Creation of complex concrete structures with augmented reality and PVC pipes


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Creation of complex concrete structures with augmented reality and PVC pipes

The reBENT project, developed by Bartlett School of Architecture (UCL) March 2019-20 Program Research Group 9, explores the interactive relationship between augmented reality (AR) and manual construction processes using PVC pipes – very durable and inexpensive – as basic research material. In addition to taking advantage of its active bending properties to interact with AR, this material provides a fast and affordable system for creating complex concrete structures made by weaving together a series of PVC pipes and rebars. folded, which is then used as formwork for glass fiber reinforced concrete (GFRC).

Until now, the exploration of this hybrid approach – neither purely analog nor purely automated – has led to the design of prototypes, architectural elements and habitable structures. Additionally, the team developed an augmented reality platform for Microsoft Hololens to guide the build and personalization process through holograms.

System design.  Cortesia image by reBENT
System design. Cortesia image by reBENT
Simple PVC rebar system.  Cortesia image by reBENT
Simple PVC rebar system. Cortesia image by reBENT

reBENT seeks to design self-supporting structures and explore complex shapes in concrete, avoiding the use of stand-alone systems such as 3D printing robots. According to team members, “our goal is to use tubular geometries, using inexpensive and universal materials as formwork, such as PVC pipes and rebar, in explorations of computer design, managing the active flexural properties of the material through generative controlled curves across polygons.

How did these explorations go? The team explains it to us. “To extend the geometric composition, we generate complex bend shapes in a computer-controlled assembled shape. We use the structural constraints of 20mm PVC pipes to analyze different bend shapes using curve tests. We generate a simple example of active bending to test the pipes and their assemblies. The results were promising as we were able to reproduce the digital model. In this first approach, we implemented augmented reality by connecting the designed components to “Fologram” via Rhino-Grasshopper. Implementation on our mobile devices enabled holographic displays to guide tube bending. “

Cortesia de reBENT
Cortesia de reBENT

“We then cataloged the design languages ​​and re-tested different types of active folding examples. We looked for a guide that could connect to previous studies, using primitive geometries. We implemented polygon explorations to find geometric shapes that would function as a computer bending frame.In addition, we use Karamba, Kiwi and Kangaroo (Grasshopper plugins) to structurally test the generated geometries with specific material constraints, by evaluating the behavior of the pipes under certain design conditions. “

Computer guidance of polygons.  Cortesia image by reBENT
Computer guidance of polygons. Cortesia image by reBENT

While these results were very positive, the researchers found some structural issues, such as brittleness and lack of strength. “For this reason, we have incorporated 4mm rods to provide a construction system with additional strength. To join the rebar to the PVC pipes, we have designed a series of 3D printed flexible TPU joints. Their shape depends on the amount of rebar. to join.”

3D printed seals.  Cortesia image by reBENT
3D printed seals. Cortesia image by reBENT

The packaging system consisted of three types:

  • 1 PVC tube of 20 mm – 4 reinforcement bars (for small interventions)
  • 4 PVC tubes of 20 mm – 8 reinforcing bars (for medium interventions)
  • 10+ 20mm PVC tubes – 12 reinforcement bars (for large-scale interventions)

The team continued their explorations with generative algorithms to produce complex curves, incorporating their structural analysis to generate a manufacturable geometry while introducing the packaging system. “We have developed computer simulations and physical explorations of concrete spraying to understand what the proposed geometries might look like after pouring. To effectively cast the tubes, we used a spray gun to cover their screens. To minimize the pouring process, we sprayed glue on the pipe and then GFRC concrete, which adheres well, and a series of tests were carried out to determine the amount of concrete, up to 3 coats for small structures in concrete and up to 10-12 coats for habitable-type structures that are structurally self-supporting. We tested this on small-scale structural objects, such as columns and architectural components, achieving a variety of possible shapes. As an example of the generative implications of this method, we have based the following examples on complex shapes that are difficult to achieve without the aid of holographic screens, ”they add.

Column study.  Cortesia image by reBENT
Column study. Cortesia image by reBENT

System setup

The team used an earlier series of curved designs to implement the system, increasing the possibility of creating a habitable structure. The system has been adapted to the proposed geometry, functioning as a self-supporting structure. To wrap these habitable spaces, “we devised a method to generate surfaces throughout the substructure, using the polygonal orientation to generate curves within the main structure. Additionally, a substructure functions as a support that connects different capsules to a single element, creating a living space on a human scale. “

Proposal for a slab house / Structure of the PVC rebar system.  Cortesia image by reBENT
Proposal for a slab house / Structure of the PVC rebar system. Cortesia image by reBENT
Slab House Proposition / Skeleton.  Cortesia image by reBENT
Slab House Proposition / Skeleton. Cortesia image by reBENT

Augmented reality platform: Hololens application

The Microsoft Hololens application collects all of the data presented to help the user create complex shapes easily and efficiently. The reBENT AR platform uses the following scheme:

  • Ease of use: Starting from a welcome screen to choose between a new project or a saved project, all the functions of the application are compressed into a single menu where the user can find:
    • Overview of the project to be built.
    • Quantity and specification of items required. A separate building section with manufacturing steps and assembly parts.
    • Manufacturing toggle menu, where the user can view model details and construction steps.
    • Review of built processes, in case a step is missed.
  • Tutorial as a platform: The different steps consist of a holographic display and an interactive menu to identify materials, components, type of assembly and positioning of the seal.
  • Using machine learning to scan and fit holograms to the real model: Manual manufacturing process may lead to inaccurate connections or component fabrication. This characteristic allows the program to analyze and detect these defects and to propose a structural solution if necessary.
reBENT / Platform concept.  Cortesia image by reBENT
reBENT / Platform concept. Cortesia image by reBENT
reBENT / Use of the Platform.  Cortesia image by reBENT
reBENT / Use of the Platform. Cortesia image by reBENT

Then the polygonal guide was implemented for a custom fabrication where the user has the possibility to build foundations, supports and spaces. “The guides are presented in the form of grids to the user, where he can continue to create different compositions. In addition, we implement generative solutions for different compositions, allowing the user to interact with different possibilities of the same model, improving the systems that generate other systems, avoiding architectural singularities in order to democratize the proposed designs ”, they add.

Architectural proposals

The team came up with three different compositions. “First of all, a pavilion that uses different components of our design language. Since not all large structures can be poured at the same time, the components are also used as concrete pieces. The process of building these spaces is no longer conventional as most of them need the structure. to build and mold according to the composition. And with the help of AR, connectors and secondary structure can also be completed quickly. The initial architecture is divided into several large parts, and it is built and molded separately for quick and easy construction On the same principle, the parts will be made on the ground. Then the AR will also guide the assembly in order , direction and angle, and will remould them to improve the stability of the structure.

Architectural components.  Cortesia image by reBENT
Architectural components. Cortesia image by reBENT

The design of the pavilion consists of a stable central structure with wings extending from both sides, which is then reinforced with the “Truss” structure, to form a complete skeleton that supports the roof with a hierarchy of five layers and two main joints used in the digital model. “Finally, we designed a habitable residence structure with the same system, promoting a stable structure that can be built with limited economic resources. The design is based on slabs that connect the structural system to each other, creating spaces livable and usable which adapt to any design to your composition “.

Flag design.  Cortesia image by reBENT
Flag design. Cortesia image by reBENT
Pavilion proposal.  Cortesia image by reBENT
Pavilion proposal. Cortesia image by reBENT
House proposal.  Cortesia image by reBENT
House proposal. Cortesia image by reBENT
House proposal.  Cortesia image by reBENT
House proposal. Cortesia image by reBENT
House proposal.  Cortesia image by reBENT
House proposal. Cortesia image by reBENT

Results

The pavilion and a component were tested in a real setting, with people from Ecuador who have never used an AR or other mixed reality devices. The holographic fabrication of the two elements was successful and they were built in just 2 days, working 5 hours on each. “The PVC tube-rod system requires you to first create a guide with a single set of tubes, and then ‘follow the shape’ with the rest of the pieces. Finally, concrete spraying is a more elaborate process; after the second coat, the concrete fully adheres to the structure, allowing the remaining coats to adhere more effectively. “

Student team: Pablo Isaac Jaramillo Pazmino (Ecuador), Xi He (China), Ziqi Song (China)
Tutors: Igor Pantic, lvaro Lopez

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