Field Measurement of Platform Behavior, Comparison With Design, and Long-Term Monitoring of Responses Stability After Three Years of Service

Field data from structural, geotechnical and wave measurements made on the concrete gravity platform TCP2 of the Norwegian FRIGG field are disclosed in this paper. Data recorded during 3 yr are interpreted and compared to design values. The stability of invariant parameters has been followed and demonstrated in view of monitoring the long-term behavior stability of the platform. The measured behavior differs from the design behavior and exhibits that design assumptions were conservative. Particularly during this 3-yr period the platform experienced very severe storms with waves up to 25.7 m, a value close to the maximum design wave (100-yr wave: 29 m). It is shown from field data how a bridge connection to a neighboring platform may influence the actual behavior compared to the design one and must be taken into account to understand the measured behavior. It is finally shown that supposed invariant parameters like natural frequencies and others are stable on a long-term basis, and how these invariants are intended to be used for the long-term stability monitoring.