combination of diagonal shear wrinkles and elephant’s foot buckling mode.
http://mcej.modares.ac.ir/article-1-20254-en.pdf
2019-05-15
235
247
Short cylindrical shells
Buckling
Transverse loading
Eurocode
Imperfections
Shervin Maleki
Maleki
smaleki@sharif.edu
1
Professor, Department of Civil Engineering,
AUTHOR
Alireza
Moazezi Mehretehran
2
Department of Civil Engineering, Sharif University of Technology, Azadi Ave., Tehran, Iran
AUTHOR