This paper presents a computationally
efficient method for analyzing the performance of short-fiber
reinforcement in cementitious composites. Each fiber is modeled
as a discrete entity. Realistic, nonuniform fibers distributions
can be specified as program input. Rigid-body-spring networks
are used to represent the matrix material. Fiber response is constrained
to the kinematics of the rigid bodies; the number of system degrees
of freedom is therefore independent of the number of fibers. Precracking
contributions of the fibers are modeled using an elastic shear
lag theory. Post-cracking contributions depend on pullout relations
based on the micromechanics of the fiber-matrix interface. In
either case, there is a direct link between fiber-local actions
and composite response. Numerical results for both aligned and
randomly oriented fiber composites are compared with theoretical
predictions based on ordinary mixture rules.