Seismic performance of pile-founded fixed jacket platforms with chevron braces: Fid-Bau Portal

Seismic performance of pile-founded fixed jacket platforms with chevron braces

Nour El-Din, Mohamed / Kim, Jinkoo

In this study, pile-founded jacket offshore structures with buckling-restrained braces (BRB) and conventional braces were designed using different methodologies such as performance-based (plastic design and displacement-based design) and strength-based (code procedure) methods, and their seismic performances for strength- and ductility-level earthquakes were compared. An analysis model of the jacket considering soil–pile structure interaction (SPSI) was developed by substituting the soil layers with equivalent nonlinear springs having pile–soil interaction characteristics. According to nonlinear static and dynamic analysis results, the application of BRB in chevron-braced jacket structures was found to enhance the seismic behaviour under ductility-level earthquakes. However, under strength-level earthquake, for which model structures mostly remained elastic, the enhancement was marginal. Among the different BRB design methods introduced, displacement-based design method produced more uniform plastic hinge distribution, while other methods provided better results in terms of maximum drift ratios. Based on the relative stiffness index and soil condition introduced in this study, it was found that for system with large ductility, simplified SPSI modelling could be used to reduce the computational cost especially for the preliminary design stage.