بررسی اثر انرژی زلزله روی رفتار لرزه‌ای سد بتنی قوسی با استفاده از تبدیل موجک

سپیده فیروزی, محسن بزرگ‌نسب, رضا تقی‌پور

چکیده


سدها از جمله سازه‌های عظیم مهندسی هستند که بررسی رفتار لرزه‌ای آنها تحت تکانه‌های لرزه‌ای شدید از اهمیت زیادی برخوردار است زیرا آسیب و خرابی این ابرسازه‌ها می‌تواند خسارات جبران‌ناپذیری به همراه داشته باشد. در این تحقیق، مدل‌سازی اجزای محدود سد بتنی قوسی مارو پوینت در نرم‌افزار سالید ورک انجام شده و تحلیل دینامیکی غیرخطی سد با در نظر گرفتن اندرکنش سد- دریاچه- فونداسیون در نرم‌افزار المان محدود آباکوس انجام گرفته است. در روند تحلیل غیرخطی از مدل پلاستیسیته خرابی بتن استفاده شده است. همچنین به‌منظور بررسی تأثیـر چگونگی توزیع انـرژی زلزله بر رفتار لرزه‌ای سد، رکوردهای ثبت شده مربوط به زلزله‌های مختلف با استفاده از تبدیل گسسته موجک به مؤلفه‌های مختلف با سطح انـرژی متفاوت تجزیه شده‌اند. نتایج حاکی از آن است که در حوزه نزدیک گسل می‌توان مؤلفه موجکی از زلزله را یافت که با وجود دارا بودن مدت‌زمان مؤثر کمتر، در حدود 60 تا 70 درصد نسبت به رکورد اصلی، پاسخ‌های نزدیک به رکورد اصلی با اختلافی کمتر از 10 درصد را حاصل نماید که این خود کاهش زمان تحلیل را در پی خواهد داشت. همچنین نشان داده شده که میزان انرژی زلزله و شدت آن در واحد زمان در چگونگی بازتاب سازه مؤثر خواهد بود.

Studying the Effect of Earthquake Energy on the Seismic Behavior of the Concrete Arch Dam Using Wavelet Transform

Sepide Firouzi, Mohsen Bozorgnasab, Reza Taghipour

Dams are infrastructures that have an important role in energy and water supply. Any damage or failure of these superstructures can lead to irreparable losses; therefore, the seismic behavior evaluation of dams under strong ground motions is important. This study aims at studying the effects of earthquakes parameters changes in the performance of concrete arch dams, considering different seismic conditions. The well-known analysis approaches such as nonlinear dynamic analysis is used. Various recorded time histories with different characteristics are considered for the analysis process. Besides, different duration definitions are applied on the selected time histories. Another goal of this paper is to find signals with similar energy characteristics as the main recorded time-histories, in order to reduce the computational volume and analysis time. By considering the special energy distribution of the near-fault records, the approach is properly acts on these types of records. The Morrow point concrete arch dam is considered as the case study, which is modeled in the Solid Work software. The Nonlinear dynamic analysis of this dam, considering the dam-reservoir-foundation interaction is conducted in Abaqus finite element software. The concrete damage plasticity is applied to model the nonlinear behavior of the concrete material of the dam body. To survey the effect of earthquake energy distribution on the seismic behavior of the dam, the selected earthquake records have been decomposed to several components with different energy levels, using discrete wavelet transform. The wavelet transform can decompose the earthquake records into components with specific frequency band. Each of these components has an energy value that is a percentage of the whole energy value of the original record. The seismic behavior of the dam under the main selected earthquake records and their components has been investigated. The results indicate that a wavelet component can be extracted from a near-fault record with a lower effective duration (about 60 to 70 percent of the main record) and similar response in comparison to the original record. Moreover, study of the arias intensity and displacement time history of the dam crest shows that the peak displacement in the dam crest occurs simultaneously with the sudden increase in the arias intensity. As this parameter can be a representative of the time history energy value and its intensity per time unit, the above-mentioned results show the effects of time history energy value and its intensity on the response of the dam body. In addition, it is shown that any changes in the time at which the effective component of the earthquake time history acts can affect the response of the dam. This effect depends on the epicentral distance of the station of the recorded time histories. The results of this study can be used for the recorded time histories at the stations near the epicenter. It is obvious that more studies should be conducted to investigate the effects of increasing the epicentral distance on the dam behavior.

Keywords: Concrete Arch Dam, Energy Earthquake, Nonlinear Response, Wavelet Transform


موضوع


سد بتنی قوسی، انرژی زلزله، پاسخ غیرخطی، تبدیل موجک.

تمام متن:

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مراجع


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