Keywords: structural analysis, structural design, complexity, systems, organization, dependability, problem solving.

This paper considers the different conceptual frameworks which enact the structural problem and lead to making sense of the results obtained from structural analysis. In fact, there are strong connections between how one frames a problem and what is then searched and solved. While the technical aspects, like mechanical nonlinearities or stochastic uncertainties, are considered today scholars have developed and almost transparently controlled these aspects. There are a number of human related factors that must be recognized and faced to have a realistic, i.e. useful or more generally ecologically effective, picture of the structure being studied. It seems that the journey in this broad context is just at the beginning.

The object of this paper is an extremely long suspension bridge, described in the web site www.strettodimessina.it, where the global geometry, essentially linear and continuous, and, at the end, the simple disposition of this structure should not hide the manifold morphology of the deck.

All the considerations made in the first part of this paper are typical of any scientific structured approach to analysis: let us think of the anatomy of a single organism or, consider at a higher logical level, to the study of all the living organisms, as presented by naturalists. Following this way, it is interesting and logical that the individuality of the different characters of the beings under study, starts from the more general and apparent aspects and ends with subtle considerations related to microscopic features.

One considers specifically two kinds of contexts which envelope the structure:

1. the first one regards the peculiar intrinsic characteristics of the structure: morphology, geometry (both global and local), topology of the resistant mechanisms; one is referring here to the domain of the structural problem;
2. the second one is the design environment: all the items that wrap the structure; these constitute the boundary conditions of the structural problem.

The modeling process necessary to simplify and to manage the real world must have the following properties:

1. necessary variety: one must consider at the same time different models of different complexity to grasp the world facets;
2. self-constructive: each model should help to increase the knowledge about the problem, both from the quantitative and from the qualitative points of view and should facilitate the refinement of the model itself;
3. self-corrective: the model must help to change the point of view or the restructuring of the problem when needed.

Figure 1 can be assumed as a symbolic representation of the system thinking which considers modeling as a very broad and deep activity. Behind the scenes, there are dungeons and dragons. Consider, as a brief list, the following aspects at different levels:

• ancestral traditions, sometimes surpassed but inexorable;
• sociological influence, always pervasive and inescapable;
• sychological biases and traps, very impressive in size and number.

Here, it is believed that the modeling process, also with the last occurrences remarked, may be governed by the following rules:

1. general culture and specific knowledge;
2. constructive exploration of the complexity;
3. attention and consciousness on enactment, selection and sense-making of the problem and the solution, enveloped in the actual context;
4. self-validating properties of the numerical models;
5. sensibility and bounding strategies.

At the highest level, if one looks at the compound system of the analysis related to a very complex structure, it is believed that one has confidence in all the results if one feels them fitting together like the pieces of a well conceived story.

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