• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.126-133
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• 2008

Geotechnical limit state design methods; LRFD of North America is an approach that estimates resistance using design model and then multiplies resistance factor by calculated resistance to reflect the uncertainty of geomaterials and design models; whereas, Eurocode of the Europe employs the partial resistance factor applied directly to each variable in the resistance equation that individual soil properties such as cohesion and angle of internal friction are applied. This discussion paper is a study on characteristic value which has globally been argued through processing of development of Eurocode 7 for geotechnical design even to the present. Estimating the characteristic value of soil properties affects not only determination of design value applied directly to design of geotechnical structures, but also economic feasibility and stability of the structures.

• 소음진동
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• 제8권5호
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• pp.821-831
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• 1998

The actual ground vibrations due to NATM and foundation blasting at Seoul(weathered rock), Pusan(weathered rock) and Youngkwang(quartz andesite) have been measured, and the data were analyzed using reliability index($\beta$) to determinate the vibration equations and the maximum charge weight for efficient blast. These were suggested with the division of ultimate limit state($\beta$=0), serviceability limit state($\beta$=1.28) and safety state($\beta$=3), respectively. The reliability index 0 mean 50% data line obtained by the least squares best-fit line. The reliability index 1.28 and 3 represent bounds below 90% and 99.9% of the data, respectively. In this study, reliability index $\beta$=1.28 with security and economy was suggested. The maximum charge weight equations for efficient blast were obtained in W=(Vc/384.90)1.5151.D3(Seoul), W=(Vc/579.82)1.4706.D3(Pusan). W=(Vc/1654.01)1.3456.D3(Youngkwang), and the blast vibration equatiions in V=385(SD)-1.98(Seoul), V=580(SD)-2.04(Pusan), V=1654(SD)-2.23(Youngkwang), respectively. From this study, inference and analysis methods of vibration equations using reliability theory were established.

• Structural Engineering and Mechanics
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• 제50권3호
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• pp.305-322
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• 2014

Reliability-based design limit states and associated partial load factors provide a consistent level of design safety across bridge types and members. However, limit states in the current AASHTO LRFD have not been developed explicitly for the situation encountered by integral abutment bridges (IABs) that have unique boundary conditions and loads with inherent uncertainties. Therefore, new reliability-based limit states for IABs considering the variability of the abutment support conditions and thermal loading must be developed to achieve IAB designs that achieve the same safety level as other bridge designs. Prestressed concrete girder bridges are considered in this study and are subjected to concrete time-dependent effects (creep and shrinkage), backfill pressure, temperature fluctuation and temperature gradient. Based on the previously established database for bridge loads and resistances, reliability analyses are performed. The IAB limit states proposed herein are intended to supplement current AASHTO LRFD limit states as specified in AASHTO LRFD Table 3.4.1-1.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.504-509
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• 2011

The military communication equipment is required the high reliability for operating adequate functions under severe conditions. This reliability is the essential element for the quality of the product, for the uncontrolled factors, such as the clearance, damage of the material, the reduction of stiffness, which are the designer is unable to handle. In this paper, the uncertainty for the design was supposed to the probability model for the military communication equipment, and the average of the objective function was minimized for reducing design uncertainty. The reliability-based design optimization which was implemented the limit state function was formulated into the mathematical model, so the reliable optimized structure was implemented than the base-line design.

• 국제강구조저널
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• 제18권4호
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• pp.1397-1409
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• 2018

Stiffened plates with high slenderness parameters show large out-of-plane deflections, due to elastic buckling, which may occur before the plates reach their ultimate strength. From a serviceability point of view, restriction of out-of-plane deflections exceeding the fabrication tolerance is of primary importance. Compressive strength at the serviceability limit state (SLS) for slender stiffened plates under uniaxial stress was investigated through nonlinear elasto-plastic finite element analysis, considering both geometric and material nonlinearity. Both normal and high-performance steel were considered in the study. The SLS was defined based on a deflection limit and an elastic buckling strength. Probabilistic distributions of the SLS strengths were obtained through Monte Carlo simulations, in association with the response surface method. On the basis of the obtained statistical distributions, partial safety factors were proposed for SLS. Comparisons with the ultimate strength of different design codes e.g. Japanese Code, AASHTO, and Canadian Code indicate that AASHTO and Canadian Code provide significantly conservative design, while Japanese Code matches well with a 5% non-exceedance probability for compressive strength at SLS.

• 한국터널지하공간학회 논문집
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• 제14권5호
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• pp.547-559
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• 2012

국내의 콘크리트 구조설계는 허용응력 설계법(ASD) 및 극한강도 설계법(USD)을 사용하고 있다. 허용응력설계 및 극한강도설계법은 경제적인 설계에 제한이 따르기 때문에 최근에 지하구조물의 설계에 극한한계상태 설계법의 채택을 다각적으로 검토하고 있는 상황이다. 이를 뒷받침하고자 본 연구에서는 일본 한계상태 설계법(LSD)에 의거한 국내 고강도 콘크리트 라이닝에 대한 발생 단면력을 산정하였으며, 이를 국내의 극한강도 설계법과 비교함으로서 경제적 설계결과 도출 가능성 및 국내 적용성을 분석하고자 하였다. 해석결과, 철근량 산정과 밀접한 관계가 있는 최대 모멘트 발생양상은 두 설계법 모두 유사하나, 발생 부재력은 일본 한계상태 설계법이 극한강도 설계법에 비하여 모멘트는 26.0%, 전단력은 26.7%감소하는 것을 확인할 수 있었으며, 이를 통하여 안정성이 확보된 조건에서 경제적인 세그먼트 설계가 가능함을 확인하였다.

• Geomechanics and Engineering
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• 제11권2호
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• pp.211-234
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• 2016

A total of 99 full-scale field load tests at 22 sites were compiled for this study to elucidate several issues related to the load-displacement behaviour of belled piers under axial uplift loading, including (1) interpretation criteria to define various elastic, inelastic, and "failure" states for each load test from the load-displacement curve; (2) generalized correlations among these states and determinations to the predicted ultimate uplift resistances; (3) uncertainty in the resistance model factor statistics required for reliability-based ultimate limit state (ULS) design; (4) uncertainty associated with the normalized load-displacement curves and the resulting model factor statistics required for reliability-based serviceability limit state (SLS) design; and (5) variations of the combined ULS and SLS model factor statistics for reliability-based limit state designs. The approaches discussed in this study are practical and grounded realistically on the load tests of belled piers with minimal assumptions. The results on the characterization and uncertainty of uplift load-displacement behaviour of belled piers could be served as to extend the early contributions for reliability-based ULS and SLS designs.

• Wind and Structures
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• 제14권2호
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• pp.113-131
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• 2011

Excessive wind-induced motion in tall buildings can cause discomfort, affect health, and disrupt the daily activities of the occupants of a building. Dynamic vibration absorbers such as the tuned mass dampers (TMDs) can be used to reduce the wind-induced motion below a specified tolerable serviceability limit state (SLS) criterion. This study investigates whether the same probability of not exceeding specified wind-induced motion levels can be achieved by torsionally sensitive structures without/with linear/nonlinear TMDs subjected to partially correlated wind forces, if they are designed to just meet the same SLS criterion. For the analyses, different structures and the uncertainty in the response, wind load and perception of motion is considered. Numerical results indicate that for structures that are designed or retrofitted without or with optimum linear TMDs and satisfying the same SLS criterion, their probability of exceeding the considered criterion is very consistent, if the inherent correlation between the wind forces is considered in design. However, this consistency deteriorates if nonlinear TMDs are employed. Furthermore, if the correlation is ignored in the design, in many cases a slightly unconservative design, as compared to the designed by considering correlation, is achieved.

• Geomechanics and Engineering
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• 제15권3호
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• pp.879-888
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• 2018

Probability-based design codes have been developed to sufficiently confirm the safety level of structures. One of the most acceptable probability-based approaches is Load Resistance Factor Design (LRFD), which measures the safety level of the structures in terms of the reliability index. The main contribution of this paper is to calibrate the load and resistance factors of the design code for tunnels. The load and resistance factors are calculated using the available statistical models and probability-based procedures. The major steps include selection of representative structures, consideration of the limit state functions, calculation of reliability for the selected structures, selection of the target reliability index and calculation of load factors and resistance factors. The load and resistance models are reviewed. Statistical models of resistance (load carrying capacity) are summarized for strength limit state in bending, shear and compression. The reliability indices are calculated for several segments of a selected circular tunnel designed according to the tunnel manual report (Tunnel Manual). The novelty of this paper is the selection of the target reliability. In doing so, the uniform spectrum of reliability indices is proposed based on the probability paper. The final recommendation is proposed based on the closeness to the target reliability index.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.223-227
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• 2004

The pultruded structural shapes are usually composed of thin-walled plate elements. Because the composite material has relatively low elastic moduli, the design of pultruded compression members may not be governed by the material strength limit state but by the stability limit state such as the local buckling or the global buckling. Therefore, the stability limit state must be checked to design pultruded columns. In this research, the local buckling analysis of pultruded I-shape column was conducted for various composite materials using the closed-form solution. To establish the design guidelines for the local buckling of pultruded I-shape compression members, the simplified form of equation to find the local buckling coefficient of pultruded I-shape column was proposed as a function of mechanical properties and the width ratio of plate components using the results obtainde by the closed-form solution. In order to verify the validity of proposed solution, the results obtained by the proposed approximate solution were compared with those of the closed-form solution and the experimental results.