Modares Civil Engineering journal
مهندسی عمران مدرس
MCEJ
Engineering & Technology
http://mcej.modares.ac.ir
1
admin
2476-6763
10.22034
fa
jalali
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2014
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ارزیابی مبتنی بر عملکرد رفتار سدهای خاکی تحت بارگذاری زلزله
Based Performance Evaluation of Earth Dams under Seismic
Loading
در این پژوهش، رفتار یک سد خاکی نوعی در دو سطح عملکردی، موسوم به سطح عمکرد <span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">"</span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">مبنا </span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">" </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">و </span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">"</span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">مطلوب </span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">"</span></span> <span style="font-family: BLotus; font-size: small;">، با</span> انجام تحلیلهای دینامیکی غیرخطی ارزیابی شده که، در هر سطح عملکرد، سطوح لرزهای معین و سطوح تخریب مجاز متناظر تعریفشدهاست <span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">. </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">همچنین، رفتار سد برای عواملی مانند شتابنگاشت ورودی، مدل رفتاری و عدد نفوذ استاندارد پوسته حساسیت</span></span> <span style="font-family: TimesNewRomanPSMT; font-size: small;">-</span> بررسیشدهاست <span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">. </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">نتایج نشان میدهد که الزامات </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">(</span></span><span style="font-family: TimesNewRomanPSMT; font-size: xx-small;"><span style="font-family: TimesNewRomanPSMT; font-size: xx-small;">SRF </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">سنجی و پایداری سد با انجام تحلیلهای کاهش پارامترهای مقاومتی </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">(</span></span> <span style="font-family: BLotus; font-size: small;">تحلیل</span> عملکرد <span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">"</span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">مبنا</span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">" </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">برای سد مطالعه شده با توجه به ویژگیهای هندسی و ژئوتکنیکی آن قابل تامین است</span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">. </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">اما تأمین عملکرد </span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">"</span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">مطلوب</span></span> <span style="font-family: TimesNewRomanPSMT; font-size: small;">"</span> برای این سد، مستلزم ایجاد تغییرات در ساختار سد و یا بهسازی لرزهای آن است <span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">. </span></span> <span style="font-family: BLotus; font-size: small;">وجود ضرایب اطمینان پایین در سطوح لرزهای</span> مطالعه شده، این مطلب را تایید می کند <span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">. </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">تحلیلهای حساسیتسنجی به شتابنگاشتهای </span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">"</span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">فریولی</span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">" </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">و </span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">"</span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">ساکاریا</span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;">"</span></span> <span style="font-family: BLotus; font-size: small;">، باوجود تفاوت در</span> پاسخ طیفی و چگالی انرژی آنها، نتایج یکسانی را ارائه مینماید <span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">. </span></span> <span style="font-family: BLotus; font-size: small;">مدل فین بسته به تراز شتاب بیشینه اعمالی، فشار آب حفره ای</span> اضافی ایجاد شده در بالادست سد را <span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">20 </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">درصد بیشتر از مدل رفتاری مور</span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">- </span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">کولمب پیشبینی مینماید</span></span><span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">. </span></span> <span style="font-family: BLotus; font-size: small;">با تغییر عدد نفوذ استاندارد</span> پوسته و تحلیل سد در شتابهای بیشینه مختلف مشاهده می شود که مدل فین در اعداد نفوذ استاندارد اصلاح شده کمتر از <span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">35 </span></span> <span style="font-family: BLotus; font-size: small;">و در</span> 0/7 <span style="font-family: BLotus; font-size: small;"><span style="font-family: BLotus; font-size: small;">، وقوع پدیده روانگرایی را در خاکریز بالادست سد پیشبینی مینماید</span></span> <span style="font-family: BLotus; font-size: small;">.</span>
Dams shall safely retain the reservoir and any stored solids, and pass environmentally acceptable flows, as required for all loading conditions, ranging from normal to extreme loads, commensurate with the consequences of failure. The new trend for performance-based design is to consider 2 levels of seismic actions and analyze the situation where the limit of force balance is exceeded for high intensity ground motions, associated with a very rare seismic event. For the design, two basic requirements are defined: (i) Non-collapse requirement (ultimate limit states), i.e. after the occurrence of the seismic event, the structure shall retain its structural integrity, with respect to both vertical and horizontal loads, and adequate residual resistance, although in some parts considerable damage may occur, (ii) Minimization of damage (serviceability limit state) , i.e. after seismic actions with high probability of occurrence, during the design life of the structure, some parts can undergo minor damage without the need of immediate repair. This study evaluates the behavior of a typical earth dam by nonlinear seismic analyses, in two performance levels, named “Base Performance Level” and “Desired Performance Level.” The level of seismic action and related acceptance level of damage are defined for each performance level. In “Base Performance Level,” with seismic levels of OBE (0.3g) and MDE (0.5g), the structure shall be serviceable and repairable and in “Desired Performance Level”, with seismic levels of MDE (0.5g) and MCE (0.7g), the structure shall be serviceable and repairable, respectively. Also, the stability of dam has been assessed by the “Strength Reduction Analysis.” The analyses are nonlinear and the constitutive law of the materials was assumed to follow "Finn" and "Mohr-Coulomb" models, incorporated into “FLAC 2D” finite difference analysis program. The factors such as initial shear modulus, variation of shear modulus versus shear strain, generation and dissipation of pore pressure and hysteretic damping are considered in this study. In addition, using the scaling method of applying maximum acceleration, the response of dam is investigated in different maximum accelerations. The results show that the dam needs to be changed in geometrical specifications or seismically improved in “Desired Performance Level”, in contrast with “Base Performance Level.” Results are confirmed by low amount of safety factors of stability in dam, which are calculated for different seismic loads. Also, the behavior of dam is examined by sensitivity analysis for type of accelerograms, constitutive model and the standard penetration number in shell of dam. Two accelerograms, including “Friulli” and “Sakaria” are considered. Maximum acceleration and duration of both of them are equalized and frequencies more than 5Hz are filtered. Sensitivity analyses of “Friulli” and “Sakaria” accelerograms, despite the difference in response spectra and specific energy density, show approximately similar results. “Finn” model predicts the amount of excess pore water pressure to be more than "Mohr- Coulomb" up to %20, and shows the occurring of liquefaction in SPT more than 35 and acceleration more than 0.7g, in shell of upstream of dam
سد خاکی,ارزیابی مبتنی بر عملکرد,تحلیل دینامیکی غیرخطی,مدل فین,تحلیلSRF
earth dam,Based Performance Evaluation,nonlinear dynamic analysis,Finn
Model,SRF Analysis
39
53
http://mcej.modares.ac.ir/browse.php?a_code=A-10-13105-6&slc_lang=fa&sid=16
H.R.
Paseh
حمیدرضا
پاسه
100319475328460053990
100319475328460053990
No
Tarbiat Modares University
دانشگاه تربیت مدرس
M.
Oliaei
محمد
علیائی
100319475328460053989
100319475328460053989
Yes
Tarbiat Modares University
دانشگاه تربیت مدرس