ارزيابي عملكرد لرزه‌اي و تعيين سطوح عملكردي سيستم دوگانه قاب - ديوار برشي فولادي

Evaluation of seismic performance and determine performance levels for dual steel moment- shear wall system

سيستم دوگانه قاب خمشي- ديوار برشي فولادي به دليل عملكرد مناسب در ساختمان هاي متداول و بلند مرتبه در كشورهاي زلزله خيز مورد استفاده قرار مي‌گيرد. نو بودن اين سيستم سازه‌اي از منظر عملكرد لرزه‌اي و بررسي سطوح عملكردي آن از يك طرف و عدم قطعيت در ويژگي‌هاي زلزله از طرف ديگر پراكندگي فراواني در نتايج حاصل از پژوهشهاي گذشته به وجود آورده است. در اين تحقيق عملكرد لرزه‌اي سيستم دوگانه قاب خمشي- ديوار برشي فولادي به وسيله تحليل ديناميكي غير‌خطي فزاينده مورد بررسي عملكردي قرار گرفته و سطوح عملكردي براي اين سيستم ارزيابي و تعيين شده است. براي اين منظور قابي از يك ساختمان 4 طبقه با ارتفاع طبقه 5/3 متر در نظر گرفته شده است. اين ساختمان مطابق استاندارد 2800 بارگذاري لرزه‌اي و بر اساس آيين‌نامه AISC360-10 و AISC Design Guide 20 طراحي لرزه‌اي شده است. جهت تحليل ديناميكي فزاينده از 20 ركورد لرزه‌اي دور از گسل استفاده شده است. با انجام تحليل‌هاي غير‌خطي فزاينده بر روي قاب مورد نظر منحني‌هاي تحليل ديناميكي فزاينده با معيار پاسخ ماكزيمم نسبت تغييرمكان نسبي طبقات و دو معيار شدت لرزه‌اي ترسيم شده است. به منظور كاهش وابستگي نتايج به تغييرات ركورد لرزه‌اي، نتايج بر اساس دو ويژگي محتواي فركانسي و زمان تداوم شتابنگاشت‌ها مورد مقايسه قرار گرفته است. در ادامه دو سطح عملكرد لرزه‌اي IO و CP براي سيستم دوگانه قاب خمشي- ديوار برشي فولادي مورد تعيين و ارزيابي قرار گرفته كه سطح IO و CP به ترتيب متناظر دريفت 1.4 و 9 درصد مي‌باشد.

Dual system of. moment frame and steel sheer wall is interesting to researchers for the good performance in absorbing lateral forces such as earthquakes and for this reason used in normal and high-rise buildings in earthquake-prone countries is used. This system, has many advantages in comparison with the conventional lateral load systems. Some advantages of steel plate shear walls rather than the other systems could be mentioned as: High ductility, strength and stiffness. Being new to this system in terms of seismic performance and functional levels and uncertainty in the seismic characteristics of the other side has created dispersion in the results of previous research. Evaluation and comparison of seismic performance of dual steel plate shear wall system is subject to far-fault ground motions is the aim of this study. To gain the aim, a four story frame with 14m in height is selected in 4-storey building with a height of 3.5 meters per floor. This building loading according to 2800 standard ad seismic design by AISC360-10 cod and AISC Design Guide 20. To verify the finite element model was used to model the driver and co-workers. The entire infill plate and boundary elements were using shell elements. The fundamental period of the structure T was estimated 0.39 s. Twenty real earthquake records have been used far-fault acceleration with a magnitude 6 to 7.5 on the soil type II for Incremental dynamic analysis with nonlinear behavior in geometry and material specimen. The real earthquake records which represented a scenario of the probable earthquakes have been gradually increased in their intensity and applied to the frame steel plate shear walls to specify the Seismic behavior. An engineering demand parameters which appropriately characterizes the seismic response of the dual steel shear wall system and its related damage is selected. The IDA curves have been drawn for two Intensity measure the 5%-damped first-mode spectral acceleration Sa (T1; 5%) and Peak ground acceleration PGA and max inter-story drift ratio as an engineering demand parameter. each records were applied to the models incrementally by equal steps of 0.1 for IM and max inter-story drift ratio was obtained from the numerical results.The dispersion of the results by the standard deviation obtained for both intensity measured. Two seismic performance level immediate occupancy (IO) and Collapse Prevention (CP) were evaluated by conceptual definitions, Research and von Mises stress. The following dependence results were evaluated on the characteristics of records based on the frequency content of Acceleration and duration of acceleration.The finite element analyses show that the Damage Index in the elastic stage until the Instability a considerable dispersion of the results for different records. Frame at IO performance level show elastic behavior and a quick return to the original state structures and stiff behavior see and there were no fixed displacement but at CP performance level after a few seconds the system into the fixed displacement behavior. In dual steel plate shear wall system the first floor wall plate the most energy absorption through surrender among the other floor.