$f_c^{\prime }$	Concrete compressive strength
$d_b$	Rebar diameter
$l_e/d_b$	Embedment length to bar diameter ratio
$C/d_b$	Concrete cover to bar diameter ratio
$d_{cs}$	Smallest of the distance from the closest concrete surface to the center of the bar being developed or two-thirds the center-to-center spacing of the bars being developed
$k_1$	Bar location
$k_2$	Concrete density
$k_3$	Bar size
$k_4$	Bar fiber
$k_5$	Bar surface profile
$n$	Number of tests
$R^2$	Root square
$\tau$	Bond strength
${\tau }_{test}$	Experimental bond strength
${\tau }_{calc}$	Predicted bond strength
α	Significance level
$\sigma$	Standard deviation
$RMSE$	Root Mean Square Error
$AAE$	Average absolute error