Theory of plates and shells
In theory of plates and shells T.Khachatryan, O.Saponjyan and S.Ambartsumyan carried out the first investigations in Armenia in the 40-ieth of past century. However wide-range investigations began after the classical theory of laminar anisotropic shells created by Sergey A. Ambartsumyan . On the basis of this theory, a numerous important problems of calculation and design of thin-walled constructions, were solved, it became a basis for solution of thin-walled construction problems of composite materials. The obtaining results were applied in design and construction of modern techniques various objects. Fundamental results were obtained in the area of following problems investigation - stiffness, strength, static and dynamic stability, free and forced vibrations, aeroelasticity and thermoelasticity, creep and viscoelasticity of anisotropic one-layer and multilayer plates and shells. Obtaining results play an important role for the design optimization of thin-walled constructions.

The refined theories (iterative and general) of anisotropic plates and shells were suggested by Sergey A.Ambartsumyan. On the basis of these theories the problems of calculation of thin-walled systems made from modern composite materials were considered with a new point of view. Taking into account suggested theories a numerous problems of bending, vibrations and stability of anisotropic plates and shells were solved. A version of anisotropic plates refined theory considering the influence of transversal shears and normal compression had been also suggested. The results of these investigations have represented in the works of S.Ambartsumyan, S.Durgaryan, L.Movsisyan, G.Baghdasaryan, V.Gnuni, R.Kirakosyan, M.Belubekyan and others.

An asymptotic theory of one-layer and multilayered anisotropic plates and shells that gives opportunity to refine the bounds of approximate theory applicability was formulated ( L.Aghalovyan).

A number of important problems for which classical and other approximate methods bring to the wrong results have been investigated. New class of problems for strip, plates and shells, material of which possesses general anisotropy, were solved. The connection between applied models of foundation and base and obtaining results was established. The formulae of determination of foundation coefficient, which plays a significant role in seismo-stable structure design problems, were deduced. ( L.Aghalovyan, A.Khachatryan, R.Gevorkyan)

For the solution of problems concerning the static and dynamic anisotropic inhomogeneous thin-walled bodies with complicated geometrical form, a method of geometrical and physical small parameter have been suggested ( V.Sarkissyan). Due to above mentioned method the multiple problems of plates and shells that have theoretical and practical interest were solved (V.Sarkissyan and others).

A new theory of thin-walled plates and shells made from micropolar material was formulated. With a help of this theory the interesting problems were solved also the features arising from non-symmetry of materials elastic properties were revealed ( S.Ambartsumyan ).

The system of nonlinear equations regarding to laminar anisotropic flexible plates and shells, which describes possible states of thin-walled constructions from composite materials, was received (V.Gnuni). Note, that optimal selection of composite materials parameters can substantially improve the working characteristics of construction. Herein, the interesting results were obtained in the sphere of edged waves and plates and shells stability (M.Belubekyan, K.Kazaryan and others).

The questions of non-linear waves propagation as well as modulation and stability of waves and their bundles in plates and shells were investigated. ( A.Bagdoev, L.Movsissyan).

A criterion of equistrenght for the optimal design on the base of which a number of problems concerning the stiffness of elastoplastic plates was suggested (R.Kirakosyan and others).