بررسی اثرات انتخاب شتابنگاشت و شکل طیف زمین لرزه بر ظرفیت فروریزش سازه

نوع مقاله : علمی - پژوهشی

نویسندگان

1 دانشکده مهندسی عمران، واحد نجف آباد، دانشگاه آزاد اسلامی، نجف آباد، ایران

2 دانشکده مهندسی عمران، دانشگاه علم و صنعت ایران، تهران، ایران

چکیده

یکی از مهم‌ترین چالش‌ها در ارزیابی و برآورد ظرفیت فروریزش سازه‌ها، انتخاب و مقیاس نمودن مجموعه رکوردهای زمین‌لرزه می-باشد. در این تحقیق یک مجموعه کلی شامل 44 شتابنگاشت برای محاسبه ظرفیت فروریزش سازه در نظر گرفته شده است، سپس برای لحاظ کردن اثر انتخاب شتابنگاشت بر ظرفیت فروریزش سازه از روش میزان تطابق طیف پاسخ هر زلزله با طیف میانگین شرطی در سطح خطر مورد نظر استفاده شده است و شتابنگاشت‌های مناسب با هر سطح خطر انتخاب شده است. برای لحاظ کردن اثر شکل طیف بر ظرفیت فروریزش، از ضریب شکل طیف یا اپسیلون به دو روش استفاده شده است. بدین صورت که در روش اول برای مجموعه کلی از زمین لرزه‌های انتخاب شده، ظرفیت فروریزش سازه برای سطح خطر مورد نظر با استفاده از اپسیلون اصلاح شده است و در روش دوم از روش ساده سازی شده که توسط هسلتون و همکاران پیشنهاد شده است، جهت لحاظ کردن اثر اپسیلون و اصلاح ظرفیت فروریزش سازه در سطح خطر مورد نظر استفاده شده است. نتایج ظرفیت فروریزش اصلاح شده در سطح خطر مورد نظر حاصل از سه روش 1) انتخاب شتابنگاشت، 2) استفاده از مجموعه کلی زمین‌لرزه با لحاظ کردن اپسیلون و 3) روش ساده سازی شده نشان می‌دهند که نسبت ظرفیت فروریزش اصلاح شده با لحاظ کردن اثر انتخاب شتابنگاشت و اثر اپسیلون، به ظرفیت فروریزش بدون لحاظ کردن اثر انتخاب شتابنگاشت و اثر اپسیلون، در سطح خطر 2 درصد در 50 سال، برای 3 روش ذکر شده به ترتیب برابر 216/1 ، 174/1 و 197/1 است، که هر سه روش دارای براوردی تقریبا مشابه می‌باشند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Assessing the Effects of Record Selection and Ground-Motion’s Spectral Shape on the Collapse Capacity of the Structures

نویسندگان [English]

  • Mohammad Amin Bayari 1
  • Naser Shabakhty 2
  • Esmaeel Izadi Zaman Abadi 1
1 Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
2 School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran
چکیده [English]

Selecting and scaling the set of ground-motion records is among the most important challenges in collapse capacity assessment and estimation of structures. In this study, 44 records were considered to estimate the collapse capacity of the structure.Next, the response spectrum matching degree of each ground-motion with the conditional mean spectrum at the inspected hazard level was employed to account for the effect of record selection on the collapse capacity of the structure and appropriate records were selected per each hazard level. Further, the spectral shape factor or epsilon was used to incorporate the effect of spectral shape on collapse capacity. In the first approach, the collapse capacity of the structure was modified for the overall set of selected ground-motions via epsilon according to the level of inspected hazard. In the second approach, the simplified method introduced by Haselton et al. was used to assess the effect of epsilon and modify the collapse capacity of the structure at the inspected hazard level. The results of the modified collapse capacity at the inspected hazard level were collected from three respective methods of record selection. These data were collected using the overall set of ground-motions with the epsilon and the simplified method. The obtained results indicate that the ratio of modified collapse capacity with the effects of record selection and epsilon on collapse capacity, disregarding the record selection and epsilon effects, are 1.216, 1.174, and 1.197 at the hazard level of 2% in 50 years for the three discussed methods, respectively. Ultimately, these three individual methods have rendered approximately equal estimates.

کلیدواژه‌ها [English]

  • Record Selection
  • Ground-Motion’s Spectral Shape
  • Conditional Mean Spectrum
  • Spectral Shape Factor
  • Collapse Capacity of the Structure
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