Log book

THE UNIVERSITY OF MELBOURNE

Constructing Environments Log Book Name : Trishya John Student ID Number: 699579

Week 1 – Introduction to Construction Knowledge maps Loads on buildings (Ching, 2008)

Structural forces (Newton, 2014)

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Materials (Newton, 2014)

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Site Analysis (Ching, 2008)

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Theatre Session

We were introduced to the concept of loads on buildings in our first theatre session where we were given a single sheet of blank A4 paper and tape and asked to build a structure that can support a brick using only those materials. I formed a four point structure as shown below, which I strengthened by folding repetitively. I was unable to test the structure at the lecture, so I performed a test once I got back home by checking if the paper structure was able to support the load of all my textbooks.

Shape allows an even distribution of the load of the textbooks throughout the structure

It was able to support my textbooks when the thicker side of the structure made contact with the ground, but not when the thinner side made contact with the ground. One of the things that I was able to learn from this experience was that it was crucial for a structure to have a very strong base in order to support an immense load. I also realized that one of the reasons why my structure was successful was because the symmetrical shape of it may have enabled an even distribution of the load of the textbooks throughout the structure. These were some of the key elements that I tried to apply to our structure that was built during the studio session.

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Studio Session Construction procedure

In our first studio session we were divided into groups of 3 and given blocks of the same size and shape made of MDF. As this was a compression challenge, blocks were an efficient building unit as blocks are commonly used in structures that rely on compression forces, such as arches. We were then told to make a tower as tall as possible that could accommodate a toy horse provided by our tutor, which meant that we had to integrate an opening into our structure. Our first step was to measure how high the opening had to be for the object to be able to enter the structure, and we did so by stacking the blocks one on top of each other next to the horse until they were a bit taller than the horse.

However, we then realized that constructing the tower by placing the blocks as shown on the left would result in a structure that was very likely to collapse due to its instability, so we then decided to place the blocks flat on top of each other as shown below. We then had to re-estimate the height of the horse using the height shown in the image on the left.

Estimating height of the object

Re-estimating height of the object

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We then decided to slightly change the laying of the blocks and place them the conventional way bricks were laid in a building instead of merely stacking them one on top of each other. This would have been more stable than originally planned, as the load from a block will be transferred to two bricks below it instead of just one and thus be spread out more evenly.

Original block laying technique

Modified block laying technique

Aimed height of the opening

Foundation of the structure

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We then started to build the structure as shown below. Our aim was to pack the blocks as tightly as possible in the first ten rows to create a stable base and then decide on how to change the way the blocks were laid once the structure gained a reasonable height.

Packing the blocks tightly together will result in more blocks being laid at the base, which then increases the compression forces, causing the blocks to be compact. This is what will ensure stability for the whole structure.

However, this layout of the structure had to be changed once again. This was because the object had to be rotated once it was inside the building in order to make it fit inside the structure. Therefore, there was a risk of the structure collapsing if we rotated the horse while sending it into the opening.

Details of the block laying technique – high compression forces due to tightly packed blocks

We then decided to remove the blocks from one side of the structure to form an opening as shown below and covered the gap made in the original building. This would then resolve the issue of the object being able to enter the structure without having to be rotated.

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Modified layout to accommodate object

Even though we had now developed a structure that could accommodate the object, we still faced the issue of bridging the gap created in order to form a doorway. We attempted to stack the blocks in a ‘staircase’ manner on either side, but the blocks fell after about two or three of them were placed, due to the increasing load and the inability of the blocks to support them, so we were unable to create a bridge as the gap was too wide.

Our next idea was to warp the structure in order to bring the gap closer so that a fewer amount of blocks would have to be used in order to form a bridge.

Warping structure – decreases compression forces at base

Attempt at building a bridge

We attempted to bridge this much smaller gap by stacking the bricks in a similar manner to before, but unfortunately we were unsuccessful again. As we could not make the gap smaller, we decided to focus on making the structure as tall as possible. Due to the limit on the amount of MDF blocks we were given, we decided to use less blocks to build the rest of the structure. I was able to conclude that due to the fact that the blocks were packed tightly for approximately twelve rows, the base would be strong enough to produce a stable structure that was capable of supporting a heavy load. I based my conclusion on the paper structure I made in lecture 1, which was thick at the bottom due to the folds, and thus was able to support the weight of all my books. We then continued to lay the blocks on the structure, but left large gaps in between so that we would be 8

left with more blocks to add height. As the blocks are now spread out towards the top, the compression forces of the structure decrease with the height.

Figure 1: Increasing the height of the structure

We completed our structure by following the same pattern established previously.

Final structure

Compression decreases with height as blocks are spaced widely Deconstruction procedure Doorway – did not collapse due to distribution of loads through the structure

Figure 2: Structure during deconstruction process

We were then told to remove blocks from the structure one at a time in order to test the stability of the building. In the process, I was able to find a method to create a doorway.

Although we had considered this idea before, we did not think it would work as we assumed that the structure would collapse, and we only realized that it would have worked during the deconstruction process. I simply removed all the blocks in one area and created a large gap, as seen on the left.

The fact that our structure did not collapse even though all those blocks were removed indicates that the loads were transferred through the structure in a manner that was able to prevent the 9

structure from collapsing. It is possible that our structure may have been able to support a heavier load, if it had remained in a rectangular shape. This final structure may have encountered difficulties with doing so because warping the structure pushed the blocks out of proportion in the base, which may have reduced the compression forces that would have been much stronger if the blocks were packed tightly together.

Figure 3: Load path diagram of structure with a few blocks removed

Figure 4: Comparison of compression forces between original structure and warped structure

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Comparison with other groups

This group had built a structure that was most similar to ours in terms of the way they laid the blocks, and the fact that they packed the blocks tightly for the first few rows and incorporated gaps in the higher rows. The only differences were the shape of the building and the fact that they had managed to successfully integrate a doorway into their structure.

Strong compression forces enabled structure to support a load of over 5kg, which was done near the end of the studio session

This was another structure created by one of the groups, which had a very different block laying technique and shape compared to the structures of the other groups. It seems as though their technique of laying blocks, although aesthetically appealing, may have used a relatively larger amount of blocks compared to the conventional brick laying technique that all the other groups adapted.

Even though their structure was able to accommodate the object, they too appeared to be unsuccessful in bridging the gap.

The blocks are packed tightly together, which will increase the compression forces in the structure

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Although the block laying technique is not very visible in this photograph, it appears that they adopted a similar method to our structure. However, it appears that they might have encountered difficulties during the construction process as they too were unsuccessful in creating a doorway, and were not able to create a tall structure. The blocks appear to be packed tightly together and they have followed this method to create the entire structure, which means that the compression forces will be high.

Week 2 – Structural Loads and Forces Knowledge maps Structural joints (Newton, 2014)

Structural systems (Newton, 2014)

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Common Environmentally Sustainable Design Strategies (Newton, 2014)

Building systems (Ching, 2008)

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Theatre session We covered the importance of how trusses and a bracing system are key elements in supporting loads in various structures. This was illustrated by various students having to build a truss on a plastic cup with straws which had to be attached to the cup with pins. These are diagrams of two structures that were made during this exercise, one which was successful and one which was not.

Successful structure This structure was able to support a load effectively because bending the straws provided 8 paths for the load to be transferred to the ground. Folding also provided a much shorter distance for the loads to travel, and ensured structural stability.

Unsuccessful structure This structure was unable to support a load because the long straws were unable to support a load easily, which caused the whole structure to collapse. There were also only four paths for the load to be transferred.

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How unsuccessful structure can be improved

The unsuccessful structure can be improved by introducing a bracing system as shown in the figure above. The system is in the shape of triangles, which is a difficult shape to distort, and therefore adds more stability to the system. It also provides more paths for the loads to be transferred to the ground.

The concepts illustrated in the lecture were useful for the frame challenge in the studio session, as they illustrated the different ways in which long, thin members could be used to effectively carry and transfer loads.

Studio session Construction procedure This week’s studio introduced the concept of a frame structure, and to illustrate this, we were told to build a frame tower out of only 20 strips of cut balsa wood in groups of 3. The tower had to be as tall as possible, and we were encouraged to experiment with different types of joints. We were told that the towers would have a load placed on it once they were completed to see at which points they fail. Balsa wood was an efficient material for this challenge as the strips were light and had a low density, which are properties that would have been needed to make a frame structure. In order to save strips of balsa wood, we decided to make the tower in the shape of a triangle instead of a square or rectangle. We cut 3 pieces of wood, of 20cm each, and used them to form an equilateral triangle for the base. Then, we joined three strips of wood to each of the corners of the triangle.

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Sketch of structure we wanted

Foundation of structure

We then cut a second triangle with sides measuring 20cm and joined it with the three strips of wood that were stuck onto the first triangle.

The strips of wood were joined together by masking tape, which, in the context of this structure, can be considered a fixed joint. A fixed joint resists rotation and translation in any direction, and provides force and moment resistance (Ching, 2008), and as the structure was relatively stable with an additional successive level, we decided to continue using fixed joints.

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However, as the structure began to increase in height, we found that we had to add pins to the joints, thus creating pin joints, along with the fixed joints, as strips of joined balsa wood kept detaching, which suggested that just fixed joints were not strong enough to hold the members together. We joined the strips of wood with a pin, and then wrapped the pin with masking tape.

Fixed joint

Details of fixed joint

Structure is stable but a slight tilt can be observed due to weak joints

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Although we assumed that our combination of pin and fixed joints Details of pin joint were strong enough to keep the members in place, the tower began to twist and lean as it increased in height, possibly due to the increasing load of the structure.

This was an indication that perhaps the joints may have not been efficient enough to transfer the loads, possibly due to the way we had attached the members. The manner in which forces are transferred from one structural element to the next and how a structural system performs depends on the types of joints used, to a large extent (Ching, 2008). The addition of the pin may have also caused the member to fold backwards, based on the way we attached it, which may have also been a factor in causing the structure to twist because the joints were not stable enough to transfer the loads.

The members were also rectangular in shape, which results in uneven distribution of the load through the strips of balsa wood. This would have also been one of the factors that caused the torsion of the member, resulting in the whole structure twisting. If the members were in the shape of a square, there would have been a more even distribution of the load, resulting in less torsion.

Load through individual members

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Load path diagram of structure

As seen in this diagram, each joint will be connected to three members and will thus receive loads in three directions. If the joint is ineffective in transferring these loads, the whole structure will be unstable.

Due to the structure twisting and bending as a result of the joints failing, there came a point where the structure was unable to stand without support because it was unable to transfer the load effectively throughout the structure, which resulted in it being unable to support the load of the additional members.

This explains why the final structure was unable to stand without support

Our idea was to form a bracing system in order to prevent the members from twisting, so we cut a strip of balsa wood and connected it to two of the members that were twisting the most. However, it did not fix the problem since the twists were due to the joints, so we did not continue developing a bracing system.

Attempt at bracing structure 19

Lean in the structure can be observed clearly due to the increasing load

We finally added 3 more members to the 3rd triangle (excluding triangle made for the base) and joined them at the ends. These are images of the final structure which was, as seen below, unable to stand without being supported.

Structure without a support system

Point at which structure was unable to support itself

Structure with a support system

Deconstruction procedure The structures then had a load applied to them, in order to estimate at which points they started to fail.

Figure 5: Deconstruction procedure

As seen in the picture, the structure was bending at the joints when a load was applied. It was mentioned before that the purpose of a fixed joint was to prevent rotation of the members, but ours failed to do so because we connected the members incorrectly. This was why the structure was bending at the joints.

Bending occurring at the joints when a load is applied – joint should have resisted load

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Load path diagram of a section of structure during deconstruction process As the load increased, one of the members that were joined at the second triangle snapped at its mid-point. This was because the increasing load was causing an increase in the reaction force that was acting on the member. The two forces met at the middle, which then caused the structure to snap at that point.

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Comparison with other groups All of the structures built by the other groups had a member snap at its mid-point when a load was applied, due to the explanation given. However, as seen below, the members did not bend at the joints the way they did in our structure, because they consisted of more effective joints.

Less bending occurs at the structural joints when a load is applied – only the individual members bend. Structures all displayed a bracing system that would have reinforced the overall stability.

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Glossary of Terms (Ching, 2008) Beam – rigid structural members designed to carry and transfer transverse loads across space to supporting elements.

Brace - A diagonal tie that interconnects scaffold members (WebFinance Inc, 2014) Carbon footprint – measure of the amount of greenhouse gases generated during the fabrication, transportation and use of a particular product Columns – rigid, relatively slender structural members designed primarily to support axial compressive loads applied to the ends of the members Collinear forces – occur along a straight line, the vector sum of which is the algebraic sum of the magnitudes of the forces, acting along the same line of action Compression forces – an external load pushing on a structural member, resulting on the shortening of the material (Newton, 2014) Concurrent forces – have lines of action intersecting at a common point, the vector sum of which is equivalent to and produces the same effect on a rigid body as the application of the vectors of the several forces Dead loads – static loads acting vertically downward on a structure, comprising the self-weight of the structure and weight of building elements fixtures and equipment firmly attached to it Dynamic loads – loads that are applied suddenly to a structure, often with rapid changes in magnitude and point of application Fixed joint – maintains the angular relationship between the joined elements, restrains rotation and translation in any direction, and provides both force and moment resistance.

Frame – an assembly of vertical and horizontal structural members (WebFinance Inc, 2014) Impact loads – kinetic loads of short duration (moving vehicles, equipment and machinery) Live loads – any moving or movable loads on a structure resulting from occupancy, collected snow and water, or moving equipment Load path – the route a load takes through a structural system to reach the ground Masonry – building with units of various natural or manufactured products, usually with the use of mortar as a bonding agent

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Non-current forces – have lines of action that do not intersect at a common point, the vector sum of which is a single force that would cause the same translation and rotation of a body as the set of original forces Occupancy loads – result from the weight of people, furniture, stored material and other similar items in a building Pin joints – allow rotation but resist translation in any direction Point load– A concentrated load in a specific position on a structural member (WebFinance Inc, 2014) Rain loads – accumulation of water on a roof because of its form, deflection, or the clogging of its drainage system Reaction force – equal and opposite forces that resist an applied force Recyclability – potential for a product / material to be reused or transformed into a new product Roller joints – allows rotation but resists translation in a direction perpendicular into or away from their faces Site analysis – the process of studying the contextual forces that influence how we might situate a building, lay out and orient its spaces, shape and articulate its enclosure, and establish its relationship to the landscape Snow loads – created by the weight of snow accumulating on the roof Static loads – loads that are applied slowly to a structure until it reaches its peak value without fluctuating rapidly in magnitude or position Stability – the measure of the ability of a structure to withstand overturning, sliding, buckling or collapsing (WebFinance Inc, 2014) Structural joints – connectors used to joint structural elements Tension forces – external load pulling on a structural member, causing the material to elongate (Newton, 2014) Wind loads – forces exerted by the kinetic energy of a moving mass of air, assumed to come from any horizontal direction

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References Ching, F. D. (2008). Building Construction Illustrated (4th ed.). Hoboken, New Jersey : John Wiley & Sons.

Newton, Claire (2014). Introduction To Materials. Constructing Environments.

Newton, Claire (2014). Basic Structural Forces. Constructing Environments Newton, Claire (2014). Structural Systems and Forms. Constructing Environments Newton, Claire (2014). ESD And Selecting Materials. Constructing Environments Newton, Claire (2014). Structural Connections. Constructing Environments WebFinance Inc. (2014). Dictionary of Construction.com. Retrieved March 15, 2014, from http://www.dictionaryofconstruction.com/

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