Simplified Evaluation Of The Capacities Of Template-Type Offshore Platforms

During the past three decades, an immense amount of effort has been devoted to development of sophisticated computer program.∼ to enable the assessment, of storm wind, wave, and current loadings and the ultimate limit state capacity characteristics of conventional, pile-supported, template-type offshore platforms [Billington, et al., 1993; Frieze, 1993; Hellan, et aI., 1993; 1994]. These programs require high degree of expertise to operate properly, are expensive to purchase and maintain, and require large amounts of manpower and time to complete the analysis. Due to the sophistication of these, programs, experience has shown that It IS easy to make mistakes that are difficult to detect and that can have significant influences on the results. This par summarizes the second phase of development and verification of simplified procedures to evaluate environmental loadings and ultimate limit state lateral long capacities of template-type platforms. Reasonable amplifications and high degrees of "user friendliness" have been employed ID development of the software to reduce the engineering effort expertise and costs associated with the analyses, The computer program that has bee∼ developed to perform the simplified analyses has been identified as ULSLEA (Ultimate limit State limit Equilibrium Analyses) [Mortazavi, Bea, 1994]. The first phase developments were verified with comparisons of observed and computed loadings and capacities, from five 8-pile self-contained drilling and production platforms and one 5-pde well protector. The simplified static capacity bias (nonlinear analysis capacity I simplified capacity) ranged from 0.80 to 1,03 with a mean value of 0.95. Comparisons of die computed lateral load capacities base on the simplified approach with the estimated maximum loadings sustained by these platform during part hurricanes indicated good agreement [Bea, 1995). During the second phase of this research, based on the experience from the first phase developments, a number of improvement were made in the simplified analyses.