Risk-based seismic performance assessment of Yielding Shear Panel Device
Introduction
Recent seismic activities around the globe have revealed the need to identify sustainable solutions for reducing the catastrophic impacts of earthquakes. Researchers have introduced a variety of active, semi-active and passive energy dissipation devices to diminish the damaging seismic effects. Passive control mechanisms received attention due to their simplicity in design as well as some additional unique advantages over other control mechanisms. For example, passive control devices are generally more reliable due to their independence of external power, are easy to rehabilitate, economical and less complex. Some commonly used metal yielding passive energy dissipating devices include the added damping and stiffness (ADAS) device [1], [2], [3], triangular added damping and stiffness (TADAS) device [4], [5], steel plate shear wall (SPSW) [6], [7], among others. These metal yielding devices utilise the stable hysteretic response of the constituent materials to dissipate energy.
The Yielding Shear Panel Device (YSPD) [8], [9] is another recently proposed metal yielding energy dissipating device as shown in Fig. 1. YSPD dissipates energy by taking advantage of its stable hysteretic in-plane shear deformation of the steel diaphragm plate. YSPD is composed of a steel diaphragm plate welded inside a steel square hollow section (SHS). SHS provides the supporting boundary for the diaphragm plate as well as connectivity with the V-brace and the beam through bolted connection. Previous studies have focused on the device development, numerical modelling and response assessment in a deterministic fashion [9], [10], [11], [12]. Uncertainties arising from the occurrence and intensity of earthquakes, material strength and stiffness, structural response and consequences were not considered for the performance evaluation of YSPDs. Probabilistic seismic performance evaluation techniques, such as seismic fragility analysis and limit state probability analysis, consider these uncertainties and have been used to evaluate the performance of various seismic retrofit techniques for buildings and bridges [13], [14]. This paper uses a probabilistic approach to assess the performance of YSPDs using a benchmark structure to provide insights into the relative performance of an as-built and YSPD retrofitted structure. Uncertainties associated with seismic intensity and structural responses are considered for probabilistic performance evaluation of YSPDs. Probabilistic tools such as fragility curves and point estimates of risk of damage are used to uncover the impacts of these uncertainties and subsequently identify the performance of YSPDs for different design configurations. Obtained results provide some useful insight into changes in the probabilistic performance of a structure as a result of change in the device size and their relative positioning within the structure. It is worth noting that for other building configurations the probabilistic performance may vary based on the building design and the arrangement of YSPDs.
Section snippets
Structural model for seismic performance assessment
The moment resisting frame of the Los Angeles (LA) three storey SAC model structure, designed for the SAC Phase II Steel Project [15], [16] has been used by many researchers for performance evaluation of various seismic control devices [17], [18], [19], [20]. The four bayed North–South lateral load-bearing moment resisting frame of this benchmark structure is chosen to evaluate the performance of YSPD. Fig. 2 shows the floor plan and the moment resisting frame of the three storey SAC model
YSPDs within the moment resisting frame
Hossain and Ashraf [12] used the Bouc–Wen–Baber–Noori (BWBN) model [23] to represent the pinching hysteretic force deformation relationship of YSPDs and provided closed-form relationships among the physical parameters and model parameters. Haukaas and Der Kiureghian [24] implemented the BWBN model in Opensees [21] as a uni-axial material model excluding the pinching effect. This existing code is modified to incorporate the pinching effect herein for probabilistic seismic performance assessment
Probabilistic seismic performance evaluation
Probabilistic seismic performance evaluation identifies the response of a structure considering the uncertainties associated with the seismic events and the subsequent structural responses. The limit state, which is denoted by damage state (DS), probability of the seismic risk assessment is defined by Eq. (1) assuming seismic intensity demand (Q) and structural capacity (R) as random variables [25].where P[DS|Q = x] represents the seismic fragility of the structure and P[Q = x
Performance based on seismic drift demand assessment
The drift demand for design ground motion intensity for LA (Sa = 0.72 for T1 = 1 s) are compared to identify the reduction for various size and configurations of YSPDs and plotted in Fig. 7. A significant reduction in the seismic drift demand is observed after introducing YSPDs. The dispersion of seismic demand () is also shown for these configurations. The minimum median demand reduction of 3.3% is attained by YSPD 100 × 4 × 2 (Case 1) and a maximum reduction of 23.6% of the seismic drift demand
Conclusion
Probabilistic seismic performance evaluation techniques are employed herein to assess the suitability of Yielding Shear Panel Device as a passive control device. An incremental dynamic analysis has been conducted using a suite of available earthquake records and a finite element model of the SAC building [16] with a recently calibrated BWBN model [23], [33] introduced in the OpenSees platform to reflect the behaviour of the Yielding Shear Panel Device. Results obtained from the nonlinear
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