Knowledge map of week 1

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.

Studio 1 – Compression (hollow tower constructing)

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.

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.

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, ‘Beams’) created by the stretcher bond,

and also because the base is wide and firm enough to hold up the entire

structure.

Comparison with the other teams:

This team’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, ‘Structural Units’) 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.

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.

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.

Knowledge map of week 2

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’).

Studio 2 – Frame (balsa wood tower constructing)

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):

Turn over Repeat

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.

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’). 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.

This team’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.

Comparison with the other teams (2):

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,

‘Lateral Stability’).

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.