ENGINEERING CALCULATIONS IN SCIA DESIGN FORMS A link between 3D CAE software and customised design checks

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1 EUROSTEEL 2014, September 10-12, 2014, Naples, Italy ENGINEERING CALCULATIONS IN SCIA DESIGN FORMS A link between 3D CAE software and customised design checks Zuzana Hekrdlová a, Peter Van Tendeloo b, Iveta Georgieva b, Jean-Pierre Rammant b a Nemetschek Scia SRO, Prague, Czech Republic b Nemetschek Scia NV, Herk-de-Stad, Belgium z.hekrdlova@scia.cz, p.v.tendeloo@scia.be, i.georgieva@scia.be, jp.rammant@scia.be INTRODUCTION Scia Design Forms (SDF) is a computational environment for the execution of both everyday design tasks and advanced engineering calculations. The software uses programming procedures and software architecture in the background, while required user inputs are solely the formulae that describe the engineering problem. Similarly to using a spreadsheet, the user defines variables, writes formulas, includes images and graphs. SDF executes the written formulas, displays these, including the numerical substitutions and the calculated outcome. In addition, graphical reports are generated, which are comprehensible, clear and illustrative. Reports may be extended with notes and graphical descriptions so as to conform to commonly accepted layouts for civil engineering calculation reports. SDF files can be compiled as standalone tools or these can be integrated with CAE software through an Application Programming Interface (API). In this way, the user himself can create customised design checks within a 3D CAE software platform. In short, SDF can fill in the gap created by the use of sophisticated 3D models within a BIM workflow, and the need to still perform design checks according to the appropriate structural standards or technical publications. 1 THE SCIA DESIGN FORMS APPLICATION PLATFORM Algorithms in SDF are defined by means of simplified script. Coding rules are based on the C# programming language; nonetheless, the engineer does not need to delve into programming, as the scripting rules in SDF are made highly intuitive and require little to no programming experience. SDF allows users: 1. to write their own computational algorithms and checks (i.e. Design Forms); 2. to distribute these checks as commercial solutions for specialized engineering tasks; 3. to link customised tools to Scia Engineer 1 as plug-ins, where advanced GUI and 3D visualisation possibilities can be used while pre- and post-processing. 1.1 The concept of a Design Form The collection of defined input variables, formulas, calculation report and report layouts is exported as a so-called Design Form. Each Design Form may be distributed separately as a solution to a particular engineering problem. The initial assumptions on which the used calculation method is based can be described freely in the calculation report by means of text and graphical descriptions. The SDF application comes with a wide range of predefined Forms, which address the design and checks of foundations, concrete, steel, timber, and masonry elements. 1.2 SDF BUILDER and USER applications SDF is split into two applications the SDF BUILDER serves to create and elaborate each Design Form, to define report layouts and input dialogues, etc., whereas the SDF USER application can be used to open a Form, change input values and print reports without the possibility to edit the calculation algorithm itself. In addition, files created in the BUILDER can be linked to the Scia Engineer software through an Application Programming Interface (API), where the Form can be used without the need to access the USER application. 1 software for modelling, analysis, design and detailing of 3D structures

2 2 THE BUILDER APPLICATION The BUILDER application includes (see Fig. 1): an Editor Window where the user defines his/her script; a Table of Variables where all defined variables are listed; a Layout Window where the output documentation of the Form is displayed; a Dialog Tab where the user designs the Dialog (where end-users will type input values); as well as tabs for translations, annotations, license definition, an image database, etc. 2.1 User interface The Editor is equipped with a couple of assistive tools. More complex functions and commands use the IntelliSense feature (drop-down lists or pop-ups) for faster programming. Keyboard shortcuts are provided to easily switch between Latin and Greek characters, as well as between standard text, sub- and superscripts. Tools are provided for localisation of issues in the script. After compiling, an Error/Warning list points out missing delimiters, operators, ill-defined functions or arguments. Double-clicking on a report item locates the corresponding command line in the Editor. Dialog Tab Settings for visual components Editor Window Layout Window Table of variables Fig. 1. SDF BUILDER application interface Editor (top left), Table of Variables (bottom left), Report Layout (right) All defined variables are listed in the four tabs of the Table of Variables. Separate tabs are provided for variable types double, string, Boolean and structure. Each variable is defined by a symbol and a value, and can be assigned a text description. Double variables can be assigned units (metric or imperial); furthermore, unit conversions are done internally by SDF. Structured variables can be arrays, graphical objects, tables, etc. A Purge function ensures that unused variables, visual settings and translation strings can be eliminated automatically. The Layout Window displays the final version of calculation reports on an A4 size sheet. 2.2 Formatting the reports The architecture of the SDF BUILDER makes a clear distinction between the calculation method (defined in the script), and the formatting of reports. Each item in a report is a visual component, whose visibility, font, size and location can be defined through options in the Layout Window in a similar fashion to MS Word.

3 This makes it possible to create various calculation report styles (layouts) within the same Design Form e.g. different levels of detail can be adopted in a number of predefined report styles which can serve the various needs of different end-users of the Form. 2.3 The Dialog Tab in the BUILDER and the Dialog (GUI for the end-user) in the USER The Dialog should include all variables that are required input in the calculation. Input variables may represent material properties, cross-section data, internal forces, safety factors, etc. All variables that are not assigned values in the script or are not calculated by formulas are coloured in green in the Table of Variables (see Fig. 1). The user should make sure these are included in the Dialog in order for the end-users to be able to change the values of these. The Dialog Tab is furnished with a number of containers and visual settings that allow for structured representation of the Dialog (see Fig. 2) panels, tabbed containers, text labels, comboand check-boxes, etc. Input tables with a dynamic number of rows can be added in the Dialog. 2.4 Libraries SDF supports the use of libraries, where common engineering data can be stored in tabulated form. The BUILDER contains a number of built-in libraries standard European and North American steel cross-sections and materials (steel grades, concrete and timber classes), bolt data, concrete sections with reinforcement... Custom libraries can be added in XML format. A Library Editor is provided so that the user does not have to use the XML language to create libraries. Data in tabular form can simply be copied to the clipboard and pasted into the Library Editor. Libraries are accessed through the source code; when referencing a value, IntelliSense guides the user through the tree-like library structure. Libraries should be added in the Dialog if used in the source code. 2.5 Automatic tests Automated tests ensure the consistency of the calculation algorithm in new versions of a Design Form - after adding new features, the same input should continue to result in the same output. 3 THE USER APPLICATION The SDF USER provides an interface for reading Design Forms, defining input values and printing reports, without the possibility to edit the actual Forms. Only the Dialog, Layout window, and Form annotations are displayed in the USER application (see Fig. 2)Fig. 1. Any change in the input values results in immediate refresh of the calculation report; therefore, no discrepancies between input and calculated results can occur. The USER displays lists of available layouts and languages in a Design Form. Translations are prepared in the BUILDER in a semi-automated string-per-string fashion. A Form may contain translations to unlimited number of languages. The calculation results, layouts, and conditions remain the same, regardless of the displayed language. Other end-user options can be set up in the BUILDER related to the calculation method, the display of descriptions, figures, captions, etc. 3.1 The reports The straightforward approach to creating calculation reports in SDF ensures that the calculation methods built into the Design Form remain transparent. The ability to provide at the same time a detailed report, and a summary with e.g. input variables and final result, is what makes SDF unique. Reports can be stamped with a header and/or footer before printing. Header/footer settings can be saved and later applied to any Form. Form annotations are added in the BUIDER, where the theory behind the calculation is explained, along with the procedures, formulas and variables used. 3.2 Predefined Forms and National Annexes of the EUROCODES A number of Design Forms are provided with the SDF installation package. Form solutions are prepared for specific engineering problems in the fields of steel, concrete, timber, masonry structures and foundations. As most of these Forms concern design according to the EUROCODES, a special functionality has been foreseen in SDF for handling National Annex data. A combo-box in the USER application is used to switch between country-specific parameter sets and formulas.

4 Switch NA parameter set Dynamic drawings Dialog Calculation report Fig. 2. SDF USER application interface 4 GRAPHICS/TABLES/CHARTS The SDF scripting language contains commands for the creation of dynamic images, tables and charts (Fig. 3). The user may create drawings of e.g. structural components, whose shape and dimensions are defined in function of the calculation outcome. Points, lines, polygons, arrows, 2D shapes, hatches, and dimension lines can be used in drawings. Drawing functions are directly using classes of the.net framework. Reports may contain tables of which the number of rows and column can be dynamic (in function of the Form output). XY graphs can be printed with various options for the formatting of axes, labels, line styles, etc. a) b) c) Fig. 3. a) Dynamic drawing of a steel connection; b) Equation rendering; c) Table options 5 APPLICATIONS 5.1 Stand-alone solutions In addition to the predefined Forms included in the SDF installation package, SDF has already been used to provide a number of stand-alone and 3D CAE integrated solutions for the design of: steel connections (according to EN :2005 and to AISC );

5 composite beams (according to EN :2004); steel elements against fatigue failure (according to EN :2005); pad/pile foundations, concrete section design, etc. The SDF platform can be used for a broad range of engineering and scientific problems, also outside the field of structures. The open architecture of SDF ensures that new functionalities can continually be added, following the Rapid Application Development (RAD) model. a) b) Fig. 4. a) Class definition (left) and output (right); b) Cross-section classification using a built-in function More advanced scripts based on C# can handle multidimensional arrays, classes, user-defined functions and conditions [1]. The script in Fig. 4a illustrates the definition of a new class ExampleClass, which contains a numeric and a Boolean function. Thesee functions can be called by referring directly to an object of class ExampleClass. Fig. 5. Example of a plug-in check - linking Design Form to Scia Engineer

6 5.2 Toolbox functions In addition to C# commands [1], custom engineering functions can be built in as supplementary commands in the scripting language. Such functions usually describe common, well-described engineering concepts, e.g. cross-section classification in steel design, constitutive laws for concrete, etc. Fig. 4b shows a function for cross-section classification, whose arguments are the cross-section instance (taken from a library), the loaded state (bending or compression) and the maximum stress. 5.3 Form links to Scia Engineer A powerful feature of SDF is the ability to use Design Forms as plug-ins for the 3D CAE software Scia Engineer (SE). Each user can define relationships between a SDF Form and SE, in this way expanding the number of checks supported in SE. User-defined checks in Forms are executed, visualised and reported in the same way in-house checks in SE are. SDF Forms are already used as the SE hard-coded solution for concrete design according to the Brazilian standard all design checks are executed entirely in SDF as proof of concept for the open platform. The link between SE and SDF is based on interactive API. For each entity in a 3D model (e.g. a beam, node, slab) the relevant input data (e.g. cross-sections and materials, buckling data, internal forces, loads, etc.), are sent directly through a TCP/IP communication to SDF, where the calculation is executed. Results and report layouts are sent back to SE these can be displayed in SE and be added to the project documentation (see Fig. 5). 5.4 Example design of composite beams For the case of a simply supported composite beam, a set of design rules is derived from [1] and gathered into a standalone algorithm in a Design Form. Based on the defined input, the form performs all necessary calculations and checks for both the construction and composite stages. b) a) Fig 6. Composite design in SDF: a) determination of plastic neutral axis, b) design of transverse reinforcement 6 SUMMARY AND ACKNOWLEDGMENTS SDF is open-architecture software technology that enables the easy, on-the-fly writing of engineering algorithms and design checks by means of simplified programming. The obtained Forms can be reused, shared, distributed within a company, sold commercially and linked to 3D CAE software. The essence of SDF is that the user can simply type the necessary formulas, build the report layout, test the resulting outcome in the appropriate range of variables, comment and report, and thus provide a fully automated solution for the considered engineering problem. Additional features that complement the concept of open-architecture checks are the ability to make dynamic drawings, print graphs, handle unit conversions, translate to multiple languages, run automated tests and create outstanding reports with different levels of detail for different purposes. REFERENCES [1] [2] European committee for standardization, EUROCODE 4: Design of composite steel and concrete structures - Part 1-1: General rules and rules for buildings, Brussels, Belgium, [3] SDF website;