• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.69-76
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• 2003

Near-field ground motions exhibit special characteristics that are different from ordinary far-field ground motions. This paper first briefly examines the characteristics of near-field ground motions associated with fault directivity and fling-step effects. Then evaluation of near-field ground motions by inelatstic response spectrum analysis is performed and analyzed. As a result, ductility demand in near-field ground motions is larger in hanging wall than in foot wall in long period regions. Also in long period regions ductility demand in soil site is larger than that in rock site.

• Earthquakes and Structures
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• v.17 no.6
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• pp.533-543
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• 2019

This paper presents a study on the behavior of an RC bridge under near-field and far-field ground motions. For this purpose, a dynamic nonlinear finite element time history analysis has been conducted. The near-field and far-field records are chosen pairwise from the same events which are fits to the seismic design of the bridge. In order to perform an accurate seismic evaluation, the model has been analyzed under two vertical and horizontal components of ground motions. Parameters of relative displacement, residual displacement, and maximum plastic strain have been considered and compared in terms of near-field and far-field ground motions. In the following, in order to decrease the undesirable effects of near-field ground motions, a viscous damper is suggested and its effects have been studied. In this case, the results show that the near-field ground motions increase maximum relative and residual displacement respectively up to three and twice times. Significant seismic improvements were achieved by using viscous dampers on the bridge model. Somehow under the considered near-field ground motion, parameters of residual and relative displacement decrease dramatically even less than the model without damper under the far-field record of the same ground motion.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.125-132
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• 2002

In this study, a numerical method is developed for nonlinear analysis for soil-pile-structure interaction system in time domain. Finite elements considering material nonlinearity are used for the near field and boundary elements for the far field. In the near field, frame elements are used for modeling a pile and plane-strain elements for surrounding soil and superstructure. In. the far field, boundary element formulation using the dynamic fundamental solution is adopted and coupled with the near field. Transformation of stiffness matrices of boundary elements into time domain is performed by inverse FFT. Stiffness matrices in the near field and far field are coupled. Newmark direct time integration method is applied. Developed soil-pile-structure interaction analysis method is verified with available literature and commercial code. Also, parametric studies by developed numerical method are performed. And seismic response analysis is performed using actual earthquake records.

• Explosives and Blasting
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• v.29 no.2
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• pp.32-42
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• 2011

For blasting vibration analysis, there are mostly two methods, firstly, far field vibration analysis to estimate limit of building damage, secondly, near field subterranean vibration analysis to estimate rock damage and subterranean structure facilities. The former has been mainly used in our country and aboard, the latter is mostly analysed by using Homberg's model. In this model, basic input data are acquired in far field surface vibration. But in the consideration of the results of being conducted in this area over the past few decade, it is required that Homberg's model is modified. For the purpose of this, measurements of near field vibration were first conducted in our country. But it was only proposed the measurement method and the method of analysis or prediction was not suggested. Accordingly, in this paper, measurements of near field subterranean vibration were conducted and the method of analysis or prediction of near field subterranean vibration would be suggested.

• Earthquakes and Structures
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• v.5 no.6
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• pp.733-751
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• 2013

Near field ground motions have caused several structural damages in recent decades. As a result, seismic codes are being updated with related requirements. In this paper a comparative study on the seismic behavior of concentrically braced frames (CBFs) designed based on different seismic codes is performed. Reliability of various frames with different heights and bracing types are analyzed based on the results of "Incremental Dynamic Analysis" (IDA) under near field ground motions. Fragility curves corresponding to IO (Immediate Occupancy) and CP (Collapse Prevention) limit states are extracted based on IDA curves. Results imply that, frames designed based on the near field seismic design criteria of UBC-97 are more reliable under near field ground motions and their failure probability is less comparing to others.

• Structural Engineering and Mechanics
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• v.62 no.4
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• pp.497-506
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• 2017

A low damage self-centering braced frame equipped with post-tensioning strands is capable of directing damage to replaceable butterfly-shaped fuses. This paper investigates the seismic performance of rocking braced frame under near-field pulse-like ground motions compared to far-field records. A non-linear time history analysis is performed for twelve self-centering archetypes. A sensitivity analysis is carried out to examine the influences of ground motion types and modeling parameters. Findings represent the proper efficiency of the self-centering system under both far-field and near-field pulse-like ground motions.

• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.271-280
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• 2016

The need to accurate quantification of blast pressure loading in the near field is important because the focus of security design of critical infrastructure, buildings and bridges is for near-field detonations. Incident and reflected pressures for near-field detonations are very difficult to be measured by commercially available pressure transducers due to the high pressure and temperature, which requires a verified and validated computational fluid dynamics code to reasonably predict the near-field pressures and impulses. This paper presents numerical studies to verify and validate a CFD code for calculations of incident and reflected overpressures and impulses. The near field is emphasized and recommendations for mesh sizes to optimally simulate the near-field detonation are provided.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.31-38
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• 2005

Recent earthquakes have shown that near-field earthquakes can produce spectral demands significantly larger than those considered in current design code. International Atomic Energy Agency (IAEA) has recently initiated a coordinated research program on safety significance of near-field earthquakes. The purpose of this program is to focus on the assessment of vulnerability of nuclear facility structures by using and adapting the best available engineering practices appropriate to evaluate the effects of near-field earthquakes. The objective of this paper is to evaluate of seismic responses of a shear building test specimen subjected to near-filed earthquakes. To achieve the objective, the seismic responses of the test specimen, evaluated by the Displacement Coefficient Method (DCM) and Nonlinear Dynamic Analysis (NDA), are compared with those by the experimental tests.

• Geomechanics and Engineering
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• v.20 no.2
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• pp.131-146
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• 2020

Evaluation of earthquake impacts in settlements with a high risk of earthquake occurrence is important for the determination of site-specific dynamic soil parameters and earthquake-resistant structural planning. In this study, dynamic soil properties of Karliova (Bingol) city center, located near to the intersection point of the North Anatolian Fault Zone and the East Anatolian Fault Zone and therefore having a high earthquake risk, were investigated by one-dimensional equivalent linear site response analysis. From ground response analyses, peak ground acceleration, predominant site period, 0.2-sec and 1-sec spectral accelerations and soil amplification maps of the study area were obtained for both near-field and far-field earthquake effects. The average acceleration spectrum obtained from analysis, for a near-field earthquake scenario, was found to exceed the design spectra of the Turkish Earthquake Code and Eurocode 8. Yet, the average acceleration spectrum was found to remain below the respective design spectra of the two codes for the far-field earthquake scenario. According to both near- and far-field earthquake scenarios in the study area, the low-rise buildings with low modal vibration durations are expected to be exposed to high spectral acceleration values and high-rise buildings with high modal vibration durations will be exposed to lower spectral accelerations. While high amplification ratios are observed in the north of the study area for the near-distance earthquake scenario, high amplification ratios are observed in the south of the study area for the long-distance earthquake scenario.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.4
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• pp.105-111
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• 2019

In this paper, a performance analysis of waveguide broad-wall slot array antenna for millimeter-wave seeker in Ka-band was performed as using near-field measurement. The measurement of slot array antenna was conducted in both far-field and near-field. And the validation of near-field test in millimeter band was confirmed. It was confirmed that the beam pattern characteristics including beam width and side lobe level of the slot array antenna that performed the verification were the same. Differenced in the side lobe level of azimuth and elevation beam pattern were verified to be less than 1dB. Additionally, the new antenna aperture distribution was extracted as using back-projection method modifying the near-field data and then introduced the method conducting performance analysis of array antenna.