Source: Microsoft Word
Constructing Environments Logbook Abhishek Rajendran Student ID: 698670 Tutorial No. 4
WEEK ONE JOURNAL
CHANGE OF PLAN:
Due to time constraints, and our current tower’s lack of rigidity, we decided to change the design of the tower to the one depicted below in Figure 4 below.
7/3/2014 COMPRESSION ACTIVITY: Using MDF blocks, we had to construct a tower that was approximately 6 feet high, and capable of fitting a toy animal inside without collapsing in on itself. INITIAL PLAN/IDEA:
Our initial idea was to build it with crisscrossing MDF blocks much like how bricks are used in everyday construction for many buildings believing this to be a safe option due to its widespread use.
Figure 2 Figure 4 Figure 3
Placing the blocks in the planned arrangement proved difficult as it was often knocked down with nothing to hold them together. This meant that we were not sticking right to the plan as shown in Figure 2 and 3 above with there being gaps between blocks. This resulted in less than wished stability, as there was no real clear path for any load to be transferred to the ground, or for the equivalent reaction force
In order to have stronger supports along the walls, we decided to have two layers of blocks rather than just the one as depicted in Figure 5 below with one side of the tower open to accommodate the toy animal. This decision was taken purely on the belief that it would aid the tower in distributing the load more evenly, thus allowing it to hold a greater mass.
The instability of our revised design due to the lack of compression on the blocks became known to us when continuing to build the tower higher. A column collapsed; unable to hold the blocks above it as shown below.
Rather, if the initial design of the tower was stuck to, and carried out to reasonable effect, it would have been more effective in holding a large mass. There would have been greater compression of blocks throughout the structure due to the weight of the live load pushing down, and with no room for blocks to move, and thus no weak points within the tower, it would have been able to transfer that force straight into the ground. As is shown below in another group’s tower where even with blocks being removed, the structure could still hold a considerable mass.
The gaps between the blocks mean that there is room for the blocks to move when a load, force or pressure of any quantity is placed on them. The one block moving causes blocks both above and below to also shift, thus causing the whole tower to collapse. Lack of time meant that we could not make any more changes to the design, but instead had to continue with what we had.
Having to also meet the requirements of an arch that stretched across the length of the sides, we created a flat roof. The end result being an average sized tower with a bit of the side having collapsed. However, when some weight, in this case a water bottle was placed on top of it, the entire tower collapsed. Being a result of as discussed before, the lack of compression and the blocks being too far apart meant that it allowed for them to bend and thus compromise the integrity of the tower. With every gap within the structure being a weak point for the force to travel through to the ground, the tower crumbled when the smallest change was made to its overall load.
(Figure 9 & 10 sourced from Bow Vacharussiriyuth)
Figure 9 Figure 7
WEEK TWO JOURNAL 14/3/20142 FRAME ACTIVITY:
Using a strip of Balsawood 10cm x 60cm, to build the tallest possible frame for a tower that is stable and able to support it own weight (dead load).
Cutting it into 20 individual pieces, we wished to build a pyramidal type structure with a triangular base, believing that a thicker and stronger base would allow us to create a taller structure. We had originally planned on using a glue gun, but due to being unable to get one in time, we settled for masking tape.
CONSTRUCTION: Figure 2
The triangle base was chosen as a triangle equally distributes the compression forces of the structure above and as all sides are of equal size, they all have equal size, and thus one is less likely to buckle relative to one of the others. Maintaining the triangular shape throughout the frame of the tower was aimed at ensuring that like the base, all parts of the tower would have the same even distribution of load, and thus prevent it from collapsing under its own weight. Moreover, but slowly making each triangle smaller, we wished to angle the tower towards a central point at the top, ensuring that each level was lighter than the level below and thus making it easier for the tower to maintain its own weight.
CHANGE OF PLAN:
Despite our efforts, the upper layers of the tower were still too heavy, and resulted in the bending of some levels as shown in Figure 4. Though due to the extended base, the force was still being distributed sufficiently to ensure the entire structure did not break, or fall over. Therefore, we chose to create a truss of sorts within the frame of the structure by converting the parallelograms into triangles with the use of bracing. However due to a shortage in sticks, we were unable to do this to all sides of the frame, thus us choosing to alternate the side upon which to place the bracing every level as shown in Figure 3. Figure 5
However this was insufficient still as the dead load of the tower was too great for the handful of braces that were placed to make a lasting impact with the top of the tower still bending (Figure 5). The lack of proper planning initially meant that we were unable to provide adequate support to the frame to prevent it from buckling. As a result, we resorted to using masking tape as a defacto brace as shown below.
Figure 7 One of the other groups who managed to create the tallest tower in our tutorial, chose instead to create a slim tower with regular bracing. The slim design minimized the horizontal (lateral) forces on the structure making it less likely to bend over. The regular bracing worked alongside the slim design by creating a rigid frame that was unlikely to buckle as weak points were minimized. Though this would make the whole structure topple over if the load was beyond what it could hold, by extending the base beyond the actual structure, it provided stability to the whole frame by dispersing the load over a greater area. (Figure 2, 4 & 10 sourced from Bow Vacharussiriyuth)