Fiber-reinforced concrete under cyclic and dynamic compressive loadings.

The objective of this investigation is to develop a constitutive model for the stress-strain behavior of fiber reinforced concrete under a variety of compressive loadings, particularly those simulating earthquakes. The research consists of both an experimental and analytical program. Cylindrical specimens were cast using combinations of three different fiber volume fractions; three different concrete matrices; three different fiber aspect ratios; and steel, polypropylene, or glass fibers. Twelve specimens from each batch were tested under monotonic loading at either a static strain rate or at one of two dynamic strain rates. Twenty more specimens from most batches were tested under one of three high stress range cyclic loading regimes, again at either a static strain rate or one of two dynamic strain rates. The experimental results showed the existence of an envelope curve which governs the stress-strain response under cyclic loading. The envelope curve was found to coincide with the monotonic stress-strain response. The cyclic response, when normalized by the monotonic response, was found to be independent of the fiber reinforcing parameters. The toughness under cyclic loading was found to be at least as great as that under monotonic loading. Analytical models were developed to predict both the monotonic and cyclic compressive stress-strain responses. The monotonic model includes expressions for the stress and strain at peak as well as the residual stress level, all of which are functions of the fiber reinforcing parameters. Equations for the ascending and descending portions of the stress-strain curve are also proposed. The cyclic model uses the envelope unloading strain as an index of load history and can be used to predict the stress-strain response under a completely general compressive loading. The plastic strain and reloading strain are predicted as a function of the envelope unloading strain for both full and partial unloading and reloading. Expressions for the unloading and reloading curves are also given.PhDCivil engineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/162111/1/8907122.pd