Bond Stress Model of Deformed Bars in High Strength Concrete

The use of reinforced concrete as a structural material originates from two different components; Reinforcing steel, known as a highly-tensile material, combined with concrete, a highly-compressive material, act together to resist different types of loadings. However, this composite action is dependent upon the transfer of loads between the steel and concrete known as the bond and is concluded to be on a form of continuous stress along the juncture of steel and concrete. This study focused on producing a bond stress model as a function of concrete compressive strength, embedment length and bar diameter, using single pullout test, with the help of multiple regression analysis by using Microsoft Excel. For the compressive strength, 40 MPa, 50MPa and 60MPa were used, with 50mm, 75mm and 100mm embedment length and bar diameters of 12mm, 16mm and 20mm, producing a total of 27 specimens. After subjecting each specimen to pull out test, data were tabulated and analyzed using Multiple Regression producing a model with 97.81% correlation coefficient. The model was then subjected to parametric testing and it was concluded that increasing the compressive strength of concrete would result to an increase in bond stress; however, increasing the embedment length and bar diameter would result to a decrease in bond stress.