TABLE OF CONTENTS In this section we present results obtained in numerical simulations. All the computations are carried out by a research version of the computer program FEAP, developed by Professor R. L. Taylor at UC Berkeley (Zienkiewicz and Taylor, 1989). A four-noded isoparametric shell finite element with assumed strain interpolations for transverse strains (Brank et al., 1995, for details) is used to that end.
Among the above discussed possible parametrizations of the shell-director motion, we have chosen the formulation based on the incremental material rotation vector. Note that within the interpolation presented in Section 2.7, all possible parametrizations of constrained finite rotations should produce the same results, however they could differ in convergence characteristics and in the range of the allowable shell-director rotation where the solution can be obtained. Comparison of results for different rotation parameters for static loading may be found in Betsch et al. (1998) and Ibrahimbegovi? et al. (2001).
Among the discussed Newmark time-stepping schemes for constrained finite rotations two different Newmark time-stepping schemes were coded. Algorithmic approximation of velocity and acceleration of the shell-director in time is obtained either with the spatial representation procedure described in Section 5.4 (named version 1 ), or with an alternative simpler procedure in terms of the shell-director vector, which is defined in Section 5.5 (named version 2 ). For both versions of Newmark time-stepping schemes the mass matrices are presented in the Appendix.
