Flexural behaviour of concrete beams with large-diameter steel bars

Bending tests were performed on beam specimens reinforced with large-diameter steel bars of no. 14 (43 mm diameter) and no. 18 (57·3 mm diameter) to investigate the flexural behaviour, failure mode and bond performance at various loading stages. Attention was paid to studying the bond behaviour of the larger bar on the load resistance and failure mode of a beam made at full scale. Test results showed that the reinforced concrete beams with large-sized reinforcements of no. 14 and no. 18 steel bars exhibited a similar flexure response to the beam with steel bars of under no. 10 (32·3 mm diameter), but the samples differed from each other in the deflection behaviour at the period between yielding and ultimate stage. The ductility of the former was found to be greatly reduced. Bond strength can be increased with reinforcement with large-diameter bars until the bars yield; they are therefore adequate to predict the yielding strength using the conventional code method, but their ultimate strength will be overestimated.