Relaxation of ASTM A722 Bars

In 2017, we expanded our laboratory facilities and designed the first large-capacity stress-relaxation frame for testing large-diameter bars (ASTM A722 and similar) or multi-tendon bundles. We now have a frame with a capacity of 825 kips (shown here) that was built and used for a recent project conducted for the US Army Corp. of Engineers plus two additional frames with a capacity of 275 kips.

All of our large frames can be used to conduct both creep and stress-relaxation tests of prestressing bars or strand bundles.  Like our smaller frames used to test strands and wires, these large frames also utilize self-locking mechanical gear jacks and commercial dual-bridge load cells with independent excitation sources and indicators.  The frame shown is capable of testing 20-ft-long tendons and has a capacity of 825 kips