Titanium Riser Configurations

The present paper addresses mechanical design aspects for titanium riser configurations. Three main types of riser systems are considered: • Vertical top-tensioned risers suspended from a TLP; • Catenary risers suspended from a TLP; • Pliant-wave risers suspended from a Semi-submersible. For each configuration, characteristic response properties related to bending moment and axial force diagrams are presented. Critical sections for each riser system are identified. For the vertical top-tensioned riser, design of a bending stiffener located at the seabed is briefly addressed. Capacity formulations and the relative importance of the following mechanical limit states are addressed: • Yielding; • Local buckling; • Fatigue. Differences between parameters influencing the various limit states for titanium respectively steel are highlighted. The local buckling limit state is subsequently focused upon in some more detail in relation to loads due to combined external overpressure and bending.