  Two dedicated asteroid rotation-period surveys have been carried out using
data taken on January 6-9 and February 20-23 of 2014 by the Intermediate
Palomar Transient Factory (iPTF) in the $R$~band with $\sim 20$-min cadence.
The total survey area covered 174~deg$^2$ in the ecliptic plane. Reliable
rotation periods for 1,438 asteroids are obtained from a larger data set of
6,551 mostly main-belt asteroids, each with $\geq 10$~detections. Analysis of
1751, PTF based, reliable rotation periods clearly shows the "spin barrier" at
$\sim 2$~hours for "rubble-pile" asteroids. We also found a new large-sized
super-fast rotator, 2005 UW163 (Chang et al., 2014), and other five candidates
as well. Our spin-rate distributions of asteroids with $3 < D < 15$~km shows
number decrease when frequency greater than 5 rev/day, which is consistent to
that of the Asteroid Light Curve Database (LCDB, Warner et al., 2009) and the
result of (Masiero et al., 2009). We found the discrepancy in the spin-rate
distribution between our result and (Pravec et al., 2008, update 2014-04-20) is
mainly from asteroids with $\Delta m < 0.2$ mag that might be primarily due to
different survey strategies. For asteroids with $D \leq 3$~km, we found a
significant number drop at $f = 6$ rev/day. The YORP effect timescale for
small-sized asteroid is shorter that makes more elongate objets spun up to
reach their spin-rate limit and results in break-up. The K-S test suggests a
possible difference in the spin-rate distributions of C- and S-type asteroids.
We also find that C-type asteroids have a smaller spin-rate limit than the
S-type, which agrees with the general sense that the C-type has lower bulk
density than the S-type.
