  Our Galaxy is filled with cosmic-ray particles and more than 98% of them are
atomic nuclei. In order to clarify their origin and acceleration mechanism,
chemical composition measurements of these cosmic rays with wide energy
coverage play an important role. Imaging Atmospheric Cherenkov Telescope (IACT)
arrays are designed to detect cosmic gamma-rays in the very-high-energy regime
($\sim$TeV). Recently these systems proved to be capable of measuring
cosmic-ray chemical composition in the sub-PeV region by capturing direct
Cherenkov photons emitted by charged primary particles. Extensive air shower
profiles measured by IACTs also contain information about the primary particle
type since the cross section of inelastic scattering in the air depends on the
primary mass number. The Cherenkov Telescope Array (CTA) is the next generation
IACT system, which will consist of multiple types of telescopes and have a
km$^2$-scale footprint and extended energy coverage (20 GeV to 300 TeV). In
order to estimate CTA potential for cosmic ray composition measurement, a full
Monte Carlo simulation including a description of extensive air shower and
detector response is needed. We generated a number of cosmic-ray nuclei events
(8 types selected from H to Fe) for a specific CTA layout candidate in the
southern-hemisphere site. We applied Direct Cherenkov event selection and
shower profile analysis to these data and preliminary results on charge number
resolution and expected event count rate for these cosmic-ray nuclei are
presented.
