Research On New Non-destructive Testing Technology For Hydraulic Structures In Ports And Navigation-power Junction

Under the abominable external environment and complex conditions, hydraulic structures in ports and navigation-power junction were damaged inevitably in their service period. With accumulation of damage, the structure performance was deteriorating, even cause destruction. The life and property safety were threatened. A comprehensive understanding the health conditions and timely discovered of hidden damage of hydraulic structures in ports and navigation-power junction through appropriate means has been already imperative. In this paper, the new non-destructive testing technology of hydraulic structures in ports and navigation-power junction was studied on the base of two technologies integrate: the non-destructive dynamic testing technology and the local-refinement non-destructive testing technology. The focus of the study is structural modal parameter identification under fluctuating pressures.(1) Under working state, most of hydraulic structures in ports and navigation-power junction beard significant fluctuating pressures. Fluctuating pressures was random in time and space, which could be described by the probability method and statistical functions. The frequency structure could be described by spectral density. The natural excitation load was generally combination of aforesaid noise, which could be approximated as white noise excitation.(2) Hydraulic structures in ports and navigation-power junction could be simplied to multi-degree of freedom system. The modal parameters could be identified on the base of the system state space model and the conditions of controllability and observability. The idea of entropy was introduce into Eigensystem Realization Algorithm(ERA). The singular entropy technology was used to solve the order determination problem of system characteristic matrix. The modal consistency function was introduced into Frequency Domain Decomposition(FDD). The peak of singular value curve and the dominant frequency domain bandwidth played a major role was accurately determined. The ERA and Peak Picking(PP) method showed good effect on the modal parameter identification of high-piled wharf.(3) A new optimal sensor placement method, which aims on the combination of modal strain energy and linear independence, has been investigated. The improved Fisher information matrix for effective independence method is solved by stepwise accumulation style, and the sensor placement scheme can ensure the modal measurability and anti-noise ability at the same time. Based on QR decomposition and Modal Assurance Criterion(MAC) and taking advantage of integer-coded genetic algorithm, the maximum off diagonal element of the Modal Assurance Criterion(MAC) matrix decreased rapidly.(4) The method theory of structural damage detection and damage sensitive feature were introduced and analyzed on the base of modal assurance criterion, modal flexibility, stiffness change, curvature mode, strain mode, deformation curvature. An experimental study on high-piled wharf structural damage assessment was conducted based on modal parameters identification theory. The damage diagnosis method is studied based on LS-SVM and modal parameter identification, and then applied to damage localization of a guide wall structure in a large hub project.(5) A new technique, which combines the global nondestructive dynamic detection and the local refinement detection, is proposed. The paper introduces a global nondestructive dynamic detection system for hydraulic structures in ports and navigation-power junction, systematically studies a structural damage local static nondestructive detection method based on sound wave CT, and applies detection technique of sound wave CT to the quality detection of a new wharf.