  Redundancy is related to the amount of functionality that the structure can
sustain in the worst-case scenario of structural degradation. This paper
proposes a widely-applicable concept of redundancy optimization of
finite-dimensional structures. The concept is consistent with the robust
structural optimization, as well as the quantitative measure of structural
redundancy based on the information-gap theory. A derivative-free algorithm is
proposed based on the sequential quadratic programming (SQP) method, where we
use the finite-difference method with adaptively varying the difference
increment. Preliminary numerical experiments show that an optimal solution of
the redundancy optimization problem possibly has multiple worst-case scenarios.
