FLEXURAL BEHAVIOR OF HIGH-STRENGTH CONCRETE BEAMS

The results of eleven reinforced high-strength concrete beams tested i n flexure are presented All but one beam was over-reinforced, and the compression zone of the beams was confined with either lies or fibers, or left unconfined. Test results indicate that the brittle type of fa ilure in over-reinforced concrete beams can be arrested by introducing transverse ties or discrete steel fibers in the compression zone. For such a beam, both ultimate strength and ductility can be enhanced by increasing the concrete strength. Ductility also increases with an inc rease in the volume fraction of confining ties, but up to a certain li mit. The stress-strain curves for concrete in compression obtained fro m the flexural tests are remarkably similar to those generated from un i-axially loaded specimens. The analysis based on the usual flexural t heory but using the stress-strain curves for uni-axially loaded specim ens, gives close predictions of the experiment data on moment-curvatur e relationship and ultimate moment capacity of the beams. Evaluation o f the present test data and the results from available literature show that Whitney's rectangular stress block can be used in the strength d esign of high-strength concrete flexural members.