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, ‘Beams’) 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 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. 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):
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.
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 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. 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, ‘Lateral Stability’).
Knowledge map of week 3
This building is a typical concrete structure, which is qualified as rigid and non-combustible construction. The reinforced concrete columns are laid out along a regular grid, because the structure is nearly square and thus two-way system of beam-and-slab forming would be the most effective and economic one. (ref: 2.19 Ching, ‘Structural Units’)
Similarly, the concrete columns supporting this underground car park are also laid out regularly in grids. Particularly, as the car park requires massive span for cars to move and park, all concrete columns are thickened at the top to make a funnel shape. Those thickened parts act as a transition between the top plate and the columns, transferring loads from top to ground in a more smooth way. (ref: 2.20 Ching, ‘Structural Spans’)
The photo in the bottom right corner shows the resealing paint on the top plate. Due to potential deformation of concrete elements, it is common to see tiny gaps between concrete slabs which would allow moisture to get in.
This structure is a steel trapezoid-shaped ladder. Nearly all of the structure’s weight is bear by the side wall and the two supporting beams in the bottom. Thus the two hanged beams at the top are not actually load-bearing but for visual purpose only.
The main structure is formed with ‘C’ beams and the supporting elements are wide-flange ‘I’ beams. Those steel beam types are supposed to be light-weight and material-efficient, and also show good quality in resisting bending forces and shearing forces. (ref: 4.16 Ching, ‘Steel Beams’)
This is a membrane structure, using thin, flexible surface to carry loads through the development of tensile stresses. Each membrane edge is connected to a pole using steel cables, transferring loads to the ground. (ref: 2.29 Ching, ‘ Membrane Structures’)
In the middle of the membrane there is a waterhole, through which rainwater can be transmitted downwards to the ground. The steel cables here are actually loose and are not providing much tensile stress, because the self-weight of the structure is already providing the downward force for equilibrium. Yet those steel cables are still useful in fixing the gravity center and preventing the structure from being unstable under lateral forces.
This structure is a decorating steel beam, with truss frames inside. It is a simple beam supported only at both ends, as it is a light-weight structure and only needs to bear its self-weight.
This indoor swimming pool is a simple structure built with steel rigid frames and two concrete walls on both sides. The steel rigid frames are left exposed. The two side walls are shearing walls, bracing the whole structure and protecting it from lateral forces like wind.
This tongue-like three-storie structure is an extended part of the main building. To hold the overhanging part, the whole structure needs to be long enough and have a reasonably long part being placed on the base, so that the gravity center can stay within the main building.
The bracing structures underneath the extended part are mainly cross bracings, using trusses to increase rigidity.
Knowledge map of week 4
Construction workshop – Beam spanning structure
The materials we got were three solid timber beams and a thin, hard plywood board. The beam structure made by our team is a continuous beam sitting on a series of solid supports, with the plywood board pinned on one side. (ref: 2.15 Ching, ‘Beam Spans’)
Compared with simple beams, continuous beams are supposed to have greater rigidity and smaller moments, and thus can bear more pressure. We place more studs in the middle to bear more pressing force. The plywood board on one side also helps spread the loads. Nails are pinned in two directions to make the studs tight within the wood frame, increasing the rigidity of the structure. (ref: 2.15 Ching, ‘Beam Spans’)
The structure bends under the pressure in the middle. Its deflection is not satisfying, around 15mm, because the continuous beam structure is weaker in bending moment. Thus instead of slowly transforming in shape before the collapse, this structure almost stays straight all the time until it suddenly breaks. Yet due to its rigidity, the maximum load goes up to 168kg. (ref: 2.14 Ching, ‘Beams’) The first crack happens in the plywood board because it is thinnest and holds the least load in the whole structure.
The tendency of the studs’ rotation results from bending stress – tension in the bottom and compression on the top. When the pin joints can no longer hold the bending stress, the studs would fall off. (ref: 2.14 Ching, ‘Beams’)
The natural knots and the points where nails are pinned in are the weakest points, which would break more easily.
Compared with other teams (1):
This team’s structure is formed by two thin plywood boards with a series of short wood studs in between. Yet some studs in the middle are not well fixed to the plywood and thus most of them fall off later, which means they do not bear much load in this case. Their main function then changes into linking the two plywood boards at both ends.
Thanks to the accidental loss of some studs in the middle, the plywood boards become very flexible and can be rotated easily. Thus it can have an incredibly strong bending moment and high deflecting level – the maximum deflection goes to over 100mm! (ref: 2.14 Ching, ‘Beams’) Yet due to the great flexibility, this structure easily reaches its maximum deflection and then cracks. Therefore it shows very poor quality in load bearing – only 45 kg maximum.
Compared with other teams (2):
This team’s beam structure is an open-web timber joist, using trusses to reinforce the structure. (ref: 4.20-4.21 Ching, ‘Open-web Joist Framing’)
An obvious twist can be seen in both top and side boards. Similar to the previous team, this is because thin plywood boards show good quality in flexibility and bending moment. The following graph shows how the members at the two ends, which are supposed to be zero-force members and carry no direct load, can actually create a moment to resist the bending moment and help maintain the shape of the whole structure. This structure combines the rigid framing of truss and the flexibility of plywood boards. Thus it shows good load-bearing quality and medium deflection– maximum 320kg and 65mm respectively.
A thin plywood board is added on one side of the structure, but in fact it does not bear any load in the beginning because it is only attached to the bottom timber panel. Yet when the top plywood board is bended under pressure, this side board becomes useful as it is flexible enough to be twisted, which actually helps buffer the compressive force.
Knowledge map of week 5
Our team’s structure is two-storie, with a kitchen on the first floor and a public restroom on the second. The overall structure is simple and direct, but there is a slope on one side of the roof.
The rooms in our structure are framed by stud walls. In those stud walls, each section is braced with a nogging in the middle, and every adjacent noggings are slightly different in height, so that a better quality in bearing shearing forces can be achieved.
Compared with other teams
This team’s structure is one of the top parts of the roof. It is a complex, geometric structure with lots of trusses and cross bracing to create a rigid triangular roof frame.
This team’s structure is the part located just beneath the one of the previous team. It is a single-skin open-web joist, braced with trusses and cross bracings.
Knowledge map of week 6
Site 1: Box Hill North
In site 1, prefabricated roof trusses have been placed. Later a series of tile joists will also be added to make a tile roof.
The foundation uses ‘waffle pod footing’. The pods are hollow and are about to be filled with grout to create concrete footing columns.
Around the bottom of the building, there is a temporary slope to transfer rainwater away from the foundation. Additionally, a permanent guttering system is also set around the building. As a part of service system, some unfinished PVC sewage pipes can also be seen.
The main bracings in this building are ply bracing, cross bracing and hoop bracing. - Ply bracing is made of thick ply wood, but still not strong enough for load bearing, thus always used as wall connections. - Cross bracing uses truss function to make a rigid form. - Hoop bracing is similar to cross bracing, but is adjustable in tension.
Site 2:
Footscray
In site 2, the building is a townhouse and is attached to it neighbours. Thus fire-check walls and insulation foil (blue board) is used for safety issue. Also for fire purpose, many materials have fire rating signs on them, showing the fire resistance level of the material.
Stud-framing walls are widely used in this building.
Fosil joists can be seen in this site, using keyed strutting instead of other joints.
5 stages for constructing: - Slab stage - Framing stage - Fixing stage - Lock up stage - Occupying stage
Knowledge map of week 7
Knowledge map of week 8
Knowledge map of week 9 & 10
General built form & materials
The main material of this building is structural reinforced concrete, with a few steel framing and glass cladding. Recycled concrete is used, which creates less carbon footprint, but takes more time. The building is curve-shaped, not only for aesthetic purposes, but to create more space between itself and the surrounding buildings (shadowed area in the top right diagram).
In response to the curved shape of the building, all individual bedrooms are slightly different in shape and direction Besides, the interior view along the corridor also changes according to the curved shape, which creates a visual effect of ‘endlessness’.
Interior construction The bottoms of the main windows are double framed, not only to hide the wiring and concrete beams, but also to achieve better finishes with a thicker bottom. There is also flushing in the window frames to prevent water from moving in. (ref: 7.18 Ching, ‘Flushing’) The hollow spaces in the floor are left for air-conditioning piping and probably electricity wiring as well
The side walls of the entrance hall are formed with steel framing, and are ready to be filled with glass to make a good view of the surroundings
Some height differences can be seen on the floor. Those gaps are prepared for the ongoing timber frames to fit in.
Interior construction
Two shearing walls are already built up in cross directions on the third floor. They are constructed to bear lateral shearing forces like wind or earthquake
Light-weight steel frames are widely used for interior framing Between every two bedrooms, double studs are used for both fire resistance and noise separation.
Service system
The two photos above show the service systems in public spaces. Electricity systems, gas system, heating systems, water supply and sewage systems are mostly set up in site: - White pipes for water supply and sewage disposal - Red wires for electricity - Black and red metal tubes for gas or heating
The two photos on right hand side show the heating and ventilation system in the bedrooms: - Black pipes for the heater - Rectangular metal tubes for air freshening
Functions & Finishes
For both public and private spaces, concrete celling is to be exposed. Therefore, neat cutting and clean finishing are needed for aesthetic purpose.
The roof is built of concrete and is prepared for another floor to be added. From the photo above, the lift, columns and stairs are all set up and are ready to go.
Those rectangular frames are for bathrooms – using timber to create the shape, in which liquid concrete is to be poured and tiles are to be set up to make a base for water collection.
Flushing – preventing moisture form moving in Insulation – waterproof and heat separation. Gap between surface and insulation – for further insulation Wall ties – tying the surface walls and the internal walls Weepholes – for water to get out of the building Vapour barriers – for moisture proofing Steel strip and plastic/glass – forming a lighting tube.
The walls are formed with a combination of soldier course and stretcher course.
Weepholes provide an exit for the moisture to get out.
Some layers of brick work are set a few centimeters in from the surface, probably for aesthetic purpose.
Downpipes transfer the collected rainwater to the ground. The white stripe is a lighting tube.
The gutter system for this building is eaves gutter. It is exposed at the edge of the roof but is well integrated in the roof structure. Another gutter type is box gutter. It is hidden within the walls and so has a better finish and is more commonly used. But there is one main thing to be considered: rainwater may directly come into the house when there is a crevice in box gutters.