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Bridge health monitoring is increasingly relevant for the maintenance of existing structures or new structures with innovative concepts that require validation of design predictions. In the United States there are more than 600,000 highway bridges. Nearly half of them (46.4%) are rated as fair while about 1 out of 13 (7.6%) is rated in poor condition. As such, the United States is one of those countries in which bridge health monitoring systems are installed in order to complement conventional periodic nondestructive inspections. This paper reviews the challenges associated with bridge health monitoring related to the detection of specific bridge characteristics that may be indicators of anomalous behavior. The methods used to detect loss of stiffness, time-dependent and temperature-dependent deformations, fatigue, corrosion, and scour are discussed. Owing to the extent of the existing scientific literature, this review focuses on systems installed in U.S. bridges over the last 20 years. These are all major factors that contribute to long-term degradation of bridges. Issues related to wireless sensor drifts are discussed as well. The scope of the paper is to help newcomers, practitioners, and researchers at navigating the many methodologies that have been proposed and developed in order to identify damage using data collected from sensors installed in real structures. [ABSTRACT FROM AUTHOR]

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The article offers information on the development of American Society for Testing and Materials (ASTM) acoustic emission (AE) standards. The formulation, development, standardization and maintenance of test methods is the responsibility of the ASTM International, E07.04, Acoustic Emission Subcommittee. A list of the existing AE standard document numbers and titles which can be found in Volume 03.03 Nondestructive Testing, Annual Book of Standards is also presented.

There is currently a request from landowners in southeastern USA to provide a nondestructive tool that can differentiate the quality between stands of 25 and 30 years of age subjected to different thinning treatments. A typical site with various thinning regimes was used to vary the wood quality and to determine whether acoustics had the ability to separate for stiffness differences at a given age and local geography. A stand at age 29 with three different spacing (prior thinning) levels was chosen. Three hundred trees (100 per treatment) were randomly selected and acoustically tested for sound velocity using the Time-of-Flight (ToF) method for unthinned, thinned, and twice-thinned stands, respectively. The key finding of the study was that the estimated stiffness of the previously thinned treatments was actually greater than that of the unthinned group, despite having diameters as much as 28% larger. During a forest cruise, knowing that a higher-diameter stand is similar or higher in stiffness could raise the dollar value and harvest priority. [ABSTRACT FROM AUTHOR]

This article discusses a combined analytical and experimental study on the nonlinear seismic performance of two Guastavino-style masonry domes located in the United States. The seismic performance of these masonry domes is simulated with nonlinear finite-element (FE) models. To support the assumptions and decisions established during the development of the FE models, the vibration response of the domes is measured on-site and systematically compared against the numerical model predictions. Linear FE models are developed that are in close agreement with the measured natural frequencies and in visual agreement with the measured mode shapes. Next, these linear models are extended into the nonlinear range by incorporating the Drucker-Prager damage criterion. Finally, nonlinear FE models are used to assess the performance of these two domes under seismic loadings obtained from the 1940 El Centro earthquake acceleration records. The predicted displacements and internal tensile stress levels are used to make inferences about the potential behavior of these two buildings under the selected earthquake load. [ABSTRACT FROM AUTHOR]