Jinbo Chen (Ph. D.)
Published: 2016
Total Pages: 418
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The offshore pile system capacity and the pile capacity model biases are important aspects in the assessment of existing offshore platforms and in the performance reliability that is achieved using the state of practice. The objectives of this research are to improve understanding of the pile system behavior, to calibrate the pile system capacity model bias factors, and to evaluate the reliabilities of offshore pile systems. A simplified single pile failure surface in terms of three dimensional pile head loads is proposed based on the analytical lower and upper solutions, and is verified through finite element analyses. Numerical lower and upper bound models are then proposed for the ultimate capacity of a pile system, and are shown to be efficient and be effective in considering global torsion and out-of-plane failures. The evidence from the survival of offshore platforms indicates that (1) well conductors should be included in assessing the pile system ultimate capacity; (2) static p-y curves should be used which increases the pile system lateral capacity by 10 to 20%; (3) the mean value of the steel yield strength should be used; (4) jacket leg stubs should be included; and (5) site-specific geotechnical information is important. A simplified single pile failure surface in terms of three dimensional pile head loads is proposed based on the analytical lower and upper solutions, and is verified through finite element analyses. Numerical lower and upper bound models are then proposed for the ultimate capacity of a pile system, and are shown to be efficient and be effective in considering global torsion and out-of-plane failures. The evidence from the survival of offshore platforms indicates that (1) well conductors should be included in assessing the pile system ultimate capacity; (2) static p-y curves should be used which increases the pile system lateral capacity by 10 to 20%; (3) the mean value of the steel yield strength should be used; (4) jacket leg stubs should be included; and (5) site-specific geotechnical information is important. A simplified single pile failure surface in terms of three dimensional pile head loads is proposed based on the analytical lower and upper solutions, and is verified through finite element analyses. Numerical lower and upper bound models are then proposed for the ultimate capacity of a pile system, and are shown to be efficient and be effective in considering global torsion and out-of-plane failures. The evidence from the survival of offshore platforms indicates that (1) well conductors should be included in assessing the pile system ultimate capacity; (2) static p-y curves should be used which increases the pile system lateral capacity by 10 to 20%; (3) the mean value of the steel yield strength should be used; (4) jacket leg stubs should be included; and (5) site-specific geotechnical information is important.