International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 11 Issue: 03 | Mar 2024
p-ISSN: 2395-0072
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Seismic Performance Evaluation of RC MRF Under Near and Far-Field Ground Motions Aftab Ahmad1, Prof. Asif Husain2 1P.G. Student, Department of Civil Engineering, Jamia Millia Islamia, New Delhi, India 2Professor, Dept. of Civil Engineering, IIT Delhi, New Delhi, India
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Abstract - In seismic design and engineering, the choice of
of kilometers from the epicenter, pose unique challenges to structures, inducing nonlinear behavior and potential damage. On the other hand, far-field earthquakes, situated at a considerable distance, present different characteristics with lower ground accelerations, longer-duration shaking, and a broader frequency content (Bhairav, Thakur 2022) [2]. Their seismic waves experience less attenuation, resulting in a more gradual decay of ground motion amplitudes. Understanding the dynamics of both near-field and far-field earthquakes is essential for designing resilient structures. Engineers must tailor seismic design and retrofitting strategies to account for the concentrated and intense shaking of near-field events and the distributed, longer-duration shaking associated with far-field seismic waves, ensuring comprehensive resilience in seismically active regions. Seismic fragility analysis is needed to assess the probability of damage to structures during earthquakes and to estimate losses before and after an earthquake. Fragility models play a crucial role in performance-based earthquake engineering (PBEE) (V., Bui, Tran., Son 2022) [3] by representing the probability that the engineering demand parameter (EDP) exceeds a safety threshold given selected intensity measures (IMs). Various methods, such as empirical or analytical approaches, can be used to derive fragility curves that display the likelihood of different damage states being surpassed (Renato, Giannini., Fabrizio 2022) [4]. Dynamic analysis is commonly used to estimate fragility functions, and statistical inference methods can be applied to predict these functions and minimize the number of structural analyses needed. In order to calculate fragility functions, the definition of the limits states that characterize the state/performance of the structure is required. These limit states are defined in terms of an engineering demand parameter (i.e., a form of measure of the structure’s response). In this study, the maximum Interstory drift was used. The corresponding EDP (drift) values are 1%, 2%, and 4% to define a state of Immediate occupancy, life safety, and collapse prevention respectively. These thresholds were obtained from FEMA 356 (Shakeba and Hamed 2022) [5]. Seismic fragility models can be used for risk and vulnerability assessment, disaster management, emergency preparedness, and retrofitting prioritization (Vamvatsikos and Cornell 2002) [6]. The objective of this research is to gather novel insights into the responses of reinforced concrete moment frames to near-fault ground motions and assess the variations compared to far-fault
earthquake scenarios and soil conditions plays a pivotal role in ensuring the structural resilience of buildings. This study aims to develop seismic fragility curves and comprehensively evaluate the seismic response of an 8-storey structure situated on stiff soil, considering both far-fault and near-fault earthquake scenarios. The comparative analysis will shed light on the nuanced effects of ground motions originating at varying distances from the structure, offering valuable insights for seismic design and risk mitigation. For this purpose, Incremental dynamic analysis was performed and seismic fragility analysis of G+7 story moment resisting frame situated on stiff soil is utilized. Initially gravity, equivalent static and response spectrum analysis were conducted in order to design the building according to the national building code requirements then nonlinear static pushover analysis was carried out to see the failure modes and check if there are any local failures in the structure. structure's nonlinearity was modeled using lumped plasticity to simulate the inelastic behavior of beams and columns. Selection of near-field NP (Non-Pulse) and far-field ground motions was done according to ATC 63 using PEER nga-west database. IDA was performed for each group of ground motions and seismic fragility curves were developed. Modeling outcomes suggest that, in the case of two earthquakes sharing almost identical conditions, the near-fault record exhibits a greater array of displacement values. Near-fault ground motions exhibited higher recorded drift than far-field ground motions for same level of intensity both the overall and relative displacements show an incremental trend, and the significance of nonlinear behavior becomes more prominent, and the nonlinear range is achieved at lower percentile values.
Key Words: Near-Fault; Seismic Fragility Curves; Incremental Dynamic Analysis (IDA); Dynamic Time History Analysis; Far-Fault
1.INTRODUCTION In seismic studies, both near-field and far-field earthquakes hold pivotal importance, offering distinct challenges and considerations for structural engineering. Near-field earthquakes, occurring near the site of interest, exhibit higher ground accelerations and strong pulse-like motions with prominent directivity effects (Erdik, M., B. Şadan 2023) [1]. These seismic events, typically within a few tens
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