The cross-section of a thermo-mechanically treated (TMT) reinforcing bar has

Consider a reinforcing bar embedded in concrete. In a marine environment this bar undergoes uniform corrosion, which leads to deposition of corrosion products on its surface and an increase in apparent volume of the bar. This subjects the surrounding concrete to expansive pressure. As a result, corrosion cracks appear at surface of concrete. Which of the following statement is true?

Consider two $$RCC$$ beams, $$P$$ and $$Q$$, each having the section $$400$$ $$mm$$ $$ \times \,\,750\,\,mm$$ (effective depth, $$d=750$$ $$mm$$) made with concrete having a $${\tau _{c\max }} = 2.1\,\,N/m{m^2}.$$ For the reinforcement provided and the grade of concrete used, it may be assumed that the $$\,{\tau _c} = 0.75\,\,N/m{m^2}.$$ The design shear in beam $$P$$ is $$400$$ $$kN$$ and in beam $$Q$$ is $$750$$ $$kN.$$ Considering the provisions of $$IS$$ $$456$$-$$2000.$$

Which of the following statements is TRUE?

Consider a bar of diameter $$'D'$$ embedded in a large concrete block as shown in the adjoining figure, with a pull out force $$P$$ being applied. Let $${\sigma _b}$$ and $${\sigma _{st}},$$ be the bond strength (between the bar and concrete) and the tensile strength of the bar, respectively. If the block is held in position and it is assumed that the material of the block does not fail, which of the following options represents the maximum value of $$P?$$