A total of 6 full-scale glass fiber-reinforced polymer (GFRP) composite bridge deck specimens were tested to study the significance of using acoustic emission (AE) for monitoring and analysis of the structural integrity of the specimens during a predetermined loading profile. The first two specimens varied in width and were loaded to failure and last four specimens were the original specimens that were repaired after failure occurred using an FRP wrap. The objective, through the use of AE monitoring and analysis, is to identify failure prediction criteria and/or a methodology that would provide a determination of the structural integrity of the in-service FRP bridge deck during field inspection. While no codes and standards exist for these types of specimens, current standards developed for FRP tanks and vessels were used as a base reference to determine if current standards could be adopted or if new or additional criteria needed to be established. Real-time monitoring was conducted for each specimen during a standard 3-point bending test. Monitoring typically covered loading up to 80% of the calculated ultimate strength. During monitoring, a selected set of features associated with each AE hit and the associated waveform were recorded in a database for post analysis. The collected data was later analyzed using comparison and intensity analysis, linear location and waveform analysis, accompanied with pattern recognition, to identify series of hits with a particular event. Each event was investigated to determine if the type of damage, such as fiber breakage, matrix cracking, and delamination, could characterize the event. These types of events were the contributing factors to the investigated criteria and the structural performance of the specimens. In post analysis, comparison analysis was performed to observe the Kaiser Effect and the calculation of a Felicity Ratio when the Kaiser Effect broke down. For the original specimens, the Felicity Ratio fell within expected values observed from previous work, while the repaired specimens, using an external FRP wrap, were generally higher than the typically accepted value of 0.85. The second type of post analysis, linear location, was performed to pinpoint the location along the axis of the specimen in which the majority of the events occurred. In the case of the original specimens, visual inspection was difficult as the majority of the damage of the specimen occurred at the inner core. While there is some associated stress redistribution that leads to delamination of the outer flutes from the top and bottom face panels, this was the only visually observable change for the original specimens. Thus, linear location becomes an important tool for the location and isolation of major damage before reaching catastrophic failure. The failure mode of the repaired specimens was restricted due to the external wrap, and provided a visual cue of damage. The third type of analysis, waveform analysis using pattern recognition, appears promising in identifying each type of damage characteristic and training a neural network to classify incoming waveforms. This damaged-based characterization could be useful for in-field service inspection. However, further investigation is needed for verification before using this form of classification.

This book covers most of the damage mechanism in the scope of mechanical engineering and civil engineering. The failure pattern of various materials and structures is mainly discussed. The sub-topics covers fatigue damage, fatigue crack initiation and propagation, life prediction techniques, computational fracture mechanics, dynamic fracture, damage mechanics and assessment, non-destructive test (NDT), concrete failure assessment, failure on soil structures, structural durability and reliability, structural health monitoring, construction damage recovery, and any relevant topics related to failure analysis.

Two fiber reinforced polymer (FRP) bridge deck specimens were analyzed by means of acoustic emission (AE) monitoring during a series of loading cycles performed at various locations on the composite sandwich panels' surfaces. These panels were subjected to loads that were intended to test their structural response and characteristics without exposing them to a failure scenario. This allowed the sensors to record multiple data sets without fear of having to be placed on multiple panels that could have various characteristics that alter the signals recorded. The objective throughout the analysis ias to determine how the acoustic signals respond to loading cycles and various events can affect the acoustical data. In the process of performing this examination several steps were taken including threshold application, data collection, and sensor location analysis. The thresholds are important for lowering the size of the files containing the data, while keeping important information that could determine structurally significant information. Equally important is figuring out where and how the sensors should be placed on the panels in the first place in relation to other sensors, panel features and supporting beams. The data was subjected to analysis involving the response to applied loads, joint effects and failure analysis. Using previously developed techniques the information gathered was also analyzed in terms of what type of failure could be occurring within the structure itself. This somewhat aided in the analysis after an unplanned failure event occurred to determine what cause or causes might have lead to the occurrence. The basic analyses were separated into four sets, starting with the basic analysis to determine basic correlations to the loads applied. This was followed by joint and sensor location analyses, both of which took place using a two panel setup. The last set was created upon matrix failure of the panel and the subsequent investigation.

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Two fiber reinforced polymer (FRP) bridge deck specimens were analyzed by means of acoustic emission (AE) monitoring during a series of loading cycles performed at various locations on the composite sandwich panels' surfaces. These panels were subjected to loads that were intended to test their structural response and characteristics without exposing them to a failure scenario. This allowed the sensors to record multiple data sets without fear of having to be placed on multiple panels that could have various characteristics that alter the signals recorded. The objective throughout the analysis ias to determine how the acoustic signals respond to loading cycles and various events can affect the acoustical data. In the process of performing this examination several steps were taken including threshold application, data collection, and sensor location analysis. The thresholds are important for lowering the size of the files containing the data, while keeping important information that could determine structurally significant information. Equally important is figuring out where and how the sensors should be placed on the panels in the first place in relation to other sensors, panel features and supporting beams. The data was subjected to analysis involving the response to applied loads, joint effects and failure analysis. Using previously developed techniques the information gathered was also analyzed in terms of what type of failure could be occurring within the structure itself. This somewhat aided in the analysis after an unplanned failure event occurred to determine what cause or causes might have lead to the occurrence. The basic analyses were separated into four sets, starting with the basic analysis to determine basic correlations to the loads applied. This was followed by joint and sensor location analyses, both of which took place using a two panel setup. The last set was created upon matrix failure of the panel and the subsequent investigation.

ABSTRACT: Glass fiber-reinforced polymer (GFRP) decks are being used as a replacement for bridge decks, due to their light weight, fast installation time, and high strength. Several different types of deck systems are available for commercial use. The nature of the resin and glass materials of the decks results in a brittle and catastrophic failure mode. Due to this failure mode and the geometry of different deck systems, traditional structural evaluation methods such as deflection and strain may not detect possible damage in the material, which could lead to a failure. In this investigation a non-destructive detection method, acoustic emissions (AE) was used to develop a possible evaluation method for in-service GFRP bridge decks. Lab test setups were designed to replicate the positive and negative bending experienced by an in-service deck system. Three different deck systems were tested in both setups. A testing load procedure was developed based on similar testing of in-service GFRP tanks. The testing consisted of service-level loading of undamaged and damaged samples. Damage was induced on the samples by loading them to capacity in the test setups. AE data were collected during all the loadings as well as strain and deflection data. The strain and deflection data were analyzed and revealed linear behavior in all the samples up to failure. The AE data were analyzed using a structural evaluation method adapted from the Calm ratio and the load ratio, recovery ratio analysis (RRA). Calm ratio is the ratio of a selected feature AE activity during the unloading to the AE activity during the loading. The load ratio is the ratio of the load at the onset of AE activity to the previous maximum load experienced by the specimen. RRA was successful in the lab test and was then used on data collected during a bridge load test of the Hillsboro canal bridge.