Abstract:

Dynamic responses of offshore platforms and their piles under environmental excitations such as waves, currents and wind loads exist in long-term service. In this paper, the dynamic deformation monitoring of the pile of a platform in Chengdao oil field of Bohai Bay is carried out by using the H32 omnipotent GNSS RTK dual frequency receiver as the test instrument with the GPS+GLONASS+BDS three-star system. Combined with the noise reduction characteristics of Ensemble Empirical Mode Decomposition (EEMD) and Butterworth filtering methods, a hybrid filtering method, MDB, which is suitable for the working environment of offshore platform, is proposed, and the real-time curve of the measuring point of the pile is obtained by using the program compiled by Matlab software to analyze the monitoring data of the GNSS. Results show that GNSS RTK combined with MDB filtering technology is feasible to monitor the dynamic deformation of offshore platform leg, and MDB filter can effectively remove the random noise and multipath error of vibration information of offshore platforms. And from the displacement nephogram of offshore platform legs after removing multi-path errors and random noises, the reversible displacement trajectory of the legs in the horizontal direction can be clearly seen, which is of great significance to the health monitoring, diagnosis and evaluation of offshore platform structures.

Key words: GNSS RTK, offshore platform, ambient excitation, dynamic deformation monitoring, MDB hybrid filtering