STUDY ON STABILITY AND STRENGTH OF OFFSHORE DRILLING RISER

摘要

Offshore drilling riser endures marine loads from wind, wave, current and ice, and bears gravity and equipment upon it. And so riser stability and strength become main issues of safety. By using of equivalent load method, two models were established to calculate riser critical buckling load and critical length. Taking two types of riser that usually used in shallow sea in China as examples, elastic stabilities were discussed under two conditions: top free and top hinged. In addition, the stability of monocular double-well structure was discussed. Considering the influence of all loads, maximum axial stresses were calculated to investigate riser strength. Analysis showed that, in Bohai bay, free riser can't resist ice load, and so stay-cable or brace-pipe must be used. While in southwest Weizhou area, although with reinforcement the riser can withstand most harsh conditions, single pile structure is not recommended.