طراحی مطلوب دستگاه های جداسازی قاب خمشی فولادی ساختمان بلند با به کارگیری اصول بر اساس عملکرد Optimal design of isolation devices for mid-rise steel moment frames using performance based methodology

1 Introduction Seismic protective devices in the form of passive or semi-active can be used to mitigate the direct and indirect seismic losses to buildings (Lafontaine et al. 2009; Lee et al. 2006). Among which the base isolation system has been proved as an effective passive system to dissipate and deflect earthquake input energy through lengthening the fundamental structural period to avoid the dominant frequency of ground motions (Kelly 1986; Skinner et al. 1993). For the steel moment frames (SMF), the base-isolation technique becomes more favorable as it provides sufficient structural damping, which is not usually provided by the superstructure itself. To design an isolation system, although the current building design codes (e.g. ASCE 7-10 2010) provide descriptive methods, they cannot incorporate uncertainties inherent with ground motion characteristics, building modeling parameters (e.g. material properties, member stiffness and strength), capacity estimations, and variations in geometric irregularities of buildings, etc. More importantly, the isolation design cannot be directly related to the expected performance of buildings. To further define and quantify the structural performance, the performance-based design and analysis methods emerged. The concept was formally established in SEAOC Vision 2000 document (1995) and further developed in several design documents (e.g. ATC-40 1996; FEMA 273 1997a; FEMA 274 1997b; ATC-58 2012, etc.). The methodology intends to logically quantify the seismic hazards and link predictable/measurable performance requirements to design decisions based on damage levels. The outcome of the methodology is often the estimated frequency (in probability sense) with which a particular performance metric will exceed various levels for a given design at a specific location. For the SMFs, nonlinear drift estimations that are often used to define the performance levels were provided (Sabelli et al. 2003). In addition, Haselton et al. (2007) produced an analysis and design methodology for a benchmark moment frame building to address its seismic performances in terms of damage-repair cost, loss-of-use duration, as well as operability, lifesafety, and collapse potential. Such performance based earthquake engineering (PBEE) framework is particularly useful in the case of base isolation design when the device parameters can be directly related to a probabilistic performance index, which facilitates the comparison of different isolation designs. For example, Sayani and Ryan (2009) developed a response index to compare the relative performance of many systems and to predict the best system to achieve a given performance objective for both base-isolated and fixed-base buildings. Zhang and Huo (2009) developed a performance index considering both column and isolator damage for isolated highway bridges. Recently, researchers presented the total seismic loss as an intuitive performance index by providing the expected losses to stakeholders (Aslani and Miranda 2005; Dhakal and Mander 2006; Solberg et al. 2008; Bai et al. 2009; Graf and Lee 2009; Shu et al. 2017). To estimate the loss to a specific building, the damage is usually categorized into different components such as structural and nonstructural damage.