• Bulletin of the Society of Naval Architects of Korea
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• v.25 no.4
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• pp.28-38
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• 1988

This paper describes the statistical analysis method of predicting the ship resistance. The equation for the wavemaking resistance coefficient is derived as the principal dimensions and sectional area coefficients by using the wavemaking resistance theory and its regression coefficients are determined from the regression analysis of the resistance test results. The equation for the form factor is derived by purely regression analysis of the principal dimensions, sectional area coefficients and resistance test results. Also, it is shown that the wavemaking resistance can be minimize by varying the sectional area curve without changing the principal dimensions of the ship. This methods were applied to the resistance prediction of a bulk carrier. And the, the modified hull form with minimum wavemaking resistance was obtained and the reduction of effective power was confirmed by the resistance test.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.113-122
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• 2005

Application of Limit State Design in geotechnical engineering has become world-widely popular. While LRFD code in the North America presents geotechnical load and resistance factors, the values of resistance factors proposed by these methods are still unstable with limited application. CPT has been widely used for the pile design and various methods have been proposed to estimate the bearing capacity of piles. In this paper, resistance factors for representative pile design methods based on CPT results are evaluated. Field pile load test and CPT results were collected and analyzed in order to obtain necessary statistical data and resistance factors. Resistance factors of the base, shaft, and total capacity are estimated. From fisrt order second moment (FOSM) analysis, resistance factors of $0.30{\sim}0.55$ are estimated for total load capacity.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.6
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• pp.532-539
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• 2008

Kwon et al.(2008) carried out a hydraulic experiment in order to evaluate Manning coefficient, which implicates flow resistance due to bottom friction as well as drag caused by the squared piers higher than water depth and arranged with equal intervals, under the flow condition with a constant drag coefficient, $Re>10^4$. And, based on the equation of equilibrium, they proposed a formula for the equivalent resistant coefficient including empirical drag interaction coefficient obtained by using the experimental results. In this study, the hydraulic experiment was simulated using FLOW-3D, a 3-dimensional computational fluid dynamic code. The computations were compared with the experiment results as well as the semi-theoretical formula, and the comparisons show a good agreement. From the agreement, it was confirmed that when flow resistance bodies were higher than water depth, Manning n value increases with 2/3 power of water depth as shown in the theoretical formula and that drag interaction coefficient was dominated by their intervals.

• Journal of Korea Water Resources Association
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• v.46 no.12
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• pp.1209-1220
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• 2013

Roughness coefficients calibrated by flow modeling using the 1-dimensional numerical model were analyzed for the downstream section of Naesung Stream in this study. Also, the bedform configuration at the Hyangseok Station was predicted for measured and simulated hydraulic conditions of flows and total flow roughness was estimated with the coefficient of grain roughness. The Manning's n coefficients calibrated by numerical modeling and estimated by considering of grain and bedform roughness were compared and examined. As a result, the Manning's n by numerical modeling was greater than the coefficient range estimated by grain and bedform roughness at the low flow regime due to the other factors such as vegetation, sinuosity, and sand bar. However, the Manning's n by numerical modeling was included in the coefficient range by grain and bedform roughness at the transition and high flow regime over $500m^3/s$ of flow discharge.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6C
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• pp.259-266
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• 2011

Conducting statistical analysis of foundation resistance using sufficient number of well-performed load test results is prerequisite for the calibration of reliable resistance factors for foundation LRFD. In this study, a rational analysis method is proposed so that the proof pile load test results can be reflected in update of resistance statistical characteristics based on Bayesian theory. Then, resistance factors for driven steel pipe piles compatible with Korea foundation practices are updated by implementing this rational analysis method. To accomplish the resistance factor updates, (1) prior pile resistance distribution is constructed based on the results of pile load tests, which loads are imposed at least up to their ultimate limit loads. (2) likelihood function is obtained from the results of proof pile load tests, and (3) posterior pile resistance distribution is updated by combining these prior pile resistance distribution and likelihood function. The resistance factors are updated using the posterior pile resistance following the first-order reliability method (FORM). From the possible results of five consecutive proof pile load tests, the updated resistance factors vary within ranges of 0.27-0.96 and 0.19-0.68 for target reliability indices of 2.33 and 3.0, respectively. Consequently, it was found that the Bayesian theory-implemented method enables the updates of resistance factors in an efficient way when reliable resistance factors are not available due to the lack of well-performed pile load test results.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.139-146
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• 2007

The objective of the present study is to provide statistical resistance statistics for steel-concrete composite plate girder sections under positive and negative moments. Statistical properties on yield strength, tensile strength, elongation, and fracture toughness of domestic structural steel products, gathered from an analysis of over 16,000 samples, were evaluated. Using the steel samples for the plate girder, the bias factor and the coefficient of variation of the ultimate flexural resistance for representative composite plate girder sections under positive and negative flexures were presented. In calculating the ultimate flexural resistance of the composite section, the moment curvature relationships were developed using the incremental load approach considering material nonlinearity for the steel girder. The predicted statistics can be used in the future for the efficient calibration of LRFD code.

• Land and Housing Review
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• v.9 no.3
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• pp.1-8
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• 2018

In Europe and the United States, the use of limit states design has almost been established for pile foundation design. According to the global trend, the Ministry of Land, Transport and Maritime Affairs has established the basic design criteria of the bridge under the limit state design method. However, it is difficult to reflect on the design right now because of lack of research on resistance coefficient of the pile method and ground condition. In this study, to obtain the resistance coefficient of PHC bored pile which is widely used in Korea, the bearing capacity calculated by the LH design standard and the bridge design standard method, the static load test(21 times) and the dynamic load test(EOID 21 times, Restrike 21) The reliability analysis was performed on the results. The analysis of the resistance coefficient of PHC bored pile by loading test was analyzed by adding more than two times data. As a result, the resistance coefficient obtained from the static load test(ultimate bearing capacity) was 0.64 ~ 0.83 according to the design formula and the target reliability index, and the resistance coefficient obtained from the dynamic load test(ultimate bearing capacity) was 0.42~0.55. Respectively. The resistance coefficient obtained from the modified bearing capacity of dynamic load test(EOID's ultimate end bearing capacity + restrike's ultimate skin bearing capacity) was 0.55~0.71, which was reduced to about 14% when compared with the resistance coefficient obtained by the static load test(ultimate bearing capacity). As a result of the addition of the data, the resistivity coefficient was not changed significantly, even if the data were increased more than 2 times by the same value or 0.04 as the previous resistance coefficient. In conclusion, the overall resistance coefficient calculated by the static load test and dynamic load tests in this study is larger than the resistance coefficient of 0.3 suggested by the bridge design standard(2015).

• Journal of the Korean Geotechnical Society
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• v.29 no.4
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• pp.57-65
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• 2013

Assessment of uncertainties of loads and resistances is prerequisite for the development of load and resistance factor design (LRFD). Many previous studies related to resistance factor calculations of piles were conducted for short or medium span bridges (span lengths less than 200m) reflecting the live load uncertainty for ordinary span bridges. In this study, by using a revised live load model and its uncertainty for long span bridges (span lengths longer than 200m and shorter than 1500m), resistance factors are recalibrated. For the estimation of nominal pile capacity (both base and shaft capacities), the Imperial College Pile (ICP) design method is used. For clayey and sandy foundation, uncertainty of resistance is assessed based on the ICP database. As long span bridges are typically considered as more important structures than short or medium span bridges, higher target reliability indices are assigned in the reliability analysis. Finally, resistance factors are calculated and proposed for the use of LRFD of driven piles for ordinary span and long span bridges.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.170-173
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• 2011

국내 풍화지반의 토량환산계수를 정확하고 합리적으로 추정하는 것은 공사의 성패에 있어 매우 중요한 사항이다. 하지만 현업에서는 풍화지반의 풍화도를 정량화하는 것이 어렵고, 토량환산계수를 적용 시 외국의 기준을 사용하는 경우가 빈번하다. 뿐만 아니라, 국내 풍화지반의 토량환산계수에 관한 연구는 아직 미비하여, 끊임없이 토량환산계수의 정확성 및 사용성에 대해 문제 제기가 있어 왔다. 이에 본 연구에서는 TEPS (Tunnel Electrical resistivity Prospecting System)를 이용하여 화강암의 풍화 정도와 전기비저항의 상관관계를 도출하고 풍화지반 내 흙이 차지하는 비율(S/W 비)을 전기비저항과 개괄적으로 상관관계를 맺어 전기비저항을 이용하여 토량환산계수를 산정하는 방법을 제안하였다. 현장 관리자가 풍화지반에서 쉽게 토량환산계수 및 토공량에 관한 정보를 획득할 수 있도록 풍화지반 토공관리프로그램(WEMP)을 개발하고 토량환산계수 측정시스템을 설계하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.2
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• pp.331-337
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• 1994

The scatting problem by E-polarized plane wave with obique incidence on a tapered resistive strip grating with zero resistivity(perfectly conducting) at strip-edges is analyzed by the method of moments in the spectral domain. Then the induced surface current density on the strip is expanded in a series of Chebyshev polynomials of the second kind. The expasion coefficients are calculated numerically in the spectral domain, the numerical results of the geometric-optical reflection coefficient for the tapered resistivity in this paper are compared with those for the existing uniform resistivity. And the position of sharp variation points in the magnitude of the geometric-optical reflection coefficient can be moved by varying the incident angle and the strip spacing, It is found out that these sparp variation points are due to the transition of higher mode between the propagation mode and the evanescent mode.