Membrane Tension Dynamics & Tensegrity

MEMBRANE TENSION DYNAMICS & TENSEGRITY.

ARCHITETURAL DESIGN STUDIO 2 - CONSTRUCTION - PETER GHIONIS

ABOUT. Throughout this unit I will be exploring the form, function and material integration of dynamic membrane strucures.

I will be focusing on tensegrity using different types of metal elements and experimenting on how they join and interact with a dynamic membrane as their substructure.

I will achieve this through various prototyping and various tectonic detailing research and digital sketching.

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CONTENT.

01 PRECEDENCE STUDY & ANALYSIS 02 PHYSICAL PROTOTYPE 03 SKETCHBOOK PART A 04 LASER CUTTING TASK 05 TENSEGRITY I. II. III. IV. V.

Precedence Study & Analysis Prototype Analysis Design Brief & Planning Design Iterations & Prototyping Final Design

06 SKETHBOOK PART B

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PRECEDENCE STUDY & ANALYSIS

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Throughout my precedence study I have explored the works of Frei Otto, and the way in which he implemented tensile stress into his designs to create large spanning lightweight framed tensile structures.

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These structures generally are comprised of two parts, a membrane which generally comes in the form of a high strength coated polyester and a structural frame.

The frame is required in most cases as these membranes cannot derive their strength from double curvature.

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I chose this as my precedence because I believe that these structures can offer far more than their intended use and can act as a greater and more beautfiul alternative to modern building methods and design.

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PHYSICAL PROTOTYPE

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The second stage of my design research was to construct a physical prototype to help me to better understand the material of my precedence.

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My prototype acts as a way in which I can interpret the membrane layer of my structure to see different ways in which I could bend and stretch it.

This gave me a better understanding of the way in which my material acts under specific stresses and tension.

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I used a steel frame as a base for my prototype. The base acted as a frame for my nylon material to adhere to. I wanted to be able to manipulate the nylon piece in as many was as I could.

My first attempt at making this involved using hooks as the way to attach the corners of my piece to the frame but I found that this restricted the potential shapes I could create by just having set levels to hook to.

I solved this problem by using velcro as a means of fixing the material to the frame.

I found this worked much better as it did not restrict me with the locations at which I could fix the end points of my nylon piece, thus allowing me to stretch and bend the piece to my leisure.

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SKETCHBOOK PART A

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Throughout my dgital sketchbook I experiment with different shapes and designs I can create using the Rhino program and Grasshopper add on.

Whilst also familiarising myself with the software as a whole I also have used it as a tool to explore my design methedology and interests.

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LASER CUTTING TASK

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The object of this task was to design an object of our choice in grasshopper and then export and bring it to life through means of laser cutting.

We were split up into groups for this project. Our group decided to design and create a chandelier.

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The first step was to design what we wanted to laser cut using Grasshopper and Rhino.

We wanted to add some roundness to the shape as we found the triangular jagged edges were too over-bearing.

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The second step was to flatten our 3D design into 2D pieces for the laser cutter to cut.

Each piece had to have its own number indicatad on it to help for ease in putting it back together once cut.

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The third step involved exporting our file to be cut in the laser cutter.

Once cut we layed the pieces out and planned out our assembly of them.

Each peice was connected with 3.2mm rivets.

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TENSEGRITY

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Our group precedence topic that we chose to cover is Tensegrity and the way in which we could use the principles of tensegrity to create large spanning parametrically designed structures.

Our precedence study and analysis also covers the way in which Kenneth Snelson uses the principles of tensegrity in his sculptures.

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The term ‘Tensegrity” was coined by famous architect and system theorist Richard Buckminster Fuller.

The term is a combination of the words “Tension” and “Integrity”.

It is essentially a structure that derives its strength from the integrity of its tension members rather than its compression members.

Unlike compression structures, where their integrity lies within the continuity of compression stress, from unit to unit to the ground, tensile structures during stress, will evenly distribute their load throughout the structure.

As these structures are already in a pre-stressed state, they do not depend on any external forces like gravity or anchoring to maintain their state. They have a stable equilibrium which allows them to recover to their original position independently after external stress has disturbed the structure.

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A tensile structure is comprised of elements that are both in tension and compression.

The tension element (string) and the compression element (rod).

The system is established when the set of discontinuous compressive members interact with a set of continuous tensile components to combine and create a stable volume in space.

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To further understand the way in which these structures worked we created various prototypes to replicating oue precedence study to get a better physical understanding of the requirements of these complex models.

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PROTOTYPE I The first prototype we constructed was used just to get a general understanding and physical representation of the way in which these strucutres work.

Figure “a” and figure “b” shows the general rule that we followed derrived from grasshopper and through our precedence study on kenneth snelsons designs.

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Figure A Kenneth Snelson, Vortex study 1967

Figure B Forming diagrams of single module tensegrity structure. Created in Grasshopper + Rhino

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PROTOTYPE I The materials used for the first prototype were wooden dows for the rods and string as the tensioning cables.

Nails were used on the ends of the dow’s to have an anchor point to wrap the string around and tension it.

The problems we faced in Prototype I was getting the right amount of tension through the strings to reach an equilibrium throughtout the whole structure.

We then explored ways in which we could fix this in our second prototype.

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PROTOTYPE I

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PROTOTYPE II Our second prototype followed the same construction method as our first with a minor tweak to the tensioning method of the string.

We found that if we cut down some plastic nuts and bolts we could use them on each string and twist them to tighten them.

The issue we faced is that this was required on each piece of string which in turn made the overall look of the design less aesthetically pleasing but we successfully found a way in which we could tension the string, which was a major issue before.

For our main build we will use this method but instead of placing it on the string we will use the ends of the rods as the governing points for our tensioning mechanism.

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Once this was achieved connecting one module to another became quite simple as it was just a matter of rotating the module to meet the midpoints of the module prior then tensioning the strings.

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PROTOTYPE III Now that we had found out how to tension our strings, the next step was to create a version of our prototype in which we could create each module faster so we could experiment with different shapes and layouts.

As the first two prototypes were relatively time consuming, our third prototype used rubber bands as tension member as their elasticity is far more higher than string and easier to tension for indicative layouts.

The rods had to be custom built to accomodate for the rubber bands.

Aluminium was used as the rod material and was cut to size.

Once cut, we made a small timber jig to house the rods so we could cut slits in them to give good hooking points for the rubber bands. A small flat piece of metal was used to make sure the slits were cut level.

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Once one module was built, the time and process of creating each module after that was cut in half and with 4 of us it only took approximately 2 hours to construct 5 new modules.

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PROTOTYPE III

One issue that we found came up overtime is the integrity of the rubber bands but due to the simplicity of the design it was a mild repair and inconvenience.

Overall the prototype was a success, it allowed us to be able to replicate and re produce very fast with minimal effort.

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Once we had an understanding of the building and brief, we begain to digitally experiment with potential modules and forms that we could create along our facade, as well as experimentation with some physical prototypes to help better understand the construction process of these structures.

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ANALYSIS I 4-Strut Tensegrity stalactite formation.

The first facade experimention we came up with was implementing a stacked, ‘tree’ like formation of a 4 strut module.

We found that this design although was complex in nature, seemed very bulky and overbearing for the size of the building.

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ANALYSIS II

3-Strut Tensegrity stacked wall.

The second design we came up with involved stacking a 3 Strut module into a wall like formation.

The wall provided a very unique shadow and did not interfere with the existing columns.

Although visually and physically it worked well, we found that the complexity and intricacy of the design wasnt quite there yet.

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ANALYSIS III Experimenting with different size strut members.

In our third design, we started to experiment using different sized strut members.

We found that digitally we could get it to work but the process of creating it was too long and limited us to changes in module if we needed to.

Although visually and physically it worked well, we found that we were limited to one module design by doing it this way.

Opening up that north wall had been our mission from the begining and this was a closer step to that goal.

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ANALYSIS III PROTOTYPE We decided to prototype our third design as we wanted to see how different sized compression members would affect the structure physically.

The issue we faced at this small scale was that the pre tensioning of members was quite difficult, even when zip tied in place for easier assembly.

This caused the compression members to touch, which did not follow the principles of tensegrity.

We found that if we want to accurately prototype these structures we would need to add in a way in which we could tension the structure further after asembly.

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ANALYSIS IV Our fourth design implemented shade sails in the structure, as we found that this would be necessary to provide shading along that north wall.

The problem with this design was the size and lineairty of the compression members, although we did not go with this design it did aid in the idea of using one of the compression members as a replacement for the columns.

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FORM MAKING VS FORM FINDING

STANDARD PRINCIPLE

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DIGITAL MANIPULATED FORM

SIMULATED FORM

PHYSICAL SIMULATION DEMONSTRATION 85.

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ANALYSIS V

In our fifth design we found that integrating multiple strut modules throughout the facade was the most visually aesthetically pleasing design and it acted as both a shade and a structural member for support of the roof.

We found this to be the best design that accurately represented the design constrains and oppertunities that we were going for.

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The final design we are proposing consists of five different modules.

The modules are orientated in a way that heroes the tensegrity form whilst also not overbearing the original structure.

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PROPOSED DESIGN

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PROPOSED DESIGN

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PROPOSED DESIGN

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1:5 PROTOTYPE

RED PORTION TO BE PROTOTYPED

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5-STRUT BASE

3-STRUT

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DIGITAL

ASSEMBLY DIAGRAM R1 S1 S13 R2

S2

S12

R3

R1

R2

500mm

R3

300mm

R4

345mm

R5

345mm

R6

345mm

R7

470mm

R8

370mm

S10

S11 R5

R4

S5

S3

S7 S4

S8

S14

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655mm

S4

5-STRUT BASE

STRING

S1 S2 S3 S4

S

LENGTH mm

315

3

300 395

610

ROD LENGTHSROD LENGTHS R1

S1 S2 S3

655mm

S4 S8 S14

R2

500mm

S1 S13 S15

S3 S12 S14

R3

300mm

S10 S11 S12

R4

345mm

S7 S8 S9

S2 S4 S5

R5

345mm

S9 S10 S11

S5 S6 S7

R6

345mm

S16 S17 S18

S20 S22 S24

R7

470mm

S17 S19 S20

R8

370mm

S1 S19 S21

S6 S13 S15

S21 S22 S23 S18 S23 S24

STRING

S1 S2 S3 S4

S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S20 R21R22R23R24

LENGTH mm

315

300

300 395

610

305 350

515 300 360

310 350

330

265

265

185

285 380

290 240

310 385

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1:5 PROTOTYPE

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1:1 MATERIAL CONSIDERATION

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1:50 SCALE MODEL

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SKETCHBOOK PART B

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