A Method to Establish Characteristic Load Effect and Capacity Check During Installation Design for Marine Operations

This paper will present a methodology for establishing characteristic load effect and capacity check while performing installation design as part of the modelling and analysis scope of marine operation in order to establish operational parameters and limit weather criteria. The purpose of installation design is to ensure safety in terms of personnel, equipment and environment, as well as the structural integrity of the product during installation. This is achieved by analyzing the different steps of an operation in order to establish operating parameters and limit weather conditions based on a comparison of extreme and characteristic load effects and relevant limit state criteria. The methodology is customized for product design codes that require products to be verified with respect to applicable installation loads, including design formats for capacity check for combined loads on rigid pipe, umbilical and power cables, as well as capacity check for single response quantities for flexible pipes directly from the time domain analyses. The extreme value is modelled with a probability distribution of the largest response, where the extreme value is a given percentile in the extreme response distribution. The Gumbel distribution is used as a model for the extreme value distribution to fit the largest response from each simulation realization. Alternatively, a more efficient procedure may be used, including establishing response time series, establishing time series for the load effect, fitting a 3-parameter Weibull distribution of individual maxima, establishing the associated Gumbel extreme value distribution for the largest individual maxima, and finally estimating extreme value as the appropriate percentile in the Gumbel distribution. The method is implemented in a software application to be able to automate the process and which can also be used as a postprocessing tool along with a non-linear time domain analysis solver. Nonlinear time domain analysis is required to handle nonlinearities in geometric stiffness, hydrodynamic loading, material nonlinearities and contact problems. Nonlinear properties and hydrodynamic load mechanism are transforming the wave frequency of Gaussian excitation into non-Gaussian global responses. Assessment of extreme load effect for non-Gaussian response processes is required to perform capacity checks based on an irregular wave representation. In present context, the meteorological and oceanographic data analysis involves manipulating, transforming, and visualizing data based on data analysis results using descriptive and inferential statistics.