#bricksonsticks

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Bricks and Sticks Lecture 4

Module: Light and Structure

Week 4 - Materials 

3 things can control: Forces, Material, Shapes

Different geometry means different internal forces: 

Definitions:

Stiffness: Extent resists deformation in response to an applied force

Brittle: Easy to snap

Ductile: Can be drawn into wires

Tough: Resists scratching

Elasticity: Returns to original shape when deformed

Plasticity: Remains in deformed shape

Considering two structural elements (objects), differentiate properties of MATERIAL and GEOMETRY:

Hard Gums vs. strawberry laces - materially similar, geometrically different

“Homogeneous” Material: consistent all the way through

“ Composite” Material: different materials and qualities

Structural materials:

Cost

Availability 

Weight

Electrical/ Thermal conductivity

Thermal expansivity

Durability

Embodied CO2 - (CO2/energy consumed in producing material) 

Eco-toxicity - (extent material damaging environment)

Hooke’s Law: F=-kX

Strain (visible): ∑= Δ L/original L

Stress (invisible):  σ=F/A (cross-sectional area)

Young’s Modulus: E= Δσ/ Δ∑  

Measures stiffness of material 

Removes affect of geometry

Stiffer materials have steeper gradient (higher E)

Yield point: elastic to plastic

“strength quantified”

Concrete - weak in tension, ok in compression (reinforce with steel at points of tension ie. bottom of beam) (E sudden decrease after yield)

Steel - somewhat still usable in the “plastic” range (E slowly increases still after yield point)

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Bricks on Sticks Seminar 2

Module: Light and Structure

Week 4

In this seminar everyone’s designs were analysed. I found it particularly useful seeing other’s thoughts and responses to the brief. Most people had design various truss structures, adapting upon basic principals to produce “unique” and interesting designs. However when these were broken down into components, many were full of redundant members. It is important to treat this project as a structural exercise rather than focusing on elaborate design. Theoretically the more basic structures were likely to be successful. However I think due to the limitations of the material, particularly the thin sticks, it is likely that some designs will need to be reinforced, whether by glue, additional members or thickening members with multiple sticks. 

Key points:

- Build up centre of span with material and structure

- Arches will need to be tied with a tension member to create horizontal force at base

- Higher arches will redirect the load more vertically which would be more successful considering the limitations of the horizontal forces in this scenario

- Reduce members to basic triangles! Don’t over-engineer

- Pre-camber: counteract displacement in advanced structural design

Of my designs it was anticipated that the most successful ones were the tied and triangulated arches so I intend to develop along these lines. I think I shall also explore the effect of my design as a beam, and consider a truss formation as it already plays on the border between arch and beam due to the triangulation of the planar sides. 

[sgreendesign]

Bricks on Sticks Design

Module: Light and Structure

I started with some research into the basic structures which are likely to form the foundation of my design solution for holding the load of a house brick over a span of 450mm with just sticks and ties. I think the most successful potential ideas would come from trusses, beams, or arches, although a suspension span combined with a beam support is also feasible. 

My initial ideas were to design a combined beam and arch structure, or at least something which would allow me to focus most of the material in the centre of the span to resist the main load. Triangulating the planar structure of the elevations would be the most efficient use of the sticks, with cross bracing to lock the parallel planes together. 

A series of parallel truss formations which connect with a similar triangulated pattern on the top would create a solidly supported platform for the brick to sit upon. Initially I was considering three of the parallel trusses with the central one being tallest, however I thought that the force of the brick may focus too much on the central truss and cause the structure to collapse inwards under compression. With this design I had also intended to consider each of its vertical elevations as trusses, with the extra width of the three planes creating another truss perpendicular to the span, however I think this idea is not particularly efficient and perhaps, if it were to work, verging on over-engineered. 

I reflected upon the success of the prism formations we had made in our seminar using sweets and cocktail sticks, so began to develop my design into a series of connected pyramids which, from a side elevation, would arch in the centre as the height of the pyramids increased and then decreased. However the problem then was adapting the design to allow a platform for the brick to sit upon and for the load to be effectively redistributed from...

Evaluation: 

Focus material in centre (perhaps as solid arch?)

Triangulate elements

Need platform for brick

Don’t over-engineer with unnecessary components 

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Bricks and Sticks Lecture 3

Module: Light and Structure 

Week 3 - Internal forces

Simply supported beams always have “rollers” beneath one support. 

Suspension forces are the reciprocal of arches (demonstrated by Gaudi) 

Problem with tension spans: 

Cant join it to the desk

Cant get horizontal forces

(Royal Albert Bridge - Brunel)

Beams: subject to tension, compression, sheer, torsion

“UDL” - uniformly distributed load

Everything DISPLACES under a load

Strain: measured because can be “seen”

Stress: cannot be measured

How do you transfer vertical forces to the supports? Diagonal forces?

Just going to sag and move, unsuccessful, “not a structure” just a mechanism

Compression members need to be shorter and stockier

Think about the SHAPES the panels would be under a force... 

Square > Parallelogram 

Deflected shapes identify tension/ compression members

Symmetrical structures: members on opposing sides do the same thing

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Bricks on Sticks Lecture 1

Module: Light and structure

Week 1

Bricks on sticks is our first project for Light and Structure and concludes in week 5 with everyone’s designs being tested and evaluated. The challenge: to create a spanning structure from just 40 15cm applicator sticks and ties to support a standard house brick. The structure can’t be fixed to the supports. 

Report:

chart “costing” device: sticks = 500 units/m, cable = 100 units/m, glue = 0

drawings

how to develop and improve

Differentiate tension and compression members! Don’t over-engineer. 

Structural engineering: materials, shapes, forces

Compression: shorter and fatter

Tension: longer and thinner

Sheer: parallel (eg. friction)

Torsion: twisting