Since my research project is related to the design process for industrial timber housing, this work will practice the possibility to use parametric models in a CAD-software enivronment. There is a potential to standardize building models, for a more effective process, where recipes and standard configurations can be used. Lindbäcks, where I collect my data for my research, has start to standardize their building system to a concept. Their standardization work has started in some fields. Fields were Lindbäcks strives for a more standardized process is in the design phase. They have already starting to defined their own design process. Process defining is necessary if you like to plan, organize and change your process for better results. Also has Lindbäcks adopt the technology about using 3D Cad for manufacturing. Today is the CAD-models basic data for automating in the production line with cutting robots and nail portals. Wile the process defining by planning and automated production, there are possibilities to modularizes the building system within new concepts.

Lindbäcks building system is based on structure volumes where the volumes is put on each other where loads and forces handles by boards and beams in the volume. The building system allows houses up to five floors with timber construction and the elevation on site has advantage when there is lack of spaces and fast assembly is prioritized.

Assembling volumes at Porsön Sweden (Lindbäcks)

Lindbäcks has together with architect Hans Tirsén created a concept platform from Lindbäcks building system. DUO is the name for the concept house. The name (Duo 5 i.e.)bases on how many apartments each level has. Several building project, from Lindbäcks, is built on the concept platform in Sweden. The concept is standardized on a system level for the building, so standard dimensions, components and technical solutions is used on a low level. Read more about the concept at Duo Concept from Lindbäcks

Modularization is not used frequent in the DUO concept. Interfaces between volumes is defined and also placement of shaft for elevator and stairs is defined, but there gives a great possibility for more modularization at building parts and volumes with standardization and defining interfaces in the concept.

Parametric design is about define constraints between objects. These objects can desribes as processes, interactions and for my case virtual models of buildings. The aim in this course has been to use parametric design in some part of our research area. Unified Modeling Language (UML) together with the parametric design approach is to be used in our parametric design project. The UML is, as it says, a modelleing language that gives opportunity to visualize sytems, organisation, processes and software (Alhir, 1998). The visual presentation is based on diagrams in all the different areas.

Applying parametric design on a concept house is a possibility to show that technical tools and methods can support standardisation of the technical platform for industrial housing. Together with UML the hand drawing sketch on a withe board can be visualized in a standardized model in a diagram.

The aim is to create a standardized and modified setup for the DUO concept as a parametric product model. All this inside Revit Architecture with the concept model visualized in a UML diagram.

The parametric design project is a test of using parametric design as a ground for shortening the design time by repetitiveness in the design phase for industrial timber manufactures. Using UML is limited to map information and relations for parts in the building system.

CAD system is used with parametrical functions, were Autodesk Revit Architecture 2009 became my choice. The choice is based on construction functionality and not features in the software. Revit Architecture is limited with interfaces that works directly in the CAD model, in comparing to NX and Catia. Many construction companies is now choosing Revit as a 3D CAD software because the BIM functionality and parametrical functions. Therefore is it interesting to practices such a tool within design for industrial housing. My limitations in the application was to create a generic model in Revit, that could be applied to at least three different types of Duo houses from Lindbäcks. The limitation in the Duo Concept house is one apartment in the house with relations to: outer dimensions, stair/elevator module and the corridor (se picture).

2D-view of template model for the parametric design project within Autodesk Revit Architectural

To describe the model in UML, this view representing the connection between Customer view and Structural view. Connections between wall elements and spaces is not visualized in this model. Focus is to describe the connections that links views together outside a CAD software.

UML-model of interfaces from Customer view to Structural view

The “customer view” is visualized as pink in picture above and the “structural view” is visualized as blue. Both sides in the diagram is compact and do not show all levels. The purpose with the “customer view is to create a interface that meets customer and clients for industrial timber housing companies. Relations and parameters can easy catch up without getting into technicalities, such as millimeters precision in drawings. The picture shows how relations is connected between the customer view and structural view. Customer decisions, through the design phase, for spaces is one important economical parameter in a building project. Relations between spaces and the CAD-system (Revit) is handled by the grid system (read more at Revit).

Customer view for the client requirements

Structural view with constraints and design parameters within the building system

The model is built up in Autodesk Revit Architecture and the based on the Duo 5 project Västerhaninge in Stockholm, Sweden. Västerhaninge become the choice based on dimensions that is closest to standard modules for Lindbäcks Duo project houses. The horsontal (x), vertikal (y) grid and levels (z) in the product model work as backbone for the parametric modeling. To visualize and group constraints in the product model, dimensions is connected to the vertikal(A-F) and horisontal(1-9) grid.

The product model is based on three projects that Lindbäck has delivered.

1. Västerhaninge

2. Godtemplaren

3. Balder

In the real projects has all three been drawn as 2D drawings in AutoCAD, based on an architectural solution. The three projects is also production prepared with 3D CAD in DDS-CAD. Non of the project has identical volumes or used elements from a earlier projects. The profit in concept repetitiveness is only on system level and not used in the part modeling.

To change product solution for the three scenarios this was the parameters that I have tested on my model is:

• Constraints for walls to grid
• Constrained doors and windows
• Locked width dimension for wet modules near to corridor
• Minimum width dimension for corridor

Other changes is done manually in Revit (Balcony, new walls, new doors & windows)

Revit model for Västerhaninge

Västerhaninge is my template for the parametric model. It is a two rooms apartment with a small bedroom.

Balder is the latest Duo project that has been produced at Lindbäcks (2009). It is a tree rooms apartment with two small bedrooms. The solution with a volume in the corridor area separates for the other two. The whole volume row highest up is 10 millimeter wider and dimension parameter between grid A and B is driven by that change from the template. The corridor is 120 millimeter tighter than the template between grid C and D.

Revit model for Godtemplaren

Godtemplaren´s model gave opportunity to constrain walls from different directions. It is a tree rooms apartment with one large and one standard size bedroom. Inner wall for the largest bedroom had to be constrained to the toilette wall and the new volume as bedroom at AB had the same constrain as outer wall for bedroom 1 at BC. Depth of volume rows (AB) and corridor (CD) was the same as template.

The whole meaning with parametric is to create configurations with recipes for solutions from a defined building system. My work with parametric design in this course has focus on manage defined data and predefined inputs to a product CAD model. Even if Duo 5 was the most defined concept that Lindbäcks many parameters is not defined and there is no strategy to define thies parameters. In my work I have standardize dimensions and solutions to fit my own concept for Duo houses.

Revit as a parametric CAD tool has not all features that I could wish. Labeling dimensions so you can put in data from web document, functions and scripts that could give more flexibility to constraints is some of my wishes. My knowledge about Revit is at a basic level, so I do have to be a little humble about my demands on the software. Anyhow is the missing parts for a parametric tool (as Revit) not easy to find comparing to SolidWorks, NX5 and Inventor.

Visualizing my parametric model with UML was interesting. I chose the Customer view together with the Structural view because my parametric model was done to serve clients with a concept house. The concept house with flexibility in dimensions can give engineers conditions so they not have to compromise the solution. I was not able to visualize down to each constraint in the UML model, because some of the constraint in the CAD model was created by hand (replacing window, doors and walls). If you want to constraint a whole building, the building system has to be defined with tolerances both to dimensions and choices. My work became two fronted because limitations in Revit to create brides between customer and structural engineering. On the other hand have I showed by UML my thoughts about the connection.

Learning the basics in Revit was a good opportunity for me where I already have made some models for my future research in industrial housing for timber constructions. In the end gave this course important knowledge how constraints and parameters have power holding a flexible building system. The transformation from functional requirements to design parameters was interesting and I will use that for my research for process support in my next paper.

Alhir, S. S. (1998). UML in a nutshell. O'Reilly&Associates, Inc. , Sebastopol.