The T$-$beam shown below has a total length of $8$ m$,$ and the centre$-$to$-$centre spacing between its simple supports is $7\mathrm{.}6$ m$.$ Corrosion of the reinforcement has been identified as the main cause of significant deterioration requiring rehabilitation. Spalling of concrete has occurred at several locations along the soffit of the beam. Side spalling on the beam webs has also been observed at one end of the beam over a length of approximately $800$ mm$.$ The estimated mass loss of the longitudinal reinforcement at midspan is $30\%$ for the outer two reinforcing bars and $10\%$ for the inner two bars. In addition, several of the stirrups are estimated to have lost up to $20\%$ of their cross$-$section in a critical location coinciding with the side spalling.

You are required to develop a repair and rehabilitation plan for the beam based on the information provided. The factored load resistance of the strengthened beam should be $10\%$ greater than the original design resistance if the expected failure mode is ductile $($i$.$e$.$ flexure$-$dominated with yielding of steel reinforcement$)$ or $50\%$ greater if the expected failure mode is brittle $($i$.$e$.$ shear or compression$-$dominated failure$).$ Assume that the applied load is uniformly distributed.

Specify the steps of the repair, including removal and replacement of the deteriorated concrete. Propose a suitable strengthening option, with drawings, and provide design calculations to show that the resistance is adequate. Discuss the implications of the chosen strengthening method on serviceability performance $($e$.$g$.$ deflections$).$ Provide your final recommendation to the owner, accounting for structural performance, constructability, and durability of the system, as well as any other relevant factors.

Given data for the beam:

Depth of web $=100$ mm

Depth of flange $=400$ mm

Width of T beam $=500$ mm

Main reinforcement $=4$ no $25$M bars

Shear reinforcement $=10$M stirrups at $300$ mm

f$\text{'}$c $=30$ MPa

fy $=400$ MPa

Clear cover $=25$ mm

Clearly state any other assumptions used to develop your solution.