THE FLEXIBLE JUMP-FORM
I have sought to investigate the possibilities of creating to a double-sided vertical casting system that incorporates some sort of flexibility. I have throughout my experiments worked with deformation and addition as the means of manipulation. At this point I’m working with a system that combines the semi-flexible surface with a jumping formwork system. There are of course endless ways of incorporating flexibility to a vertical casting system. My physical experiments have only touched a small corner of the field. An investigation of the proposed flexible jumping formwork has uncovered both potentials and some limitations. These are the parameters that define my architectural design conditions.
A limitation of the casting technique is that it is next to impossible to cast anything besides than vertical. The cast has to be between 60 – 120 degrees on the foundation otherwise it becomes too difficult to fill the mould. This limits the casted structure to be a wall-like, horizontal oriented structure.
PLAN AND SECTION DEPENDENCE
The formwork is quite flexible, especially in the longitudinal direction one has almost unlimited shaping possibilities. The vertical deformation raises a geometrical specified issue. When the formwork is curved in a vertical direction, the structure is not able to hold a straight bottom edge. This issue arises because of the difference in curvature two surface areas. As this is a rule of geometry, I see no way of ‘solving’ this problem without taking a change of direction of my investigation. Instead I would like to work with this issue as a designing factor: For instance the foundation and plan design of the structure determine how much the structure is allowed to deflect in the sections. This would create a sort of essential cross-reference between the horizontal plan design and the vertical sections of the structure. The proposal of using the substrate or foundation as a designing factor generates a whole new and more site-specific perspective to the forthcoming experiments.
When casting a double-sided structure, the sides can be held parallel to secure an even thickness of the structure. This however consequence a problem when trying too obtain a steep curvature. By allowing nonparallel sides, you are able to cast a more kinked geometry. This ability to create different thicknesses within the same structure can be exploited to generate an optimized construction or achieve a specific architectural design intent.
MANIPULATION OF THE FORM
The manipulation of the form is quite a complex matter as the triangles and thereby the geometry all is interdependent. Once a bend is employed the rest of the geometry are forced to follow. E.g. If the corners of two triangles a pinched together, the in between edge will kink out. Actually the same form can be achieved in various ways. In my identification of the forces in play, it is understood that most form-scenarios are attained by employing a combination of the forces.
As the formwork is an insitu-system, it is possible to use the surroundings and terrain to obtain the desired shape. As mentioned the terrain can employ an upward force by lifting the bottom edge, forcing the sides to curve or kink. However it is also possible to use the clamps of the formwork as anchor-points. By tying together two anchor-points, you are able to control the in-between geometry.
CONTROLLING THE THICKNESS
The length of the wire controls the thickness of the structure.
The wire is also used to hold the formwork together and clamping the jump-form to the existing cast.
I have been able to develop a grasshopper script that allows me to predict and evaluate different curves. This script can be used in both plan and section to envisage the faceted surface. The script subdivides a curve into a facets defined by a variable geometry. This allows me plan out the composition and choose the ideal geometry for the structure.
VERTICAL ORIENTATION THE LANDSCAPE
The casting system of the climbing formwork envisages a horizontal orientated structure. The structure will resemble an undulating wall that meanders through the terrain of the great northern walks plateau. Like the plateau on which it rests, the structure will be horizontally oriented.
INDIVIDUAL PIECES THAT CREATE A WHOLE
The structure will consist of several individual wall sections, but will be perceived as a coherent structure. Like a band that ‘dips’ into the earth and arise further ahead. The coherence between the sections will be achieved by the their resembling appearance, a joined curvature of the overall structure as well as the design of the ‘dips’.
CULTIVATING THE QUALITIES OF THE SITE
The structure creates new spaces and shelter as well as it accentuates the existing qualities of the site. The structures are places on either side of the trail of the great northern walk. As people walk the trail from either direction there are the structure can be approached from either side. The westerly entrance offers the most dramatic passage, whereas the eastern side is more accommodating and provides access to the higher level of the plateau.
The structure is oriented so that the view is visible from either entrance. The view is the attraction of the site and the outlook ahead is what guides you through the structure. The structure acts as a framing of the view, the framing and angle of the view changes continuously as you move through the structure. The widest outlook being when you a directly centered within the structure.
The western passage is perceived almost as a portal or a tunnel with the walls caving in at a height of 4 meters. It appears the trail is almost carving its way through the terrain, with the retaining wall defining the border between the natural and the cultivated space.
The larger space near the eastern access can acts as a shelter or a campsite for hikers and bypassers. The in closure provided by the curvature protects the area from strong winds and offer an area out of the sun. From this area it is possible to still enjoy the stunning view over the valley in a northwesterly direction. Also the plateau of the retaining wall is accessible from this area,
EXPLORING THE POTENTIALS OF THE SYSTEM
Another aim of the structure is to showcase some of the potentials of the proposed system. Particular intersting is the the variations within sections the when structure is exposed to a terrain. When the structure is positioned across contours a change of the curvature is nesseary in the sectional design.
The coherence between the rise in the terrain and the curvature in the sections needs to be planed into the plan-design. If you need a steep curve in a certain section, it is necessary to make the structure climb to a higher terrain. Notice how the two smaller wall pieces incorporate and demonstrate opposite scenarios.
When using the formwork to cast a retaining wall you have less restrictions as the you are casting up against a surface and thereby only need one side of formwork. When the formwork is one-sided, the limitations from having to keep two sides the same length becomes irrelevant.
The structure will build along the great northern walk. The lack of machinery access and the remoteness of the site was the inspiration behind my initial investigation of the insitu-systems. It seemed somehow irrational to work be working towards an industrialized production if the elements would have to be helicoptered in place. The proposed flexible jumpformwork seems be the ideal way to deal with the remoteness of the site. The separable double-layered formwork is a lightweight construction, that doesn’t require heavy transport. The flexible inner membrane can be folded up and the rigid geometry can be handled separately.
THE HUMAN SCALE
The nature of the casting system is a faceted surface. The size of the basegeometry, and thereby the creasepattern is a balance between the facets being perceived as a pattern or as a shape. A to large subdivision can be alianating and out of touch with the human scale. A to small basegeomtry will be perceived as a pattern rather than a faceted shape. Because the formwork is casted on site, the scale of the formwork (and thereby the surface pattern) will be limited to what is physically manageable by a human. This part of the construction ensures that a relation to the human scale always will be present in the final structure. I envisage that the basegeometry of the formwork will be 200 x 300 cm, this is subdivided into 8 triangles.
The structure will be casted on site. The materials used will be a mixture of local earth from the site only added a minimum amount of concrete and water. The use of local and sitespecific materials emphezise the tie between the site and structure. Even though the form may be alien in its surounding, the materials used ensure a visual connection between the texture and colours of the site.
LIFE AS A RUIN
The using a earth instead of sand in the concrete mixture consequense that the structure are subject to erosion. In time the structure will decay back into nature. Time will enhance the structures consporance with the site, as the faceted surface slowly will erode to a smoother surface. In time nature will take over and the structure will evolve from the man-made destined creation to a ruin designed by nature.
EXPERIMENT V JUMPING FORMWORK
In this experiment I sought to incorporate the semi-flexible surface to the jumping formwork system
– Investigate the possibility of incorporating a semi-flexible surface to a jumping formwork system
– Casting in a larger scale
– Exploring different formwork materials
– Achieving a higher quality of formwork that allows the mould to be reused
– Investigate the detailing of the formwork
EXECUTION AND PRELIMINARY CONSIDERATIONS
SIZE OF FORMWORK
Not being set on a fixed geometry yet, I choose to work with what in the previous experiment is referred to as pattern II. Mainly because the formwork of this design is easy to produce and the geometry fitted the materials at hand. Each triangle had a height and width of 210 mm. This translates into a scale of roughly 1:5 of the actual final formwork. I envisage that each triangle of a full-scale formwork would have dimensions from 1000 – 1500 mm. It’s a balance of choosing a scale where the design produce panels that is able to generate a spacious quality (and not merely is perceived as a pattern) and having a formwork that is physically manageably by a human.
I decided to produce a mould where the base-geometry was repeated 6 times (12 triangles on each panel). As it is a jumping formwork system I need to always use 1 row of geometry to clamp the formwork to the structure. This requires that the base-geometry always is repeated minimum 2 times in each panel. By using an extended version of the essential formwork, it is possible to build larger structure in fewer castings.
I conctructed my formwork as a double layered surface: A flexible surface to incorporate the bends and a reinforced backside to hold the rigid geometry. The rigid geometry was made up by 0,5 mm MDF. The edges of the triangles where all cut in a 45 degree angle, allowing the geometry to bend both ways. Each triangle had 0,7 mm hole drilled in the middle, which were to be treaded with a 0,6 mm cable. The cable where to act as a clamp, replacing what in the previous experiments where screws. I used cable glands to fix the length of the cable. The glands were tightened to maintain the desired distance between the formwork panels.
Finding a material suited to the flexible surface proved to be quite the challenge. Unsure of how much plasticity to allow I decided to test a few different types before applying it to my rigid formwork. I found a ribbed rubber that seemed to have the desired amount of flexibility without the elasticity. Despite having conducted a glue test on the rubber, where everything seemed fine. The material once applied to the formwork, had some sort of chemical reaction with the glue. The conclusion being that I decided to change to a more firm plastic material. The new material was a polyethylene, estimated 0,2 mm.
The jumping formwork structure is casted in sections. Once the first casting has cured, the formwork can be removed and reattached to cast the next section. In addition to the original cast I was able only able to produce a recast in the longitudinal direction before the submission deadline of this rapport. Nevertheless I intend to cast my next extension of the structure in a vertical direction.
The 0,5 MDF was easy to work with (it was possible to cut it without using a saw), but had the disadvantage that it doesn’t respond well to moisture. The MDF would be acceptable as a disposable formwork. However I would like to use a more durable material, possibly plywood or a steel sheet, in my further experiments.
The flexible plastic membrane did the job. The structure had a beautiful surface and sharp edges. The only problem being that the plastic had fractured in a few of the cuts and allowed the glue to react with the concrete. When concrete cures alongside contract glue, the chemical reaction leaves sandy trails in the cast. In my further investigations I have been looking into using a 0,75 -1 mm PET plastic. It seems once it has been pre-cut, it has the ability to bend without shoving any signs of fracture.
The cables and cable glands held up perfectly. They were able to withstand the pressure of the concrete and where easily removed. I think even in a larger scale it will be necessary to use some sort of flexible cable or wire, as it has to be able to incorporate the slight difference of the entry/exit holes. I imagine that it is possible to obtain cables that are suitable and well proportioned in a 1:1 scale.
The formwork only had one hole positioned in each triangle. Surprisingly the single hole was enough to clamp the formwork with minimal leakage during the recast. Ideally I should have placed a series of clamping holes along each triangle edge. This would allow the formwork to have a tighter grasp with a smaller chance of the concrete leaking on the already cured cast.
REINFORCEMENT AND JOINTS OF THE CASTINGS
I had no problem joining the second cast to the original. Despite second cast had to join a smooth concrete surface, the bond between the two seems quite strong. In a larger scale one could imagine that reinforcement would be added to take the tension in the joint. I would like to do an experiment where the reinforcement is casted into either side of the cast to strengthen the joints.
AN ADHESIVE-FREE DOUBLESKIN FORMWORK
I imagine that my final formwork will be a glue-free mould. Instead of permanently attaching the two layers of the formwork I want to keep them separable. The rigid and heavy outer-formwork will be elements that can be assembled and dismantled on site. The flexible inner-formwork will be a lightweight membrane that likewise can be de/attached to the mould. I envisage that the two layers of formwork could be held together by the same bolts/cable glands that control the deformation.
SEMI-FLEXIBLE SURFACE AS A JUMPING FORMWORK
I succeeded to use the semi-flexible formwork as a jumping formwork. Casting additional sections in either direction is straightforward. There are however some limitations of the formwork: Same issue as noticed in experiment III. Forcing the formwork to obtain a too steep curvature will generate difficulties when having to fill the mould. Also when the formwork is curved in a vertical direction, the structure is not able to hold a straight top and bottom edge. This issue arises because of the difference between a straight and curved surface area. As this is a rule of geometry, I see no way of ‘solving’ this problem without taking a change of direction of my investigation. Instead I would like treat this issue as a designing factor: For instance the base and plandesign of the structure determine how much the structure are allowed to curvate in section. This would create a sort of essential cross-reference between the horizontal plan design and the vertical sections of the structure.