توابع شکنندگی لرزه‌ای مشروط ساختمان‌های بتن‌آرمه قاب خمشی ویژه با ارتفاع‌های مختلف در معرض رویدادهای لرزه‌ای متوالی

اغلب رویدادهای لرزه‌ای با پس لرزه‌های قابل توجه همراه هستند. این امر باعث می‌شود تا ساختمان هایی که در زمان وقوع رویداد اصلی دچار آسیب شده‌اند به دلیل کاهش ظرفیت و زوال در سختی و مقاومت، عملکردی کمتر از حد انتظار برای ساختمان در زمان وقوع پس‌لرزه بروز می‌دهند. یکی از عوامل موثر بر رفتار لرزه‌ای ساختمان‌ها ارتفاع سازه است که به‌طور مستقیم بر مشخصات دینامیکی اثر گذاشته و عملکرد لرزه‌ای ساختمان‌ها را متفاوت می‌کند. در این مطالعه اثر ارتفاع بر رفتار مورد انتظار ساختمان‌های بتن‌آرمه قاب خمشی در زمان مواجهه با دو رویداد لرزه‌ای متوالی به روش احتمالاتی بررسی شده است. به این منظور سه قاب خمشی ویژه 4، 8 و 15 طبقه بر مبنای ویرایش چهارم استاندارد 2800 ایران طراحی شدند. تعریف توابع شکنندگی لرزه‌ای مشروط در این مقاله مورد استفاده قرار خواهد گرفت. توابع شکنندگی مشروط مقدار شکنندگی لرزه‌ای قاب مورد نظر را به‌شرط رویداد سناریوی زلزله‌ی اول با بیشینه شتاب مشخص ارائه می‌کند. برای این‌ کار مدل عددی این سه قاب در نرم‌افزار opensees ایجاد شد. از 20 جفت نگاشت رویدادهای لرزه‌ای متوالی در مطالعه بهره گرفته شد. معیار جابه‌جایی نسبی طبقه مطابق نشریه شماره 360 سازمان برنامه و بودجه در ارزیابی تحلیل‌های غیرخطی فزاینده مورد استفاده قرار گرفت. بر اساس این مطالعه، نتایج محاسبه شده برای پارامترهای تابع شکنندگی لرزه‌ای مشروط در قاب‌های با ارتفاع مختلف ارائه شده‌اند و میزان افزایش احتمال شکست برای ارتفاع‌های مختلف قاب در اثر سناریوهای مختلف رویداد اول ارائه گردید.

the expected seismic fragility of code-conforming rc moment resisting frames under twin seismic events

after each intense mainshock, a series of aftershocks typically occur, which can have a detrimental impact on already-damaged buildings. when buildings have already lost some of their structural integrity during the main shock, the occurrence of aftershocks can lead to complete failure. the height of buildings is a critical parameter that directly influences their seismic behavior during an earthquake. in this research paper, the effect of building height on the seismic behavior of reinforced concrete (rc) moment frames is evaluated under twin earthquake events. to conduct this study, three rc moment resisting frames are designed with varying heights: 4, 8, and 15 stories. the structural design procedures are conducted based on the latest version of the iranian code for seismic construction of buildings, known as standard no. 2800 (std 2800). by modeling these frames in the opensees software, their seismic behavior is evaluated using conditional fragility curves, specifically considering the damages inflicted by the mainshock. to simulate real-world scenarios, the frames are subjected to 20 actual twin earthquake events. the maximum inter-storey drift, a commonly used damage index, was considered during the evaluation process. the criteria for collapse damage limit states were derived from the iranian instruction on seismic rehabilitation of existing buildings, pbo publication no. 360. by comparing the increase in probability of failure at conditional fragilities for frames of different heights, the impact of the mainshock on the likelihood of failure due to aftershocks is discerned. findings indicated that the probability of failure due to aftershocks substantially increases with the intensity of the mainshock. furthermore, this increase is particularly pronounced in buildings with more stories. the research demonstrates that taller buildings face a higher risk of failure when subjected to aftershocks following an intense mainshock. the additional height amplifies the vulnerability of the structure, potentially compromising its seismic resistance. this phenomenon highlights the importance of considering building height as a critical factor in seismic design and risk assessment. the study also emphasizes the significance of adhering to seismic construction codes, such as std 2800, which provide guidelines and regulations to mitigate the impact of earthquakes on buildings. compliance with these codes ensures that structures are designed to withstand seismic forces and reduce the risk of damage or collapse. the findings from this research can inform engineers, architects, and policymakers involved in seismic design and urban planning. they provide valuable insights into the behavior of rc moment frames under twin earthquake events, allowing for more informed decisions regarding building design, risk assessment, and the implementation of appropriate mitigation measures. it is crucial to continue advancing our understanding of the complex interactions between seismic events, building characteristics, and structural behavior. by conducting further research and refining these models, the resilience of structures can enhance, the risk to human life is minimized, and resulted to the development of more robust and safer communities in earthquake-prone regions. in conclusion, this study investigates the impact of building height on the seismic behavior of rc moment frames under twin earthquake events. the results underscore the heightened vulnerability of taller buildings to aftershocks following an intense mainshock. the research highlights the importance of adhering to seismic construction codes and offers valuable insights for professionals involved in seismic design and urban planning.