FLEXURAL ANALYSIS OF REINFORCED-CONCRETE BEAMS CONTAINING STEEL FIBERS

The flexural behaVior of reinforced concrete beams containing steel fibers is investigated in the present study. An experimental program was set up and nine reinforced concrete beams have been tested, including two series of singly reinforced concrete beams and one series of doubly reinforced concrete beams. The fiber contents of reinforced concrete beams for each series were 0%, 1%, and 2% by volume. The load was applied in four-point flexural loading condition. The deflections and the steel and concrete strains were automatically measured at the various locations. The crack widths and crack spacings at each loading step were observed during the loading process. It was found from these measurements that the crack widths increase almost linearly with the increase of steel stress and the crack widths at the same loading stages arc greatly reduced as the content of steel fibers increases. The present study also indicates that the ductility and the ultimate resistance are remarkably enhanced due to the addition of steel fibers. The design implication of fiber-reinforced concrete beams is also discussed. A method for incorporating fiber effects in the flexural analysis of singly reinforced concrete beams is redrived, slightly modified and used to analyze the singly reinforced concrete beams. A new method to analyze doubly reinforced concrete beams containing steel fibers is derived and proposed for future use. It was found from this study that the neglect of fiber contribution may considerably underestimate the flexural capacity of fiber-reinforced concrete beams. The present study allows more realistic analysis and design of reinforced concrete beams containing steel fibers.