Correct option is C
Assertion (A): According to IS: 456; over-reinforced sections are not permitted.
This is true.
IS 456:2000 does not permit over-reinforced sections because they fail in a brittle manner.
Over-reinforced sections have more steel than the balanced reinforcement, causing the concrete in compression to reach its ultimate strain before the steel yields.
This brittle failure is sudden and catastrophic, which is unsafe for structural design.
Reason (R): There is ductile failure of over-reinforced section.
This is false.
Over-reinforced sections do not exhibit ductile failure.
Instead, they experience brittle failure, as the concrete crushes in compression without any warning or significant deformation.
Ductile failure, which provides prior warning and significant deformation, occurs in under-reinforced sections, where the steel yields before the concrete fails.
