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8. Reliability-based calibration of resistance factors for static bearing capacity of driven steel pipe piles

Author

Kwak, Kiseok, Kim, Kyung Jun, Huh, Jungwon, Lee, Ju Hyung, and Park, Jae Hyun

Subjects
Steel pipe -- Mechanical properties -- Research -- Methods, Calibration -- Methods -- Research -- Mechanical properties, Reliability (Engineering) -- Research -- Methods -- Mechanical properties, Piling (Civil engineering) -- Mechanical properties -- Methods -- Research, Earth sciences
Abstract

As part of a study to develop load and resistance factor design (LRFD) codes for foundation structures in South Korea, resistance factors for the static bearing capacity of driven steel pipe piles were calibrated in the framework of the reliability theory. A database of 52 static load test results was compiled, and the data from these load test piles were sorted into two cases: a standard penetration test (SPT) N-value at pile tip (i) less than 50 and (ii) equal to or more than 50. Reliability analyses and resistance factor calibration for the two static bearing capacity analysis methods adopted in the Korean Design standards for foundation structures were performed using the first-order reliability method (FORM) and the Monte Carlo simulation (MCS). Reliability indices and resistance factors computed by the MCS are statistically identical to those computed by FORM. Target reliability indices were selected as 2.0 and 2.33 for the group pile case and 2.5 for the single pile case. The resistance factors recommended from this study are specific for the pile foundation design and construction practice and the subsurface conditions in South Korea. Key words: bearing capacity, calibration, load and resistance factor, load test, driven steel pipe pile, reliability. Des facteurs de resistance pour la capacite; portante de pieux faits de tuyaux d'acier ont ete calibreis dans le cadre de la theorie de fiabilites, ceci en tant que partie d'une etude sur le deiveloppement de codes de facteurs de chargement et de resistance pour des fondations de structures en Coree du Sud. Une base de donneee de 52 essais de chargement statique a ete compile, et les domtoes de ces pieux d'essais ont etee classees en deux categories : essai de penetration standard (SPT) N a la pointe du pieu (i) de moins de 50 et (ii)eegal ou superieur a 50. Les analyses de fiabilitee et le calibrage des facteurs de resistance pour les deux methodes d'analyse de la capacite; portante adoptees par les normes Design standards for foundation structures de la Coree ont ete effectueees a l'aide de la meethode de fiabilitee de premier ordre (FORM) et la simulation Monte Carlo (MCS). Les indices de fiabilitee et les facteurs de resistance obtenus avec la MCS sont statistiquement identiques a ceux obtenus par FORM. Les indices de fiabilitee vises ont etee choisis comme 2,0 et 2,33 pour le cas de groupement de pieux, et de 2,5 pour le cas de pieux uniques. Les facteurs de resistance recommandees suite a cette etude sont specifiques a la conception et a la construction de pieux dans les conditions de la Coree du Sud. Mots-cles: capacite portante, calibrage, facteur de chargement et resistance, essai de chargement, pieu enfonce fait de tuyau d'acier, fiabilite;. [Traduit par la Redaction], Introduction Geotechnical design practice in locations such as the USA, Canada, European Union, and Japan has been gradually changing in recent years from allowable strength design (ASD) to limit-state design [...]

Published
2010
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35. Lateral Response of Large-Diameter Monopiles for Offshore Wind Turbines from Centrifuge Model Tests

Author

Choo, Yun Wook, Kim, Dongwook, Park, Jae-Hyun, Kwak, Kiseok, Kim, Jae-Hyun, and Kim, Dong-Soo

Abstract

Centrifuge tests were carried out to investigate the lateral response of 6-m-diameter monopiles used for offshore wind turbine foundations. Well-instrumented large-diameter model monopiles were tested in dense sands under different end bearing layer conditions and different pile rigidities. A lateral load was applied to monopiles at a level of 33 m above the seabed on a prototype scale to simulate the combination of a high lateral load and significant overturning moment acting on the piles at the seabed level. The test results showed that the measured lateral displacements and moments along the shaft for a given lateral load are much greater than those predicted from p–yanalyses using the typically used models of the American Petroleum Institute (API) (1993, “Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms—Working Stress Design,” API Recommended Practice 2A-WSD, 20th ed., API, Washington, DC) and Reese et al. (1974, “Analysis of Laterally Loaded Piles in Sand,” Proceedings of the 6thOffshore Technology Conference, Houston, TX, Paper No. OTC2080, pp. 473–483. In addition, p–y analyses using these two methods underestimated the effect of vertical load on the lateral response of the monopiles, whereas the effect was more pronounced in the centrifuge test results. Monopiles generally support large vertical loads transferred from the self-weight of the tower shaft and wind turbine compartment. Therefore, more studies are required to develop new p–ycurves for large-diameter monopiles to replace the existing API and Reese et al. p–ycurves, which were developed for small- or medium-diameter driven piles.

Published
2014
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