جستجوی مقالات مرتبط با کلیدواژه "peak ground acceleration" در نشریات گروه "عمران"
تکرار جستجوی کلیدواژه «peak ground acceleration» در نشریات گروه «فنی و مهندسی»-
در مطالعه‌ی حاضر، ارتباط بین تعاریف مختلف دوام با بیشینه‌ی شتاب سطح زمین، عمق کانونی و شرایط خاک ساختگاه با استفاده از رکوردهای شتابنگاشت در ایران، محاسبه و ارایه شده است. در این راستا، از 1054 رکورد سه مولفه‌ی مربوط به 197 رویداد لرزه‌یی ثبت شده با بزرگای گشتاور بزرگ‌تر یا مساوی 5/0 استفاده شده است. نتایج نشان می‌دهند که با افزایش شتاب اوج زمین، دوام بازه‌یی و یکنواخت افزایش می‌یابند؛ در حالی که در مورد دوام موثر، عمده‌ی رکوردهای با دوام موثر طولانی، عمدتا شتاب اوج زمین کمی داشته‌اند. همچنین روابط ریاضی تغییرات هرگونه دوام با شتاب اوج زمین و عمق کانونی و تغییرات نوع خاک نشان داده شده است. رابطه‌ی بین مدت دوام و بیشینه‌ی دامنه‌ی حرکات قوی زلزله برای حرکت ورودی در طراحی لرزه‌یی سازه‌ها به‌خصوص سازه‌های بتن مسلح که در سیکل‌های پیاپی زلزله دچار افت سختی و کاهش مقاومت می‌شوند، اهمیت زیادی دارد.
کلید واژگان: دوام معنی دار, دوام بازه یی, دوام یکنواخت, بیشینه ی شتاب سطح زمین, شرایط خاک ساختگاهIn this study, the relationship between different definitions of duration with peak ground acceleration, focal depth, and soil conditions of the site using accelerometer records in Iran was calculated and presented. Then, 1054 three-component records of 197 seismic events recorded with a moment magnitude greater than or equal to 5.0 were used. All data for this study were obtained from the Road, Housing, and Urban Development Research Center (BHRC) in Iran. All records were for sites with focal depths and shear wave velocities within the first 30 m of depth. After preparing the records, the baseline correction was performed on them using Fortran programming and durations with g0.05 acceleration thresholds, uniform durations with g0.05 acceleration thresholds, significant durations 5-95% were calculated. Then, according to the Iranian 2800 earthquake code, soil type was grouped and the data were classified into three categories according to soil type. The data with soil group 4 were very low and unreliable. The results showed that with increasing peak ground acceleration, bracketed and uniform duration increased, while for significant durations, records with high significant durations generally have minor peak acceleration. Mathematical relationships were also shown for variations in any durations with peak ground acceleration and focal depth and soil type variations. Also, with softer soil, the slope of the bracketed and uniform duration relationship with PGA increased. Increasing the focal depth decreased the durability with different definitions. After a focal depth of 20 km, a threshold of 0.05g is usually less than 10 seconds. The relationship between shear wave velocity at 30 m depth and significant duration indicated that with increasing shear wave velocity, significant duration decreased. The relationship between the duration and maximum amplitude of earthquake ground motions was important for the seismic design of structures, especially reinforced concrete structures, which suffered from stiffness and reduced strength in successive earthquake cycles.
Keywords: Earthquake duration, peak ground acceleration, amplitude, local site conditions -
The Applicability of Different Earthquake Intensity Measures to the Seismic Vulnerability of a High-Speed Railway Continuous BridgeThere are two common intensity measures (IM), i.e., the peak ground acceleration (PGA) and the spectral acceleration (Sa), for earthquake waves. PGA is a simple peak value of wave, while Sa considers more complex spectral characteristics. And it is necessary to identify which one is suitable for evaluating the seismic vulnerability of high-speed railway (HSR) bridges rapidly developed in the world. A finite element model of a (48 + 80 + 48)m continuous girder HSR bridge with track structure was built by OpenSEES software, and was calculated via an incremental dynamic analysis using both PGA and Sa. The seismic fragility curves of bridge and track components were developed by comparing the seismic demand and capacity of components. The comparison results, respectively, using PGA and Sa, show that both PGA and Sa are suitable for evaluating the seismic vulnerability of HSR bridges, and the using of PGA obtains more conservative fragility curves. Those severely nonlinear components, such as the sliding layer and the sliding bearings, etc., do not have constant local natural vibration periods and their seismic responses are not sensitive to the spectral characteristics of earthquakes. The dispersion of engineering demand parameters (EDPs) using PGA is larger or less than that using Sa for those severely nonlinear components. However, the dispersion of EDPs using PGA is always larger than that using Sa for those linear or slightly nonlinear components.Keywords: High-speed railway, Continuous bridge, Seismic vulnerability, Intensity measure, Peak ground acceleration, Spectral acceleration
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International Journal of Optimization in Civil Engineering, Volume:8 Issue: 1, Winter 2018, PP 1 -14In the present study, two new hybrid approaches are proposed for predicting peak ground acceleration (PGA) parameter. The proposed approaches are based on the combinations of Adaptive Neuro-Fuzzy System (ANFIS) with Genetic Algorithm (GA), and with Particle Swarm Optimization (PSO). In these approaches, the PSO and GA algorithms are employed to enhance the accuracy of ANFIS model. To develop hybrid models, a comprehensive database from Pacific Earthquake Engineering Research Center (PEER) are used to train and test the proposed models. Earthquake magnitude, earthquake source to site distance, average shear-wave velocity, and faulting mechanisms are used as predictive parameters. The performances of developed hybrid models (PSO-ANFIS-PSO and GA-ANFIS-GA) are compared with the ANFIS model and also the most common soft computing approaches available in the literature. According to the obtained results, three developed models can be effectively used to predict the PGA parameter, but the comparison of models shows that the PSO-ANFISPSO model provides better results.Keywords: ANFIS, metaheuristics, PSO, GA, peak ground acceleration
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One of the serious damages of tremendous earthquakes is the damage to bridges as the major components in an arterial road network, as relief operation is interrupted following cutting roads. Regardless of the magnitude and severity of an earthquake, other factors are also important in the strength and seismic performance of concrete bridges. Freezing-thawing cycles are among the factors, which erode the piers of concrete bridges over time. Therefore, it is necessary to evaluate the seismic vulnerability of bridges for future designs.
This research aims at discussing the effect of freeze-thaw cycles on the seismic performance of concrete bridges using fragility curves. Fragility curves express the conditional probability to reach or exceed a level of damage as a function of ground motion parameters. The curves have been developed analytically using a probabilistic method. Ground motion parameter, peak ground acceleration, structural criterion, and relative displacement of piles were considered. The non-linear time history analysis in OpenSees was used for demand determination. The curves were drawn for the slight, moderate, and extensive damage levels in two modes of before and after damage caused by thawing and freezing, i.e. the mode in which the compressive strength of column section expose reduced. With respect to the fragility curves, the strength reduction increases bridge vulnerability, especially on slight damage levels. Comparing with the cyclic curves of the most vulnerable column in two modes of before and after the damage showed that energy absorption capacity lowered with the expose compressive strength reducing.Keywords: Concrete bridges, Concrete Compressive Strength, Freezing-Thawing Cycles, Seismic Vulnerability, Fragility Curve, nonlinear time history analysis, Damage Levels, peak ground acceleration -
یکی از روش های مناسب جهت بررسی زلزله های مختلف و تعیین میزان خطرپذیری در هر منطقه پیش بینی پارامترهای جنبش نیرومند زمین می باشد که نقش مهمی را در ارزیابی اثرات زلزله در طراحی پروژه های مهندسی ایفا می کند. در پژوهش حاضر از مدل ماشین بردار پشتیبان و شبکه عصبی شعاع محور که از تکنیک های هوش مصنوعی هستند برای برآورد بیشینه شتاب زمین استفاده شده است. بدین منظور از پارامترهای لرزه ای شامل بزرگای زلزله، فاصله محل رخداد زلزله تا سایت، عمق کانونی زلزله و شدت زلزله به عنوان پارامترهای ورودی مدل های ماشین بردار پشتیبان و شبکه عصبی شعاع محور استفاده شده است. مقایسه نتایج برآورد بیشینه شتاب زمین با ماشین بردار پشتیبان و شبکه عصبی شعاع محور با روابط کاهندگی تجربی و روش های رگرسیون بیانگر آن است که روش ماشین بردار پشتیبان و شبکه عصبی شعاع محور ارائه شده می توانند ارتباط مناسبی را میان مقادیر مشاهداتی و محاسباتی برقرار نمایند. همچنین این روش ها از دقت بالاتری نسبت به روش های کلاسیک پیشین برخوردار هستند به طوری که ضریب تبیین برای روش ماشین بردار پشتیبان 996/0 و شبکه عصبی شعاع محور 997/0 و برای روش های رگرسیونی خطی و رگرسیونی غیرخطی به ترتیب 790/0 و 153/0 می باشد.کلید واژگان: مدل های داده کاوی, ماشین بردار پشتیبان, شبکه عصبی شعاع محور, حداکثر شتاب زمینPrediction of the ground strong motion parameters is one way to evaluate the various earthquakes and to determine the amount of risk in each area which plays an important role in the evaluation of earthquake effects on the engineering projects design. In this study, the support vector machine (SVM) and neural radius-based function (RBF) network models as new artificial intelligence techniques were used to estimate the peak ground acceleration (PGA). For this purpose, the seismic parameters such as the magnitude, epicentral distance, focal depth, earthquake intensity were applied as input parameters of proposed models. Evaluation of obtained results for the estimation of PGA using the SVM and RBF models with empirical attenuation relationships and regression methods indicated that the presented SVM and RBF models can establish an appropriated relationship between the observed and calculated PGA values. Also, proposed models have more accuracy than classical approaches. The determination coefficient is 0.996 and 0.997 for SVM and RBF models, respectively where as the determination coefficient is 0.790 and 0.153 for linear regression and nonlinear regression, respectively.Keywords: Data driven models, Support vector machine, Neural radius-based function network, Peak ground acceleration
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In the present study two popular approaches for the seismic fragility evaluation of RC buildings are considered. First approach is based on series of time history analysis and a power law representing probabilistic seismic demand model. Second approach is based on Incremental Dynamics Analysis to determine the median collapse intensity measure. The two methods are formulated with different assumptions and methodologies for evaluations. The fragility curves and reliability indices are developed for a typical four storeyed frame by both the approaches and a comparison study is performed. The both methods yield almost the same results at same total dispersions.Keywords: Fragility, reliability index, peak ground acceleration, performance levels, hazard curve
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During January – December 2012 more than 1341 records were recovered from permanent Iran strong motion stations operated by the Road, Housing and Urban Development Research Center. Accelerograms were recovered from ISMN triggered by 634 earthquakes in the magnitude 2.0 to 6.4 ranges. Peak ground acceleration was recorded in Chaykandi1 station about 607 cm/s2 on September 27th, 2012 earthquake.Keywords: Accelerogram, accelerograph, earthquake, strong motion, peak ground acceleration
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During January–December 2011 more than 311 records were recovered from permanent Iran strong motion stations operated by the Road, Housing and Urban Development Research Center. Accelerograms were recovered from ISMN triggered by 199 earthquakes in the magnitude 2.0 to 7.2 ranges. Peak ground acceleration was recorded in Baba Monir station about 299 cm/s2 on March 5th, 2011 earthquake.Keywords: Accelerogram, accelerograph, earthquake, strong motion, peak ground acceleration
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During this year, 329 accelerograms were recorded by 196 accelerographs, which were triggered by 176 earthquakes with different magnitudes. The Reygan earthquake of 2 th December 2010 in Kerman province was the greatest earthquake in this year that triggered 24 accelerographs. The maximum PGA of about 0.61g was recorded in Koohezar station on August 27, 2010 earthquake.Keywords: Accelerogram, accelerograph, earthquake, strong motion, peak ground acceleration
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خطوط بالاستی از مهم ترین زیرساختهای آسیب پذیر شبکه خطوط ریلی در زمان وقوع و پس از وقوع زلزله است که با وجود اهمیت کارآیی مناسب آن در سیر ایمن قطار، مطالعات اندکی در خصوص میزان تاثیرپذیری این خطوط در شرایط زلزله انجام شده است بنابراین در مقاله حاضر که ابتدا یک مدل سه بعدی اجزاء محدود مناسب برای تحلیل لرزه ای، توسعه داده شده که در آن ریلها و تراورسها با استفاده از المانهای تیر خمشی به عنوان روسازه خط و بالاست و زیربالاست با استفاده از المانهای جرم- فنر- میراگر به عنوان زیرسازه خط مدلسازی شده است. در مدل مذکور اثر مقاومت خط در راستای طولی و جانبی با استفاده از مدل فنر در نظر گرفته شده است. اعتبار سنجی مدل با انجام مقایسه بین نتایج حاصل از آزمایش میزلرزه و نتایج به دست آمده از تحلیل عددی لرزه ای انجام گرفته است. در ادامه، رفتار خطوط ریلی بالاستی در برابر زلزله با ساخت شتابنگاشت مصنوعی بررسی شده است. شرایط سازه ای خط شامل نیروهای محوری، نیروهای برشی و لنگرهای خمشی ایجاد شده در ریلها و تراورسها نیز مورد بررسی و تحلیل قرار گرفته است.
نتایج بیانگر آن است که حداکثر تغییرمکان طولی و جانبی خط به ترتیب از مقدار 0/07و 20/35میلیمتر در تحریک با شتاب اوج 200 gal به مقدار0/035 و 101/8میلیمتر در تحریک با شتاب اوج 1000 gal می رسد که می تواند موجب مشکلات بهره برداری از خط شود. نتایج همچنین نشان می دهند هرچند تحریکات لرزه ای تاثیرسازه ای قابل توجهی بر تراورسها ندارند، اما می توانند بر ریلها اثرات نامطلوبی برجای گذارند، بویژه آن گه موجب کمانش آنها حتی در شتاب اوجهای پایین می شوند.
کلید واژگان: خطوط ریلی, مدل سه بعدی عددی, شتاب اوج تحریکSeismic stability of infrastructures against earthquakes is one of the most important engineering challenges in railway transportation systems. Present literature shows that there are many considerable technical shortages in this issue. Therefore a 3D FE model including the beam elements for modeling the rails and sleepers as track superstructures components, a series of lumped masses with spring and dashpot for modeling the ballast, subballast and subgrade as track substructure components and a number of stiffness and damping for considering of longitudinal and lateral resistance was developed. For validation of the model, comparing the results of a shaking table test with seismic analysis outputs of the model is compared. Accordingly this numerical model can be employed for seismic railway track analysis. The influence of earthquake on seismic behavior of railway track by imposing the artificial accelerograms with variation of peak ground accelerations (PGA) from 200gal to 1000gal was studied. For above mentioned assessments, the operational conditions including longitudinal and lateral deflections of track, as well as structural conditions consisting of axial forces, shear forces and bending moments of rail and sleeper were investigated.Keywords: Seismic analysis, railway track, 3D numerical model, peak ground acceleration -
International Journal of Optimization in Civil Engineering, Volume:1 Issue: 4, Autumn 2011, PP 597 -607The main objective of this study is to present new method on the basis of genetic algorithms for attenuation relationship determination of horizontal peak ground acceleration and spectral acceleration. The proposed method employs the optimization capabilities of genetic algorithm to determine the coefficients of attenuation relationships of peak ground and spectral accelerations. This method has been applied to 361 Iranian earthquake records with magnitudes between 4.5 and 7.4 obtained from two seismic zones, namely Zagros and Alborz-Central Iran. The obtained results indicated that the proposed method can be characterized as a powerful tool for prediction horizontal peak ground and spectral accelerations.Keywords: Attenuation relationship, genetic algorithm, peak ground acceleration, spectral acceleration
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