Remote MonitoringAn acoustic emission waveform and strainmonitoring system was developed andinstalled on a bridge for weeks.10Thesystem recorded acoustic emissionwaveforms from two wide band acousticemission transducers only during specifiedportions of truck loadings as determinedby strain gage monitoring. Periodically,the system reported remotely to alaboratory system, downloaded storeddata files and occasionally uploaded amodified monitoring protocol.No acoustic emission believed to becaused by crack growth was detected andno crack growth was observed during thethree-month monitoring period, eventhough many acoustic emissionwaveforms were recorded.The Federal Highway Administrationsponsored the development of a bridgemonitoring system that could collectacoustic emission waveforms and straingage signals and report the data remotelyto a base station. The local areamonitoring system developed was batterypowered and could report through acellular telephone modem. A prototype ofthis system was used to monitor persistentcracking in the Coleman Bridge,Yorktown, Virginia. The problem isdescribed elsewhere in the literature.11Acoustic emission monitoring seemsideally suited for detecting crack growthin steel bridge structures. One studyincluded laboratory testing and fieldmonitoring12,13A steel bridge hanger withthree fatigue cracks was monitored foracoustic emission using combined sourcelocation, strain gage monitoring andwaveform analysis (Fig. 5).Results from laboratory tests onUnified Numbering System K11430(ASTM A588) alloy steel, compact tensionspecimens under variable amplitudetension fatigue loading were used to aidin interpreting acoustic emission datafrom the hanger (Fig. 6). Crack growthacoustic emission from these tests weredetected only on overload cycles mostlyabove 92 percent of maximum loadwhereas acoustic emission from crack face310Acoustic Emission TestingPART2.Acoustic Emission Monitoring of CrackGrowth in Steel Bridge ComponentsFIGURE5.Bridge hanger dimensions and location of cracks.13123456789175 mm(7 in.)225 mm(9 in.)610 mm(24 in.)165 mm(6.5 in.)Legend1.Crack 1.2.Crack 2.3.Crack 3.4.Wideband transducer.5, 6.Source location transducers.7, 8, 9.Guard transducers.
Subscribe to view the full document.
rubbing occurred throughout the loadcycle.Acoustic emission activity from allthree cracks were clearly identified andwere classified as crack growth or noisesignals using location, strain magnitude,position on strain cycle and uniqueness ofwaveforms as the primary criteria (Figs. 7).A vast majority of acoustic emissionsignals from the cracks were found to becaused by crack face rubbing and thecrushing of corrosion products betweenthe crack faces (Figs. 8 to 10) whereaslimited crack growth emission wasdetected.
As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.
Temple University Fox School of Business ‘17, Course Hero Intern
I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.
University of Pennsylvania ‘17, Course Hero Intern
The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.