تحليل هزينه- فايده‌ي ساخت و بازسازي قاب‌هاي فولادي مهاربندي‌شده داراي ميان‌قاب با استفاده از منحني‌هاي شكنندگي خسارت لرزه‌‌يي

Cost-Benefit Analysis of Construction and Rehabilitation of Steel Braced Frames with Infill Panels using Seismic Damage Fragility Curves

هزينه‌ي سازه شامل مجموع هزينه‌هاي ساخت به‌علاوه‌ي هزينه‌هاي مربوط به بازسازي خسارت ناشي از زلزله، نگهداري و مديريت سازه در طول عمر مفيد آن است. ساخت سازه در سطوح عملكرد مختلف از لحاظ هزينه متفاوت است. در اين نوشتار، برخي معيارهاي طراحي براي عملكرد مناسب ساختمان با مقايسه‌‌ي هزينه‌هاي ساخت و بازسازي خسارت ناشي از زلزله در سطوح عملكرد مختلف توسعه داده شده است. سازه‌هاي مورد مطالعه، قاب‌هاي فولادي داراي ميان‌قاب با مهاربندي X هستند. با انجام تحليل ديناميكي فزاينده، سطوح عملكرد روي منحني‌هاي IDA تعيين و سپس با استفاده از توابع شكنندگي، منحني احتمال تجاوز سازه از سطح عملكرد طراحي به‌دست آمده است. همچنين براي بررسي اثر ميان‌قاب در رفتار احتمالاتي سازه، منحني‌هاي شكنندگي قاب‌هاي طراحي‌شده در حالت حذف ميان‌قاب نيز توليد شده است. تخمين خسارت و ارزيابي اقتصادي قاب‌هاي داراي ميان‌قاب به روش "نسبت منافع به مخارج" انجام شده است، كه نشان مي‌دهد در شرايط اقتصادي موجود، انتخاب سطح عملكرد مطلوب‌تر، از نظر اقتصادي مقرون به صرفه است و نتايج حساسيت چنداني به تغييرات كمينه‌ي نرخ جذب و عمر مفيد سازه ندارد.

Damage from earthquake reconstruction is mainly due to the poor performance of structures under seismic loads. Structural costs include constructional costs, plus all costs related to damage from earthquake reconstruction, maintenance and the management of the structure. The cost of construction for various structures is quite different at different performance levels. A question may arise that if the primary constructional cost is less, will the plan be economical or not? In the case of a positive answer, engineers tend to select the lower performance level. In this paper, a comprehensive comparison has been conducted between the primary cost of construction and reconstruction, due to the damage from credible earthquakes, during the useful life of the structure, at various levels of performance. The analysis and design of the structures have been conducted in Perform (3D) package. A structural design criterion was developed to support the proper functioning of the building and reducing earthquake damage. Furthermore, infill panels can increase the stiffness and strength of structures. So, they should be considered in the phase of building design. In this study, steel braced frames with infill panels, with three and six stories, are considered. The frames have three spans, in which X braces have been used in the middle span for all stories. Incremental dynamic analysis (IDA) was carried out, and the performance levels were determined from the IDA curves. Then, fragility curves were obtained for the braced steel frames with infill panels, which show the probability of exceedance from the performance level that the structure had been designed for. To investigate the effect of infill panels on the probabilistic behavior of structures, the fragility curves were obtained for the braced steel frames without infill panels. After that, performance levels were assessed using the cost benefit analysis method. Results show that selection of a higher performance level has more economic justification; and the immediate occupancy (IO) is the most economical performance level for these types of structure. Finally, sensitivity analyses on the results of the cost benefit analysis show that changes in the useful life of structures and minimum absorption rate have no significant sensitivity.