CASA, Computer Aided Structural Analysis, is a family of structural analysis software now in its 4th generation. From the beginning every CASA has been shaped by the belief that structural analysis software should be a tool to fit the needs of the engineer, where the power of the computer is used to provide not just high-speed number crunching abilities but also immersive interactive user interfaces.
Possibly uniquely, each generation is recreated anew to take best advantage of the computing systems available at the time. CASA has always benefitted from careful in-house algorithm development and code profiling to achieve high-speed analysis, and its user interface and feature-list undergoes continual improvement through the encouragement of feedback and suggestions from users.
Twenty years ago the first CASA was a pioneer in interactive graphics in multi-tasking windowing systems, transforming the ergonomics of structural engineering software through its innovate blending of inputing, editing, and previewing into a single operation where the visual representation of the structure was the primary basis of interaction and manual numerical input was secondary.
The CASA family was also a pioneer of mainstream generalised second-order analysis, having offered P-delta as a fast everyday method for 2D and 3D structures on ordinary desktop computers over the past two decades.
CASA has many advanced features, introduced below, though not all of them will be required by all engineers and as such there are several versions available to suit. Please refer to the Feature List to see which features are available in which version to help you decide which suits you best.
The interface is designed to create a fludity of work, clarity of detail, and minimum error. Graphical interaction with simple point-and-click and drag-and-drop is widespread, with 3D rendering, colouring, material textures, real-time animation, translucency, illumination, and various other visual cues to enhance the experience.
While real-time fully rendered views are easily utilised, be assured that the structure can also be depicted as a simple stick framework for a conventional appearance and greater clarity of dense detail.
Above all, CASA is intended to be comfortable to use through simple and predictable behaviour.
A major problem encountered by many engineers is maintaining a numbering scheme for nodes and members. Most software has exactly that — a numbering scheme. The problem is made worse when items need to be inserted or moved, making it difficult to find them according to their number. The usual solution is to simply renumber everything according to some arrangement, such as spatial position, but this introduces more problems if some parts of the model need to maintain their original numbering.
While CASA defaults to the familiar numbering scheme, it offers a solution to the problem by allowing the engineer, if they so wish, to use naming schemes — every node, member, load, etc. can have a proper name. This allows different parts of the structure to be given meaningful nomenclature, such as “Base 1”, “East gantry”, “Drifted snow”, and so on. Renaming, renumbering, and reordering within each set of similar names is possible without disrupting other sets; a real boon for complex and changeable models.
An important aspect of this is that it introduces self-documenting models, where the intent and purpose of a construction, a load, or a settlement, can be embodied in its name, reducing the need for additional explanations and cross-references.
As loads are put into loadcases, so nodes and members can be (optionally) divided into groups. These geometry groups allow for easy distinction between parts of the model, each with their own colours and graphical visibility settings. This makes isolating areas for easier vision or interaction simply a matter of a mouse click or two. In addition, groups can be marked as annotation, meaning that they do not take part in the analysis — ideal for including architectural details, out-buildings, or existing structures.
Sophisticated transformation and replication facilities allow quick and easy generation of geometry and loads, from simple grids and multibay frames through to helical staircases and multistorey towers.
An extensive standard-section library is built-in, with wide coverage of British, European, American, Australian, South African, and more.
Two generators are available according to the version of CASA. Common types can be generated by simply choosing the shape (e.g. channel, beam, etc.) and entering their dimensions. For more complex and arbitrary shapes there is a graphically driven generator in which by simply drawing parametrically associative lines and circles and inking around the outline, the section can be quickly drawn and generated in only a few clicks.
Flights around and through the model can be easily achieved through the use of cameras. This is ideal for presentation to clients, and the flights can be recorded for use with web browsers.
In addition, to more easily visualise natural modes of oscillation, these too can be animated in slow-motion, real-time, or high-speed to suit the mode frequency.
From around 20 years ago, CASA was a pioneer in providing second-order analysis to the mainstream market on mainstream hardware at mainstream prices. Engineers will be happy to know that CASA-IV continues this tradition.
Second-order, or P-delta, analysis is one in which the deflections of the structure under load are taken into account, as these will cause a redistribution of force leading to further deflection.
Normal modes of oscillation can be determined, giving the frequencies and mode shapes at which the structure will freely oscillate. This can include masses added to the self-weight of the structure, described by means of node and member loadings.
The static analysis results can take into account the Relative Amplification Factors due to forcing frequencies relative to natural frequencies.
To make it easier to share information with clients, CASA includes a Reader program which can be freely passed to clients along with the model file. Clients can thus browse and interrogate the model and results, and print reports themselves, as well as view any presentation flights and views set up by the engineer.
Not all features are available on all versions. Specifications and differences between versions are correct at time of publication, but are subject to change.
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