maandag 11 oktober 2010

First Results

First results
Following are the first results of the first 4 weeks of SA.
The results consist of three parts:
1. Grasshopper and Rhino model
2. DIANA input
3. DIANA output
4. Conclusions

Grasshopper
The first step in the research is a parametric model made using Grasshopper. The model describes a hyperbolic paraboloid (hypar); a double curved surface build up from straight parts. The hyper is cut and mirrored, so the result is a pavilion standing on 3 points and resembling a butterfly.




DIANA input
To make mechanical calculations a few steps must be taken to create a DIANA model.
1. The parameters are set at a certain value
2. The models are exported from Grasshopper (Baked) to Rhino
3. In Rhino all the lines are cut into small pieces
4. The model is exported as a IGIS
5. DIANA imports the IGIS

The next step is preparing the DIANA model
1. All the lines are put into sets
2. Each set gets physical and material properties
3. Each set gets a mesh division and type

Output #1 (bake #1)
Arm 1: 20 meters
This arm is mirrored, so the length of the pavilion is 40 m
Arm 2: 20 meters
This arm is angled
sin (angle 1) * arm 2 è sin 45 x 20 = 14.1 m

Angle 1: 45˚ (wing tip angle)
Angle 2: 0 ˚ (mirror angle)

Height 1: 6 m
Height 2: 6 m
This height is cut at 30%, so 1.83 m

Division: 8

DIANA input
First input is the IGIS, based on the dimensions of #1 bake of Grasshopper
Second input is the material: Bamboo
Young's modulus: E = 15000 N/mm2 è 15E9 N/m2
Poisson's ratio: 0.32
Weight: 600 kg/m3
Dimensions
Straight frame: Tube
ø = 0.1 m
t = 0.02 m
Diagonals: Strip
a = 0.02 m
b = 0.07 m


Mesh
Type: CL18B (BE3)
Division: 2
Loads
Gravity: factor 1
(dead weight)

DIANA output
The output from DIANA can be seen in three categories:
1. Shape
2. Local tensions
3. Local force

Shape
The maximum deflection of the wingtips is about 0.01 meters.


Local tensions
The maximum tensions can be divided into positive and negative, also tension and compressive.
Maximum tensile stress: 0.552 N/mm2
Maximum compressive stress: -0.626 N/mm2


Local normal force
The maximum local force is almost -2,000,000 N. The number doesn’t really give extra information, but the shading shows a better division of the forces.


Conclusions
One of the first conclusions is:
Bamboo is strong.
The pavilion has a lot of potential, because the stresses stay well below the maximum allowed levels.

Next conclusion to be made is that the model isn’t perfect yet. It needs lot of improvement. The following things will be altered:
1. The size of the pavilion
2. The dimensions of the bamboo
3. The loads on the pavilion
Grasshopper and Rhino will be used for 1
DIANA will be used for 2 and 3

1 opmerking:

  1. Jaap,

    Seems to be going well. Which improvements/alterations do you still plan to include in the report and final presentation? All three, or will you need to make a selection. If the last, please make the selection early and argue it. Don't just have it be depending on progress and time.

    Best,
    -Rudi

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