The results of prototype tests of the jacket offshore platforms of Cheng Bei Oilfield A and observation data of new strong motion observation station on one of these platforms in Bohai Bay, China in 1988 were presented in this paper. Tests show that jacket platforms vibrated in complex spatial and coupling vibration mode with interactions between structures and structural members. The finite element method of the space Jacket structural model is used for the analysis. More than ten mode frequencies and mode shapes of two jacket platforms are calculated. The calculated values of frequencies are in good agreement with the results of prototype tests.
More than ten fixed jacket offshore platforms have been constructed in the Bohai Bay, China since 60ths and they are developed to the Liao Dong Bay recently, which is located in the northeast part of the Bohai Bay. The purposes of prototype tests are to identify the characteristics, dynamic responses and behaviour of jacket offshore platforms under wind, waves current excitations and under boat ramming, in addition to check the analytical method of jacket structure. The tested platforms are drilling & production platform and utility & accommodation platform of Cheng Bel Oilfield A. They are located in the southeast part of the Bohai Bay apart from Tanggu 74 Km, on the site of 38°26" north latltude and 118°25" east longitude. The sea water depth of platforms is in the range of 15-16 m. The Cheng Bei Oilfield is the first offshore field developed by Chinese and Japanese, Cooperation. It divides into two parts, one is the Oilfleld A and the other is the Oilfleld B. The Oilfleld B has a storage-tank-platform and a oil wharf, except both have the same drilling & production and utility & accommodation platforms in two oilflelds.