Containment Surveillance by Monitoring Stress-Strain

When measurements of stress-strain in a prestressed concrete structure are made, extraneous strains due to creep and shrinkage of concrete and relaxation of steel are also recorded. In the presence of these extraneous strains, the significance of making the measurements for surveillance of grouted tendon containment structures is critically examined from a statistical standpoint. The discriminating power of stress-strain measurement schemes to unmistakably detect the occurrence of abnormal losses in prestress due to various causes, including corrosion, is expressed in terms of power functions. The measurements of stress or strain by meters cannot be relied upon for detection of abnormal situations which may arise due to excessive corrosion of tendon steel. Elaborate instrumentation for the purpose of surveillance seems unnecessary.