TY - CONF A1 - Niederleithinger, Ernst A1 - Sens-Schönfelder, C. A1 - Grothe, Sven A1 - Wiggenhauser, Herbert T1 - Coda wave interferometry used to localize compressional load effects on a concrete specimen T2 - 7th European workshop on structural health monitoring N2 - Coda Wave Interferometry (CWI), a method to evaluate subtle changes of elastic wave velocity in a medium, has been proven to be effective to detect small changes or ultrasonic velocity in concrete caused by load, temperature, moisture, damage or other means. While classical CWI is just able to determine velocity changes globally in relatively large areas between and around pairs of transmitters and receivers, several approaches have been proposed to identify the area affected by the changes more precisely. Most of them are based on the calculation of sensitivity kernels for de-correlation of signals measured at a specific state against a reference. Others follow simplified approaches. In a laboratory setup a concrete specimen of 1:5 x 1:5 x 0:5 m3 was compressed at a certain point. Maximum loads of 20 to 100 kN have been applied in 5 to 10 kN steps in various cycles. The specimen is equipped with 18 embedded ultrasonic broadband piezo transceivers (60 kHz central frequency). Ten of these receivers have been connected to a multiplexer and ultrasonic transmitting and receiving equipment in a way that allowed almost continuous two way measurements between all sensor pairs. Even simple ways to evaluate the data (e.g. crosscorrelation between signals at different load states) allowed pinpointing the load center at least approximately. A more detailed data evaluation either using CWI or even more one of the more sophisticated localization algorithms gave “sharper” results in terms of localization and a better correlation between load and velocity change/de-correlation. The results are used in upcoming monitoring systems for concrete structures. T2 - 7th European workshop on structural health monitoring CY - Nantes, France DA - 08.07.2014 KW - Concrete KW - Ultrasound KW - Coda wave inteferometry KW - Tomography KW - Correlation KW - Stress KW - Monitoring PY - 2014 SP - Paper WeBT6.3, 1427 EP - 1433 AN - OPUS4-31204 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -