• Journal of the Korean GEO-environmental Society
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• v.16 no.6
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• pp.5-11
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• 2015

Recently the necessity of developing the Load and Resistance Factor Design (LRFD) for shallow foundation has been raised to implement to the domestic design codes related to geotechnical engineering since the limit state design is requested as international technical standard for the foundation of structures. In this study, applicability of LRFD for shallow foundation on weathered soils was investigated and resistance factor for this case was proposed. The quantitative analyses on the uncertainty and resistance bias for shallow foundation on weathered soil ground were performed by collecting the statistical data about domestic case studies for design and construction of shallow foundation. Reliability analyses for shallow foundation were first performed using FDA (First-order Design value Approach) method. Resistance factors were calibrated using the load factors obtained from the specifications of shallow foundations on weathered soil ground. The influence of the load factors developed in this study on the resistance factors were discussed by comparing with the resistance factor obtained from using AASHTO load factors.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.357-362
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• 2000

Allowable stress design(ASD) method has been widely used to design steel structures such as boiler and heat recovery steam generator(HRSG) of power plant. However, many researchers are recently intrested in road and resistance factor design(LRFD) method which may take the place of ASD. In this work, the weight calculation of steel structure was compared when ASD and LRFD were applied respectively. For the calculation of weight of steel structure, computer program was developed and applied to obtain beam weight. Using this program and GTSTRUDL, structural design program, weight of steel structure is calculated. As a result of weight calculation, maximum 5.4% of weight reduction is achieved among examples of this study by applying LRFD comparing with the result of ASD, and those results quite dependent on the applied load and member classification.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.309-314
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• 2007

Recently, the LRFD and the PSF based on structural reliability assessment have been applied to NPP designs in behalf of the conventional deterministic design methods. In the risk-informed structural integrity, it is especially possible to optimize design procedures considering cost, manufacturing and maintenance because the structural reliability concepts have confirmed the reliability for which a designer aims. Generally, in order to evaluate the PSF, the LRFD which is the design concept for evaluating safety factors respectively on the limit state function including load and resistance. This study certifies the concept and its applications of the PSF using the LRFD based on the structural reliability engineering.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.495-501
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• 2011

The load combinations in current KCI Design Code are determined with reference to those in ACI 318-05, which adopts the LRFD (load and resistance factor design) format. The load and resistance factors in LRFD format should be determined to meet the required levels of reliability index or probability of failure for various predetermined failure modes, which are also based on the statistical data reflecting locality and contemporary situation. However, the current KCI Design Code has been written utilizing foreign data, because of insufficiency in accrued data in Korea. This study considered the current safety levels of KCI Code based on published domestic data to evaluate appropriateness of the current KCI regulations. Based on the calibrated reliability index of the existing Code, the new resistance factors are suggested. The results presented in this paper can be considered as a basic research for establishment of unique design format for future Korean Codes.

• Geomechanics and Engineering
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• v.1 no.1
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• pp.17-34
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• 2009

There has been growing agreement that geotechnical reliability-based design (RBD) is necessary for establishing more advanced and integrated design system. In this study, resistance factors for LRFD pile design using CPT results were investigated for axially loaded driven piles. In order to address variability in design methodology, different CPT-based methods and load-settlement criteria, popular in practice, were selected and used for evaluation of resistance factors. A total of 32 data sets from 13 test sites were collected from the literature. In order to maintain the statistical consistency of the data sets, the characteristic pile load capacity was introduced in reliability analysis and evaluation of resistance factors. It was found that values of resistance factors considerably differ for different design methods, load-settlement criteria, and load capacity components. For the total resistance, resistance factors for LCPC method were higher than others, while those for Aoki-Velloso's and Philipponnat's methods were in similar ranges. In respect to load-settlement criteria, 0.1B and Chin's criteria produced higher resistance factors than DeBeer's and Davisson's criteria. Resistance factors for the base and shaft resistances were also presented and analyzed.

• 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.

• Steel and Composite Structures
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• v.7 no.3
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• pp.201-217
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• 2007

Two combinatorial optimization algorithms, tabu search and simulated annealing, are presented for the minimum-weight design of geometrically non-linear steel plane frames. The design algorithms obtain minimum weight frames by selecting suitable sections from a standard set of steel sections such as American Institute of Steel Construction (AISC) wide-flange (W) shapes. Stress constraints of AISC Load and Resistance Factor Design (LRFD) specification, maximum and interstorey drift constraints and size constraints for columns were imposed on frames. The stress constraints of AISC Allowable Stress Design (ASD) were also mounted in the two algorithms. The comparisons between AISC-LRFD and AISC-ASD specifications were also made while tabu search and simulated annealing were used separately. The algorithms were applied to the optimum design of three frame structures. The designs obtained using tabu search were compared to those where simulated annealing was considered. The comparisons showed that the tabu search algorithm yielded better designs with AISC-LRFD code specification.

• Geomechanics and Engineering
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• v.22 no.5
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• pp.433-439
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• 2020

Tunnels are one of the most important constructions in civil engineering. The damage to these structures caused enormous costs. Therefore, the safe and economic design of these structures has long been considered. However, both applied loads on the tunnels as well as the resistance of the structural members are naturally uncertain parameters, hence, the design of these structures requires considering the probabilistic approaches. This study aims to determine the load and resistant factors of lining tunnels concerning the earthquake extreme events limit state function. For this purpose, tunnels that have been designed according to the previous design codes (AASHTO Tunnel LRFD 2017) and using reliability analysis, the optimum reliability of these structures for different loading scenarios is determined. In this paper, the tunnel is considered circular. Finally, the proper load and resistance factors are calculated corresponding to the obtained target reliability. Based on the performed calibration earthquake extreme events limit state function, the result of this study can be recommended to AASHTO Tunnel LRFD 2017.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.77-87
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• 2012

Recently, Load and Resistance Factor Design (LRFD) based on reliability analysis has become a global trend for economical and rational design. In order to implement the LRFD, quantification of uncertainty for load and resistance should be done. The reliability of result relies on input variable, and therefore, it is important to obtain exact uncertainty properties of load and resistance. Since soil stress is the main reason causing the settlement or deformation of ground and load on the underground structure, it is essential to clarify the uncertainty of soil stress distribution for accurately predict the uncertainty of load in LRFD. In this study, laboratory model test on silty sand bed under probabilistic load is performed to observe propagation of upper load uncertainty. The results show that the coefficient of variation (COV) of soil stress are varied depending on location due to non-linear relationship between upper load increment and soil pressure increment. In addition, when the load uncertainty is transmitted through ground, COV is decreased by damping effect.

• International Journal of Highway Engineering
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• v.5 no.1 s.15
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• pp.1-10
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• 2003

The objective of pavement design, just as with the design of other structures, is to obtain the most economical designs at specified levels of reliability. Methods that yield designs with different levels of reliability are undesirable, and over the course of time design approaches in the U.S. and Europe have converged toward the Load and Resistance Factor Design (LRFD) format in order to assure uniform reliability. At present the LRFD format has been implemented in concrete, steel, wood and bridge design specifications. In this paper, reliability theories are used to illustrate the development of an LRFD format for Mechanistic-Empirical (M-E) design of flexible pavements as an alternative of its reliability module. It is shown in this paper that ten candidate pavement sections designed with a reliability level using the AASHTO design guide (1986) do not have uniform structural reliability in terms of pavement mechanistic distress such as fatigue cracking and the uniform reliability can be achieved by using the LRFD format.