معیارهای پیشرفته سختی اسکالر برای پیش بینی ظرفیت فروپاشی
Abstract
1- Introduction
2- Selected IMs
3- Structural modeling and analysis
4- Investigating the efficiency of the IMs for collapse capacity prediction
5- Investigating the sufficiency of the IMs for collapse capacity prediction
6- Proposing optimal IMs
7- GMPEs for the proposed IMs
8- Conclusions
References
Abstract
Nowadays, passive energy dissipation systems are used in the seismic design of new structures and the retrofit of existing structures. Fluid Viscous Dampers (FVDs) are one of the important types of passive energy dissipation systems. Using FVDs can considerably decrease the seismic demands on structures. In this study, seismic collapse behavior of steel Special Moment Resisting Frames (SMRFs) equipped with FVDs is investigated using different scalar Intensity Measures (IMs). Incremental Dynamic Analysis (IDA) method is applied to determine the collapse capacity, IMcol, values for low- to mid-rise steel SMRFs equipped with FVDs. After determining the collapse capacity, IMcol, values by using each of the IMs, the efficiency and sufficiency of the IMs for predicting the seismic collapse capacity of the structures are investigated. Then, advanced scalar IMs, including the effects of spectral shape and ground motion duration, are proposed to reliably predict the collapse capacity of steel SMRFs equipped with FVDs. The results indicate that the proposed IMs possess high efficiency and sufficiency for collapse capacity prediction of steel SMRFs equipped with FVDs.
Introduction
Using passive energy dissipation systems, including Fluid Viscous Dampers (FVDs), hysteretic dampers, viscoelastic dampers and friction dampers, is one of the effective ways to mitigate excitations due to strong ground motions [1,2]. FVDs are a type of passive energy dissipation systems that are extensively used for the seismic design of new structures and the retrofit of existing structures [3,4]. For elastic structures, using FVDs reduces both displacements and accelerations simultaneously [5,6]. However, as pointed out by Karavasilis and Seo [7], for highly inelastic structures, FVDs may increase accelerations, as the damper forces are not out of phase with the peak drifts and internal member forces, due to the nonlinearity of the structure. FVDs provide a velocity-dependent force and can behave as linear or nonlinear elements. The force developed by a FVD is as follows: F Cv v d =⋅ ⋅sgn( ) αd (1) where C is the damper coefficient, v is the relative velocity between the two ends of the damper, αd is the velocity exponent, and sgn is the signum function. In seismic applications, the exponent αd is in the range of 0.2–1.0 [8]. When αd is equal to one, the damper is called "linear FVD", and values of αd lower than one represent nonlinear FVDs. Several researchers have investigated the seismic response of structures equipped with FVDs (e.g., see [9,10]). Although a number of procedures have been developed for the design of these structures [11–13], the seismic collapse of these structures has not been extensively investigated. The collapse of structural systems due to strong ground motions is the primary source of casualties and loss of life during earthquakes. Seismic collapse occurs when a structural system is unable to withstand gravity loads under earthquake shaking. In recent years, due to significant advancements in the computational capability of computers and the methods of nonlinear analysis, assessing the seismic collapse of structures has become an interesting field of study for researchers. Thus, several studies have been performed to assess the seismic collapse of structures [14–16], and to develop engineering approaches for seismic collapse assessment. The ATC-63 document [17] presents a new methodology for seismic collapse assessment of structures, to assess design criteria and seismic performance factors existing in seismic codes. Recently, some studies have been performed to assess the seismic collapse of structures equipped with FVDs. For instance, Hamidia et al. [18] proposed a simplified approach to assess the seismic collapse of structures equipped with FVDs. Seo et al. [19] investigated the seismic resistance of steel Moment Resisting Frames (MRFs) with supplemental FVDs against collapse.