Method for the non-destructive evaluation of prestressed concrete structures

摘要

A method for detecting degraded pipe used in water mains monitors detected sound waves and observes the characteristics of those waves. Water main pipes have coiled therearound highly tensioned steel wire which holds the concrete comprising the pipes in compression. When the steel wire is corroded by water seeping through mortar encapsulating the pipe, the steel wire eventually ruptures, thus relieving compression in the concrete adjacent the rupture. Sonic and ultrasonic sound waves traversing the concrete of pipes have different characteristics for pipe in good condition as compared to the characteristics of sound waves traversing pipe in poor condition due to decompression and/or other causes. The sound waves in pipe in poor condition travel slower with shear waves having less amplitude and reflections occurring at later times. In addition, the frequency domain characteristics of pipe in poor condition differ from the frequency domain characteristics of pipe in good condition. In pipe in poor condition, resonance occurs at lower frequencies than pipe in good condition. In addition, a drum head effect is apparent in pipe in poor condition, which drum head effect does not occur with pipe in good condition.