C.S.E. (Connection Study Environment) is an important and ambitious software project which is under continual development by Castalia s.r.l. The program aims to provide a suitable working environment for designing, verifying and drawing the connections in steel structures.
The study of such connections involves some formidably complex issues, and can currently be considered one of the main challenges to be overcome in the field of design automation.
There are two sides to this problem of the connections: drawing and calculation.
Connections can only be drawn efficiently through a three-dimensional approach to handling the solids which make up the actual connection. To draw a connection, it will generally suffice to generate a list of the three-dimensional objects, suitably positioned, and to render the objects graphically with suitable hidden surface algorithms. The ability to generate images obtained by intersecting the connection with appropriately chosen secant planes must also be provided.
This three-dimensional approach eliminates the problem of the coherence of the representations, which is what makes for such a laborious checking process, one that most design teams are currently still unable to avoid.
If drawing the links is a complex problem, calculating them is even more so, for various reasons:
1.There are no universal rules for calculating a simple joint, as various models are acceptable as long as they are balanced;
2.There are no universal rules for calculating the proportion of the stress transferred to a simple joint in the presence of other simple structural joints;
3.The addition or removal or a component can make a considerable difference to the stresses involved;
4.A given component can function in a completely different way depending on the context in which it is used;
Analysing and calculating the connections is one factor which makes steel structures more computationally complex than those made of reinforced concrete. The current state of play is that although extensive approaches (creating a certain number of typical connections with limited validity) have been advanced, no sufficiently general intensive approach yet exists. The major problem with the extensive approach to automatic computation is its inflexibility, which does not allow software users either to add new connections or to vary or add to existing ones.
An intensive-type connection calculation program should provide:
•a general facility for defining connections between n members (generality)
•the ability to create connections by freely adding or removing elementary components (flexibility)
•the ability to define the checking rules for individual components quickly and easily, so that the calculation code “learns” how to execute the computation (extendibility and customisability)
•the ability to run consistency checks which prevent inefficient connections from being created or which detect inefficiency at the calculation stage (safety and consistency).
CSE has been developed in order to provide a tool which meets these requirements as fully as is possible, thus considerably simplifying design practice. The Supplement to issue 32 of the journal “Analisi e Calcolo” (Analysis and Computation) in October 2008 contained an article which discussed the CSE project as at September 2008 and which may be useful as a clear overview of the project in its entirety. Please note that this article refers to the status of the program as at October 2008; please refer to the Release Notes for full details about the current version.
CSE successfully relieves the designer of a mountain of calculations which are highly subject to error, as it automatically carries out all computations needed to transfer the actions correctly from the extremities of the members to all the components of the joints (distributing the forces suitably among the various components), whilst of course adding all the moments of transport required without “throwing away” any stress component. It is an extremityly laborious, difficult and error-prone job, as anyone who has had to do it at least once can testify, which CSE takes care of completely automatically. This is a highly significant development.
CSE is a major step towards an acceptable engineering solution to all the problems associated with the computation of the connections in steel structures. It is a strategically important project which will certainly continue to be extended and enriched over the years to come.
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