Vibration-based damage growth monitoring in beam-like structures

Damage growth monitoring plays an important role in providing early warning of structural failure. The existing methods for damage growth monitoring are mainly local inspection methods, such as acoustic emission. These methods need a priori knowledge of accessible damage vicinity, which may not be realized in practice. Hence, vibration-based global approach is adopted to overcome these difficulties. Natural frequency, as a global modal parameter, can be measured easily and is used for vibration-based damage growth monitoring in this study. A concept of damage-induced relative natural frequency change (RNFC) curve is defined first and its relation with mode shape is then derived analytically, giving a good way to approximate RNFC curves. For monitoring damage growth, a damage growth indicator is proposed based on RNFCs between two damaged stages of a beam. The effectiveness of the indicator for damage growth monitoring is proved by both numerical and experimental cases in beam-like structures

Effect of geotextile sewing method on dewatering performance of geotubes: an experimental study

Geotubes are made by sewing geotextiles together and geotextiles are woven with warp and weft threads of different mechanical properties. This research explores effect of geotextile sewing method on dewatering performance of geotubes using a hanging bag test. Two types of hanging bags are made by different geotextile sewing methods: horizontal bag with the warp threads along its circular direction and vertical bag with the warp threads along its axial direction. The test results show that the dewatering performance of the bag is better if its weft stress is greater than warp stress. Combined with the stress analysis of a simplified geotube, the effect of geotextile sewing method on dewatering performance of geotubes is obtained: when the circumferential direction of geotubes is consistent with the weft threads, dewatering performance of geotubes will be better. This finding has the potential to act as a guideline for construction of geotubes in engineering

Damage localization in beams based on the analysis of modal parameters

This paper presents a two-step method for damage localization in beams by combining natural frequencies and mode shapes. The general locations of the damage are first identified from an indicator developed using relative natural frequency change (RNFC) curves and the values of RNFCs. A curvature-mode-shape-based method is then utilized to determine the specific location of the damage in the second step. The proposed two-step method is verified by detecting damage in a simulated simply-supported beam. The identified damage location agrees well with the actual damage location. A strategy for fast and accurate damage localization based on general localization using natural frequencies and specific localization using mode shapes is the main novelty of the paper