مطالعه اثر میرایی و شکل‌پذیری تغییرمکانی سازه بر طیف انرژی ورودی زلزله

نوع مقاله: علمی - پژوهشی

نویسندگان

1 استادیار، دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

2 دانشیار، دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

3 دانشجوی دکتری مهندسی زلزله، دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

چکیده

برای ارتقای طراحی لرزه‌ای سازه‌ها، ارایه معیارهای جامع‌تر نسبت به معیارهای رایج در طراحی لرزه‌ای برای جامعه مهندسی ضروری است. در مجامع تحقیقاتی استفاده از مفهوم انرژی به عنوان فلسفه طراحی لرزه‌ای مورد توجه قرار گرفته است لیکن برای کاربردی شدن مفهوم انرژی و توسعه آن در طراحی لرزه‌ای خلأ‌هایی وجود دارد که هدف اصلی این پژوهش پُرکردن بخش کوچکی از این خلأها است. معیار انرژی کمیتی ساده، اسکالر و مفهومی است. سهولت استفاده از طیف‌ها به عنوان ابزار کارآمد در مهندسی مورد توجه است؛ لذا مطالعه اثر میرایی و شکل‌پذیری بر روی طیف انرژی ورودی زلزله به سازه، برای بکارگیری معیار انرژی در طراحی لرزه‌ای گامی مؤثر است. در این پژوهش با استفاده از تحلیل دینامیکی غیرخطی برای 4 نسبت میرایی و 4 مقدار شکل‌پذیری، طیف‌های انرژی ورودی نسبی بر واحد جرم سازه برای 4 زلزله ایران تولید شده است. با بررسی 64 طیف تولید شده در این پژوهش، نتایج بدست آمده مورد بحث قرار گرفته است. بررسی طیف‌ها نشان می‌دهد که افزایش نسبت میرایی و شکل‌پذیری موجب هموارتر شدن طیف انرژی ورودی نسبی و کاهش تغییرات این طیف می‌شود. همچنین اثر تغییرات شکل‌پذیری بر طیف انرژی ورودی نسبی محسوس‌تر از اثر تغییرات نسبت میرایی بر طیف مذکور می‌باشد. تغییرات نسبت میرایی و شکل‌پذیری تأثیر ناچیزی بر تغییر پریود متناظر با قله طیف انرژی ورودی نسبی دارد. در مجموع و با تقریب مهندسی و در محدوده نسبت‌های میرایی و شکل‌پذیری مطالعه شده در این پژوهش نتیجه گیری شده است که در حوزه رفتار غیرارتجاعی و در محدوده وسیعی از پریودها، طیف انرژی ورودی نسبی بر واحد جرم سازه حساسیت چندانی نسبت به تغییرات نسبت میرایی و شکل‌پذیری ندارد و تابعی از پریود سازه می‌باشد؛ و با توجه به عدم اطلاع مهندسان طراح از مقادیر واقعی نسبت میرایی و شکل‌پذیری در زمان طراحی سازه، این موضوع یک مزیت محسوب می‌شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Structural Damping and Displacement Ductility Effects on Input Energy Spectrum of Earthquake

نویسندگان [English]

  • Reza Vahdani 1
  • Mohsen Gerami 2
  • Mohamad Ali Vaseghi Nia 3
1 Assistant Professor, Department of Civil Engineering, Semnan University, Semnan, Iran
2 Associate Professor, Faculty of Civil Engineering, Semnan University, Semnan, Iran
3 PhD Student in Earthquake Engineering, Department of Civil Engineering, Semnan University, Semnan, Iran
چکیده [English]

To improve seismic design of structures, providing more comprehensive criterion than the common criterions in structural seismic design is essential for the engineering community. The concept of energy has been considering as a seismic design philosophy in research communities; But there are some gaps for application of energy concept and its development in seismic design, and filling a small part of these gaps is the main objective of this study. Energy criterion is simple, scalar and conceptual quantity. Easy using of spectrum as an efficient tool in engineering is noteworthy; therefore, study on effects of damping and ductility on input energy spectrum is effective step to exert the energy criterion in structural seismic design. In this research, by using nonlinear dynamic analysis for 4 damping ratios and 4 ductility factors, relative input energy spectra per unit mass of structure have been produced for 4 Iranian earthquakes. Then 64 spectra that produced in this study have been reviewed and obtained-results have been discussed. Scrutiny of spectra show that increasing of damping ratio and ductility have reduced spectrum’s changes. Also, variation of ductility factor is more effective than the variation of damping ratio on relative input energy spectrum. Variation of damping ratio and ductility factor have little effect on changing of peak corresponding period in relative input energy spectrum. Overall, with engineering estimate and in the range of damping ratios and ductility that have been studied in this research, has been concluded that in inelastic behavior range, input energy spectrum per unit mass has little sensitivity to changes of damping ratio and ductility in wide range of periods, and it is a function of structure’s period. Because lack of design engineer's awareness on real amounts of damping ratio and ductility when designing structure, it is one advantages of relative input energy spectrum.

کلیدواژه‌ها [English]

  • Energy Spectrum
  • Damping Ratio
  • Displacement Ductility
  • Relative Input Energy
  • Input Energy Per Unit Mass

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