Acoustic Emission Testing of Shielded Metal-Arc Welds Using ASTM A 36 Steel

Manual, shielded metal-arc welds on ASTM A 36 structural steel were monitored with acoustic emission equipment. The listening device detected operator inconsistencies and improper electrode deposition during the welding operation. On completion of the weld, acoustic emission monitoring detected slag inclusions, cracking, and martensite formation

Acoustic Emission Monitoring of Bascule Bridge Components

During September 4-16, 1986, Kentucky Transportation Research Program (KTRP) personnel conducted a two-week inspection of welding operations on bascule bridge components for the Wisconsin Department of Transportation (WisDOT). Welding was performed by the Phoenix Steel Company at Eau Clair, Wisconsin. The inspection was conducted using acoustic emission (AE) monitoring on in-process welds. KTRP investigative experience with AE weld monitoring and testing of bridges began in 1973. Since that date, KTRP has performed nine series of laboratory and fabrication shop weld monitoring tests and conducted 20 field tests of bridges using a series of increasingly sophisticated AE devices. Over the past four years, KTRP has had success with the Acoustic Emission Weld Monitor (AEWM) developed by GARD, Inc. of Niles, Illinois. That device was originally intended to monitor in-process welding operations to detect defect formation. KTRP has determined that the unit is also suitable for detecting fatigue-crack growth on in-service bridges. The operation of the AEWM and a summary of KTRP/GARD bridge experience with that device is contained in a technical paper, which is included in the Appendix

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)

Acoustic Emission, Fatigue, and Crack Propagation

Acoustic emission was used in conjunction with tensile tests to evaluate the condition of structural steel specimens subject to various tensile fatigue lives. The results indicate that the acoustic emissions detected were the result of plastic deformation. There was no apparent relationship between fatigue history of the steel specimens and the amount of plastic deformation they can accommodate. Further tests revealed that acoustic emission has the physical capability of detecting cracks on large structural steel members. This may prove beneficial for the comprehensive testing of steel bridges

Long-Term Evaluation of the Acoustic Emission Weld Monitor

The Kentucky Transportation Research Program conducted an extended 10- month evaluation of the Acoustic Emission Weld Monitor (AEWM) in a bridge fabrication shop. That device was used to detect welding flaws during typical production of butt-welds on flanges and webs used in steel bridges. A total of 153 welds were monitored. AEWM test results were compared with visual inspection and double- blind results of conventional nondestructive testing routinely conducted on the welds. The AEWM did not miss any flaws detected visually or by nondestructive testing. Three AEWM flaw indications were confirmed by conventional nondestructive testing (radiography). A large number of AEWM indications were not related to any detected flaws (228 of 263 indications). Those were attributed to AE noise that occurs away from the weld and small flaws that were either missed or overlooked by visual and nondestructive inspection or were removed prior to inspection by normal fabrication procedures. The AEWM has shown the sensitivity to detect AWS code-rejectable defects. In part, the high number of overcalls was caused by use of excessive system sensitivity. Due to the success of the unit in detecting flaws, further development is warranted. Specific recommendations for further research are provided

Acoustic Emission Testing of High-Strength Steel Weldments

Manual arc welds were made on high-strength ASTM A 514 and A 588 steels. Different weldment configurations were employed in order to vary the restraint on the welds during cooling. The weldments were monitored \u27in-cooling\u27 with acoustic emission equipment. Weldments having greater restraint produced more acoustic emission, usually for longer periods of time. Weldments which fractured during cooling produced more acoustic emission than those which were unflawed

Ohio River Suspension Bridges: An Inspection Report

For many years, suspension bridges have been employed to economic advantage where long uninterrupted spans were required. While they have been supplanted for most common applications by cantilever and arch bridges in the United States, suspension bridges are a valid design type. Two American suspension bridges have been in service for over 100 years. A new form of suspension bridge, the cable-stayed bridge, is widely used in Europe and is expected to be as popular in the United States. The key to the success of suspension bridges lies in the use of high-strength wires that are consolidated into the main cables. These cables support very heavy loads, compared to common structural-steel members. This allows designers of suspension bridges to employ lower dead loads than necessary for other types of bridges for equivalent live loads and spans. Unfortunately, to achieve economy of construction, load-bearing redundancy is usually sacrificed in most suspension-bridge designs. If a main cable of a suspension bridge should beak, the bridge would collapse in a catast rophic manner. Therefore, defects in the main cable wires of a suspension bridge may be significantly more critical than defects in structural members of other bridge types

Deterioration Modelling of Bridges on BrM 5.2.3

The Kentucky Transportation Cabinet (KYTC) initiated the study KYSPR 17-532, “Deterioration Modelling of Bridges on BrM 5.2.3,” so it could receive assistance identifying and employing bridge deterioration and cost forecast modeling for its bridge maintenance program. The Kentucky Transportation Center (KTC) was to help coordinate KYTC in adapting BrM 5.2.3’s deterioration and cost modelling features and update the existing guide material to reflect all changes for BrM 5.2.3. This study included acquiring access and becoming familiar with AASHTO Bridge Management (BrM 5.2.3) software. It was also to explore opportunities for any training on BrM and BrM 5.2.3’s deterioration and cost modeling capabilities and adapt them to best meet KYTC’s maintenance needs for four National Bridge Elements (NBE) — Reinforced Concrete Deck (12), Steel Open Girder/Beam (107), Strip Seal Expansion Joint (300), and Moveable Bearing (311). But the lack sufficient and reliable data for element-level deterioration modelling has proved a hindrance and impeded the completion of the research. As data points are collected, deterioration rates should be checked occasionally to see if they require calibration

Safety and Health Concerns for KYTC and Contractor Personnel

This study was initiated to provide a review of safety and health issues related to Kentucky Transportation Cabinet (KYTC) construction activities including both KYTC and contractor personnel. Work included a literature search, interviews with KYTC resident engineers, and both a survey of and subsequent meeting with district construction safety coordinators. Recommendations are provided for implementing changes to improve safety and health regulatory compliance for both KYTC and contractor personnel

Fatigue Analysis of the I-75 Bridge over the Kentucky River at Clays Ferry

Fatigue analysis was performed on AASHTO category E welded connections on the southbound I 75 bridge over the Kentucky River at Clays Ferry, Kentucky. That analysis was based on the stress-range histogram data provided by Law Engineering of Louisville, Kentucky. That data were obtained from strain gages installed at 6 test locations on the downstream truss. The fatigue analyses consisted of safe-life and fatigue-crack growth analyses. Safe-life predictions were based on AASHTO fatigue design (SN) curves. To use those curves, equivalent constant-amplitude stresses were derived from the stress histograms. Those stresses and loading frequencies were modified to reflect anticipated increases in traffic volume and loading over the life of the structure by appropriate multiplicative adjustment factors. Four different methods of load prediction were used with combinations of the stress summing methods, total traffic, and truck traffic. In the majority of cases, the safe-life estimates exceeded 50 years. One overly conservative load-prediction method provided safe-life estimates as low as 15 years. Fatigue-crack growth analyses were performed at each test location using iterative crack-growth calculations by computer. The software program employed for that purpose required assumptions regarding initial and final size of the crack, crack geometry, and material properties. Analyses of hypothetical cracks at each test location was performed assuming a 1-inch initial size and a 6-inch final size. The fatigue-crack growth analyses predicted very slow growth of the cracks over that crack-length interval. For the present loading rates, those crack-length interval growth rates exceeded 350 years at all test locations. The fatigue analyses indicated that the six test locations (gusset connections) were in a reasonably reliable condition from a fatigue standpoint to allow their continued use in the bridge over the next 50 years. Supplemental inspections, analyses and, possibly, gusset retrofits are warranted if the truss is to be retained in the new bridge. Existing cracks in the gusset connections should be repaired to preclude further crack growth