“…It is to be noted that the literature on shape optimization problems, including unknown or variable domains, is mainly devoted to second order elliptic equations. Concerning fourth order boundary value problems, for instance plate models, there are papers Kawohl, Lang [8], Muñoz, Pedregal [11], Sprekels, Tiba [20], Arnautu, Langmach, Sprekels, Tiba [1] studying thickness optimization problems that may be reduced to optimal control problems by the coefficients. In Neittaanmäki, Sprekels, Tiba [14], Ch.…”