In this paper a practical procedure for damage estimation of offshore tubular members under accidental loading is formulated taking the interaction effect of the local dent and the global bending damage into consideration. A tubular member subjected to lateral loading whose boundary condition is considered to be axially restrained and rotationally free is taken. Since the impact effect is supposed to be negligible when the loading velocity IS relatively slow the deformation characteristics of the member under quasitatic lateral load IS firstly evaluated through theoretical and experimental study. Then an explicit form of the relation between the load and the damage amount is derived taking account of the interaction effect between the local dent and the global bending deformation. Also. a series of test for the tubular member under Impact loading is conducted with varying the magnitude of the loading velocity. Based upon the experimental results obtained here, the characteristics of the impact loading is Incorporated Into the above derived procedure which IS for the quasi-static loading condition.
With the strengthening of code requirements for the structural integrity the safety assessment of offshore platforms against the accidental impact loads due to minor collision associated with supply vessel falling objects such as drill collar hydril, winch, mud pump, riser pipe and major collision with large vessel passing around the platforms becomes of great importance. Of these accidental events major collision with large vessel such as oil tanker passing around the platforms IS very dangerous because this event may result in the collapse of the platforms as a whole. Thus, a protect system against major collision IS necessary in which for instance safety zone around the platforms is set and as a result the probability that major collision is occured is usually smaller than 10-7 .