Experimental strain modal analysis for beam-like structure by using distributed fiber optics and its damage detection

Abstract

Modal analysis is commonly considered as an effective tool to obtain the intrinsic characteristics of structures including natural frequencies, modal damping ratios, and mode shapes, which are significant indicators for monitoring the health status of engineering structures. The complex mode indicator function (CMIF) can be regarded as an effective numerical tool to perform modal analysis. In this paper, experimental strain modal analysis based on the CMIF has been introduced. Moreover, a distributed fiber-optic sensor, as a dense measuring device, has been applied to acquire strain data along a beam surface. Thanks to the dense spatial resolution of the distributed fiber optics, more detailed mode shapes could be obtained. In order to test the effectiveness of the method, a mass lump—considered as a linear damage component—has been attached to the surface of the beam, and damage detection based on strain mode shape has been carried out. The results manifest that strain modal parameters can be estimated effectively by utilizing the CMIF based on the corresponding simulations and experiments. Furthermore, damage detection based on strain mode shapes benefits from the accuracy of strain mode shape recognition and the excellent performance of the distributed fiber optics.

Resonance Monitoring of a Horizontal Wind Turbine by Strain-Based Automated Operational Modal Analysis

“…This phenomenon occurs due to the mass imbalance of the blades and plays a large role in the operation of wind turbines because it causes heavy vibrations of the wind tower [1,2]. In addition, a strain-based automated operational modal analysis algorithm has not yet been reported, although strain measurements have been successfully used for the experimental modal analysis (EMA) [17][18][19] and OMA of beam and planar structures [20][21][22][23]. Efforts are still needed to develop a strain-based automated operational modal analysis because strain measurement can be used not only for wind load estimation [2] and fatigue evaluation [24,25] but also to extract the modal parameters.…”

A revisit to normalization methods for purpose of stress mode shapes

“…As the function of second derivatives of the classical displacement mode shapes (DMSs), strain mode shapes [9] have been applied in structural dynamic modelling, damage detection and dynamic design due to having high sensitivity [10][11][12][13][14]. In recent years, strain measurement based methods have been successfully developed to improve the local outperformance of model updating [15][16][17].…”

An analytical perspective about structural damage identification based on transmissibility function

“…To achieve more sensing information, distributed fiber optics has been applied to damage detection tests. 19,20 A simpler and clearer approach on damage detection and localization is proposed in this article, given the sensitivity analysis of transmissibility between two consecutive masses on mass and stiffness changes. This article is organized as six sections, and it starts with a literature review of the transmissibility function.…”