Presented is the numerical method algorithm of jacket type offshore stationary platforms dynamic calculation for the effect of two-dimensional random waves of finite, heights described by different spectra. Numerical research of single- and multilegged structures of different pliability with various diameters supports station and dynamic reactions under the action of random waves are cited. It is shown that structures dynamic reactions do not practically depend on wave spectrum type; probability of exceeding functions reactions mainly depending on wave load velocity and inertial components relation, structure pliability and its length along wave ray.
Nowadays known are analytic methods of dynamic offshore structure calculation for random wave effect based on linear spectral wave theory and wave load linearization /1 2/. The limited use of these methods results in impossibility to define correctly distribution (probability of exceeding) functions of structures reactions. Well-defined theoretical solutions of offshore structures dynamic calculations for random wave of finite height are absent. This is explained by the difficulty of considering such factors as wave load non-linearity, wetted height variation of structure supports in time and space, structure length. To overcome these difficulties method of dynamic numerical calculation of deep water stationary jacket-type platforms under the action of two-dimensional random waves of finite height was developed. In wave load calculation the real three dimensional structure is replaced by a system of vertical supports of different diameters ("package of supports"), the wave load of which is equal to that of real structure. In dynamic calculation the structure design scheme is considered as linear damping system of single approximable leg rigidly fixed to the bottom. Distributed along the leg mass m is assumed constant and is equal to the sum of distributed mass of platform structure and added water mass.