Title: Measured Strains in Post-Tensioned Concrete Parking Deck Made with Shrinkage-Compensating Concrete
Author(s): Jim Richardson, Sam Eskildsen, Ben Schiller, and Mike Jones
Publication: Structural Journal
Appears on pages(s): 718-725
Keywords: field measurement; post-tension; shrinkage-compensating concrete; strains
This paper describes the monitoring of axial strains and curvatures in the slabs and columns of a flat-plate post-tensioned concrete parking deck. Shrinkage-compensating concrete (SCC) was used for the parking deck in lieu of pour strips to speed up construction. The 59 vibrating-wire strain meters were installed during construction in the spring and summer of 2008 and have hourly recorded strains and temperatures until present. Measured axial strains in the slab clearly show expansion due to the SCC, elastic shortening due to post-tensioning, contraction due to creep and shrinkage, and thermal expansion and contraction due to daily and seasonal temperature variations. Preliminary analyses indicate that the SCC experienced significantly less creep and shrinkage than that predicted by design equations for normal concrete. Visual inspections of the slab revealed essentially no cracks due to slab contraction (caused by creep, shrinkage, and temperature change).