STUDIES IN BOND STRENGTH IN RC FLEXURAL MEMBERS

This paper presents results of an experimental investigation of actual performance of the reinforced concrete beam in bond under flexure, when reinforced with tension steel (TMT Rebar) is going to consider. The major variables studied include lap length and percentage of steel. Five different lap lengths and three different type longitudinal steel were used. Bond strength comprises two basic components identified as adhesive bond and friction bond. It is observed that adhesive force increases with the increase in compressive strengths of concrete (34 MPa and 37 MPa concrete). The frictions bond component is observed to increase with the increase in bar diameter. Frictional bond strength exhibits increasing characteristics with increase in lap length up to about 400 mm. beyond which it remains constant. For the same lap length, it is observed that bond strength increases by as much as 35 percent with increasing bar diameter. The value of development length obtained using ACI 318: 1999, BS 8110: 1985 and IS 456: 2000 is compared, it is observed that the value of development length obtained in tension using IS Code is 8% more as compared to BS Code and 11% more as compared to ACI Code, while the development length obtained in compression using IS Code is 3.5 % more as compared to BS Code and 17 % more as compared to ACI Code.