DNV has, in cooperation with partners from the industry, carried out a joint industry project with the aim to develop recommended practice with respect to the design of titanium risers. As a part of this work, calibrated design formulae for combined loading have been established. The considered load situation is a combination of internal overpressure, bending moment and axial force. The data basis for the calibration study encompasses results from 12 finite element simulations with varying diameter to thickness ratio and internal pressure exposed to bending moment and axial force. With the design equation for steel risers, taken from the DNV Offshore Standard (OS-F201) Dynamic Risers, as a basis, the titanium data basis was investigated using state-of-the art methodology with an uncertainty modeling for load effects in compliance with recent research and development projects for risers and pipeline design. The outcome of this work is a design equation with reliability based calibration of safety factors that comply with the overall safety objective in the above offshore standard.

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