For the simply supported end-condition (Figure B-4) epoxy adhe- 

 sive was placed between the concrete and steel ends to correct for 

 unevenness at the mating faces. Later, steel stiff eners were placed in 

 the interior at the top and bottom, and expansive-cement grout was 

 packed between the stiff eners and the concrete wall. For the free 

 support end-condition (Figure B-4), a 1/8-in. (3-mm) neoprene rubber 

 gasket was placed between the steel and concrete. A thin layer of 

 epoxy adhesive or quick-setting gypsum was used between the concrete 

 and the neoprene gasket. 



When the specimen was assembled to the stage where the center 

 shaft was centered at the top and bottom , radius measurements were 

 taken using the following procedure. An arm off the center shaft had 

 a scribe marker mounted to it. A fixed position table was placed 

 beneath the arm, so when the center shaft was rotated, a circle was 

 scribed on the table. The radius of this circle, r' , was measured after 

 the table was removed from the specimen. At the circumferences of 0, 

 90, 180, and 270 degrees, the distance from the scribe to the wall, r", 

 was measured using a steel rule accurate to 0.01-inch (0.25-mm). By 

 adding r' and r", the inside radius of the specimen was obtained at the 

 circumference locations. Deviations in radius around the circumference 

 were obtained from deflectometer data, so by using the deflectometer 

 data and the measured radius data, average radius values for the 

 specimens were determined. 



Instrumentation 



Instrumentation of the specimens consisted of mounting a deflec- 

 tometer system to measure radial displacements, applying strain gages 

 (to some specimens), installing a television camera, and installing a 

 high-speed motion picture camera. These systems are described below. 



Deflectometer . The measuring device of the deflectometer system 

 was a potentiometer (linear position transducer) which had a maximum 

 displacement of ±0.650 in. (16.51 mm) and a measurement accuracy of 



43 



