A NEW KIND OF SINGULAR STIFF PROBLEMS AND APPLICATION TO THIN ELASTICSHELLS

We consider the asymptotic behavior of the solution of a class of prob lems involving a small parameter epsilon and epsilon2. This generalize s the ''singular stiff'' problems arising in classical thin shell theo ry. The new problems appear in theory of composite shells, when the lo cal structure implies coupling between membrane stresses and flexions. According to specific hypotheses, this kind of problems contains sing ular perturbations and penalty problems where the limit solution belon gs to a subspace G1 of the general configuration space V. In addition to the coercive problem, spectral properties are considered in the sma ll and medium frequency ranges, including spectral families in the cas e without compactness.