Abstract: Method and apparatus for detecting failure of tensioned reinforcements in a structure by means of a plurality of acoustic or seismic detectors disposed about the structure in a known arrangement, processing signals from the detectors to determine frequency contents and origins, and identifying simultaneous signals as due to the failure of tensioned reinforcements in the structure when they meet spectral and origin criteria.

Abstract: A method and apparatus for non-destructive testing of the load bearing characteristics of a structure are disclosed. An interferometer is supported by a beam which is supported away from the surface of the structure to be tested. The interferometer is used to measure a quantity which varies with the distance between the interferometer and a reflecting means supported on the location to be tested. The reflecting means is supported in such a manner as to move responsively with deformations to the said location, and is typically attached to a probe which is urged against the said location. Preferably a force is applied or varied near the location to be tested and comparisons are made over time or as the said force varies. Such a system does not damage the structure, and does not require complicated equipment or processing.