Analysis of Reinforced Fibrous Concrete Beams

A method has been developed to predict the ultimate strength of concrete beams reinforced with a combination of steel bars and randomly distributed steel fibers. Strengths of three full-size beams were obtained experimentally to verify the analytical method. The method, which applies to beams using a cement-rich mortar mix with the steel fibers, shows good correlation with experimental results. A dynamic bond stress of 333 psi was assumed for the fibers. Fiber lengths were from 1-1/2 in. to 2-1/4 in. and the fiber amount was varied from 1.22% to 1.51% by volume. The test programs showed that: (1) Steel fibrous concrete increased the flexural load capacity of the reinforced beams by about 25%; (2) crack width and crack spacing were less than in a conventional reinforced beam; and (3) the post-cracking stiffness of the fibrous beams was greater than a conventional beam.