Dome and Bridge

AR1327

STRUCTURAL PRINCIPLES

ASSIGNMENT 3

DOME & BRIDGE

A DESIGN COLLABORATION BY: ESTHER TAN SZE ERN A0185878A JOSHUA ANDREW DE SOUZA A0184272A LEE HONG XUAN A0169997W TENG YING SHI A0192379N

CONTENTS

1.

IN TR O D UCTIO N

7

2.

G E O M E TR Y & M O D ULE S

9

M ATER I A L S HAP E S I ZE LAYERS

11 13 15 19

S TR UCTUR E 1 : D O ME

23

DES I GN DEV ELOPM ENT M ODULE CONNECTI ON LOADI N G TECHNI CAL DR AWI NGS

27 29 33 39 40

S TR UCTUR E 2 : B R ID G E

45

DES I GN DEV ELOPM ENT M ODULE CONNECTI ON LOADI N G TECHNI CAL DR AWI NGS

49 51 55 63 66

2.1 2.2 2.3 2.4

3.

3.1 3.2 3.3 3.4 3.5

4.

4.1 4.2 4.3 4.4 4.5

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6

1.

INTRODUCTION

“There are two causes of beauty – natural and customary. Natural is from geometry consisting in uniformity, that is equality and proportion.

Customary beauty is begotten by use, as familiarity breeds a love of things not in themselves lovely…”

- Sir Christopher Wren

The idea is to create a light-weighted structure (both Dome and Bridge) that is able to sustain the load of two drink cans using paper sheets.

Therefore our group’s focus is mainly on how a singular module can tessellate to form both the dome and the bridge structure. We first started to resolve the dome structure, before moving on to the bridge. Through many iterations, failures, and improvements, the main issues were always trying to strengthen the flimsiness of the paper and distribute the forces equally.

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GEOMETRY & MODULE

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2.1

MATERIAL

Given the options of wood, paper, and string (from the brief), we picked paper as we wanted to test a material that is not conventionally used in structures.

When the sheet of paper is flat, it is floppy and weak in all directions, hence not capable to withstand any load. When it is folded or layered, the paper is then able to withstand tension and caompression forces.

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2.2

SHAPES

We first explored a V-shaped module stacked in a parallel configuration to form the dome structure. Even though this V-shaped module were of the same size and shape, the slots had to be cut accordingly to different angles in order to form the dome. This configuration itself hence pose the problem of the module not being modular.

Working from the triangular V-shaped form, we redesigned a modular form for our second prototype model. From here we explored both 4-sided and 3-sided slot modules. Although tension were created using both modules, the 4-sided module will ultimately end up in a rectilinear or arc form, rather than a dome structure. On the other hand, the 3-sided module showed potential in forming a dome structure

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2.3

SIZE

It started off with a 10cm X 10cm module. In which it did not manage to support the load.

Therefore we reduced the size of the module to 9cm & 8cm. This is to increase the quantity of the modules in the overall structure to increase the vertices and edges, providing more and dispersed structural interactions. The size of modules were minimized to increase structural support on each module where the load can be transferred evenly. It created more resistance between each module and strengthens the overall structure of the dome.

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2.4

LAYERS

After the first mockup, we see that single layered modules are unable to withstand the load of the cans due to its lightweight structure. In order to create volume to it, we tried to mirror the module. However, it further weakened the structure by adding weight to the modules above, since both of the modules are now sharing the same web structure. The increment of the web’s height also caused buckling. We then tested stacked layering which allowed the load to be transferred to the flange of the top module, down to the web of the module and then transferred to the web of the second module thus creating a more robust and strong structural system which was able to support the given load.

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STRUCTURE 1

DOME

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26

3.1

DESIGN & DEVELOPMENT The loads were unable to distribute evenly to the ground as the last module should be designed to distribute the load evenly off the flat surface onto the ground.

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3.2

CONNECTION Slotting and weaving

There was no slotting or interlocking system between each module, causing the web of the module to flex outwards. Thus, the dome was not able to support itself and will sag.

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3.3

LOADING

A masonry dome produces thrusts down and outward. The optimal shape for the dome of equal thickness of the module provides for perfect compression.

The hoop force of the base module increases the compression at the top and tension at the base. This allows the compression forces to create a dome shape with a volume beneath it.

When pressure is applied to an edge of the triangular module, the force is evenly distributed and it transfers the pressure to the other two sides of the adjacent triangular module. That cascading distribution of pressure is how the modules efficiently distribute stress throughout the entire structure.

The edges of the modules transfers its load to the web structure, then through the opening of the adjacent module of the web structure. The loading occurs throughout.

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3.4

MODULE

The dome is a rounded vault made of shells of triangular modules.

By multiplying the modules, it creates a double volume and strengthens the web. The top module is wider than the one below as it interlocks in the 3 edges and it forces the entire structure to to be curved up into a dome.

After many test and iterations, the height of 1cm for the module was optimal to withstand the load of the dome compared to other heights and lift the dome to the desired height. Furthermore by increasing or decreasing the height of the module, it will not be able to achieve the same structural tenacity as it will flex and warp.

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PLAN TOTAL MODULES : 122

40

ELEVATION

41

STRUCTURE 2

BRIDGE

45

48

4.1

DESIGN & DEVELOPMENT The same method was utilised as the dome to make the bridge which is slotting the modules horizontally. The whole structure will be supported by the two foundations at the end. Even with 2 layers per module, the span was too light and weak to even support its own weight.

We also tried to alternate the modules, to provide more tension within the whole structure but we still had issues on how to resolve the base module and stopping the whole structure from sagging and flexing.

We decided to try another option while keeping the alternating modules, which is to slot the modules vertically instead horizontally(used for the dome structure). This changes the distribution of the forces as it is using the same approach as a normal bridge structure and not the one of the module.

We tried to reinforce the whole structure by having 2 layers joined together by dowels, but it did not manage the support its own weight due to the large span (more than 60cm) and the intersections between each module were weak, especially the area around the end of the span. Thus, to strengthen the whole structure, we had an additional layer between the existing layers at the base and near the span.

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4.2

CONNECTION By using a dowel that funnels through 2 or 3 layers, it causes the forces to distribute evenly towards the base of the modules.

This also reinforces the modules and maintains the interlocking systems between each module, especially at weakened areas such as modules near the span.

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4.3

LOADING

The span of the initial bridge design was thin in relation to the width, causing it to sag and eventually collapse. We then redesigned the bridges foundation on both sides to withstand more weight by adding an additional layer of modules.

The bridges span was also strengthened with the addition of modules at the buckling points.j Bridges support loads through tension and compression.

Structures need to dissipate or transfer these forces to be able to effectively hold immense loads.

We decided to incorporate the arched bridge. Instead of the having loads that act vertically downwards at the centre, loads in arched bridges are transferred outward along the curve of the arch to the members at both ends. Employment of an arched bridge is capable of withstanding significant loading which meant more room to explore the bridge’s form and design.

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4.4

MODULE

When doing the module layers for the bridge, we originally tried out tessellating it the same way as the dome, which was having the modules face one side. But this causes the layer to be flimsy and end up curving. To solve this, we alternate the modules layer by layer and the module’s edges and opening creates a pushing and pulling action. This strengthens and holds the whole structure together. Thus, this allows the forces to be balanced out laterally.

63

64

65

PLAN

FRONT ELEVATION

66

SIDE ELEVATION

67

68

69