Study on the structural monitoring and early warning conditions of aging jacket platforms

In this paper, the structural monitoring methods and early warning conditions were proposed based on the characteristics of the aging jacket offshore platforms, including the monitoring and early warning condition of the displacement, the bearing loads of pile end and the platform subsidence. On the basis of pushover analysis, the curves of base shear force versus deck displacement were drawn. Furthermore, the anticipated risks were classified into three levels due to different deformations in the collapse process; the three level early warning conditions were established. A method of the monitoring of the bearing loads of pile end was put forward, with the calculating of the load transmission function. The early warning condition that the bearing loads of pile end should not exceed half of the ultimate pile capacity was provided based on API RP 2A-WSD. The long-term monitoring method of the platform subsidence was presented based on the calculating of the difference of elevation between any two pile tops. The early warning conditions considering the stress and tilt requirements were established. The monitoring method has been applied to a jacket offshore platform on the South China Sea, and the result illustrates the feasibility of this method.