A minimum ductility design method for non-rectangular high-strength concrete beams

The flexural ductility of solid rectangular reinforced concrete beams has been studied quiternextensively. However, many reinforced concrete beams are neither solid nor rectangular; examples includernT-, -, - and box-shaped beams. There have been few studies on the flexural ductility of nonrectangularrnreinforced concrete beams and as a result little is known about the possible effect of sectionalrnshape on flexural ductility. Herein, the effect of sectional shape on the post-peak flexural behaviour ofrnreinforced normal and high-strength concrete beams has been studied using a newly developed analysisrnmethod that employs the actual stress-strain curves of the constitutive materials and takes into account thernstress-path dependence of the stress-strain curve of the steel reinforcement. It was revealed that thernsectional shape could have significant effect on the flexural ductility of a concrete beam and that thernflexural ductility of a T-, -, - or box-shaped beam is generally lower than that of a solid rectangularrnbeam with the same overall dimensions and the same amount of reinforcement provided. Based on thernnumerical results obtained, a simple method of ensuring the provision of a certain minimum level ofrnflexural ductility to non-rectangular concrete beams has been developed.