ارتقا سطح عملكرد سازه‌ها با استفاده از كنترل فعال بهينه‌ي‌ لحظه‌‌يي

IMPROVING PERFORMANCE OF STRUCTURES USING ACTIVE INSTANTANEOUS OPTIMAL CONTROL

كاهش پاسخ سازه با اعمال نيروي كنترلي را مي‌توان مطابق الزامات آيين‌نامه‌هاي طراحي براساس عملكرد با استفاده از روش‌هاي تحليل غيرخطي بهينه ساخت. در اين نوشتار با استفاده از سيستم كنترل فعال، رفتار سازه در جهت رسيدن به عملكرد مورد نظر بهبود بخشيده مي‌شود. نيروي كنترل با الگوريتم بهينه‌ي لحظه‌يي به قاب‌هاي 4، 8، و 12 طبقه با فرض رفتار غيرخطي سازه اعمال مي‌شود، تا جابه‌جايي سازه را در محدوده‌ي جابه‌جايي‌‌هايي حاصل از تحليل استاتيكي غيرخطي در سطح عملكردي هدف نگه ‌دارد. درواقع، نقطه‌ي عملكرد سازه معيار مقدار نيروي كنترلي اعمالي است. نتايج نشان مي‌دهند الگوريتم بهينه‌ي لحظه‌يي قادر به كاهش زياد جابه‌جايي سازه در نسبت c/r =1E+9 است؛ كه اين نسبت به نيروي كنترل قابل ملاحظه‌يي نياز دارد. براي سازه‌هاي مورد مطالعه نسبت c/r بين 1E9 تا 5E9، سازه را در محدوده‌ي عملكردي IO حفظ مي‌كند. اين نسبت براي سازه‌هاي مشابه نيز قابل استفاده است.

During recent earthquakes, the behavior of structures has demonstrated that the main reason for building collapse is the big deformation during strong seismic events. Therefore, the structural designers would like to reduce the lateral displacement of structures under a specified level. Using the shear walls and bracing and increasing the members’ size are the common ways which can protect the buildings against the earthquake or wind load. In two recent decades, a new method has been invented which is called Active Structural Control. Applying the external force, when it is needed; not only can reduce the response displacement but also is able to make a high reduction in response velocity and acceleration. Predict the building behavior during an earthquake event has an important role in order to have a safe structure. The structure engineers usually use two methods to compute the structure response: i) Dynamic Analysis or ii) Nonlinear Static Analysis. Since the dynamic analysis depends on several items such as frequency content of earthquake record, the most structure specialists prefer to employ the nonlinear static analysis (pushover analysis) to compute the target displacement in IO, LS and CP levels. The essential goal of this research is to create a combination between active structural control concept and nonlinear static analysis. Three reinforced concrete buildings with 4, 8 and 12 floors are selected. All buildings have three bays and are analyzed using the pushover method and for each case a performance level is found. The main purpose of using active structural control equipment in the selected buildings is to keep the building performance in that limit which is found at the analytical part. An important aspect of this investigation is the incorporation of the possibility of inelastic deformation of the members into the control algorithm. In analytic investigation, in order to solve the control formula, the Instantaneous Optimal Control algorithm is employed which is conducted to introduce “c/r” ration. This ratio shows the importance of the amount of control force against the importance of reduction in structural response. The results show that the best c/r ratio for the selected structures is between 1x109 and 5x109 which can keep the structures in IO performance level. Generally, the optimal amount of c/r ratio to get the target performance level depends on different items such as the primary strength of structure (the initial performance level) and probable seismic hazard, therefore; it seems that the hazard risk analyses is necessary as an additional analysis.