advanced building skins 14 | 15 June 2012 - lamp.tugraz.at - Graz ...

2.1 Methodology and Hardware
Advanced Building Skins
Important unique feature of the development is the holistic approach of a total fabrication that can be
managed by one single robot. The adaptive formwork can be driven just as well as the finishing, like
trimming or drilling the connecting points, can be done by changing the die heads.
The plant that is installed and that is used for practical testing and realization is an ABB IRB 6660 6-
Axis industrial robot mounted on a high precision track. The whole of the facility is designed for wet
conditions. A 12 kW milling spindle can carry the special tool for wet machining.
2.2 Digital Process Chain
A digital process chain that is broken down in eleven steps integrates every work step and transfers the
required information. The organigram [Figure 2: Organigram of the digital process chain] shows the
production sequence and how the different work steps are connected to each other. Another
distinctiveness is the abdication of electronic or hydraulic parts by a pure mechanical drive. Because
the robot can achieve all these work steps, quantity of the required components can be reduced and the
costs decrease. That allows an economical production of a whole series of formworks that are simple,
cheap, robust, transportable and universal applicable in different environments (autoclave, factories).
The work steps can be categorized in 3 topics: digital formfinding and generating, production,
finishing and post production.
The three subjects of the current investigations are the adaptive formwork, high performance materials
and connecting methods and will be explained more precisely in the chapters 3, 4 and 5.
2.3 Digital Formfinding and Generating
Shell structures are mainly stressed by membrane forces. This feature that causes their high efficiency,
refers to a simple geometrical formfinding process: The reverse of catenaries and suspended models.
The resulting structures are characterized by the correlation between the flux of force, bearings and
geometry.
Even before the computer age allowed numerical methods, complex structures where realized using
this method, like the “Multihalle Mannheim” by Frei Otto or the “Sagrada Familia” by Antoni Gaudí.
At the Institute for Structural Design digital tools like “Rhinceros 4.0” in combination with plug-ins
like “KangarooPhysics” allow designing digital based free forms and suspended net models. That
enables a direct transfer of a generated model into FE-simulation (A.1).
2.4 Production
After the geometry is found, it is loaded in another Rhino-plug-in “Grasshopper” that cuts the model
into segments according the boundary values of the adaptive formwork (A.2). The boundary values
depend on the size, curvature and the demand of the surface quality. In addition the aspects of
prefabrication and assembling are taken in account.
The originated elements are sorted in two categories: Elements that can be mould by the adaptive
formwork (A.3a, A.4a), and segments with a special geometry like the abutments or border elements
(A.3b). After the reinforcement for both types is planned (A.5), the robot drives the adaptive
formwork and mills the mould construction (A.6a, A6b) to prepare them for concreting (A.7).
2.5 Finishing and Post Production
Both segment types need a special finishing. The element made by the adaptive formwork has to be
cut exactly on size (A.8), and to maximize the surfaces contact for the “dry joint” connection, contact
faces are grinded (A.9). Depending on the connection that was chosen, connection points are drilled
and fasteners or anchors are placed, and the structure can be built up by assembling all segments on a
falsework (A.10).
Final part of the project is the analysis of the structures load bearing behavior (A.11).
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