## Q. 2.13

The bond between reinforcing bars and concrete is tested by means of a “pullout test” of a bar embedded in concrete (Figure 2.24). A tensile force P is applied to the end of the bar, which has 10 mm in diameter and embedded length is 500 mm. If pull is 100 kN, what is the shear stress between the steel and concrete?

## Verified Solution

When the rod is pulled out in the test, the resistance against pulling is developed on the surface of the rod that is in contact with concrete matrix.
The surface area where resistance is built to resist the pulling is = πdL

\begin{aligned} & =\pi \times 10 \times 500 \\ & =15707.96 mm ^2 \end{aligned}

The stress is essentially shear stress

∴        $\tau=\frac{\text { Pulling force }}{\text { Resisting area }}$

\begin{aligned} & =\frac{100 \times 10^3}{15707.96} \\ & =6.366 N / mm ^2 \end{aligned}