Constructing Environments Log Book Interim
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Transcript of Constructing Environments Log Book Interim
MATERIALS Obviously construction materials need to be suited to their purpose. When deciding what materials to use in a particular constructions we need to consider strength, stiffness, shape, material behaviours, economy and sustainability The forces that will be acted upon the materials also needs to considered; whether there will be compression or tension forces involved and from which direction. Different materials will be suited to different parts of a construction, for example the strength, stiffness and rectangular tridimensional shape of bricks make them suitable for building walls (Newton, 2014b).
Bluestone (basalt) is used extensively as a building material in Melbourne, in both modern and early constructions. This is because it is widely available and sourced from the local area, making it a more sustainable and economic material to use. It is a volcanic rock that is hard to fashion, making it ideal for building foundations and paving stones. However over time it can show water and impacts damage, as seen by observing the wheel ruts in the old cobblestone lanes in Melbourne (Walking The Constructed City 2014). As well as having a structural function in the city, bluestone is what gives Melbourne its dark grey aesthetic.
(Ashworth, 2013)
(Groves, 2014)
Impact damage: wheel ruts from carts Shape allows stacking
Hollow tubes along brick giving mortar a better hold meaning more stability
Stiffness of brick means shape doesn’t change
FORCES Definition: A force is any influence that produces change in the shape or movement of a body Forces have both magnitude and direction, which is represented in the way you draw them. The length of an arrow correlates to its magnitude, and its direction is shown through its position in the space. (Newton, 2014a)
(Rigney, 2013)
Tension and Compression Forces Tension: This is when the particles of a material are pulled apart by an external load, stretching the material. The amount of elongation the material undergoes depends on the magnitude of the load, the stiffness of the material and cross sectional area. Compression: This is when particles of a material are pushed together by an external load, resulting in the material shortening. (Newton, 2014a)
(Glade, 2010)
Compression holds the arch up. The
force is transferred downwards
Because the material is being pulled tightly, tension is applied. The load is transferred to the masts and ground.
BUILDING OUR TOWER Material: The material used (MDF blocks) suited our purpose as it was light, rectangular with flat surfaces making it easy to stack, withstood compression forces and rigid. Compression forces: Compression forces act upon the MDF blocks in the tower. As the tower gets higher the self-‐load increases, meaning that the blocks are compressed together more tightly. This prevents the tower, and entrance, from collapsing. Brief:
• Build a tower that can fit a toy elephant so that it can turn around in the space comfortably
• Has a doorway for the elephant • Is as tall as possible • Using MDF blocks only
An unbroken circular base is easy to construct and uses minimal blocks. The shape allows the elephant to turn around, as required in the brief. The entrance is added in the final stages of construction.
The tower is built directly upwards, without tapering at this stage, to form a strong, supporting base. Using one layer of block in the wall is more economical but not as stable as building a thicker base.
Alternating to orientation of the blocks helped to increase stability. When the blocks faced this way the wall becomes thicker and more stable. At this point the tower is just higher than the elephant so efforts were made to further stabilize the structure before tapering.
Due to inaccurate construction the tower developed a straight wall and a tapered wall. This meant that more of the load was distributed onto the straight side, putting more pressure on it. To distribute the load more evenly, effort was made to straighten continuing construction so more of the load would be transferred to the tapered wall.
The entrance was constructed as the final stage, on the tapered side of the tower. If the entrance was built into the straight wall of the tower, it would weaken the load bearing wall and the compression forces would cause it to collapse. The straight wall acts as the main support of the tower.
Load disperses at wider base
This structure has a thick, multilayered base to give it great strength. The shape of the base is almost a dome shape, which distributes the load
around the whole structure. The side with the entrance is weaker because there are no blocks for the load to be distributed onto. Although the base is strong, it isn’t as economical as a smaller base, and only allows a smaller tower to be built on top as a concentrated load.
This structure is built with a square base and a tapered circular roof. The entrance is built in the corner rather than the centre and has been reinforced by filling any gaps with blocks. However, the entrance isn’t wide
enough to allow the elephant to enter.
This tower also has a square base and the blocks forming the entrance have been stacked directly in line with each other to create a neater
entrance. At this stage the load isn’t being transferred to the blocks in the entrance from above, so the strength isn’t being tested.
The construction process started from base of tower. The base uses a triangular shape, as this is more stable than a rectangular base and is more economic as it uses less materials. Our design has a wide base at the bottom tapering to a point and taking advantage of the triangular shape as it reaches this point.
Our structure is a frame structure with fixed joints. Having fixed joints meant that all the joints impacted on each other and it was important to try and keep the lines of the frame linear. It also meant that as the tower increased in height bending occurred at the joints and in the frame itself. This bending compromised the stability of the structure.
The construction system of the tower was purely structural, and it would not have been strong or stable enough to allow for an envelope or mechanical system to be added to this scaffold. This is partly due to the weak joints and partly to do with the efficiency of the material.
Triangle: A compression shape Bending under self load
Brief fulfilled: Reaches roof
Point of collapse
Efficiency of material: Thin strips of balsa wood were used in the construction. In the process of cutting the wood into strips, some were weakened due to the tendency of the cut to follow the grain.
Our tower could have been strengthened with more bracing, if we had enough materials to do this effectively. The sticks used in the construction were long and so prone to bending. Shortening the length of the building components would have made it more stable but would have required more bracing.
The tower buckled at one of the vertical joins towards the bottom of the structure. This caused the join where the triangular frame and the vertical supports met to also buckle and the structure subsequently collapsed. Triangles kept their shape while rectangles proved to be weaker shapes.
The material was suited to its purpose because eit was light but the flexibility, although useful as it allowed bending while using fixed joints (instead of buckling), also meant that the structure became unstable and couldn’t withstand a large load. Originally glue was used to create the joins but masking tape proved to be stronger and quicker. Tape was efficient for and linear joins but less efficient for more complicated joins (at the corners).
Fixed
Join
Bending – more reinforcement needed
Narrower, more economic, cables crucial to stability (ABC, 2013)
All other towers in the tutorial were based on the triangle framework in some way, showing intuitive knowledge of the strength of triangles in construction. This one used a network of shorter supports to brace the structure and increase strength and stability. However, it was less economical (also because it didn’t taper) and didn’t reach the required height of the roof outlined in the brief. This was because there was more labour involved with more joins to complete.
This structure was similar in design to ours but with smaller dimensions of the base, increasing the stability of the base structure. The tower tapered to a point at a lower height meaning that the spire had to be longer, and so prone to bending under the forces of gravity as ell as any external forces (wind, human contact). Similarly they didn’t use any form of bracing and had a vertical spire at the top of the structure to increase height without significantly increasing the load.
Below is a real life example of a frame tower, in the form of a radio tower. Similarly the structure is triangular in shape but it has more bracing. It also has pin joints at the base which allows the frame to resist bending in windy conditions, or when temperature changes cause the metal to expand and contract. The structure uses a combination of compression and tension forces for stability.
GLOSSARY
Forces – defined my direction, sense and magnitude Sense (+,-‐) Direction – angle, position in relation to space
Isotropic – materials that display similar characteristics no matter which direction the forces are applied in
Anisotropic – materials that display different characteristics depending on which direction the forces are applied
Embodied Energy – total energy used during all stages of a material’s life
Reference list:
ABC. (2013). Radio Australia's transmission site in Shepparton, Victoria. Retrieved 17th March, 2014, from http://www.abc.net.au/news/2013-‐07-‐02/radio-‐australia-‐transmitter-‐shepparton/4793766
Ashworth, B. (2013). Why Double Brick. Retrieved 10th March, 2014, from http://www.anewhouse.com.au/2013/01/why-‐double-‐brick/ Glade, P. (2010). High Style at Burning Man: Arhcitecture of Black Rock City -‐ Sparseland. Retrieved 10th March, 2014, from http://news.cnet.com/2300-‐
13772_3-‐10010457-‐5.html Groves, M. (Producer). (2014, 10.3.14). Melbourne's Bluestone. [Video] Retrieved from http://www.youtube.com/watch?v=CGMA71_3H6o&feature=youtu.be Newton, C. (2014a). E N V S 1 0 0 0 3 : Constructing Environments: Basic Structural Forces (i)
. Retrieved 6th March, 2014, from https://app.lms.unimelb.edu.au/bbcswebdav/courses/ENVS10003_2014_SM1/WEEK%2001/Basic%20Structural%20Forces%201.pdf
Newton, C. (Producer). (2014b, 5.3.14). Introdcution to Materials. [video] Retrieved from http://www.youtube.com/watch?v=s4CJ8o_lJbg&feature=youtu.be Rigney, M. (2013). The Tales of Gemen the Antiques Dealer: From Idea to Publication. Retrieved 7th March, 2014, from
http://www.blackgate.com/2013/08/06/the-‐tales-‐of-‐gemen-‐the-‐antiques-‐dealer-‐from-‐idea-‐to-‐publication/
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