The bars of nominal diameter 16 mm used in compression for an RCC work consists of M30 grade concrete for which design bond stress is 1.5 N/mm². The stress in bars at design load is 50N/mm². What is the development length bars as per IS: 456-2000?

Correct option is D

$$\text{Given: } \phi = 16\,\text{mm},\; \tau_{bd} = 1.5\,\text{N/mm}^2,\;$$
$$\sigma_{st} = 50\,\text{N/mm}^2$$

Since the bar is in compression, bonds stress increased by 25 %

$$\tau_{bd(\text{comp})} = 1.5 \times 1.25 = 1.875\,\text{N/mm}^2$$
$$\text{Development length:}L_d = \frac{\phi\,\sigma_{st}}{4\,\tau_{bd}}$$
$$L_d = \frac{16 \times 50}{4 \times 1.875} = 106.66\,\text{mm}$$

So as per options we use nearby value is 108.5 mm (don't consider smaller value)