Abstract

SIMPACT is a finite element computer system developed at the International Center for Numerical Methods in Engineering (CIMNE) in Barcelona, Spain, for analysis of structures subjected to dynamic and impact loading. Typical application of SIMPACT include among others the seismic analysis of structures, the study of structures subjected to internal of external vibrations, the prediction of ship motions originated by waves crashworthiness studies in automobiles, aerospace and maritime vehicles, analysis of structures subjected to blast pressure loading and a wide range of impact problems typical of defense applications.

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A state of the art on simulation methods in stochastic structural analysis is presented. The purpose of the
paper is to review some of the di erent methods available for analysing the effects of randomness of models
and data in structural analysis. While most of these techniques can be grouped under the general name of
Monte Carlo methods, the several published algorithms are more suitable to some objectives of analysis than
to others in each case. These objectives have been classiffed into the following cathegories: (1), The Statistical
Description of the structural scattering, a primary analysis in which the uncertain parameters are treated as
random variables; (2) The consideration of the spatial variability of the random parameters, that must then
be modelled as Random Fields (Stochastic Finite Elements); (3) The advanced Monte Carlo methods for
calculating the usually very low failure probabilities (Reliability Analysis) and, (4), a deterministic technique
that depart from the random nature of the above methods, but which can be linked with them in some cases,
known as the Response Surface Method. All of these techniques are critically examined and discussed. The
concluding remarks point out some research needs in the field from the authors' point of view.

Abstract

Qualitative reasoning is an alternative problem-solving technique useful for the conceptual design of structures. Qualitative reasoning represents the relationships between parameters in a model, and a search computation assigns values represented by intervals and relevant points in the behavior. The traditional difference between analysis and design or input and output parameters in a procedural computation is not existent in qualitative reasoning, since all the parameters in a model are equally represented. Qualitative reasoning derives values for parameters even with incomplete and imprecise knowledge about the model. This work presents a qualitative structural analysis framework, suitable for the evaluation of conceptual designs as well as for tutoring systems. The framework has been implemented in a computer program called Agrippa using the computer language Prolog. Based on a representation of fundamental principles of equilibrium, compatibility, and force-deformation and an incomplete knowledge of geometry and topology, Agrippa derives the signs and relative magnitude of forces and displacements for three-dimensional models of structures.

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The paper presents a general and straightforward procedure based on the use of the strain energy density for deriving symmetric expressions of the secant and tangent stiffness matrices for finite element analysis of geometrically non‐linear structural problems. The analogy with previously proposed methods for deriving secant and tangent matrices is detailed. The simplicity of the approach is shown in an example of application

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