Designed by Marks Barfield Architects
Today it is not difficult to create ultra complex geometry with advanced digital technology, but it will escalate to another level of complexity once you try to build it. No doubt Xtrata Kew Tree Top Walkway(XKTTW) is another milestone project of Marks Barfield. Without parametric design tools, it would have been extremely difficult to deliver the project in time and within budget, the most importantly, to fulfil the original design concept. There were a series of significant design and manufacture issues during the process. We will only focus on the design challenges by breaking them down into components.
1.Dynamic chain
The location of each pylon was vital to the whole scheme, as we wanted to balance between the intention of getting close to tree canopies and avoiding any harm to tree roots. A 5m radius circular zone around each tree was established. Ideally there should be no construction within these circles (Pic 2, the blue lines show the refined final locations). A parametrically controlled chain model was built in Digital Project, which allowed us to manipulate in real time to minimize the pylons within 5m zones. Eventually the outcome was acceptable for Kew when there was only one pylon located right on the perimeter of one 5m zone.
1.Dynamic chain
The location of each pylon was vital to the whole scheme, as we wanted to balance between the intention of getting close to tree canopies and avoiding any harm to tree roots. A 5m radius circular zone around each tree was established. Ideally there should be no construction within these circles (Pic 2, the blue lines show the refined final locations). A parametrically controlled chain model was built in Digital Project, which allowed us to manipulate in real time to minimize the pylons within 5m zones. Eventually the outcome was acceptable for Kew when there was only one pylon located right on the perimeter of one 5m zone.
2.Complex walkway module
The complexity of the balustrade and the deck structural beams makes it unrealistic to manually build up a digital model. It would become a nightmare for us should the general dimension are changed in the early stage as the span is subdivided based on the Fibonacci sequence. Every thing would have to be redone even the change is as small as cm. With a parametric model in DP, everything will automatically re-propagated even you change the initial geometry setting out.
3. Sophisticated staircase tower
Due to the site constrains of the pylon location, a cantilevered staircase was proved to be appropriate solution. The complex relationship between the taped trunk, the trifurcated top branches picking up the main platform, the cantilevered sub-branches supporting the landing, the deck beams, the Fibonacci balustrade, the spiral running and the handrail would have been too difficult to articulate without DP model. Working in parametric modelling environment can spot on the clashing between different parts instantly. There will be no hidden geometry clash as long as the digital model is well done. What you see on your screen will turn up to what you will have in reality. In this sense, architects and contractors can organize the construction more efficiently, foresee all the potential construction and fabrication issues, maximize the off-site production, as well as providing more accurate cost information.
4.Slender pylons
The proportion and dimension prove to be appropriate among trees. The trifurcation geometry is particular problematic at the knuckle joint, which should continue the edge of the main pylon to the branches to make it look like growing out of one part, in the meantime all the surfaces have to be flat faces due to the requirements of Corten steel fabrication. Other than that, the main pylons and branches are subtly tapped, therefore all the geometry will have to be re-drawn should the height of knuckle joint or the sections of pylons and branches change. The parametric model in DP made us focus on resolving the relationships between different parts without worrying about the final dimension and proportion, which would be as easy as clicking a button after the engineers confirm the sizes.
5.Adaptable node platform configuration
To subdivide a line into Fibonacci sequence is straightforward, whereas for curve the model needs to be intelligent to adapt to different setting out. Although the radius of each node platform is same, yet the configurations of balustrade and deck support are various, due to the difference of the angles connected to each walkway module. Instead of spending 10 times to manually build each node, we made one parametric node which adapted to all different connecting angles. Time was saved.
6.Articulated Rhizotron
This isn’t rather complex geometry as we thought. All it has are several inclined flat surfaces joining together. However it would have confused the concrete structure engineer forever without our information extracted directly out of the 3d surface model. All we need to provide are coordinates of the corner points of the surface. It was pity that the concrete engineer didn’t have the 3D tool as the steel fabricator. Engineers will have to cop with the advanced 3d model environment today.
The complexity of the balustrade and the deck structural beams makes it unrealistic to manually build up a digital model. It would become a nightmare for us should the general dimension are changed in the early stage as the span is subdivided based on the Fibonacci sequence. Every thing would have to be redone even the change is as small as cm. With a parametric model in DP, everything will automatically re-propagated even you change the initial geometry setting out.
3. Sophisticated staircase tower
Due to the site constrains of the pylon location, a cantilevered staircase was proved to be appropriate solution. The complex relationship between the taped trunk, the trifurcated top branches picking up the main platform, the cantilevered sub-branches supporting the landing, the deck beams, the Fibonacci balustrade, the spiral running and the handrail would have been too difficult to articulate without DP model. Working in parametric modelling environment can spot on the clashing between different parts instantly. There will be no hidden geometry clash as long as the digital model is well done. What you see on your screen will turn up to what you will have in reality. In this sense, architects and contractors can organize the construction more efficiently, foresee all the potential construction and fabrication issues, maximize the off-site production, as well as providing more accurate cost information.
4.Slender pylons
The proportion and dimension prove to be appropriate among trees. The trifurcation geometry is particular problematic at the knuckle joint, which should continue the edge of the main pylon to the branches to make it look like growing out of one part, in the meantime all the surfaces have to be flat faces due to the requirements of Corten steel fabrication. Other than that, the main pylons and branches are subtly tapped, therefore all the geometry will have to be re-drawn should the height of knuckle joint or the sections of pylons and branches change. The parametric model in DP made us focus on resolving the relationships between different parts without worrying about the final dimension and proportion, which would be as easy as clicking a button after the engineers confirm the sizes.
5.Adaptable node platform configuration
To subdivide a line into Fibonacci sequence is straightforward, whereas for curve the model needs to be intelligent to adapt to different setting out. Although the radius of each node platform is same, yet the configurations of balustrade and deck support are various, due to the difference of the angles connected to each walkway module. Instead of spending 10 times to manually build each node, we made one parametric node which adapted to all different connecting angles. Time was saved.
6.Articulated Rhizotron
This isn’t rather complex geometry as we thought. All it has are several inclined flat surfaces joining together. However it would have confused the concrete structure engineer forever without our information extracted directly out of the 3d surface model. All we need to provide are coordinates of the corner points of the surface. It was pity that the concrete engineer didn’t have the 3D tool as the steel fabricator. Engineers will have to cop with the advanced 3d model environment today.
7.Details development in 3D
It was the accuracy of Digital Project model that ensured us to develop all the details in 3d environment. The advantage of 3d detailing is that you can not only see the visual effect directly, but also detect clashing instantly. All of the sudden, detailing work becomes much more fun.
8.Communication
Rather than the design itself, it is the efficiency of communication with all the other sub-consultants that drives how fast the project can progress. The efficiency can be understood into several levels. One is about how to extract information out of the model. In Kew project, part from the 2d drawings, we also published the DP model and issued it to other consultants for them to understand the geometry better. There were spreadsheets and drawings for every single component with number and dimension in line with position. Technically they were generated directly out of the contractor’s 3D model (Tekla), as such it ensured the consistence of the information easily. Secondly, it is how to avoid building redundant information into the model. For instance, structure engineers most likely only care about the wire frame model rather than the surfaces. The service engineers may purely interested in the surface areas or pitch angle, etc. Consequently you should also manage the model in parallel of continuously developing the model as designer. This requires the knowledge of the cooperation among different consultants. Thirdly, it is how to update the model as per other consultants’ feedback. This is the fundamental advantage of working on parametric model, which saves architects’ a lot of time on repeating labouring work as long as the process of the geometry is agreed. The last one is to check other contractor’s information. This was carried out more intuitively in Kew Walkway. As architects, we are more interested in the fact that the contractors’ drawings should be as close as the original design. What we did was simply overlapping contractor’s model with ours. In another word, we exchanged the 3D model with the contractor.
Conclusion
In this project, parametric design tool was essentially the vehicle to deliver the scheme in terms of rationalization and building construction information. It was introduced after the concept design stage. We were also very lucky to have Britland as the main contractor, who had continuously developed the parametric model in Tekla throughout. There are also some other projects we applied the parametric design technique from the concept design stage, which will be released soon.
It was the accuracy of Digital Project model that ensured us to develop all the details in 3d environment. The advantage of 3d detailing is that you can not only see the visual effect directly, but also detect clashing instantly. All of the sudden, detailing work becomes much more fun.
8.Communication
Rather than the design itself, it is the efficiency of communication with all the other sub-consultants that drives how fast the project can progress. The efficiency can be understood into several levels. One is about how to extract information out of the model. In Kew project, part from the 2d drawings, we also published the DP model and issued it to other consultants for them to understand the geometry better. There were spreadsheets and drawings for every single component with number and dimension in line with position. Technically they were generated directly out of the contractor’s 3D model (Tekla), as such it ensured the consistence of the information easily. Secondly, it is how to avoid building redundant information into the model. For instance, structure engineers most likely only care about the wire frame model rather than the surfaces. The service engineers may purely interested in the surface areas or pitch angle, etc. Consequently you should also manage the model in parallel of continuously developing the model as designer. This requires the knowledge of the cooperation among different consultants. Thirdly, it is how to update the model as per other consultants’ feedback. This is the fundamental advantage of working on parametric model, which saves architects’ a lot of time on repeating labouring work as long as the process of the geometry is agreed. The last one is to check other contractor’s information. This was carried out more intuitively in Kew Walkway. As architects, we are more interested in the fact that the contractors’ drawings should be as close as the original design. What we did was simply overlapping contractor’s model with ours. In another word, we exchanged the 3D model with the contractor.
Conclusion
In this project, parametric design tool was essentially the vehicle to deliver the scheme in terms of rationalization and building construction information. It was introduced after the concept design stage. We were also very lucky to have Britland as the main contractor, who had continuously developed the parametric model in Tekla throughout. There are also some other projects we applied the parametric design technique from the concept design stage, which will be released soon.
