Method of constructing a twin hulled, column stabilized, semi-submersible derrick barge

摘要

The derrick barge comprises a pair of laterally spaced elongated hulls having a plurality of upstanding columns spaced therealong supporting a working platform and a heavy duty derrick or crane in spaced relation above the hulls. The hulls bouyantly support the vessel including its deck load in the floating condition with the hulls having freeboard. The hulls have ballast compartments to submerge the hulls and portions of the stabilizing columns to a distance of approximately one-half the effective height of the stabilizing columns to maintain the vessel in a semisubmerged floating condition with the platform and derrick elevated above the waterline. However, the vessel also may be ballasted or deballasted to submerge or emerge to a greater or lesser extent from the semisubmerged condition such that the distance between the mean water surface and either the underside of the deck or top side of the hull is not less than 0.75 of the mean wave height. The columns stabilize the vessel in the semisubmerged condition about roll and pitch axes. The heavy duty derrick is located adjacent the stern portion of the vessel with its vertical axis of rotation intersecting the vessel centerline. This novel twin hull column stabilized derrick barge arrangement has excellent motion minimizing characteristics under wave action in operations at sea.