PSI - Issue 70

Pradeep Ushakumari Abhinand et al. / Procedia Structural Integrity 70 (2025) 129–136

133

the respective plastic hinges according to the modified Ibarra – Medina – Krawinkler (IMK) deterioration model (Ibarra et al ., 2005; Lignose & Krawingler, 2011), which incorporates cyclic degradation in both strength and stiffness using calibrated deterioration parameters. The panel zones, which represent the joint regions between beams and columns, are modelled using nonlinear force-deformation relationships. These are enhanced with strain-hardening behaviour incorporated through concentrated nonlinear springs (Krawingler, 1978). The configuration of each panel zone includes a combination of rigid link elements, three frictionless springs, and one concentrated spring hinge that follows a tri-linear force-deformation relationship. This hinge is calibrated to emulate realistic joint behaviour, including shear distortion, while excluding significant cyclic deterioration, in accordance with recommendations from existing literature (Ibarra et al ., 2005; Lignose & Krawingler, 2011; Krawingler, 1978). A schematic representation of the typical connection panel zone, highlighting the key components and associated inelastic behaviours, is presented in Figure 3. To account for first-order geometric nonlinearities, commonly referred to as P-Delta effects, a leaning column mechanism is employed. This auxiliary column is located one bay (8.0 m) away from the main moment resisting frame. The base of the leaning column is pinned, and its upper joints are released for moment to eliminate any lateral stiffness contribution. It is connected to the main frame solely through axial rigid links with pinned ends, ensuring that no lateral forces or unintended moment transfer occurs. This approach allows for the accurate simulation of gravity-induced stability effects without compromising the integrity of the moment-resisting frame, and it aligns with established best practices for nonlinear dynamic modelling of frame structures.

Fig. 3. Typical details of inelastic model for the beam-column connection panel zone.

4. Seismic Record Details and Analysis Procedure To evaluate the R -factor of the selected 4-storey SMRF, a suite of representative seismic ground motion records is required. In this way, it can fulfil the record-to-record variability criterion to ensure broader applicability of the results. In this study, the ground motion dataset comprises a set of Far-Field records-defined as recordings obtained at sites located at least 10 km away from the fault rupture zone. This selection criterion ensures that the ground motions reflect typical seismic demands on structures not situated in the immediate vicinity of fault rupture zones. A total of forty four ground motion records are selected for analysis, based on the FF record set recommended in FEMA P-695 and sourced from the pacific earthquake engineering research (PEER) NGA database (PEER, 2025). These records are chosen to represent a broad range of seismic intensity and duration characteristics. Specifically, the peak ground acceleration (PGA) values for the considered records range from 0.21 g to 0.82 g , where g denotes the acceleration due to gravity. The durations of the selected records vary from 19.99 seconds to 99.92 seconds, covering both the short and long-duration seismic events adequately. Again, the moment magnitudes of the records range between 6.6 and 7.6, and all the records have closest distance to the fault rupture are greater than 10 km. Figure 4 presents the acceleration response spectrum of the adopted individual records, along with the mean as well as mean + standard deviation acceleration response spectra of these ground motions in logarithmic scale.