• 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 Acoustical Society of Korea
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• v.18 no.6
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• pp.31-37
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• 1999

This paper describes the far-field estimation using the near-field measurement data. Measurement in far-field region gives us the acoustical characteristics of the source but in general measurement is made in near-field such as acoustic water tank or anechoic chamber, so far-field acoustical characteristics of the source should be predicted from near-field data. In this case, the number of measurement points in the near field which relates to the accuracy of the predicted field and the amount of data processing, should be optimized. Existing papers say that measurement points is proportional to kL and depends on geometry and directivity of the source. But they do not give us any definite criterion for the required number of measurement points. Boundary Collocation Method which is one of the far-field prediction methods, is analyzed based on Helmholtz integral equation and Green function and it has been found that the number of measurement points is optimized as 0.54kL which is about one half of the existing results.

• Structural Engineering and Mechanics
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• v.1 no.1
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• pp.103-118
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• 1993

The near field is discretized into finite elements, and the far field into infinite elements. Closed form far-field solutions to three fundamental problems are used as the shape functions of the infinite elements. Such infinite elements are capable of transmitting all surface and body waves. An efficient scheme to integrate numerically the stiffness and mass matrices of these elements in presented. Results agree closely with those obtained by others.

• Earthquakes and Structures
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• v.18 no.3
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• pp.391-405
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• 2020

The use of passive energy dissipation devices has been widely used in the construction industry to minimize the probability of damage occurred under intense ground motion. In this study, collapse margin ratio (CMR) and fragility curves are the main parameters in the assessment to characterize the collapse safety of the structures. The assessment is done on three types of RC frame structures, incorporating three types of dampers, viscoelastic, friction, and BRB dampers. The Incremental dynamic analyses (IDA) were performed by simulating an array of 20 strong ground motion (SGM) records considering both far-field and near-field seismic scenarios that were followed by fragility curves. With respect to far-field ground motion records, the CMR values of the selected frames indicate to be higher and reachable to safety margin more than those under near-field ground motion records that introduce a high devastating impact on the structures compared to far-field excitations. This implies that the near field impact affects the ground movements at the site by attenuation the direction and causing high-frequency filtration. Besides that, the results show that the viscoelastic damper gives better performance for the structures in terms of reducing the damages compared to the other energy dissipation devices during earthquakes.

• Coupled systems mechanics
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• v.12 no.2
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• pp.167-181
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• 2023

The determination of the blast protection level and the corresponding minimum load-bearing capacity for a laminated glass (LG) window is of crucial importance for safety and security design purposes. In this paper, the focus is given to the window response under near-field blast loading, i.e., where relatively small explosives would be activated close to the target, representative of attack scenarios using small commercial drones. In general, the assessment of the load-bearing capacity of a window is based on complex and expensive experiments, which can be conducted for a small number of configurations. On the other hand, nowadays, validated numerical simulations tools based on the Finite Element Method (FEM) are available to partially substitute the physical tests for the assessment of the performance of various LG systems, especially for the far-field blast loading. However, very little literature is available on the LG window performance under near-field blast loads, which differs from far-field situations in two points: i) the duration of the load is very short, since the blast wavelength tends to increase with the distance and ii) the load distribution is not uniform over the window surface, as opposed to the almost plane wave configuration for far-field configurations. Therefore, the current study focuses on the performance assessment and structural behaviour of LG windows under near-field blasts. Typical behavioural trends are investigated, by taking into account possible relevant damage mechanisms in the LG window components, while size effects for target LG windows are also addressed under a multitude of blast loading configurations.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.1
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• pp.65-72
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• 2009

For the evaluation of far-field performance by using the near-field probing on the base station dipole array antenna, the effects of mutual coupling depending on the heights between the array antenna with reflector and the probe were analyzed. When the height is varied in the near-field region, S parameters on the input ports of antenna and probe are measured and analyzed to decide the height for the minimum mutual coupling effect and the maximum probing efficiency. This height will be applicable to the near-field probing system design to achieve the precision far-field performance of a base station array antenna system.

• Water Engineering Research
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• v.1 no.2
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• pp.137-146
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• 2000

A windows-based software package, named DREDGE, is developed for estimating sediment resuspension and contaminant release during dredging operations. DREDGE allows user to enter the necessary dredge information, site characteristics, operational data, and contaminant characteristics, then calculates an array of concentration using the given values. The program mainly consists of the near-field models, which are obtained empirically, for estimating sediment resuspension and the far-field models, which are obtained analytically, for suspended sediment transport. A linear equilibrium partitioning approach is applied to estimate particulate and dissolved contaminant concentrations. This software package which requires only a minimal amount of data consists of three components; user input, tabular output, and graphical output. Combining the near-field and far-field models into a user-friendly windows-based computer program can greatly save dredge operator's, planners', and regulators' efforts for estimating sediment transports and contaminant distribution.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.136-143
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• 2001

In this study, a numerical analysis for soil-pile interaction systems in multi-layered half planes under a forced vibration is presented. The soil-pile interaction system is divided into two parts, so called near field and far field. The near field soil using finite elements and piles using beam elements are modeled. The far field soil media is implemented using boundary elements those can automatically satisfy the condition of wave radiation. These two fields are numerically coupled by imposing displacement compatibility condition at the interface between the near field and the far field. For the verification, the forced vibration test was simulated and the response under horizontal and vertical harmonic loads at the pile cap in the layered half plane was determined. The results are compared to the theoretical and experimental results of the literatures to verify the proposed soil-pile interaction analysis formulation.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.443-450
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• 2000

In this study a numerical method for soil-pile interaction analysis buried in multi-layered half planes is presented in frequency domain using FE-BE coupling. The total soil-pile interaction system is divided into two parts so called far field and near field beam elements are used for modeling a pile and coupled with plain strain elements for soil modeling. Boundary element formulation using the multi-layered dynamic fundamental solution is adopted to the far field and coupled with near field modeled by finite elements. In order to verify the proposed soil-pile interaction analysis method the dynamic responses of a pile on multi-layered dynamic fundamental solution is adopted to the far field and coupled with near field modeled by finite elements. In order to verify the proposed soil-pile interaction analysis method the dynamic responses of a pile on multi-layered half-planes are performed and compared with experiment results. Through this developed method the dynamic response analysis of a pile buried in multi-layered half planes can be calculated effectively in frequency domain.

• Earthquakes and Structures
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• v.18 no.5
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• pp.625-635
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• 2020

Suspension bridges have the extended in plan configuration which makes them prone to dynamic events like earthquake. The longer span lead to more flexibility and slender of them. So, control systems seem to be essential in order to protect them against ground motion excitation. Tuned mass damper or in brief TMD is a passive control system that its efficiency is practically proven. Moreover, its parameters i.e. mass ratio, tuning frequency and damping ratio can be optimized in a manner providing the best performance. Meta-heuristic optimization algorithm is a powerful tool to gain this aim. In this study, TMD parameters are optimized in different-length suspension bridges in three distinct cases including 3, 4 and 5 TMDs by observer-teacher-learner based algorithm under a complete set of ground motions formed from both near-field and far-field instances. The Vincent Thomas, Tacoma Narrows and Golden Gate suspension bridges are selected for case studies as short, mean and long span ones, respectively. The results indicate that All cases of used TMDs result in response reduction and case 4TMD can be more suitable for bridges in near and far-field conditions.