• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.324-337
• /
• 2010

For the development of load and resistance factor design, reliability analysis is required to calibrate resistance factors in the framework of reliability theory. The distribution of measured-to-predicted pile resistance ratio was constructed based on only the results of load tests conducted to failure for the assessment of uncertainty regarding pile resistance and used in the conventional reliability analysis. In other words, successful pile load test (piles resisted twice their design loads without failure) results were discarded, and therefore, were not reflected in the reliability analysis. In this paper, a new systematic method based on Bayesian theory is used to update reliability index of driven steel pile piles by adding more pile load test results, even not conducted to failure, into the prior distribution of pile resistance ratio. Fifty seven static pile load tests performed to failure in Korea were compiled for the construction of prior distribution of pile resistance ratio. Reliability analyses were performed using the updated distribution of pile resistance ratio and the total load distribution using First-order Reliability Method (FORM). The challenge of this study is that the distribution updates of pile resistance ratio are possible using the load test results even not conducted to failure, and that Bayesian update are most effective when limited data are available for reliability analysis or resistance factors calibration.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.07a
• /
• pp.35-52
• /
• 1999

This paper addresses on new codes of practice, limit state design; load resistance factored design and Eurocode 7, which have recently been adopted by foundation engineers in North America and European Communities. A brief description of the limit state design concepts and some introductions to Australia and Sweden national code for pile foundation are made on behalf of pile capacity determination. Also, simple closed form solution for rational resistance factor when resistance is log-normally distributed, has been derived for pile foundation.

• Journal of Korean Association for Spatial Structures
• /
• v.3 no.3 s.9
• /
• pp.85-93
• /
• 2003

Steel, concrete and their combination materials are the most 6commonly used materials for civil engineering structural systems such as buildings, bridge structures and other structures. Recently, however, fiber reinforced polymer (FRP) composites, a relatively new composite material made of fibers and polymer resins, have been gradually used in structural systems as an alternative structural material. This paper describes a comparison of design strength equations for steel column and FRP composite column based on design philosophies. The safety factors used in allowable stress design (ASD) are relatively higher in FRP structural design than steel structural design. Column critical stress equations of FRP composites column from an experimental study can be represented by Euler elastic buckling equation at the long-range of slenderness, and an exponential form at the short-range of slenderness as defined in Load and Resistance Factor Design (LRFD) of steel column. The column strength of steel and FRP composite columns in large slenderness is independent of material strength, this result verified the elastic buckling equation as derived by Eq. (15) and Eq. (5).

• Geomechanics and Engineering
• /
• v.11 no.2
• /
• pp.211-234
• /
• 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.

• Journal of the Korean Geotechnical Society
• /
• v.30 no.11
• /
• pp.51-60
• /
• 2014

Load and Resistance Factor Design (LRFD) is one of the limit state design methods, and has been used worldwide, especially in North America. Also, the study for LRFD has been actively conducted in Korea. However, the data for LRFD in Korea were not sufficient, so resistance factors suggested by AASTTO have been used for the design in Korea. But the resistance factors suggested by AASHTO represent the characteristics of bedrocks defined in the US, therefore, it is necessary to determine the resistance factors for designs in Korea, which can reflect the characteristics of bedrocks in Korea. Also, the calculated probabilities of failure from conventional reliability analyses which commonly use log-normal distribution are not realistic because of the lower tail that can be extended to zero. Therefore, it is necessary to calibrate the resistance factors considering the lower-bound resistance. Thus, this study calculates the resistance factors using thirteen sets of drilled shaft load test results, and then calibrates the resistance factors considering the lower-bound resistance corresponding to a target reliability index of 3.0. As a result, resistance factors from conventional reliability analyses were determined in the range of 0.13-0.32 for the shaft resistance, and 0.19-0.29 for the base resistance, respectively. Also, the lower bounds of resistance were determined based on the Hoek-Brown failure criteria (2002) and GSI downgrading. Considering the lower-bound resistances, resistance factors increased by 0~8% for the shaft, and 0~13% for the base, respectively.

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

• Structural Engineering and Mechanics
• /
• v.89 no.2
• /
• pp.171-179
• /
• 2024

The market of the floating solar photovoltaic system is rapidly growing around the world with the rise of renewable energy that can replace fossil energy. While the floating solar photovoltaic system is operating and being installed in several countries, the system is exposed to the risk in terms of structural safety due to the absence of the proper design guideline. In this paper, design loads suitable for the floating solar photovoltaic system are presented. Utilizing the existing reliable design standards such as ASCE 7-16 (ASCE 7-16 2016) and DNV-RP-C205 (DNV-RP-C205 2010), the appropriate design loads for the floating solar photovoltaic system are presented. The proper load combinations are also presented by putting wave load based on DNV standards (DNV-OS-C101 2015 and DNV-OS-C201 2015) into the load combinations in ASCE standards (ASCE 7-16 2016). We present the load combinations for the allowable stress design and load and resistance factor design, respectively.

• Fire Science and Engineering
• /
• v.17 no.2
• /
• pp.10-16
• /
• 2003

The main purpose of this study is to raise the point at issue and to propose reform direction about the current performance criteria of fire resistance through the examination of the fire resistance required for each use of compartment by using performance-based fire safety design method. To examine the performance criteria of fire resistance, this study compared the equivalent time of fire exposure which was calculated by using time-equivalent formulae with the required fire resistance time determined by existing prescriptive code, and surveyed factors such as the fire load energy density, ventilation factor, fire compartment materials and fire compartment geometry in order to calculate the equivalent time of fire exposure.

• Journal of the Korean Geotechnical Society
• /
• v.31 no.10
• /
• pp.5-16
• /
• 2015

Considering the conversion of the Korea Construction Standards to Limit State Design (LSD), we analyzed the resistance bias factor for pullout resistance, as a part of the development of the Load and Resistance Factor Design (LRFD) for soil nailing; very few studies have been conducted on soil nailing. In order to reflect the local characteristics of soil nailing, such as the design and construction level, we collected statistics on pullout tests conducted on slopes and excavation construction sites around the country. In this study a database was built based on the geotechnical properties, soil nailing specifications, and pullout test results. The resistance bias factors are calculated to determine the resistance factor of the pullout resistance for gravity and pressurized grouting method, which are the most commonly used methods in Korea; moreover, we have relatively sufficient data on these methods. We found the resistance bias factors to be 1.144 and 1.325, which are relatively conservative values for predicting the actual ultimate pullout resistance. It showed that our designs are safer than those found in a research case in the United States (NCHRP Report); however, there was an uncertainty, $COV_R$, of 0.27-0.43 in the pullout resistance, which is relatively high. In addition, the pressurized grouting method has a greater margin of safety than the gravity grouting method, and the actual ultimate pullout resistance determined using the pressurized grouting method has low uncertainty.

• International Journal of Highway Engineering
• /
• v.13 no.2
• /
• pp.147-157
• /
• 2011

As a background study to apply the reliability-based resistance factors to the domestic concrete bridge design code, a comparative study is conducted for the design results and the reliability indexes obtained by adopting different resistance factor formats to yield the design strength of concrete structures. The design results which are calculated by applying the section resistance factors of the current domestic design code and the material resistance factors of Eurocode are compared for the concrete beam bridge. The reliability index is calculated by considering the uncertainties involved in material, dimension and strength equation during the design procedure to get the strength of concrete structure. Also, the sensitivity analysis is performed to figure out which design variables have great impact on the reliability index. The resistance factors of the current domestic bridge design code, AASHTO LRFD and Eurocode are applied to the bridge design for flexure and shear strength and the results show that the resistance factors of the domestic code give the largest reliability indexes. It is observed that the probabilistic distribution of the live load makes difference for the reliability index and the yield strength of reinforcing steel and the live load have great impact on the reliability of both flexural and shear strength of concrete beam through the sensitivity analysis.