BOND STRESS-SLIP RESPONSE OF REINFORCING BARS EMBEDDED IN FRC MATRICES UNDER MONOTONIC AND CYCLIC LOADING

The bond stress versus slip response of reinforcing bars embedded fibe r reinforced cement based composites is investigated. Three types of l oading were carried out: I) monotonic loading, 2) unidirectional cycli c loading, i.e. loading-unloading by equal increments of slip, and 3) fully reversed cyclic loading in a pull-pull mode. Two types of failur e were observed: a frictional type of pull-out failure, and a splining mode type of failure. Typically, for all applied loading, the failure of all bars embedded in SIFCON matrices was by frictional pullout, wh ile failure of all bars embedded in plain concrete was by splitting of the concrete around the embedded bar: When fiber reinforced concrete was used a mixed type of failure occurred depending on the test parame ters. The confined plain concrete specimens failed by spalling of the concrete outside the confined region, i.e, the concrete cover Generall y in the absence of fibers, failure was rather brittle; the addition o f steel fibers resulted in a more ductile failure. Reinforcing bars em bedded in SIFCON showed much greater bond strength, higher energy abso rption, and maintained substantially larger slips at high stresses, th an bars embedded in plain concrete, confined concrete, or fiber reinfo rced concrete.