Knowledge map of week 1
Studio 1 – Compression (hollow tower constructing) Our team chose an approximate rectangular shape which we thought can best fit the shape of the object given by tutor, has the least space wasted and costs the least amount of materials (MDF). Plus, as our base was the smallest among three groups, it actually saved our time so that more time could be spent on wall rising.
When building the walls of the tower, we chose stretcher bond, which is most frequently used in real building constructing because it has the longest load path – with a longer pathway, the load is more separated (the shadow shows the areas in which loads are separated) and therefore the structure becomes more stable and can hold more load (ref: studio 1). A technical problem showed up when we created the opening – in order to make it wide enough to let the object get through, we need to tie up at least three bricks horizontally with rubber band, but it would become very unstable when more bricks are loaded onto it because the three bricks are not strongly compressed together and they would break up easily from the crevices between them. Thus we did not build an enclosed structure but left it semi-closed.
During the deconstruction process, we found that the most easily-removed bricks are either on the open edges of the walls, or at the turning corners where the walls change direction. The latter is because the plane walls are the main support of the whole structure and thus the corner bricks are the weakest parts which do not bear much load as the plane walls do. The marginal bricks are even easier to remove because they are only compressed at one end.
At first we were just making holes within the structure, but after an accidental crush, the structure then became shuttle-shaped with a wide body and a relatively narrow base. This is probably due to the strong bending stress (ref: 2.14 Ching, â€˜Beamsâ€™) created by the stretcher bond, and also because the base is wide and firm enough to hold up the entire structure.
The final collapse happened when we tried to remove some of the bricks from the middle part, which eventually caused a shift of the gravity center and thus the whole body biased to one side and fell down.
Comparison with the other teams: This teamâ€™s structure is not very high but must be the strongest among the three groups. It has a base shape between circle and square, which behaves as a two-way system (ref: 2.19 Ching, â€˜Structural Unitsâ€™) that spread the load equally in four directions. Additionally, they thickened the base by adding several more layers of bricks both vertically and horizontally, thus the load path is even longer and the base is even stronger. Their walls are also built in a different way, laying bricks facing two directions alternately, to make it more efficient to build the tower higher. However, as the contact area between two brick layers becomes smaller, the stability of the whole structure is also declined.
This team made a circular base for their tower, which uniformly spreads the load in all directions to make the foundation stable. It is also a large base which can bear more loads and thus theoretically the tower can be built higher. However, the grandness of the base also causes some problems, including a waste of space and materials, and a much longer constructing period, which actually limited the final height of their tower. Their walls are also based on stretcher bond. And they created an opening which we did not have. Yet they did not upload many bricks onto the opening either, probably because they met the similar problem as we did.
Knowledge map of week 2
Studio 2 – Frame (balsa wood tower constructing) This time the three groups coincidently chose the same equilateral-triangle instead of square base, because triangle is relatively rigid and stable. Also, among all polygons, triangle has the least sides so it can help reduce material usage (ref: 2.17 Ching, ‘Frames & Walls’).
Our team decided to build a triangular prism. To increase its stability, in each storey, we joined every top vertex with the mid-points of its corresponding side, so that three truss frames (ref: 2.16 Ching, ‘Truss’) can be created within one single storey. In this case, the load pressed on each vertex (except for the ones on the ground or at the top-end of the tower) can be separated into four different pathways. In addition, we joined the three spatial sticks together to further separate the load, and in the meantime, when one of the three sticks is overloading and tends to bend, the tension provided by the other two can help prevent it from deforming.
To prevent the three vertical legs from moving and strengthen the base, we added a small piece to each base corner, perpendicular to the bisector of that angle, and then glue the four pieces all together to create a strong joint.
Due to the lack of super glue, we had to try another two ways to join the sticks, using pins and tape respectively. Pin connection is not suitable in this case because the materials are thin balsa wood sticks, which are very crisp and can be easily broken when drilling holes on them. Super glue is the best choice as it can realize butt joint which is ideal for light materials like balsa wood (ref: 2.30 Ching, ‘Joints & Connections’). Tape doesn’t fit this structure either because we were building a three-dimensional structure but tape can only work well on a plane. Yet tape can be very useful for two-dimensional joining, especially when joining three sticks together to make a right angle, because it actually creates a triangular shape at the corner to make it a rigid frame. The following shows how to make the best use of tape joint (based on experiments in studio 2):
Comparison with the other teams (1):
This team made a complex structure with four different bracing patterns to reinforce the tower, namely K-brace, cross bracing, Knee bracing and the simplest one-member brace (ref: 2.22 Ching, ‘Lateral Stability’). All of them are based on triangular frames to spread out loads and make them rigid.
The final structure is bamboo-shoot-shaped, with the storeys becoming narrower as the tower grows up. Unlike prism ones, this structure has bevel sides in some storeys. Because those bevels have the same length, they need to have very similar inclination angles to make the top plane even. Obviously this requirement is hard to achieve manually, and that’s why their tower biased to one side for several times. However, since the materials are very light, the slight shift of the gravity center didn’t matter a lot. Thus their tower finally grew very high and reached the ceiling.
They cut the materials into very thin pieces, which actually lightened the dead loads provided by the self-weight of the structure (ref: 2.08 Ching, ‘Loads on Buildings’).
Comparison with the other teams (2): This teamâ€™s structure is a combination of a few separate triangular prisms, and each of them is a completed frame without any shared side with others. This means those sections can be built separately at the same time and thus the constructing process can be much more efficient. The challenge is to make sure the base and top of two adjacent storeys have the common mid-point or center of gravity, so that the whole structure can stay steady with a gravity center right in the middle as it grows up.
Similarly, they also chose a K-brace-like frame to strengthen the tower walls. But they made a difference by inserting a right-trapezoid-shaped frame to each side plane, which meant there were three triangular frames within one side plane and this structure should be the most stable one among the three groups (ref: 2.22 Ching, â€˜Lateral Stabilityâ€™).