Title: Evaluation of Effective Moment of Inertia for Calculation of Short-Term Deflections of Steel Fiber-Reinforced Concrete Flexural Members
Author(s): G. Parra-Montesinos, L. B. Fargier-Gabaldón, M. Shahraiz Bajwa, and M. Al-Tameemi
Publication: Structural Journal
Appears on pages(s): 79-89
Keywords: effective moment of inertia; fiber-reinforced concrete; short-term deflections; slabs; tension stiffening
The effect of steel fibers on the post-cracking effective moment of inertia of lightly reinforced flexural members was evaluated through four-point bending tests of seven pairs of slab specimens. Variables investigated were steel fiber type (end hooks with either three or four legs) and content (0.26% or 0.38% by volume), and amount of longitudinal reinforcement. Five pairs of specimens were reinforced with minimum reinforcement according to ACI 318-14, while the two other pairs were reinforced with three times the minimum reinforcement. For each reinforcement ratio, one pair of specimens was constructed with regular concrete for comparison purposes. The use of steel fibers led to an increase in effective moment of inertia compared to the companion slabs without fibers, particularly in the slabs with minimum longitudinal reinforcement. The expression proposed by Bischoff (2005) for calculating effective moment of inertia led to reasonable estimates of deflections in the fiber-reinforced concrete slabs when using a tension-stiffening factor βc = 1. For regular concrete slabs, the use of a stiffening factor equal to the ratio between the cracking moment and the applied moment was found to be adequate.