Modal parameter identification of offshore platforms under ambient excitation

This paper intends to identify the model parameters of an offshore platform under ambient excitation, and compare the identified results with theoretical solutions. Using ambient sources of excitation to determine the model characteristics of large civil engineering structures is desirable for several reasons. The forced vibration testing of such structures generally requires a large amount of specialized equipment and makes the tests quite expensive. Also, an automated health monitoring system for a large civil structure is most likely use ambient excitation. The eigensystem realization algorithm (ERA) is applied in conjunction with the common basis-normalized system identification (CBSI) to identify structural modal parameters (natural frequency, damp ratio, mode shape), with limited acceleration information. The offshore platform numerical model gets output response data under ambient excitation. Simulation data from numerical model of an offshore platform under ambient excitation is used for the identification of the system. According to the comparison results, the proposed method is shown to be effective for modal parameter identification under ambient excitation