The Studies On Damage Detection For Offshore Platform

Recent advances in research on structural damage detection are reviewed in the paper.It is a challenging task to detect the structural damage for civil engineering.Nondestructive Damage Detection (NDD) methods based on vibration measurement in large and complex structures were shown to be promising . However offshore platform structures are very complex, and not easy to be excited artificially and they are often suffered from natural (ambient) loads that cannot be controlled easily. The thesis focuses on the key issues for Structural Health Monitoring via vibration in real offshore platform structures.Nondestructive Damage Detection in large/complex structures is investigated via vibration monitoring of three dimensional frame structures. An accurate, efficient method for the damage locations and evaluation of damage based on the employment of the cross modal strain energy (CMSE) is presented. While traditional modal strain energy methods must compare the modal information from the same ith mode for the baseline (analytical) and damaged (measured) structures, such constraint isn't required for the CMSE method.The major advantages associated with the CMSE method is that minimal measured modal information is required — often a single measured mode is sufficient. Additionally, the CMSE method does not require the analytical and measured modes to be consistent in scale, or to be normalized in any specific way. Numerical studies in this paper have been carried out conducted for shear building, three-dimensional frame structure and template offshore structure based on modal parameters generated from finite element models. This study demonstrates that the developed method is capable of detection damages for template offshore platform structures under ambient excitation no matter of the damage located either at a vertical pile, a horizontal beam or a slanted brace.Two particular tasks, single-damage and multiple-damage scenarios, are to be performed.With random measurement errors and modal parameters identification errors in damage detection, CMSE can estimate damage severity availably.but this method can't indicate damage localization accurately.This dissertation focuses on the core problem of "structural damage detection ", which is the key techniques of structural health monitoring system. The national 15th 863 program and Na-tional Nature Science Foundation sponsored the research project related with this thesis. This dissertation proposed and developed a method for offshore platform structural health monitoring. Numerical model, field testing and model experiment were used for the verification of these techniques. The techniques in this paper make some progress in damage detection of offshore platform structures.