Evaluation of strand bond equations for prestressed members cast with self-consolidating concrete

A total of 26 rectangular concrete beams were constructed, instrumented, and tested over the course of several research projects which all focused on examining the bond of prestressed strand with self-consolidating concrete (SCC). The same concrete cross-section was used for all specimens, but SCC using Type I and Type III cements and a conventional high strength concrete mixture were tested using a 0.6 in. (15.2 mm) prestressed strand and a lightweight SCC was used along with a 0.5 in. (12.7 mm) prestressed strand. Transfer length was measured using concrete surface strains and development length was determined using iterative flexural tests. The results of these tests were then compared to the transfer and development length equations proposed from nine different research projects conducted using several different sets of variables. Since the concrete types used in this research were different from those utilized to develop the current code equations, it was desired to examine whether other proposed equations were more applicable. While the different variants of SCC examined using these specimens were also very different from those used to develop all of the examined transfer and development length equations, several of these equations were found to be adequate for use with SCC.

► Twenty-six rectangular concrete beams were cast with self-consolidating concrete.
► Transfer and development lengths were measured for all beams.
► Measured values were compared with predicted values.
► Overly conservative equations were found.
► Equations that best estimate bond in lightweight and normal SCC were identified.