PAULINA PYTKA CONSTRUCTING ENVIRONMENTS WEEK 01 – 03 JOURNAL
KEY CONCEPTS COMPARISON OF IGLOO AND TEEPEE • Differing structural systems – tension vs. compression • Structure depends on conditions – teepee is made from light canvas and easy to assemble frame for portability while igloo’s rigidity is essential to resisting dynamic loads such as wind • Materials readily available from environment – teepee originally made from animal hide while igloo made from compact snow LESSONS FROM NATURE • Tendons’ resistance to tension in the human body reflected in reinforced concrete • A honeycomb allows for maximum amount of wall and in turn, optimal storage. • Gecko’s ability to cling to a wall applied to Velcro MASS CONSTRUCTION • Uses high density material • Effectively absorbs heat when indoor temperatures rise, slowly releasing it when they drop • Compression structural system • Relies on vertical load bearing members to transfer forces to the ground.
OUR MODEL: THE COLUMNS The initial idea for the structure was to build four columns to support a roof while enabling four entry points as per the projectâ€™s constrains.
Another Groupâ€™s stacking technique. Signs of separation.
Evenly distributed load
When a load is applied to the block formation on the left, the edges of the blocks are pushed away from one another. Overlapping them, as shown on the right, counters this force. The decision to hollow out the columns is believed to have distributed the weight away from the center and improved rigidity.
This top view shows the way in which overlapping was applied to the columns.
OUR MODEL: THE ROOF In order to form a larger surface out of blocks, rubber bands were used. These employed tensile forces to hold the blocks together.
Rubber band Concentrated gravity load
By further layering overlapping sequences of blocks, any load applied to this structure relies on their compressive qualities rather than the rubber alone. The curving of the roof structure, observed from the side, when a load was applied showed some degree of a tensile system supporting the weight. This reinforces the grid lay out of beams and loadbearing walls discussed by Ching (2008), where intersections represent the location of columns in response to concentrated gravity loads.
OUR MODEL: THE ROOF CONT’D Although our roof system was of a flat form, it managed to support a load better than others. This is attributed to the compression resulting from having more than one layer of blocks. Nonetheless, the top right image shows an approximation of an arch. According to Ching (2008), arches are compression structures that “support the load above an opening by allowing a stress to flow around the opening to adjacent sections of the wall”.
A suggested way of achieving an Lining up a series of such arches arch could have involved the use could be used to create a vault. of elastic bands.
OUR MODEL: LOAD BEARING WALLS The walls were a final addition believed to further improve the structures ability to support bear a load. This proved helpful in straightening the curve that developed in the roof however, adding another floor would have also been of assistance. The effects of adding another floor were observed in another groupâ€™s model.
The red arrows indicate an equal but opposite force to that of the blue arrows, thus straightening out the curve in the roof structure.
GLOSSARY TERM: ARCH
KEY CONCEPTS STRUCTURAL SYSTEM • A structural system of a building allows applied gravity and lateral loads to be transmitted to the ground • Main structural elements include columns, beams and loadbearing walls • The superstructure describes the part of the building which is above ground level • The substructure describes that which forms the foundation of a building. FRAME • • • • •
A rigid frame is the result of force and momentum resisting joints A fixed frame relies on fixed joints A hinged frame relies on pin joints Applied loads produce axial bending The strength of triangles against both tension and compression forces is explored through trusses.
Step 1. A cube was assembled
Step 2. Another cube was added to the structure
Step 3. A framed structure resulted
Step 4. Bending of the tower indicated the weakest joints
Step 5. The weakest, middle section was reinforced with diagonal components
Step 6. The stability was improved through the use of triangles though a curve in the form remained
The failure of this model lies in the lack of additional bracing as the height of the tower increases. In step one, the figure did not show as much instability as it did later in the construction process. By step 4, it was necessary to choose between diagonal bracing or a rigid core as discussed by Ching (2008).
In order for the tower in step 3 to be considered a tube structure, and improve the model’s load bearing ability, the columns should be more closely spaced.
More rigid connections would have also been beneficial. i.e. Using superglue as opposed to tape. Depending on the way in which the tape is wrapped, the sticks can flex in different directions, whereas the glue holds all sticks involved in a joint in one position.
As shown in step 5, bracing only the middle section was the result of time constraints. The lower level should also be braced as this is where the greatest lateral force resistance is needed (Ching, 2008).
Little consideration was given to lateral force resistance during the construction of this model.
A lattice truss tube may have improved lateral force resistance but collapsed under a vertical load which would cause the structure to act like a spring.
A trussed tube is essentially what this model aspired towards. The success of this form depends on the spacing of the columns for effective force distribution across the beams, through the columns and to the ground.
The triangular base of this model proves to be more stable than one with a square base and can hold some degree of a load without deforming. Triangles are the strongest type of shape because they are regular polygons and once all of their sides are joined, their interior angles cannot be changed. This teepee inspired model depicts the balance that can be achieved through tapering. This form could be improved by modeling it against a pyramid, and linking the columns at the base with a triangle Once the edges meet at the vertices, they can no longer move.
Although this model had a triangular form, it is not composed of triangles. It’s base ‘y’ frame has four joints which are all capable of flexing in various directions. The ‘y’ layers approximate the rigid core concept discussed by Ching (2008), however, they could be completed by an additional column running vertically through each intersection to better support a load.
GLOSSARY TERM: SPACING
KEY CONCEPTS THE OVAL PAVILLION • Between the design and construction process, negotiation between project managers is necessary - one represents the design firm and another represents the client • The project cannot progress until each stage has been approved and complies with the budget • Consideration is required when working around, and trying to incorporate, a heritage building into a design • Some ambitions cannot be brought into existence due to structural constraints, thus requiring the approval and advice of a structural engineer CONTEXT • Choice of structural system depends on the context • The choice of foundation is governed by soil conditions and the slope of the terrain as much as the structure which it will support • Planning ahead is required for creeping, stiffness and thermal stress when choosing materials MELBOURNE’S BLUESTONE • An example of how the natural environment informs the cultural environment • Availability of a material based on proximity to construction site • Local materials are accustomed to climate on site and thus, may be more durable than that foreign to the conditions
Week 03 Timber grain textured concrete columns of Ormond college.
• White tubes are used for electrical purposes so that no conduits are exposed • Encasing the concrete in timber leaves a patterned finish on it corresponds to that of preexisting buildings in that context. • The external timber frame is supported with buttresses.
• A long pit has been dug into the ground to create a foundation for a load bearing wall which will be attached through the protruding metal wires.
Diagram of *mber framework
• Service entry point • Gravel storage • Skip
• Strip footings under load bearing walls with out piers have been used to create a shallow foundation. • The slab thicknesses are 230mm and 100mm respectively. • Piers, as part of a deep foundation, are required when the design load is large or the site’s soil is poor at shallow depth. • The pavilion will have a light concrete and plywood soffit. • Some advantages of using footing slabs include their ability to adapt to sloping site and simple framework that does not require internal beams. • Sloping to drainage points has been applied as part of stormwater management.
• A water tight fabric blanket sheet has been used underground so that water in the soil will not cause the concrete to reopen.
EASTERN PRECINCT CENTRE (LINK BETWEEN BUILDINGS)
Potential construction constraints: Longer sized beams would have required custom engineering so that no columns are needed. Links to other buildings: This link between the ERC and Doug McDonell Building caters to the height difference between the two with its pitched roof. Together with the use of dark glass on the exterior is creates a visual relationship the flows from the older concrete structure to the smoother, newer glass structure. Construction type: Type II A. Two hour fire resistant exterior walls, ceiling and floor with a one hour fire resistant frame. Structural systems: Cantilevered beam system. Dough McDonell
ERC SIDE VIEW
Materials: Polished concrete floor with metal separator, timber cladding and steel frame. Metal separators allow the concrete to expand and contract. They also allow cracking to occur in predictable spots making the squares easier to replace.
MSLE BUILDING (LINK BETWEEN BUILDINGS)
Potential construction constraints: The narrow site would have limited the amount of workers able to move within it during the construction process. This may have also affected the delivery of materials and thus lead to the choice of the snap panel steel planks. Links to other buildings: The use of raw, earthy colours and coarse textures in this link is consistent with the rustic appeal of the surrounding MSLE buildings. Construction type: Type III B. Use of steel reduces the fires resistance of the exterior. Structural systems: Plank load bearing wall system. Materials: Standing seam steel panels and glass. Head gutter and pipe drainage system.
Vents are have been placed to either bring air in or out. Their low location suggests that these bring air in as warm air, subjected to human respiration, rises.
QUEENS COLLEGE (EXTENSION)
Potential construction constraints: Positioning a wall adjacent to a pre-existing one requires underpinning so that the expansion and contraction or subsidence of one does not affect the other. Links to other buildings: Initially it may seem as though there is no connection to the heritage building to the left of it, however this addition is consistent with others such as that to the right of it, whose modern stream lined form contrast the original buildings as to avoid distracting away from them. Construction type: Type II B given the fire-resistant concrete exterior and asphalt floor. Structural systems: Frame and wall system on horizontal slab with cantilevered porch. Materials: Timber frame with pre-made concrete walls and asphalt.
ORMOND THEOLOGY CENTRE (RECEPTION)
Potential construction constraints: A completely glass faรงade may have been desired however the load bearing ability of the material is limited thus, steel columns have been used. These act as a primary support while having a minimal impact on the aesthetics of the building. Links to other buildings: The cube-like reception corresponds to surrounding geometric forms. Construction type: Type III A. Use of aluminum and concrete provide internal fire resistance whereas the use of steel and glass externally is not as effective. Structural systems: Column system where external columns have a greater cross sectional radius of gyration than those on the interior to reduce buckling. Materials: Steel columns, concrete column, glass blocks and aluminum. The water collected on the roof is drained through a concealed pipe with an outlet on the side.
Three textures have been achieved on the concrete; a linear fan-like effect, a chiseled hole patter and a wood grain imprint.
GLOSSARY TERM: PIERS
REFERENCES Build Right 2013, N/A, N/A, viewed 22 August 2013, <http://toolboxes.flexiblelearning.net.au/demosites/series10/10_01/content/ bcgbc4010a/09_footing_systems/06_concrete_slabs/page_003.htm>. Wikipedia 2013, N/A, N/A, viewed 22 August 2013, <http://en.wikipedia.org/wiki/Deep_foundation>. Ching, F 2008, Building Construction Illustrated, John Wiley & Sons, Inc., Canada. Rogerâ€™s Connection 2011, N/A, N/A, viewed 12 August 2013, <http://www.rogersconnection.com/triangles/index.html>.