ارزیابی شاخص قابلیت اطمینان قاب‌های خمشی بزرگ‌دهانه فولادی تحت اثر مؤلفه قائم زلزله

نوع مقاله : Articles

نویسندگان

1 دانشگاه آزاد اسلامی واحد علوم و تحقیقات تهران

2 پژوهشگاه بین المللی زلزله شناسی و مهندسی زلزله

چکیده

زلزله‌های حوزه نزدیک عموماً دارای مؤلفه قائم بزرگتری نسبت به مؤلفه افقی می‌باشند و با همین ویژگی از زلزله‌های حوزه دور متمایز می‌شوند. این موضوع در قاب‌های بزرگ‌دهانه دارای اهمیت بیشتری هستند. در این پژوهش اثر مؤلفه‌های افقی و قائم زلزله در قاب های بزرگ دهانه، با شبیه‌سازی دو نوع سازه  با دهانه های مختلف، با استفاده از نرم‌افزارهای اجزاء محدود مورد بررسی قرار گرفته است. به این گونه که ابتدا سازه ها را تحت اثر مؤلفه‌های افقی زلزله قرار داده و در مرحله بعد علاوه بر مؤلفه‌های افقی، مؤلفه قائم زلزله نیز وارد شده و در هر حالت عملکرد آن مورد بررسی قرار گرفته است. برای بررسی عملکرد سازه نیز مطابق دستورالعمل بهسازی لرزه‌ای، از تحلیل‌های استاتیکی و دینامیکی خطی و غیرخطی استفاده شده است. در بخش پایانی مقاله که با هدف ارزیابی قابلیت اطمینان سازه صورت گرفته است، مقادیر افزایش لنگر، برش، نیروی محوری ستون ها، افت میان دهانه تیرها و ... بررسی شده و با استفاده از یک نرم‌افزار آماری مناسب، قابلیت اطمینان سازه نسبت به پارامترهای مذکور محاسبه شده است.Evaluation of Reliability Index for Long Span Steel Moment Frames Subjected to Vertical Earthquake ComponentMohammad Sadr Ara, Panam Zarfam and Mahmood HosseiniRecords in the near-fault areas indicate the strong vertical ground motion. Near-fault earthquakes are different from far-fault earthquakes due to the adverse effect of their vertical component, which can be very destructive for long span frames. The Vertical Component of earthquake is different from the horizontal component. Vertical component of earthquake occurs when the compression P waves separate. Whereas the horizontal component occurs as the shear S waves separate. The frequency content of vertical component of earthquake is higher than the horizontal component. The natural frequency of structures in the vertical direction is more than that of the horizontal direction. These factors may cause the resonance in the structures. The first step in the examination of the effects of vertical component of an earthquake on structures is identifying the stimulating source of vertical component of the earthquake, response spectrum of the vertical component and affecting parameters on the vertical component. In this research, the effect of horizontal and vertical components of earthquakes has been investigated in long span building frames by modeling two types of such structures with various openings sizes in a powerful finite element software. For this purpose, in the first phase of the study, the structures have first been evaluated under the effect of horizontal component of earthquake alone, and then, the vertical component of earthquakes has been added and performance of the structures has been evaluated again. To evaluate the performance of structures, both linear and nonlinear as well as static and dynamic analyses according to the seismic rehabilitation of structures guidelines have been performed. In the second phase of the study, for more confident evaluation, the reliability indices as suitable tool, recommended in recent researches, have been used. For this purpose, the amounts of moment, shear force, axial force of columns, and deflection of the long span beams have been calculated, and the corresponding reliability indices have been obtained by using an appropriate statistical software.Keywords: Seismic Reliability, Reliability Indices, Vertical Component of Earthquake Ground Motion, Long Span Building Frames.

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مراجع

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