BEHAVIOR OF FIBER-REINFORCED HIGH-STRENGTH CONCRETE UNDER DIRECT SHEAR

This paper reports the results of an investigation on the strength and ductility of fiber reinforced high-strength concrete under direct she ar. Both experimental and modeling studies were performed. In the expe rimental study, fiber reinforced high-strength concrete pushoff specim ens were tested. Two types of fibers, polypropylene and steel fibers, in conjunction with or without conventional stirrups, were used. An ex isting model was developed further and used in the analytical predicti on of the shear stress-strain relationships for these specimens. In ge neral, fibers proved to be more effective in high-strength concrete th an in normal strength concrete, increasing both ultimate load and over all ductility. This is attributed to the improved bond characteristics associated with the use of fibers in conjunction with high-strength c oncrete. For the specimens with steel fibers, significant increases in ultimate load and ductility were observed. With polypropylene fibers, a lower increase in ultimate load was obtained when compared to the i ncrease due to steel fibers. Ductility of the polypropylene fiber rein forced specimens was greater than that of the steel fiber reinforced s pecimens. In the tests involving the combination of fibers and convent ional stirrups, slight increases in ultimate load with major improveme nts in ductility were observed in comparison to the values for plain c oncrete specimens with conventional stirrups. In general, good agreeme nt between the model and the test results was found.