ABSTRACT This paper describes a digital methodology for estimating damping and related structural parameters and the application of this methodology to a preliminary set of offshore platform data. The method involves a discrete Laplace transform and its implementation on a Time/Data minicomputer based Time Series Analysis System. The theory is perhaps complicated, however its application is simple. Data from analog tape is digitized and analyzed in a matter of minutes. We emphasize that this paper reports on a technique and methodology. The example data analysis illustrates the power of the Laplace transform but is incomplete in that adequate data was not available to provide sufficient accuracy for confidence in results at this time. The data was made available by Shell Oil Company and thoroughly described in Reference (2). The approach has been used successfully for determining damping in aircraft wings (Ref. 4), and the example preliminary analysis presented in this paper shows the method also has promise for use with offshore platform response data. The mini-computer based Laplace transform technique provides a powerful tool to aid the structural dynamicist in proper design of offshore structures to solve an important problem facing this industry today. INTRODUCTION The problem discussed in this paper is that of taking dynamic data recorded on an off shore structure and applying contemporary powerful techniques of digital time series analysis to estimate the structural parameters. Such structures may, to a useful degree, be approximated by linear structural models .incorporating resonant frequencies, damping ratios and energy factors associated with these resonances. When interpreted as a linear system, the estimation of these quantities (parameters) is often termed "system identification." One approach to system identification is empirical and involves the following steps:record dynamic data (both forcing function and response if possible)digitize the dataconvert the time history (time series) data to its frequency domain representation via the numerical Fourier transform.estimate the empirical transfer function via the time series data analysis method of cross spectral analysis Given this transfer function decomposition one example of an important application is to obtain accurate estimates of the number of excursions of given amplitudes of a structure when this structure is hypothetically excited by simulated input forcing functions. This information can then be employed in linear fatigue models (see Ref. (1)) based on accumulation of damage. That is, each excursion of a structure to a given amplitude causes a given amount of stress. These various stresses are accumulated and the fatigue damage is totaled. Hence if one knows the amount of "damage" a given material can Withstand, then fatigue life estimates can be made by knowing the number of cycles to be expected to a given amplitude per unit time. Damping is particularly important deter-mining the response of the structure, and thus damage, when the period of wave forces is close to the natural period of the platform.