In this article, we shall deal with the problem of calculation of the controllability radius of a delay dynamical systems of the form x(t)=A(0)x(t)+A(1)x(t-h(1))++A(k)x(t-h(k))+Bu(t). By using multi-valued linear operators, we are able to derive computable formulas for the controllability radius of a controllable delay system in the case where the system's coefficient matrices are subjected to structured perturbations. Some examples are provided to illustrate the obtained results.