Parametric Design Project

Currently I am working with a research project called “CBBT technical platform for high rise wood buildings”. This project we are constructing a modular system that is product oriented and separated from specific projects (http://www.traplattform.se). By doing this it is possible to put extra effort in designing modules that can live through several projects.

The building system is designed for buildings that have 4-8 stories. In the early design stage we concluded that there were primly 3 problems with buildings made out of wood. This was; the stability of the building, the noise resistance between apartments and the fire protection. In earlier projects the fire resistant has been solved by using fire resistant gypsum wallboard which has been relatively easy to adapt. When it comes to the stability and noise resistance, the problems has bean hard to solve. When referring to the noise between apartments the solution has been to separate the apartments, but referring to the stability the solution has been to connect the different apartments, which has lead to short-circuiting the different apartments with flanking transmission.

Our solution to the problem is trying to see the building as a skeleton that should resist the wind forces and inside this structure the apartments are connected with impulse damper. By doing this we can use a larger moment of inertia and therefore smaller connections to the basement. In figure 1 the plan drawing and erection of the building system is illustrated.

Figure 1: First real project with the CBBT building system

The aim of this project is to see how parametric objects and assemblies can be constructed and used in the building industries. This will be done in one subassembly of a house that is well-defined and easy to separate from the whole building.

The project of designing a modular building system for CBBT is done in a CAD- application called Solid Works, it is therefore interesting to se the limitation with this system.

The technical platform that is designed must have a well defined structure to be able to know how the systems are linked together. By using UML/SysML a product structure can evolve and makes it easy to understand possible constrains and descriptions of specific modules. According to L Hwam et.al these structures can have different views depending on which person that are observing the system. In figure 2, a building is illustrated and the different views that can be observed. The customer view reefers to what the customer wants to change and what the building system can do (2.a). I figure 2.b the engineering view is illustrated and refers to how the building is constructed and the reason why it is done like this. The third figure (2.c) describes what the production rules are made of and put on the system.

Figure 2: Customer view (a), Engineering view (b), Production view ©

One module that is easy to divide and separate from the product structure is the floor construction. The possibility to parameterize the block so it can be customized to different projects (buildings) is essential for reducing development time. By doing this we can easily define the specifications that are handle in each project otherwise. In figure 3, the first outline of the floor is illustrated and also the first floor ever built .

Figure 3. First outline of beams /floor

The floor construction consists of two subassemblies called “Golv” and “Undertak”. The floor support construction “Golv” are made out of wooden beams that have a pattern of 600mm between them. On top of the beams a 12mm thick wood chipboard are fasten, and on top of it there is an installation area that also works as a sandwich construction to reduce the deflection and increase the bending resistance when fire.

On the “Golv” a false ceiling is connected, but only in the assembly of the floor construction. When the floor is well in place of the building it is seperated from the floor support construction and are self bearing. This “Undertak” has the meaning of dividing the two apartments from impact sound.

UML

With the initial point described in theory, a product can be described in different views depending on the person/persons inspecting the feature. This way of locking at the product gives therefore different UML descriptions. According to L Hwam et.al a product can be described in three views. In this report we are just focusing on the engineering view and the production (part) view. In the engineering view the products (subassemblies) rules are described and what the relations between them are. figure 4 the UML-code for the engineering view is illustrated. In figure 5 the production view is illustrated with all components used in the product “bjälklag” In this view the “Golv” and the “Undertak” is separated and the object that are used in each subassembly.

Figure 4: Engineering view

Figure 5: Part view

Configurator

Things that have been parameterized are how many beams that needs according to the width and how chipboards lengths will change, insulation etc. This way of working can then be implemented on the walls and the rest of the construction. In this model it is only possible to change the length and the width but later I will parameterizes the possibility of tilting the framing of joists and changes when the floor is used in a bathroom. In figure 6 a screenshot from Solid Works is shown.

Figure 6: Bjälklags configurator

The CAD-system that has bean used earlier in the design process is called Solid Works. Therefore this CAD application was used instead of NX as suggested. The problem when using Solid Works was that the parametric could only be described thru relative equations, so for example the height of a component could be described relatively the base etc. Therefore an extra application had to be used called Tacton Works were relations could be described and put into dialog boxes to be used when the configuration should be made.

I believe that this relatively easy product can illustrate the possibility of using parametric design in the construction industry. Only in this example the possible solutions can be 4×35 solutions, and when putting in the possibility of tilting the framing of joists and that a bathroom needs extra height the solution space will be 4x4x10x10x35=56000 different solutions which leads to even more different components used in the assembly.

I also believe that it is essential that the products that are developed in a parametric way needs to be a part of a building system were the development cost can be shared between several projects.

Erixon, G. (1998), Modular Function Deployment – A Method for Product Modularization, Doctoral Thesis, Dep. of Manufacturing Systems, Royal Institute of Technology, Sweden.

Johnsson H, Persson S, Malmgren L, Tarandi V, Bremme J (2006), (In Swedish), IT-stöd för industriellt byggande i trä, Department of Civil and Environmental Engineering, Division of Structural Engineering, Luleå University of Technology.

Hvam L, Mortensen N. H, Riis J (2007) Product customization, Springer-Verlag Berlin And Heidelberg

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