Instrumentation
    Description
 

The instrumentation (see Figure 12) consisted of a Novatechnic LVDT placed between the end flanges of the specimen to measure the actual displacement in the specimen, a LVDT and a load-cell internal to the MTS actuator, and strain gages placed circumferentially and along the length of the specimen barrel (normally at about 5 mm from the ends and at the bell section). The specimens were filled with water and a pressure transducer was inserted into the specimen to measure internal water pressure leakage, if any. A low level of internal water pressure was applied at about 20 to 28 kPa (3 to 4 psi) in order to monitor water leakage without creating a substantial artificial hydrostatic restraining force that would alter the actual load applied to the specimen.