Seismic Analysis of Cranes on Jack-Ups

Seismic Analysis of Cranes on Jack-Ups

Linthorst, Joost (TU Delft Mechanical, Maritime and Materials Engineering)

van der Meulen, Ronald (mentor)
Tsouvalas, Apostolos (mentor)

Delft University of Technology

Offshore and Dredging Engineering

2019-07-26

GustoMSC, an NOV company, is a market leader in the design of offshore wind installation jack-ups. Offshore wind turbine installation has been situated mainly in the North Sea, which is not very seismically active. As a consequence, wind turbine installation jack-ups have been designed and analysed for low seismic excitations. The offshore wind industry is expanding to East Asia, where it finds itself in seismically active regions where seismic excitations are significantly higher. Therefore, operators are requesting GustoMSC to supply input for risk analyses of their jack-ups and its crane. GustoMSC requires a tool to conduct ultimate limit state analyses of a jack-up and its crane under seismic conditions. This tool has been created and applied in this work.

The main challenge of this thesis is related to the estimation of the probability of exceedance of a predefined structural limit of a crane on a jack-up given a set of seismic ground motions. To tackle this challenge, suitable models of the jack-up and crane substructure are developed and verified. With use of a data package, containing two months worth of wind turbine installation data, a Monte Carlo analysis is conducted to determine the probability of exceedance of the structural limit in a 50-year period.

When constructing the jack-up model, the mass and stiffness distribution of the jack-up is important for an accurate response, a slight eccentricity in the mass of the jack-up leads to a very different response. A tool has been created which ensures the mass distribution and eccentricity are incorporated to the degree of accuracy required.

To determine the probability of exceedance of the structural limit in a 50-year period, the seismic analysis tool has been used to conduct a Monte Carlo analysis. Using data from a previous wind park installation operation and ISO 1990X-X standards and Eurocode 8, probability distributions have been created for the boom angle, slewing angle, hook load, earthquake time-trace, angle of incidence of excitation and probability of occurrence of the earthquake. By including all relevant variables, the work in this thesis has determined the probability of exceedance of the structural limit for a 50-year period to be 7.7%.

The tools and method created in this thesis allows for the probability of exceedance of the structural limit due to seismic excitation to be determined. Creation of this tool allows GustoMSC to consider high seismic excitations in future designs.

Earthquake
Earthquake analysis
Earthquake Engineering
Seismic
seismic analysis
Cranes
Jack-up

http://resolver.tudelft.nl/uuid:d4085d73-4646-4e83-8e0b-c564facb7497

Student theses

master thesis

© 2019 Joost Linthorst