A continuum-based, laminated, stiffened shell element is used to investigate the static, geometrically nonlinear response of composite shells. The element is developed from a three-dimensional continuum element based on the incremental, total Lagrangian formulation. The Newton-Raphson or modified Riks is used to trace the nonlinear equilibrium path. A number of sample problems of unstiffened and stiffened shells are presented to show the accuracy of the present element and to investigate the nonlinear response of laminated composite plates and shells. INITE-ELEMENT analyses of the large displacement the- ories are based on the principle of virtual work or the associated principle of stationary potential energy. Horrigmoe and Bergan1 presented classical variational principles for non- linear problems by considering incremental deformations of a continuum. A survey of various principles in incremental form in different reference configurations, such as the total Lagran- gian and updated Lagrangian formulations, is presented by Wiinderlich.2 In the total Lagrangian description, all static and kinematic variables are referred to the initial configura- tion. Finite-element models based on such formulations have been used in the analysis of arch and shell instability prob- lems.3'6 A special numerical technique must be adopted to trace the path of the load-deflection curve near the limit point (i.e., critical buckling load) and in the postbuckling region, because the stiffness matrix in the vicinity of the limit point is nearly singular, and the descending branch of the load-deflec- tion curve in the postbuckling region is characterized by a negative-definite stiffness matrix. Many methods have been proposed to solve limit-point problems. Among these are the simple methods of suppressing equilibrium iterations,7'8 the introduction of artificial spring,3 the displacement control method,7'8 and the constant-arc-length method of Riks. 11-12 Reviews of these most commonly used techniques are con- tained in Refs. 13 and 14. Among these methods, the modified Riks appears to be the most effective in conjunction with the finite-element method. Many investigators11'15 have used this in its original or modified form to determine the pre- and postbuckling behavior of various types of struc- tures such as arches, shells, and domes. In most of these works, only isotropic material was considered. Very few works of the nonlinear buckling analysis of laminated com- posite structures are reported in the literature.16 When solving the problems of shells with stiffeners by the finite-element method, a beam element whose displacement pattern is compatible with that of the shell is required. In analyzing eccentrically stiffened cylindrical shell, Kohnke and Schnobrich17 proposed a 16-deg-of-free dom (DOF) isotropic beam finite element that has displacements compatible with