• Journal of the Earthquake Engineering Society of Korea
• /
• v.15 no.6
• /
• pp.1-10
• /
• 2011

This study presents the results of parametric studies of the P-M interaction diagram of hollow prestressed concrete bridge columns. Among the numerous parameters, this study concentrates on concrete compressive strength, prestressing steel reinforcement ratio, effective prestress, the Ds/Do ratio, and the Di/Do ratio. The strength and ductility of hollow prestressed concrete bridge columns were evaluated through quasistatic tests. The P-M interaction diagrams from the codes were different from that of the results, which were in good agreement with AASHTO-LRFD. Nondimensionalized P-M interaction diagrams were developed to predict the design resistance of hollow prestressed concrete bridge columns.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.4
• /
• pp.53-60
• /
• 2019

In this study, a method for updating the finite element model of bridges with genetic algorithm using static displacement were presented, and verified this method using field test data for PSC girder bridge. As a field test, static load test and pseudo-static load test were conducted, and updated the finite element model of test bridge using each test data. Finally, evaluated the bridge load carrying capacity with updated model using pseudo-static load test's displacement data. To evaluate the bridge load carrying capacity, KHBDC-LSD, KHBDC and AASHTO LRFD's live load model were used, and compared the each results.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.7
• /
• pp.17-24
• /
• 2010

Load Resistance Factor Design method is used increasingly in geotechnical design world widely and resistance factors for drilled shafts are suggested by AASHTO. However, these resistance factors are determined for intact rock conditions; by comparison, most of bedrocks in Korea have weathered condition, so that applying the AASHTO resistance factors is not reasonable. Thus, this study suggests the proper resistance factors for design of drilled shaft in Korea. The 22 cases of pile load test data from 8 sites were chosen and reliability-based approach is used to analyze the data. Reliability analysis was performed by First Order Second Moment Method (FOSM) applying 4 bearing capacity equations. As a result, when the Factor of Safety (FOS) was selected as 3.0, the target reliability indexes (${\beta}_c$) were evaluated as 2.01~2.30. Resistance factors and load factors are determined from optimization based on above results. The resistance factors ranged between 0.48 and 0.56 and load factors for dead load and live load are evaluated as approximately 1.25 and 1.75 respectively. However, when the target reliabilities are considered as 3.0, the resistance factors are evaluated as approximately 50% of the results when the target reliability index was 2.0.

• 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 Korea institute for structural maintenance and inspection
• /
• v.7 no.2
• /
• pp.219-229
• /
• 2003

The objective of this work is to verify the Code specified girder distribution factors for short and medium span bridges. To accomplish this objective, field tests were carried out on seventeen simply supported highway bridges. This paper presents the procedure and results of field tests that were performed to verify girder distribution factors. Finite Element analyses previously performed at the University of Michigan indicated that in most cases currently used girder distribution factors specified in AASHTO Codes are too conservative. However, these studies also showed that for short spans and short girder spacings, the girder distribution factors can be too permissive. Therefore, this paper focused on experimental evaluation of girder distribution factors for short and medium span steel girder bridges. The results were compared with the distribution factors specified by AASHTO Standard (2000) and AASHTO LRFD Code (1998). It has been found that the measured girder distribution factors are lower than AASHTO values in most cases, and sometimes the code specified values are overly conservative. The research work involved formulation of the testing procedure, selection of structure, installation of equipment, measurements, and interpretation of the results.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.4
• /
• pp.139-149
• /
• 2019

For retaining wall designs, horizontal earth pressure induced by traffic loads over the walls is calculated based on equivalent uniform pressure height. The AASHTO LRFD design standards propose equivalent uniform pressure height of traffic loads; however, the equivalent uniform pressure height is calibrated using the US standard trucks. As the domestic standard trucks are different from the US standard trucks, in this study, new domestic equivalent uniform pressure height is proposed using the Boussinesq theory varying vehicle directions, Poisson's ratios of pavement layers, and retaining wall height. The proposed equivalent uniform pressure heights are generally higher than those proposed by the AASHTO design standards because the axle loads and their densities of two domestic standard trucks are higher than those of the US standard trucks. The most highest equivalent uniform pressure height was found for traffic direction perpendicular to longitudinal direction of retaining wall.

• Journal of Korean Society of Steel Construction
• /
• v.19 no.6
• /
• pp.643-653
• /
• 2007

The ultimate bending strength and flexural ductility performance of longitudinally stiffened plate girders fabricated with mild steel were investigated utilizing nonlinear incremental finite element analysis. AASHTO LRFD (2002) design specifications were reviewed for possible application of longitudinally stiffened plate girders as compact sections. In order to investigate compact section requirements for plate girders with longitudinal stiffeners in webs, a number of full-scale plate girders were modeled and analyzed up to the collapse under pure bending condition. It was found that the slenderness of sub panel of the webs, the stiffness of longitudinal stiffeners, and the slenderness of compression flanges are key parameters governing the flexural ductility of the plate girders. It was also found from finite element analysis that longitudinally stiffened plate girder sections can satisfy compact section requirements both in full plastic moment capacity and flexural ductility requirement. New design equations have been proposed for longitudinally stiffened plate girders to be treated as compact sections.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.2B
• /
• pp.149-152
• /
• 2012

This study is carried out to analyze the design method and safety rate degree for IEC 61400-3, DNV-OS-J101, GL Wind, EUROCODE, AASHTO and domestic design standard used for offshore wind turbine foundation design. The findings will provide a design parameter for domestic offshore wind turbine foundation design. The design of the steel Support Structure of an offshore wind turbine can be based on either the Allowable Stress Design(ASD) approach or the Load and Resistance Factor Design(LRFD) approach. The design principles with the use of LRFD method are described with various limit states. A limit state is a condition beyond which a structure or part of a structure exceeds a specified design requirement. Design by the LRFD method is a design method by which the target component safety level is obtained by applying load and resistance factors to characteristic reference values of loads (load effects)and structural resistance. When the strength design of the steel Support Structure is based on the ASD approach, the design acceptance criteria are to be expressed in terms of appropriate basic allowable stresses in accordance with the requirements specified. After comparison an economics domestic offshore wind turbine foundation standard will be developed.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.8
• /
• pp.107-116
• /
• 2007

Load and Resistance Factor Design (LRFD) method is being used increasingly in geotechnical design practice worldwide, and is expected to completely replace the current Allowable Stress Design (ASD) method in the near future. LRFD has advantages over ASD in that it allows the design of superstructures and substructures at a consistent reliable level by quantification of failure probability based on reliability analysis. At present, resistance factors for cast-in-place piles embedded in rocks are determined by AASHTO only for the intact rock conditions. In Korea, however, most of the bedrocks in which piles are embedded are heavily weathered. Thus, this study will try to determine the resistance factors of heavily weathered rocks (so-called intermediate goo-materials). To this aim, reliability analysis was carried out to evaluate the resistance factors of cast-in-place piles embedded in intermediate geo-materials in Korea. Pile load test data of 21 cast-in-place piles of 4 construction sites were used for the analysis. Depending on the method which calculates the pile capacities, the resulting resistance factors ranged between 0.1 and 0.6.

• Journal of the Korea Concrete Institute
• /
• v.26 no.5
• /
• pp.573-579
• /
• 2014

Typical composite girder has been composed with conventional concrete deck and steel girder. Recently, ultrahigh-performance-concrete (UHPC) deck is proposed in order to enhance durability and reduce weight of deck as well as to increase stiffness and strength of the composite girder. This study investigates that a headed stud is still compatible as a shear connector for the UHPC deck and steel girder composite beam. Twelve push-out specimens are prepared to evaluate the static strength of stud shear connectors embedded in the UHPC deck. The test program proves that the static strength of the stud shear connectors embedded in UHPC well meets with design codes described in AASHTO LRFD. Chosen experimental variables are aspect ratio of height to diameter of stud, thickness of deck and thickness of concrete cover over the head of stud. From the test program, aspect ratio and cover thickness are investigated to mitigate the regulations of the existing design codes. The minimum aspect ratio and the minimum cover thickness given in AASHTO LRFD are four and 50mm, respectively. This limitation hinders to lower the thickness of the UHPC deck. The results of the experiment program give that the aspect ratio and the cover thickness can be lower down to three and 25mm, respectively. Eurocode-4 regulates characteristic relative slip at least 6mm. However, test results show that stud shear connectors embedded in UHPC provide the characteristic relative slip only about 4mm. Therefore, another measures to increase ductility of stud should be prepared.