Service load deflections of high-strength fiber reinforced concrete beams

Abstract EN

Test results of eighteen beams of high-strength concrete of 85 MPa (12,300 psi) compressive strength are presented to study the influence of steel fibers and longitudinal tension and compression reinforcements on their immediate and long-term deflections.

The results show that the addition of fibers in singly reinforced beams reduces immediate and long-term deflections.

For beams with compression bars and fibers, the excessive amount of two reinforcements may have an unfavorable effect on the long-term deflections.

The beams having the ACI Code’s minimum longitudinal tension reinforcement showed much higher time-dependent deflection to immediate deflection ratio, when compared with that of the beams having about 50 percent of the balanced tension reinforcement.

The theoretical method presented in the paper for predicting deflections considers the effect of steel fibers on material and section properties.

The computed values for the tested beams and those of a parametric study indicate that the influence of steel fibers in increasing the moment of inertia of cracked transformed sections is most pronounced in beams having small amount of longitudinal tension reinforcement.