Monitoring and Failure Analysis of Corroded Bridge Cables under Fatigue Loading Using Acoustic Emission Sensors

Cables play an important role in cable-stayed systems, but are vulnerable to corrosion and fatigue damage. There is a dearth of studies on the fatigue damage evolution of corroded cable. In the present study, the acoustic emission (AE) technology is adopted to monitor the fatigue damage evolution process. First, the relationship between stress and strain is determined through a tensile test for corroded and non-corroded steel wires. Results show that the mechanical performance of corroded cables is changed considerably. The AE characteristic parameters for fatigue damage are then established. AE energy cumulative parameters can accurately describe the fatigue damage evolution of corroded cables. The failure modes in each phase as well as the type of acoustic emission source are determined based on the results of scanning electron microscopy. The waveform characteristics, damage types, and frequency distribution of the corroded cable at different damage phases are collected. Finally, the number of broken wires and breakage time of the cables are determined according to the variation in the margin index

Civil Engineering Applications of Acoustic Emission

In 1939, a suspension bridge at Portsmouth, Ohio, experienced stress-corrosion cracking of the main-cable wires at anchorage points located at each end of the bridge. Watchmen were placed in the anchor chambers where the fractures had been detected. Subsequently, they reported hearing the sounds of further wire breakage on quiet nights. When this was reported, a decision was made to recable the bridge (1). That was one of the earliest documented instances of the use of the acoustic emission phenomena in a structural application. Also, in the late 1930\u27s, L. Obert and W. I. Duval at the U. S. Bureau of Mines were performing sonic tests on rock mines. They were surprised to find that stressed rock pillars emitted micro-level sounds (2). Those noises were later termed rock-talk. Unlike the early acoustic emission structural monitoring at Portsmouth, the rock-talk phenomena has been the subject of continuous ongoing geotechnical research since the late 1930\u27s. Over the years, much progress has been made in civil engineering applications using acoustic-emission (AE) testing. However, most of those applications are still in developmental stages. Also, some of the past research is contradictory. Therefore, the potential AE user should perform preliminary tests to ascertain the viability of the intended AE procedure. Both laboratory and field tests should be performed under controlled conditions to ensure the applicability and usefulness of that test method before it is employed in service. While this approach is expensive, subsequent cost savings from AE in-service testing, compared to other nondestructive methods, usually justifies those expenditures. The following three sections discuss the primary applications of acoustic emission in civil engineering. Those are 1) geotechnical, 2) structures, and 3) special component testing. Due to the vast scope of AE research, these reviews are certainly not complete. There are several state-of-the-art AE reviews that provide reference to specific applications (3, 4)

Nondestructive Evaluation of Steel Bridges: Methods and Applications

Nondestructive evaluation (NDE) methods can be used to assess in-service steel bridges for problematic conditions caused by factors such as design, manufacturing, fabrication, and the service effects of traffic and corrosion. This report discusses typical NDE test methods used on bridges, including penetrant testing, magnetic particle testing, eddy current testing, ultrasonic testing (including phased array testing), radiography, and acoustic emission testing. NDE operations such as flaw location, characterization, and sizing are covered as well. Results of a national survey of departments of transportation’s (DOTs) use of NDE are presented. A simple procedure for using NDE to address DOT bridge concerns is proposed along with a risk-based inspection approach to scheduling/scoping bridge inspections

Structural health monitoring based on acoustic emissions : validation on a prestressed concrete bridge tested to failure

The increasing number of bridges approaching their design life has prompted researchers and operators to develop innovative structural health monitoring (SHM) techniques. An acoustic emissions (AE) method is a passive SHM approach based on the detection of elastic waves in structural components generated by damages, such as the initiation and propagation of cracks in concrete and the failure of steel wires. In this paper, we discuss the effectiveness of AE techniques by analyzing records acquired during a load test on a full-size prestressed concrete bridge span. The bridge is a 1968 structure currently decommissioned but perfectly representative, by type, age, and deterioration state of similar bridges in operation on the Italian highway network. It underwent a sequence of loading and unloading cycles with a progressively increasing load up to failure. We analyzed the AE signals recorded during the load test and examined how far their features (number of hits, amplitude, signal strength, and peak frequency) allow us to detect, quantify, and classify damages. We conclude that AE can be successfully used in permanent monitoring to provide information on the cracking state and the maximum load withstood. They can also be used as a non-destructive technique to recognize whether a structural member is cracked. Finally, we noticed that AE allow classifying different types of damage, although further experiments are needed to establish and validate a robust classification procedure

Acoustic emission monitoring and quantitative evaluation of damage in reinforced concrete members and bridges

A considerable proportion of highway bridges in the US, are made of reinforced concrete. The vulnerability of these structures during their long service life is a cause of major concern for civil engineers. Since there is a need to detect and recuperate the condition of the bridge structures numerous innovative non-destructive testing (NDT) techniques have come into the forefront. Of the many available technologies, acoustic emission (AE) monitoring has been the most popular non-destructive technique used on highway bridges. Acoustic emission is a passive monitoring technique. Thus, it can be appropriately used for field bridge monitoring applications. Usually AE monitoring is used to obtain qualitative results by observing the trends of the conventional AE parameters recorded by the data acquisition system. The extent of damage is then determined using other NDT techniques. The current study aims at applying the intensity analysis technique of damage quantification to conventional AE parameters generated from reinforced concrete members. A few reinforced concrete beams are subjected to varied cyclic load patterns in the laboratory to study the trends that may be observed in the intensity chart during damage propagation. The results thus obtained are then compared to other prevalent damage assessment techniques as well. Additionally, AE data collected from two field bridge tests are also subjected to intensity analysis technique of damage quantification to evaluate the practical viability of the technique in assessing the severity of the damage in the monitored structures