Title:
Influence of Steel Fibers and Compression Reinforcement
on Deflection of High-Strength Concrete Beams
Author(s):
Samir A. Ashour, Khalid Mahmood, and Faisal F. Wafa
Publication:
Structural Journal
Volume:
94
Issue:
6
Appears on pages(s):
611-624
Keywords:
beams (supports); deflection; effective moment of inertia; flex-ural
rigidity; high-strength concrete, immediate (instantaneous) deflection;
long-term (time-dependent) deflection; reinforced concrete; steel fibers.
DOI:
10.14359/9721
Date:
11/1/1997
Abstract:
The paper presents an experimental and theoretical study on immediate and long-term deflections of high-strength concrete beams. Twelve beams with 85 MPa (12,300 psi) compressive strength and having tension and compression rebars and steel fibers were tested. The experimental results show that the addition of fibers increases the flexural rigidity of the beams thus reducing the immediate and total long-term deflections under sustained service load. The beneficial effect of the compression reinforcement in controlling the long-term dejection is observed in beams without fibers. However; for beams having steel fibers and compression reinforcement, the behavior depends on the amount of the two types of reinforcement, and their excessive amount may have an inauspicious effect on the long-term deflection. A method is pre-sented for computing the effective moment of inertia of fibrous concrete beams and a modification is suggested to the long-term multiplier of the ACI Code to include the effect of fibers and high-strength concrete.