Design of the offshore platform model similar to the natural frequency of original shape

The conditions satisfied for the design of the similar offshore platform model are derived based on the Bockingham's pi-theorem.The basic conditions for realizing every similar ratios are analyzed.The analysis shows that it is the most difficult to satisfy the similarity of the natural frequency of model to that of original shape,but the similarity is very important to the dynamic similarity of model to original shape.For this reason,a parameter——the relative error of natural frequency ratio—— is introduced,which is used for measuring the extent of the actual natural frequency ratio approaching to the theoretical natural frequency ratio.All the factors of influencing the relative error are analyzed in order to minimizing it.This method provides a practical technique for the design of the similar models of offshore platforms.An actual model is designed for W12-1 offshore production platform sited in South China Sea using this method and a satisfactory result is obtained.