Yazar "Mehdi Kashani, Mohammad Mehdi" seçeneğine göre listele

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    A STUDY ON PULSE CHARACTERISTICS OF 06.02.2023 KAHRAMANMARAS EARTHQUAKES
    (International Association for Earthquake Engineering, 2024) Kocakaplan Sezgin, Sedef; Ahmadi, Ehsan; Georgantzia, Evangelia; Mehdi Kashani, Mohammad Mehdi
    On February 6, 2023, two destructive earthquakes occurred with magnitudes of Mw = 7.7 in Pazarcik (Kahramanmaras, Turkey) and Mw = 7.6 in Elbistan (Kahramanmaras, Turkey), respectively. The earthquakes caused loss of lives and properties (heavy damage and collapse of structures). In the scope of this study, a multi-pulse decomposition method of ground motions is used to investigate the time-position, frequency, amplitude, pulse width, and phase angle of the wave packets. The investigation focuses particularly on time-localization, period, and amplitude of the extracted pulses using two ground motion ensembles: 103 ground motions from the Pazarcık earthquake and 79 ground motions from the Elbistan earthquake. The elastic and inelastic response spectra of the original ground motions and those from the multi-pulse decomposition method were generated for the ground motion ensembles. The distribution of pulse characteristics among the fault ruptures was presented for the Kahramanmaras earthquakes. © 2024, International Association for Earthquake Engineering. All rights reserved.
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    Seismic Performance of Precast Post-Tensioned Segmental Bridge Piers with Shape Memory Alloy (SMA) Bars
    (Earthquake Engineering Research Institute, 2022) Kocakaplan Sezgin, Sedef; Ahmadi, Ehsan; Mehdi Kashani, Mohammad Mehdi
    In recent years, accelerated bridge construction (ABC) has led to substantial application of precast posttensioned segmental (PPS) bridge piers in bridge construction. However, PPS piers are not to be used in high-seismicity regions due to their low-energy dissipating capacity. To address this deficiency, this paper examines a segmental bridge pier with unbonded post-tensioned superelastic Shape Memory Alloy (SMA) bars through a Finite Element (FE) framework. The seismic performance of the PPS piers with SMA bars is investigated using far-field ground motions and incremental dynamic analysis (IDA). IDA curves of PPS piers are obtained for top drift and normalized base shear, and results are compared with the ones without SMA bars. It is seen that the PPS piers with SMA bars developed higher normalized base shear responses, which is mainly due to their higher stiffness compared to the ones without SMA. However, the PPS piers with SMA bars reduced the drift responses of the piers. © 2022 12th National Conference on Earthquake Engineering, NCEE 2022 All rights reserved.
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    SEISMIC VULNERABILITY ASSESMENT OF PRECAST POST-TENSIONED SEGMENTAL PIERS
    (International Association for Earthquake Engineering, 2024) Sezgin, Sedef Kocakaplan; Ahmadi, Ehsan; Mehdi Kashani, Mohammad Mehdi
    Precast post-tensioned segmental (PPS) bridge piers mitigate global and local damages of bridge structures through natural hinges. The application of PPS piers has increased recently in Accelerated Bridge Construction (ABC). Therefore, to increase their use in high-seismicity regions, this paper examines seismic vulnerability assessment of post-tensioned segmental bridge piers with Shape Memory Alloy (SMA) bars through a Finite Element (FE) framework. First, to investigate the energy dissipation capacity of the PPS piers with SMA, an extensive parametric study performed on the key design parameters including, (i) number of segments or aspect ratio, (ii) length, area, and post-tensioning of the SMA bars, and (ii) area and post-tensioning of the tendon. The results are also compared with the piers without SMA bars. Furthermore, an equivalent reinforced concrete (RC) pier to one of the PPS piers is also analysed. Incremental dynamic analysis (IDA) is performed, and fragility curves are generated to evaluate seismic performance of the PPS piers with and without SMA bars using a suite of 44 far-fault ground motions. The IDA results show that, slenderizing the PPS piers tends to change failure criterion from the yielding of the post-tensioning tendon to strength loss of the pier. For squat piers, the yielding of the tendon governs the failure of the pier while for very slender PPS piers, the strength of PPS piers drops due to second-order effects at small drift values prior to the yielding of the post-tensioning tendon. Furthermore, the equivalent RC pier reaches slight and medium damage states in lower intensity measures compared to the PPS piers. Finally, IDA results of PPS piers with SMA bars show that their median IDA curves for drift responses are lower than the ones without SMA bars. © 2024, International Association for Earthquake Engineering. All rights reserved.