Structural Performance of Reinforced Concrete Beams Reinforced With Tmt Bars

Abstract

TMT (Thermo Mechanically Treated) rebar has been in use in Nepal for last couple of years. There has been a state of confusion among designers to go into TMT or still use CTD (Cold Twisted Deformed) bars. It is the right time to investigate the comparative performance of TMT reinforced structural member and compare its performance to similar CTD counterpart. In this research work, eight reinforced concrete beams of size: 2000 mm × 230 mm × 300 mm. Four of them were reinforced with TMT bars from local market and the other four with CTD bars. The reinforcement detail in all the beams are identical including shear reinforcement; except four had TMT and other four had CTD longitudinal bars. Out of four in each case, two were tested in monotonic loading and the other two were tested in cyclic loading using Universal Testing Machine. The crack propagation pattern in all the eight beams was almost similar. The load deflection curve showed clear system yielding in case of TMT where as it was having smooth path in case of CTD. All the beams showed failure mode as crushing of concrete as designed except one which failed in shear. It was noted that the ratio of deflection of the centre point of the beam at the crushing load to that at the yielding load were more or less similar for both TMT and CTD reinforced beam. TMT reinforced beams showed greater ultimate load which was due to its higher strength. In both the TMT and CTD reinforced beams, the monotonically loaded beams showed greater ultimate load than the corresponding cyclically loaded beam. This investigation showed that the TMT reinforced structural beams behave more or less similar structural performance up to the rupture of tension reinforcement.