l) Some new efficient hybrid/mixed thin～moderately thick plate bending elements with 5- node (HP5) and 6-node (HM6-l4) and shell elements (SHEL4-l6-0, SHEL4-18-2, SHEL4-l6-2, SHEL4-18-0) are presented based on the Helling-Reissner variational principle . The convergence of elements are proved. The rate of convergence is achieved for very low number of degrees of freedom. Some remarkable properties of elements are shown that the elements have invariability to geometric distorted mesh situations, to axial rotation, and to node positions and no extra zero-energy modes and Shear locking phenomenon in thin plate limit. Numerical studies show these elements can provide acceptable results even if coarse meshes are used Some efficient elements have been established to develop adaptive hybrid/mixed finite element method.

　　2) Some a-posteriori error estimates of HMFEM for two-dimension, three-dimension plate and shell bending problems are developed, tested and swown that they are asymptotically exact estimate. Numerical analyses show that the rate of convergence of presented error estimates is exponential with respect to the number of fteedom degree. A local version of the presented a-posteriori error estimates was used to optinize mesh and to improve the accuracy of solution The study of effectiveness of a-posteriori error estimates provides an important basis for the development of AHMFEM.

　　3) The presented HMFEM of plate and shell bending problems can evaluate stresses and deflections in the shell structures of arbitrary form subjected to arbitrary loads and boundary conditions.

　　4) Variable-node elements for plate and shell bending problems are developed for HMFEM. The h-version, p-version and hp-version AHMFEM for plate and shell are presented, respectively. The various types of geometric meshes are designed with quadrilateral and curvilinear quadrilateral elements.

　　5) The formulation of HMFEM for orthotropic and circular plate under polar coordinate, three-dimension axisymmetrical and solid problems are derived, respectively. The four-node, eight-node nine-node quadrilateral elements and eight-node solid element are preeented for HMFEM. The numerical results indicate that the presented method has favorable accuracy and computational efficiency.

　　6) Preprocessing and post-processing of numerical analyses are developed for HMFEM. The meshes of model are demonstrated to clearly see the analysis process and results. The computational problem of AHMFEM is implemented for elasticity problems.

　　7) Many engineering problems have been settled by the presented AHMFEM and appeared in this doctoral dissertation, such as the stress analyses of adhesive-bonded cylindrical lap joints, structural, modal and dynamic analyses of press-ress timbered bridge, structural analysis of continuous footing made with EPS styrofoam, etc.

　　8) The presented method has wide application in structural engineering. The most of contents of above researches have been published by author.