یک الگوی بار جانبی اصلاح شده در تحلیل استاتیکی خطی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی عمران، دانشگاه شاهد، تهران، ایران

2 دانشکده مهندسی عمران، دانشگاه صنعتی کرمانشاه، کرمانشاه، ایران

3 دانشکده مهندسی عمران، دانشگاه کردستان، سنندج، ایران

چکیده

روش ­های متفاوتی جهت تعیین الگوی بار جانبی استاتیکی ارائه شده است. علی­رغم سادگی روش ­های موجود، دقت این روش ­ها به ویژه در مورد سازه ­هایی که اثر مودهای ارتعاشی بالاتر در آن‌ها حائز اهمیت است، مطلوب نیست. در این مقاله یک روش جدید جهت اصلاح الگوی بارگذاری در تحلیل استاتیکی خطی ارائه شده است. در روش پیشنهادی ابتدا پاسخ میانگین سازه از تحلیل دینامیکی تحت چند رکورد زلزله محاسبه می ­گردد. سپس الگوی استاتیکی متناظر با این پاسخ از طریق محاسباتی مبتنی بر دینامیک سازه ­ها بسط می­ یابد. در پایان جهت کاربردی نمودن این ایده، با استفاده از یک جامعه آماری، رابطه و گرافی جهت محاسبه الگوی بارگذاری در سایر ساختمآن‌ها به دست می­آید. با توجه به استخراج این روش بر اساس پاسخ سازه تحت تحلیل تاریخچه زمانی خطی، نشان داده می­ شود که این روش دقت مناسبی در تخمین پاسخ سازه در برابر نیروی زلزله دارد. علاوه بر این دارای سادگی و کارآئی روش ­های سنتی نیز می ­باشد. روش توسعه یافته در تحقیق حاضر، برای سه قاب 5، 10 و 14 طبقه با دوره تناوب­ های مختلف و تحت تحریک 14 شتاب‌نگاشت، مورد ارزیابی قرار می ­گیرد و نتایج آن با الگوهای پیشنهادی استاندارد 2800 و دستورالعمل FEMA-356 مقایسه می­ گردد. نتایج نشان می‌دهد، متوسط خطای روش پیشنهادی در سازه 5، 10 و 14 طبقه تقریباً در حدود 7، 5 و 7 درصد است. در حالی که مقادیر خطای الگوهای پیشنهادی دو آیین­ نامه تقریبا 20، 10 و 25 درصد است. ضمناً مقایسه توزیع جابجایی نسبی در ارتفاع این قاب ­ها برای روش پیشنهادی و تحلیل دینامیکی، نشان از عملکرد مطلوب روش پیشنهادی دارد. نتایج حاصل از این بررسی نشان می ­دهد که روش پیشنهادی در محاسبه پاسخ سازه در مقایسه با روش تحلیل استاتیکی معادل استاندارد 2800 و دستورالعمل FEMA-356 از دقت بالاتری برخوردار است و می ­تواند جهت تعیین یک الگوی بار جانبی مناسب در آئین ­نامه ­های لرزه ­ای پیشنهاد گردد. 

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

A modified lateral load pattern for linear static analysis

نویسندگان [English]

  • Alireza Habibi 1
  • Mehdi Izadpanah 2
  • Hooman Saffari 3
1 Department of Civil Engineering, Shahed University, Tehran, Iran
2 Department of civil engineering, Kermanshah university of technology, Kermanshah, Iran
3 Department of Civil Engineering, University of Kurdistan, Tehran, Iran
چکیده [English]

linear static analysis is one of the most widely used methods proposed by the codes for the seismic analysis of structures. Several methods have been presented for determining the static lateral load pattern. In spite of the simplicity of these procedures, their accuracy, especially for structures in which the influences of higher modes are significant, is not desirable. In this study, a new method is developed to improve the lateral load pattern in linear static analysis. To achieve the proposed lateral load distribution, firstly, the average responses of some structures subjected to some earthquakes are acquired. Then, regarding the dynamic responses of the structures, the static lateral load pattern compatible with the average responses is developed. Eventually, to derive a straightforward and hands-on lateral load distribution, using a statistical study, some relations coupled with a graph are developed. Since the proposed method is developed based on the structural responses resulting from linear dynamic analysis (time-history analysis), it is shown that the suggested way, despite its simplicity and efficiency, presents appropriate accuracy in predicting the responses of the structures subjected to seismic excitations. The developed lateral load is applied for three frames with 5, 10 and 14 stories. The inter-story drifts of these frames are achieved under 14 earthquake excitations. After that, the proposed lateral loads of code 2800 and FEMA 356 are used on these frames and the responses are derived. The outcomes show that whereas the average error of the proposed lateral load for these frames is around 7, 5 and 7%, the average errors of code 2800 and FEMA 356 are almost 20, 10 and 25%. Comparing the inter-story drifts for the developed lateral load pattern with the dynamic results, validates its performance. The developed method is evaluated for a set of structures with different fundamental periods. Results show that the method gives higher accuracy in comparison with the static method of Iranian standard 2800 and FEMA 356. Also, the developed procedure can be considered as an appropriate technique for determining lateral load distribution in seismic codes.

کلیدواژه‌ها [English]

  • Linear static analysis
  • Lateral load pattern
  • Higher modes effect
  • Dynamic analysis
  • Seismic codes

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نشریه مهندسی عمران امیرکبیر
دوره 54، شماره 8
آبان 1401
صفحه 3197-3214

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