TOWARDS AN ADAPTIVE SEMIIMPLICIT SOLUTION SCHEME FOR NONLINEAR STRUCTURAL DYNAMIC PROBLEMS

This paper presents considerations regarding the search for improved c omputational efficiency in the solution of structural dynamic problems . Beginning with an overview of the procedures traditionally employed for the solution of such problems, it proceeds with a critical survey of 'hybrid' time integration schemes. that try to combine the advantag es of explicit and implicit algorithms. These schemes include: 'partit ioning' and 'operator-splitting' methods, 'semi-implicit' methods, and integration schemes employing element-by-element techniques. Next fol low some remarks regarding a natural evolution of this line of researc h, into the study of iterative solvers for the effective' linear syste ms of equations that result from the application of implicit methods. An integration scheme for nonlinear dynamic problems is then proposed. based on an iterative solver and with 'semi-implicit' characteristics . Its potential is demonstrated by numerical studies on the finite ele ment model of a guyed tower for offshore oil exploration and productio n. The following aspects are considered: the solver itself and its pre conditioner: the strategy for the definition and variation of converge nce tolerance values: the computational implementation (whether global or element-by-element); and the incorporation of this scheme into the adaptive time integration strategy presented in Jacob and Ebecken [Eu r. J. Mech., A /Solids 12, 277 298 (1993)], by devising adaptive selec tion criteria for the identification of applications and situations wh ere a direct or an iterative solver is more adequate.