Week 5 compressed
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Week 5
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Transcript of Week 5 compressed
Week 5
Key Terms Stud – an upright piece of timber in the wall of building. Nogging – the brickwork ina imeber frame Lintel – A horizontal support across the top of the door or window. Axial Load – the force acting along the axis of an object. Buckling – the bending of an object due to compressive stress, Seasoned Timber – When the moisture of the timber has been removed. Short And Long Columns Columns are vertical structural members designed to transfer axial compressive loads. All columns are considered slender members and for axial loads, they can be classified as either the short or long. Short columns
-‐ Shorter (length) -‐ Thicker (cross-‐section) -‐ Less than 12:1
Long columns
-‐ Taller (length) -‐ Slimmer (cross-‐section) -‐ Greater than 12:1
Short Columns Columns are considered short if the ratio of effective column length to the smallest cross-‐section dimension is less than 12:1. e.g. 3000mm tall column with a 450mm x 300mm will have a ratio of 10:1 Short columns become shorter when a compressive load is applied and then failed by crushing (shear) when the compressive strength is exceeded. (Either by applying too great a load of if the cross-‐section is too small).
Long Columns Columns are considered long if the ratio of effective column length to the smallest cross-‐section dimension is greater than 12:1. E.g. 6000mm tall column with a 450mm cross-‐section will have a ratio of 20:1 Long columns become unstable and fail by buckling. The shape of the column cross-‐section determines the direction of the bucking. The actual length of long columns and how they are fixed at the top and bottom of the columns determines how they will buckle and how much force loads the column can carry.
-‐ The effective length of the column is changed because of the different fixing methods the effective length is measured between the points of contraflexure.
SHORT COLUMNS
Columns are considered SHORT if the ratio of effective column length to the smallest cross section dimension is less than 12:1.
For example: a 3000mm tall column with a 450mm x 300mm cross-section will have a ratio of 10:1.
Therefore it would be considered a short column.
SHORT COLUMNS will be structurally adequate if the load applied to the column cross section does not exceed the compressive
strength of the material.
Compressive Strength (Pa) = Load (N) / area (mm2)
SHORT COLUMNS become shorter when a compressive load is applied and then fail by CRUSHING (shear)when the compressive
strength is exceeded (either by applying too great a load or if the cross-section is
too small).
Shear failure of column at the Chemistry Building, Tohoku University, Sendai, JAPAN 2011!http://reidmiddleton.files.wordpress.com/2011/06/chemistry-bldg-colum-shear-failure.jpg
Illustration from CHING ‘Building Construction Illustrated’ p 2.13
Walls, Grid And Columns Walls enclose protect the interior from the exterior, moderate the climate for interior used of occupants, used to filter out light, insulate from the cold and heat. Walls may be the mayor structural component of a buildings system. It may carry the load from the wall to the ground. Wall systems Structural Frames
1. Concrete frames-‐ commonly fund in cities
2. Steel frames – industrial building 3. Timber frames (post and beam)
less common in Australia Stud Walls
-‐ Light gauge steel framing -‐ Timber framing
Structural frames Concrete Frames-‐ typically uses a GRID of columns with concrete beams connecting the columns together.
-‐ Beam is interconnected into the column to make a rigid joint (moment joint). The reinforcement of the square column is shown.
-‐ Circular columns have spiraling reinforcement going down it. That is also interconnected with a footing system.
Concrete frame building system needs to have columns (each) needs to be strong enough to support an area of dead/live loads above it.
Steel Frames -‐ typically use a GRID of steel columns connected to steel girders and beams. Frames needs to be stabilized by bracing, bracing sheer walls, by making the joints rigid. Columns are known to buckle at the weaker, smaller dimension hence why they need to be equal to be more efficient. Timber Frames (post and beam)-‐ typically uses a grid of timber posts or poles connected into timber beams. BRACING of members between bays or at the corners of post/beam junction is required to stabilize the structure. This structure is commonly used in traditional Japanese but less common in Australia’s construction. Keeping the beam and column can be done to the same way as steel. Occasionally the joints might also be made rigid with the beam is connected to the column. Loading bearing walls
Columns are considered LONG if the ratio of effective column length to the smallest cross section dimension is greater than 12:1.
For example: a 6000mm tall column with a 450mm x 300mm cross-section will have a ratio of 20:1.
Therefore it would be considered a long column.
LONG COLUMNS become unstable and fail by BUCKLING.
The shape of the column cross-section determines the direction of the buckling.
The actual length of LONG COLUMNS and how they are fixed at the top and bottom of the columns determines how they will
buckle and how much load the column can carry.
The EFFECTIVE length of the column is changed because of the different fixing
methods. The effective length is measured between the points of CONTRAFLEXURE.
LONG COLUMNS
Illustration from CHING ‘ Building Construction Illustrated”, 2.13 (2008)
Illustration from CHING ‘ Building Construction Illustrated”, 2.13 (2008)
CONCRETE load bearing walls can be achieved using either in situ or precast elements. The load bearing PANELS may also provide support for SPANDEL PANELS over and link into other structural elements (such as floor slabs, roof structure etc.) Apartment buildings are occasionally the wall themselves, are load bearings. REINFORCED MANSONRY load bearing walls can be constructed from CORE FILLED hollow concrete blocks or GRANT FILLED cavity masonry. TRUSS BEAMS over openings can be created using special concrete blocks, which are filled with concrete to bond the individual units together. After the concrete has cured, the temporary propping can be removed, leaving only the appearance of the concrete block wall. Bond beams are used as an alternative to steel or concrete LINTELS. SOLID MASONRY load bearing walls can be created with single or multiple skins of concrete masonry units or clay bricks.
The skins of masonry are joined together using a brick (with HEADER showing in face of wall) or with metal WALL TIES placed within the mortar bed.
Solid walls could have two skins of brick work together, which could be used in garages, or fences, or sub floor levels where waterproofing is so crucial. Once waterproofing is necessary, a cavity about 50ml is usually constructed between the two layers of brickwork and there is flashing that allows water to soak through the panel to be taken outside the building. The wall in the solid masonry wall can be tighten together with a brick on its side with the header showing its face or can be tie together with the ball. Lintel are commonly used and made out of steel.
CAVITY MASONRY walls are typically formed from two skins of masonry. Advantages of this construction solution include: better thermal performance and opportunities for insulation within the cavity, better waterproofing liability to drain water from the cavity and the opportunity to run services within the wall cavity. The presences of a DAMP PROOF COURSE AND WEEP HOLES in a wall are indicators that the wall is a cavity wall rather than a solid wall. The vertical water joint called a ‘perpen’ is left open which allows any water to run outside. A line across the wall would have a damp proof course, which prevents any water that is soak from the ground.
Stud Framing METAL AND TIMBER STUD FRAMED walls use smaller sections of FRAMING TIMBER OR LIGHT GAUGE FRAMING STEEL to meet the structural demands of the construction. P5.42 The smaller sections mean that the structural members are repeated at smaller intervals and require restraining along their lengths with rows of
NOGGINGS to prevent the long thin members from BUCKLING. STUD FRAMING generally consists of TOP PLATES, BOTTOM PLATES, VERTICAL STUFS, NOGGINGS, CROSS BRACING AND PLY BRACING. In Australia in the suburbs, stud framing is commonly used, particularly timber frame stud walls. The studs are placed together where plaster board can span from the… Horizontal noggings are placed to prevent from each stud from buckling. Very efficient used of material, some bracing is needed, and this could be diagonal or steep bracing. BRICK VENEER CONSTRUCTION
Combinatory of 1 skin of non-‐structural masonry and 1 skin of structural frame wall are widely used in the construction industry. The brick is connected to the timber or steel structural system. The brick work is a cladding system which is tied to the stud work. The roof loads are carried down through the stud, through the bottom plates, onto the joist, onto the beamers, onto the pears and onto the stumps (if the building has stumps) [Effectively the brickwork is a non-‐structural skin] This is used on the Oval Pavilion. FROM WOOD TO TIMBER
At the centre of the wood is the hearth udder. It is not useful in constructing; it does not last as long. The extra ring gets place each year. Provenance Early wood-‐ rapid growth at beginning of growing season Late wood-‐ slower growth, often limited by lack of water, thick and small cells, darker color Growth-‐ generally one ring per year/ same climates may have more than one-‐growth season pear year/ fires or disease may produce an extra ring Structural nature of wood Grain direction-‐ determines the structural performance of wood. This would be the direction, strength and stiffness of the wood
The timber is strong parallel to the grain and stiff parallel to the grain.
Therefore if there compression or tension on the timber, parallel to the grain, it would be strong. The timber is weak perpendicular to grain. If a force were applied to the grain, either pulling the fibre apart or compressing the fibre, it would be weaker. The timber would not carry the load effective. Seasoning (drying) Timbers are parallel vessel. By moving the water from the vessels and cells the timber would be strengthen. This process is called “seasoning” This leaves less than 15% of water left. WHY is timber seasoned?
-‐ To adjust the moisture content so the timber is appropriate for the intended use.
-‐ Provide increased dimensional stability
WHAT moisture is removed from the cell?
-‐ Free moisture (voids in cells) -‐ Bound moisture (cell walls)
HOW is moisture removed? Timber is generally seasoned in one of the three ways:
-‐ Air seasoning (drying) – cheap but slow – 6 months to 2 years per 50mm thickness
-‐ Kiln seasoning (drying) – typically 20-‐40 hours to dry to – 12% (very common)
-‐ Solar Kiln seasoning (drying) – less expensive to run, same energy cost
At the beginning of the seasoning process, the first water to leave is the cell. The bond water is the next section to evaporate off. This is classified as
seasoned timber when it is less 15% of its growing tree. Types Different woods have different properties. We group them based on their biological provenance land not based on their strength or density. Softwoods The pines are considered the softwood. In Australia common softwoods include all conifer species:
-‐ Radiata pine -‐ Cypress pine -‐ Hoop pine -‐ Douglas fir
Hardwoods Nature Australian hardwoods include all eucalyptus species:
-‐ Victoria ash -‐ Brown box -‐ Spotted gum -‐ Jarrah -‐ Tasmanian oak -‐ Balsa wood (not an eucalypt nor
an Australian timber but, surprisingly, a hardwood)
Green sawning Quarter sawn -‐ growth rings parallel to short edge. (less common in structural timber)
ADVANTAGES -‐ Brain grain shows on face -‐ Good … surface for floors,
furniture -‐ Radial face preferred for coatings -‐ Lower width shrinkage on drying -‐ Less cupping and warp than
other cuts -‐ Can be successfully
reconditioned DISADVANTAGES
-‐ Slower seasoning -‐ Nailing on face more prove to
splitting
Back sawn-‐ rings parallel to long edge of piece. (more common in structural timber)
ADVANTAGES -‐ Season more rapidly -‐ Less prove to splitting when
nailing -‐ Wide sections possible -‐ Few snots on edge
DISADVANTAGES -‐ Shrink more access width when
drying -‐ More likely to warp and cup -‐ Collapsed timber more difficult to
recondition Radial sawn-‐ face is always a radial cut. This is the most efficient used of the timber. Sometimes used for a weather board cladding system for buildings and
fences. Therefore, there are less waste but some difficulties with it. Stacking could be one difficulty. The structural properties aren’t as clear as a quarter and back s awn.
ADVANTAGES
-‐ Dimensional stability -‐ Less prove to warping, cupping
less wastage in milling DISADVANTAGES
-‐ Wedge shaped cross section -‐ More difficult to detail -‐ More difficult to stack
GO TO RESHAPING SECTION TIMBER PROPERTIES AND CONSIDERATION
Timber is a living material. Both its strength and weakness. Express work carefully with this material. They could be furniture design, construction experts, building designers, structural experts. Properties Hardness-‐ medium-‐low. Most timbers can be reasonably easily marked. Not as hard as stone. Fragility-‐ medium-‐ low. Geometry dependent, generally win not shatter or sreak Ductility-‐ low. Some timbers in their green state can be manipulated into a range of shapes (steam pressured) Flexibility/ Plasticity-‐ high. Varies depending on seasoning, finishing (protection) and fixing Density-‐ extremely varied depending on timber type Conductivity-‐ poor conductor of heat and electricity Durability/ Life span-‐ can very durable if detailed correctly. Varies depending on type, seasoning, finishing (protection) and fixing
Reusability/ recyclability-‐ very high-‐ second hand timber is very desirable Sustainability and Carbon footprint-‐ very low embodied energy. Fully renewable if correctly soured. Cost-‐ generally cost effective. Harbor dependent for on-‐site work but also seized to highly efficient factory based manufacturing processes. (Depends on the country). Japan is commonly seen to use timber in prefabrication process. Specifying and handling Timber is not available for all shapes and sizes. Design detailing can and should minimize exposure to hazards. Always specify timber for a particular use/ scenario. Consider: Size
-‐ Depth x breadth -‐ Make sure size is available before
specifying -‐ Length (0.3m increments)
common maximum 6m trees can provide longer lengths in limited sizes.
Strength grade
Timber is rated by its strength. F grades MGP grading’s are commonly used to identify the strength of particular timber elements. This is used to determine the particular size of timber for a particular load bearing. Moisture Season < 15% (typically used in furniture, in flooring where there’s not many variation over time, and harder timber)
-‐ any timber > 15% is sold as unseasoned
Species of wood-‐ different timber types provide variation in performance and appearance. Treatment or insect repellent treatments will be required Availability-‐ not all timber types or sizes are available in all locations Considerations Knots-‐ weak points // cause slope of grain. Strength around the snot would likely to be weaker compare to across the grain.
They consist of -‐ Arris knot -‐ Centre knot -‐ Edge knot
If you look at the timber at a load bearing system, the timber would tend to bend under its load. You would want the part of the timber to be pulled apart in tension to not have the knots. In a normal beam situation, the top of the timber that has the bending would be under compression while the bottom would be under tension, the knot should be at the top of the beam. Load compressing on the load would not be a point of weakness but you if you are pulling against the knot, you tend to find the timber to break parallel with the grain. Durability-‐ good practice Water related damage Fungal attack often occurs when moisture content of wood > 20% Swelling, shrinkage can cause cracks Protection against water
-‐ Avoid exposure (when possible)
-‐ Seal against moisture movement-‐ paint
-‐ Particular care needed with end grain-‐ seal before assembly
-‐ The end can be protected by detailing, painting or both
TIMBER CAN BE DAMAGE
-‐ Isolate timber from INSECT attack (termites and borer etc) chemical barrier/ physical barriers between ground and timber
Protect timber from sunlight and heat -‐ Direct sunlight can cause
excessive dying, shrinkage -‐ Direct sunlight breaks down
wood/ Cellulose -‐ Light and color paints are best
Other Hazards
-‐ Fire -‐ Chemical exposure
ENGINEERED TIMBER PRODUCTS Timber can be engineered and manufactured into larger sections. This
has a couple of benefits such as it can be used in structural situations (curve forms or long spans), alternative, it can be used more effective. Solid products LVL-‐ Laminated Veneer Lumber Uses-‐ Mainly structural (beams, posts, portal frames) Made from laminating thin sheets of timber, most laminates with grain aligned to longitudinal direction, very deep and long sections possible, high strength. This is where the walls and roof section are connected together. GLULAM-‐ Glue Laminated Timber Uses-‐ Mainly structural (beams, posts, portal frames) Made from gluing pieces of dressed sawn timber together to form a deep member, most laminates with grain aligned to longitudinal directions. CLT-‐ Cross Laminated Timber Uses-‐ structural panels (horizontal and vertical) Made by gluing and pressing thing laminates together to form a sheet, laminate grain laid in alternate
directions (90o), provides strength in two directions Look at-‐ The forte building-‐ Melbourne Docklands. This is a relatively new product in the market place Australia has the tallest CLT building, The Forte building. SHEET PRODUCTS-‐ commonly in the construction industry Plywood Uses-‐ Structural bracing/ structural flooring/ formworks/ joinery/ marine applications. Made by gluing and pressing thin laminates together to form a sheet, grain in laminate in alternate directions strength in two directions. There are different qualities of plywood, the surface good be exposed, or uncial carpet. MDF-‐ Medium density fiberward Uses-‐ non-‐ structural applications (joinery) Made by breaking down hardwood or softwood waste into wood fibres, combining it with wax and a resin binder by applying high temperature
and pressure. MDF is generally more dense than plywood. It is even in quality. Clipboard and strandboard Uses-‐ as part of structural systems (e.g. flooring)/ cladding finish Made by layering hardwood or softwood residuals (chips/ strands) in specific orientations with wax and a resin binder by applying high temperature and pressure, OTHER MANUFACTURED PRODUCTS The rationale to the following set of product lies in their ability to use materials very efficiently and their ability to accommodate services within their depth. I Beams Uses-‐ floor joists/ rafters Timber/ LVL flanges, plywood/ USB webs Lightweight, suitable for medium span BOX BEAMS Uses-‐ floor joists/ rafters Timber/ LVL flanges, two plywood/ USB webs
Suitable for larger spans, stiff, can use decorative plywood
Timber Flanged steel web joists
Uses-‐ joists/ rafters Lightweight, open webs save access for service webs by light tubes, solid rounds, and corrugated sheets Sometimes there’s a hybrid use of material where the timber is joined together with the steel structure be with light tubes or solid rounds. Sometimes
this can be a sheet material with holes in it that hold the two timber flanges together. GEHRY’S OWN HOME Dr Hannah Lewi Frank Gehry’s house
-‐ Famous architect -‐ House in Santa Monica in Los
Angeles -‐ The new house was the wrapping
and the old house was the core -‐ This house shows a lot about
contemporary architecture -‐ Everyday materials, wrapping,
collisions and fragments, under construction
Everyday Material
-‐ Worked from 1970-‐1980, in Los Angeles
-‐ Quote: ‘I get my inspiration from the streets. I am more of a street fishier than a exam scholar’
-‐ Worked hands on, on everyday materials from the street. Most controversially materials such as chain links for fencing, metal sheet, cardboard in furniture. These found on the streets. These
materials are lightweight, they throw away and sort of ticky tacky.
-‐ Materials are found objects, that has been discarded by conventional traditional Architecture
Wrapping
-‐ The favourite materials of his used, normally came from the things which wrap other more precious objects. These are used in packaging. EG. Gene things in with chain links, use plywood for form work, for concrete, we box things in with cardboard
-‐ Wrapping building with lightweight material was partly an exploration what local construction method might be able to do. In Los Angeles, trot dominantly known as ‘stick frames’ or ‘stucks’ or ‘stud frames’ which timber construction that clad with light weight material.
-‐ Quote: ‘I had a funny idea that you could made architecture that you could bump into before you would realize it was architecture. Obviously I have not been able to do that… I’d love to’.
Collusions and fragments
-‐ Collapse or design idea adding together material and forms rather than subtracting by using the rule of symmetry. This was a popular notion at the time in the 70’s in architecture. It can be clearly seen in Gehry’s models and drawing and translated into his work also shared a great friendship with American sculptors, explored ideas of unexpected geometry. Generated ideas of the colliders together and adding together of shapes.
-‐ Took about a month to design a window that wasted all his money
-‐ You can see how forms twist and burst through and expose the structure. The skin is peeled off
and replaced with a lightweight wrapping.
Under Construction
-‐ This building reminded him of unfinished or incompleteness
-‐ He worked on a seemingly conventional old house that is made out of timber, plasterboard and clad stick frames
-‐ He added and removed bits to make it seem unfinished which holds the possibilities of change
-‐ He thought about adding clipboards and painting it pink to submerge into the old house
-‐ The house was humorous and very much reflected the chaos of family life. It can be seen by the interior of the house
-‐ Quote: ‘I deliberately de-‐sophisticate elements of my work. I would rather call it undersign?’
-‐ The house caused a lot of complaints. The neighborhood
-‐ wanted to sue him and send him to jail for visually disturbing the peace
-‐ He disrupted a lot of convention on what a house should be. Reorganizing the room differently to where it should be. He said that the dining room in the drive way
-‐ It took many years for Gehry to recover from this incident over this house
-‐ The house has been declaimed a historie monument. This meant that it was finally finished.
-‐ Over years, this started inspiring many architects award the world in the 1990’s
-‐ It has been described as cheapscape architecture because the material it uses.
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