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This paper presents a hybrid non-destructive testing (NDT) approach based on (non-contact) infrared thermography (IRT), (passive) acoustic emission (AE), and (active) ultrasonic (UT) techniques for effective damage assessment of partially grouted concrete masonry walls (PGMW). This hybrid monitoring approach could be implemented for the health monitoring of concrete masonry structures. The implementation of this system assists the cross validation of in-situ recorded information for structural damage assessment. NDT was performed on PGMW subjected to cyclic horizontal loading. The obtained IRT, AE, and UT results successfully monitored the progressive damage process throughout the loading history. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a data fusion approach based on digital image correlation (DIC) and acoustic emission (AE) to detect, monitor and quantify progressive damage development in reinforced concrete masonry walls (CMW) with varying types of reinforcements. CMW were tested to evaluate their structural behavior under cyclic loading. The combination of DIC with AE provided a framework for the cross-correlation of full field strain maps on the surface of CMW with volume-inspecting acoustic activity. AE allowed in situ monitoring of damage progression which was correlated with the DIC through quantification of strain concentrations and by tracking crack evolution, visually verified. The presented results further demonstrate the relationships between the onset and development of cracking with changes in energy dissipation at each loading cycle, measured principal strains and computed AE energy, providing a promising paradigm for structural health monitoring applications on full-scale concrete masonry buildings. [ABSTRACT FROM AUTHOR]

This article deals with the monitoring of the composite wing skin-to-spar joint in unmanned aerial vehicles using ultrasonic guided waves. The study investigates simulated wing skin-to-spar joints with two different types of bond defects, namely poorly cured adhesive and disbonded interfaces. The bond-sensitive feature considered is the ultrasonic strength of transmission through the joints. The dispersive wave propagation problem is studied numerically by a semi-analytical finite element method that accounts for viscoelastic damping, and experimentally by ultrasonic testing that uses highly durable, flexible macro fiber composite transducers. The discrete wavelet transform is also employed to de-noise and compress the ultrasonic measurements. Both numerical and experimental tests confirm that the ultrasonic strength of transmission increases across the defected bonds. [ABSTRACT FROM AUTHOR]

A fundamental understanding of the response of piezoelectric transducer patches to ultrasonic waves is of increasing interest to the field of structural health monitoring. While analytical solutions exist on the interaction of a piezoelectric actuator with the generated Lamb waves, the behavior of a piezoelectric sensor has only been examined for the limited case of a piezo-actuated Lamb wave in a pitch-catch configuration. This paper focuses on the fundamental response of surface-bonded piezoelectric sensors to ultrasonic waves. The response to both Rayleigh waves and Lamb waves is examined, starting with harmonic excitation fields and moving to broadband and narrowband excitation fields. General oblique incidence of the wave on rectangular sensors is treated first; parallel incidence is then derived as a particular case. The solutions are developed analytically for the harmonic and the narrowband excitations, and semianalytically for the broadband excitation. The results obtained can be used to design ultrasonic sensors that are either particularly sensitive to a given mode or possess unique directivity behavior which, in turn, can greatly simplify current algorithms for damage detection and localization. [ABSTRACT FROM AUTHOR]

Summary: Insufficient information on existing bridge substructures and foundations poses significant challenges for structural condition evaluation and can cause significant uncertainties for the safety and serviceability of bridges. Characterization and condition evaluation of bridges substructure and foundations will not only help to decrease the vulnerability to natural hazards but also provide opportunities for their reuse with considerable benefits. In this paper, the feasibility of leveraging structural identification techniques to characterize bridge substructures and foundations is investigated. A three‐span simply supported bridge located in Mossy, West Virginia, USA, is used as a study case. Modal analysis and finite element model updating techniques are used to investigate and estimate the uncertainties and conditions of the substructure. Updated finite element model for this structure provides valuable information for bridge condition assessment and proves how structural identification is a viable tool for the case considered. [ABSTRACT FROM AUTHOR]

• A new method for sensitivity-based model updating is proposed. • Ill-conditioning is mitigated by a multiplicative regularization approach. • A trust region Sequential Quadratic Programming with bound constraints is used. • The size of the trust region is a parameter of the regularization functional. • The damaged bearing of an in-service bridge is identified by leveraging modal data. The paper focuses on the development of an iterative minimization algorithm for structural identification. The algorithm consists of a Gauss-Newton method in which the ill-conditioning caused by noise pollution is mitigated by means of a multiplicative regularization technique used in conjunction with a bound constrained trust region method. Unlike the classic additive regularization technique, the amount of regularization is not determined a priori, but computed in an automatic fashion at each step of the iterative procedure. Specifically, the strength of the regularization is controlled by the norm of the model parameters weighted by a factor proportional to the current values of the least-square cost functional and the size of the trust region. The iterative procedure consists in solving a sequence of regularized local quadratic subproblems in a Sequential Quadratic Programming framework, for which a local convexity condition is given. The proposed method is finally tested in the retrieval of the equivalent stiffness of the soil and bearings of a real, in-service bridge pier that was tested using experimental modal analysis. [ABSTRACT FROM AUTHOR]

A hybrid Finite Element-Plane Wave Expansion method is presented for the band structure analysis of phononic crystal plates with two dimensional lattice that are in contact with acoustic half-spaces. The method enables the computation of both real (propagative) and imaginary (attenuation) components of the Bloch wavenumber at any given frequency. Three numerical applications are presented: a benchmark dispersion analysis for an oil-loaded Titanium isotropic plate, the band structure analysis of a water-loaded Tungsten slab with square cylindrical cavities and a phononic crystal plate composed of Aurum cylinders embedded in an epoxy matrix. [ABSTRACT FROM AUTHOR]

Abstract: A semi-analytical finite element (SAFE) method is presented for analyzing the wave propagation in viscoelastic axisymmetric waveguides. The approach extends a recent study presented by the authors, in which the general SAFE method was extended to account for material damping. The formulation presented in this paper uses the cylindrical coordinates to reduce the finite element discretization over the waveguide cross-section to a mono-dimensional mesh. The algorithm is validated by comparing the dispersion results with viscoelastic cases for which a Superposition of Partial Bulk Waves solution is known. The formulation accurately predicts dispersion properties and does not show any missing root. Applications to viscoelastic axisymmetric waveguides with varying mechanical and geometrical properties are presented. [Copyright &y& Elsevier]

Summary: Remote measurements using images are particularly useful in structural health monitoring cases in which the installation of contact sensors is difficult. Some limitations, though, associated with photogrammetry‐type optical metrology involve the application of speckle patterns, which become even more important with variable working distance or when the required resolution and sensitivity are not a priori known which are both very practical common issues. In this context, multispectral sensing can circumvent some of the challenges of acquiring data at different working distances. The objective of this investigation is therefore to use multispectral imaging combined with the method of digital image correlation to demonstrate an approach for remote sensing related to deformation measurements at the structural level. To demonstrate this novel approach, two speckle patterns were designed for measurements at specified working distances; one was set to work in the visible and the second in the ultraviolet spectrum. The results show that the spectral specific reflectivity of the speckle patterns can be used for spatial overlay without affecting imaging in either spectral range considered, which allows the extraction of multiscale deformation information. [ABSTRACT FROM AUTHOR]