• Geomechanics and Engineering
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• v.22 no.1
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• pp.49-63
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• 2020

Studying the critical response characteristics of box culverts with diverse geometrical configurations under seismic excitations is a necessary step to develop a reasonable design method. In this work, a numerical parametric study is conducted on various soil-culvert systems, aiming to highlight the critical difference in the seismic performances between three- and four-sided culverts. Two-dimensional numerical models consider a variety of burial depths, flexibility ratios and foundation widths, assuming a visco-elastic soil condition, which permits to compare with the analytical solutions and previous studies. The results show that flexible three-sided culverts at a shallow depth considerably amplify the spectral acceleration and Arias intensity. Larger racking deformation and rocking rotation are also predicted for the three-sided culverts, but the bottom slab influence decreases with increasing burial depth and foundation width. The bottom slab combined with the burial depth and structural stiffness also significantly influences the magnitude and distribution of the dynamic earth pressure. The findings of this work shed light on the critical role of the bottom slab in the seismic responses of box culverts and may have a certain reference value for the preliminary seismic design using R-F relation.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1331-1344
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• 2021

This study is to evaluate the seismic capacity of the fire-damaged cabinet facility in a nuclear power plant (NPP). A prototype of an electrical cabinet is modeled using OpenSees for the numerical simulation. To capture the nonlinear behavior of the cabinet, the constitutive law of the material model under the fire environment is considered. The experimental record from the impact hammer test is extracted trough the frequency-domain decomposition (FDD) method, which is used to verify the effectiveness of the numerical model through modal assurance criteria (MAC). Assuming different temperatures, the nonlinear time history analysis is conducted using a set of fifty earthquakes and the seismic outputs are investigated by the fragility analysis. To get a threshold of intensity measure, the Monte Carlo Simulation (MCS) is adopted for uncertainty reduction purposes. Finally, a capacity estimation model has been proposed through the investigation, which will be helpful for the engineer or NPP operator to evaluate the fire-damaged cabinet strength under seismic excitation. This capacity model is presented in terms of the High Confidence of Low Probability of Failure (HCLPF) point. The results are validated by the proper judgment and can be used to analyze the influences of fire on the electrical cabinet.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.53-64
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• 2010

Seismic fragility curves of structures represent the probability of exceeding the prescribed structural damage state for a given various levels of ground motion intensity, such as peak ground acceleration (PGA). This means that seismic fragility curves are essential to the evaluation of structural seismic performance and assessments of risk. Most of existing studies have not considered the near- and far-fault earthquake effect on the seismic fragility curves. In order to evaluate the effect of near- and far-fault earthquakes, seismic fragility curves for PSC box girder bridges subjected to near- and far-fault earthquakes are calculated and compared. The seismic fragility curves are strongly dependent on the earthquake characteristics such as fault distance. This paper suggests that the effect of near- and far-fault earthquakes on seismic fragility curves of PSC box girder bridge structure should be considered.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.2
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• pp.77-84
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• 2021

A sampling-based approach was devised as a nuclear seismic probabilistic risk assessment (SPRA) method to account for the partially correlated relationships between components. However, since this method is based on sampling, there is a limitation that a large number of samples must be extracted to estimate the results accurately. Thus, in this study, we suggest an effective approach to improve the existing sampling method. The main features of this approach are as follows. In place of the existing Monte Carlo sampling (MCS) approach, the Latin hypercube sampling (LHS) method that enables effective sampling in multiple dimensions is introduced to the SPRA method. In addition, the degree of segmentation of the seismic intensity is determined with respect to the final seismic risk result. By applying the suggested approach to an actual nuclear power plant as an example, the accuracy of the results were observed to be almost similar to those of the existing method, but the efficiency was increased by a factor of two in terms of the total number of samples extracted. In addition, it was confirmed that the LHS-based method improves the accuracy of the solution in a small sampling region.

• Computers and Concrete
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• v.26 no.6
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• pp.483-495
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• 2020

Dams are vital infrastructures that are expected to maintain their stability during seismic excitations. Accordingly, cemented material dams are an emerging type, which are being increasingly used around the world owing to benefiting from advantages of both earth-fill and concrete gravity dams, which should be designed safely when subjected to strong ground motion. In the present paper, the seismic performance of a cemented sand and gravel (CSG) dam is assessed using incremental dynamic analysis (IDA) method by accounting for two failure modes of tension cracking and base joint sliding considering the dam-reservoir-foundation interactions. To take the seismic uncertainties into account, the dam is analyzed under a suite of ground motion records and then, the effect of friction angle for base sliding as well as deformability of the foundation are investigated on the response of dam. To carry out the analyses, the Cindere dam in Turkey is selected as a case study, and various limit states corresponding to seismic performance levels of the dam are determined aiming to estimate the seismic fragilities. Based on the results, sliding of the Cindere dam could be serious under the maximum credible earthquake (MCE). Besides, dam faces are mostly to be cracked under such level of intensity. Moreover, the results indicate that as friction angle increases, probability of sliding between dam and foundation is reduced whereas, increases tensile cracking. Lastly, it is observed that foundation stiffening increases the probability of dam sliding but, reduces the tensile damage in the dam body.

• Computers and Concrete
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• v.21 no.6
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• pp.717-726
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• 2018

Concrete pipelines are the most efficient and safe means for gas and oil transportation over a long distance. The use of nano materials and nono-engineering can be considered for enhancing concrete pipelines properties. the tests show that $SiO_2$ nanoparticles can improve the mechanical behavior of concrete. Moreover, severe hazard for pipelines is seismic ground motion. Over the years, scientists have attempted to understand pipe behavior against earthquake most frequently via numerical modeling and simulation. Therefore, in this paper, the dynamic response of underwater nanocomposite submerged pipeline conveying fluid is studied. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via Classic shell theory and Hamilton's principle. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. As well, the effect of external fluid is modeled with an external force. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite. 1978 Tabas earthquake in Iran is considered for modelling seismic load. The dynamic displacement of the structure is extracted using differential quadrature method (DQM) and Newmark method. The effects of different parameters such as $SiO_2$ nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios, internal and external fluid pressure and earthquake intensity are discussed on the seismic response of the structure. From results obtained in this paper, it can be found that the dynamic response of the pipe is increased in the presence of internal and external fluid. Furthermore, the use of $SiO_2$ nanoparticles in concrete pipeline reduces the displacement of the structure during an earthquake.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1340-1352
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• 2008

In this study, S-wave velocity range is gauged in every field test method at the total 5 locations in the marine deposits in Incheon area. field test method is accomplished the SPT(Standard Penetration Test), CPT(Cone Penetration Test), SPS(Suspension PS Logger), SCPT (Seismic Cone Penetration Test) and so on. The S-wave velocity of SCPT in the downhole test method is measured lower than SPS logger at the N value > 15 range. But at the N value < 15 range, SPS logger and SCPT result is measured same. In this result, although the soil strength of the downhole test method increased, the rate of S-wave velocity is tend to be slowed. This result shows that the downhole test is difficult to apply at the place that the intensity of soil is more extreme and harder soil. And it shows that the existing Imai(1982) type that is mostly used within the country is not suitable for the marine deposits. Thus, the empirical formula that can show the range of S-wave velocity in each N value for domestic soil is needed.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.1-11
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• 2006

This paper presents a seismic fragility analysis method for a cable-stayed bridge with energy dissipation devices. Model uncertainties represented by random variables include input ground motions, characteristics of energy dissipation devices and the stiffness of cable-stayed bridge. Using linear regression, we established demand models for the fragility analysis from the relationship between maximum responses and the intensity of input ground motions. For capacity models, we considered the moment and shear force of the main tower, longitudinal displacement of the girder, deviation of the stay cables tension and the local buckling of the main steel tower as the limit states for cable-stayed bridge. As a numerical example, fragility analysis results for the 2nd Jindo bridge are presented. The effect of energy dissipation devices is also briefly discussed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.448-454
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• 2000

Piled multi-block system has been frequently adopted in the historic structures or monuments of cultural heritage. It is well known that such a structural system is very vulnerable to the earthquake shaking. If the structure is of slender type, then it may experience overturning at very low level intensity of ground shaking. One of the methods used to protect such structures from earthquake is seismic isolation system. But the behavior of multi-block systems mounted on the isolated basis is not well understood yet. In this paper we investigate the dynamic behavior of single slender rigid block mounted on the three different isolation systems, i.e., P-F system, FPS and LRB system. Sliding at the isolation interface of P-F system and FPS is formulated based on Coulomb friction. The mounted single block is assumed undergoing rocking or sticking only. Impacting of a single block is described using distinct element method (DEM). Free vibrations due to a prescribed initial conditions are studied. Responses to the harmonic excitation and earthquake motions are calculated

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.5 s.57
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• pp.149-159
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• 2009

The main purpose of this study is to evaluate the seismic safety of Korean R/C school buildings built in the 1980s, based on "the Japanese Standard for Evaluation of Seismic Capacity of Existing R/C Buildings", the nonlinear static and the nonlinear dynamic analyses. The evaluation result of the Japanese Standard showed that R/C school buildings built in the 1980s have 0.2 through 0.4 of seismic indices($I_S$). This result indicates that more than medium damage could be potentially occurred under a medium intensity level of ground motion(150g). The results of the nonlinear analyses and the post-earthquake damage evaluation method showed that Korean R/C school buildings can be suffered moderate and severe damages under a 150gal and a 200gal intensity levels of ground motions, respectively. These results reveal that R/C school buildings should be urgently required a actual earthquake preparedness measures including seismic strengthening for future earthquake.