W01M1: Introduction to Materials -
-
Strength : e.g. Steel > timber Stiffness Shape : mono-dimensional/bi-dimensional/tri-dimensional Behaviours : isotropic or anisotropic Economy : price + availability Sustainability
W01S1: Load Path Diagram Applied load: Dead load + Live load Load path diagram shows how a load is transferred down to the ground. - Loads take the most direct routes to the ground - They go in both directions - For every force there is a reaction force to keep the structure stable. - Reaction forces are equal but opposite direction to the applied load.
W01: “Walking the Constructed City” –Dr Margaret Grose Melbourne
Sydney
-Bluestone/Basalt cobblepaths formed from volcanoes in Victoria.
-Abundance of sandstone structures due to high numbers of sandstone quarries.
-Dark colouring of the city due to dominance of basalt.
-Light colouring of the city due to sandstones.
-Wheel ruts from 19th century cartwheels. ‘Bubble marks’ from lava flow. -St. Paul’s Cathedral: basalt foundation but mostly sandstone. -Interchange between clean and rough bluestones showing a change in road level over time.
Perth -Clay, bricks and limestone.
W01: Tutorial Universal Column:
Universal Beam:
Scales 1:1000 – used to pin point location on maps 1:500 – ditto 1:100 – plans, elevation, section 1:50
1:20> – construction details Two types of mass construction: Small module
Large Module
-uses mud/clay (adobe, bricks, concrete blocks)
-uses mostly precast concrete
-alignment of bricks makes bonds and allows for creating shapes and patterns.
Bricks
Concrete Blocks
-made off-site through baking clay in moulds
-precast -quicker in manufacture and laying
-pressed brick: variations in colour due to spread of heat -extruded bricks: wire cut bricks, more uniform in shape and colour -slow process in making and requires expensive labour for laying
-can be manufactured at the same time along with other processes -harder to make shapes and patterns in buildings
**
-length is 10mm more than double the width to allow for mortar.
*
*: http://www.stegbar.com.au/~/media/Images/Stegbar/about%20windows%20and%20doors/brick_std.gif **: http://www.recoore.com/hardware/images/detailed/1/Concrete_Block-02137484473251f2773c06bdf.jpg
W01: Ching Reading Static Loads Applied slowly to a structure until it reaches its peek unit without fluctuating rapidly in magnitude and position. Live loads compromise any moving or moveable loads on a structure. E.g.: occupancy loads, snow loads, rain loads, impact loads
Dynamic Loads Applied suddenly to a structure, often with rapid changes in magnitude and point of application. Wind load: -
May cause long, thin structures or membrane structures to flutter. Requires measure to prevent sliding, uplifting and overturning
Earthquake load (due to seismic force)
Forces A force is any influence that produces a change in the shape or movement of a body. It is considered a vector quantity possessing both magnitude and direction. Collinear forces occur along a straight line and the vector sum is the sum of magnitudes. Concurrent forces have lines of action intersecting at a common point, the vector sum is equivalent to the application of the vectors of the several forces. Non-concurrent forces have lines of action that do note intersect at a common point, the vector sum of which is a single force that would cause the same translation and rotation of a body as the set of original forces.
WEEK 1 STUDIO ACTIVITY To the side is a photograph of the model my group pieced together in week 1 studio. It is a mass construction building model aimed to extend vertically as tall as possible. It is based on the concept of modern skyscrapers with a larger, solid base to lower the centre of gravity allowing for the tower on top to extend tall. Two types of material are used in making this model, rectangular MDF blocks and rectangular bricks. The bricks are used in higher levels of the base to apply compression onto the lighter blocks below and keep them in place.
This is a photo of Bayoke Sky Hotel in Bangkok, Thailand. The shape of our structure greatly resembles this modern skyscraper where the base is strongly reinforced for the tower to stand tall.
http://i2.cdn.turner.com/cnn/dam/assets/130124160413-skyscraper-hotels-baiyoke-bangkok-horizontal-gallery.jpg
The upper layers of the structure is built with a 3x3 block alignment facing different directions so that the blocks create a bond in between and the path of load is not simply going directly downwards.
The above sketch shows the main load path of the tower into the ground. The blocks along the middle of the building are essential in the transfer of load while the blocks unmarked are the ones that do little to support the structure and, as later proven, can be removed without causing the structure to collapse.
The two photos above are examples of work done by other groups. Both models have a similar difference to my group’s tower being that the general shape of is circular. These structures have thinner walls surrounding the space as opposed to thicker walls as my group employed. While this limits the ability for the structure to sustain great height, it certainly allows for making shapes and patterns. (curved walls)
W02S1: Structural Systems Solid Systems
Surface Systems
Skeletal Systems
-compression
-‘shell’ structure
-frame structure
Membrane Systems
Hybrid Systems
-covers large areas cheaply and efficiently -less used in built structures
W02: Structural Joints Roller Joints – only resist vertical forces
Pin Joints – can resist horizontal and vertical forces
Fixed Joints – resist horizontal, vertical and rotational forces.
W02: “Column and Wall, Point and Plane” – Dr Alex Selenitsch Column and wall
http://upload.wikimedia.org/wik ipedia/commons/d/de/AlAzhar_Mosque,_Cairo,_Egypt8.j pg
Point and plane – starts with a point, then becoming a line, the line further extending into a plane, the plane folding and bending to become a volume. Differences: column and wall have a clear demonstration of structure and construction while in point and plane it is sometimes unsure what is structure or simply spatial division.
W02: Tutorial (Material) Concrete = cement + water + fine aggregate + course aggregate Compared to: Mortar = cement + water + fine aggregate Base metal – aluminium/bauxite Non-base metal – alloys (e.g. bronze = copper+zinc)
W02: Ching Reading Structural System Superstructure: vertical extension of a building above the foundation Columns, beams, and loadbearing walls support floor and roof structures. Substructures: underlying structure forming the foundation of a building.
Enclosure System Roof and exterior walls shelter interior spaces from inclement weather and control moisture, heat and air flow. Dampen noise and provide security and privacy. Doors provide physical access. Windows provide access to light, air and views. Interior walls and partitions subdivide the interior of the building into spatial units.
Mechanical Systems Water supply, sewage disposal and electrical systems. Heating, ventilating and air-conditioning systems. Vertical transport systems. Fire-fighting systems. Waste disposal and recycling systems.
FACTORS Performance Requirements Aesthetic Qualities Regulatory Constraints Economic Considerations Environmental Impact Construction Practices
Week 2 Studio Activity Activity Overview This week’s studio activity requires us to build a structure out of thin, long balsa strips. The objective was to build a stable tower as high as possible within the given resources. My group’s plan was to create a triangular prism-shaped tower that extends vertically upwards. The photos (left) show the process in the making of this structure. By first creating an equilateral triangular base, vertical columns are added to each of the edges which connect to a second triangular plane and so forth. The building of this tower employs the frame system learned in the E-learning materials in week 2. As the tower’s body is mainly hollow, diagonal bearings are included to help resist external forces as discussed in the previous week. In this context, the main problem is the wind force (disregarding possible occurrence of collusions) which might cause the structure to collapse. Single bracings are placed in different directions at each side due to limited resources. As a result, in each section, one edge gets the most support; one edge receives medium support while the last gets least support. This pattern rotates for each of the four sections so that each side would receive some extent of support against wind forces. It is proven at the end that this method works well as the structure is able to withstand light forces acting from each direction.
Week 2 Studio Activity Structure Overview This is a frame structure made out of balsa strips connected together by tape. The area size of the tower is uniform vertically through the body of the structure, only decreasing to a tip point at the very top. The equilateral triangular shape of the tower helps place the centre of in the middle of the horizontal plane so that all sides are equally resistant to overturning forces. Due to the structure bring hollow within the frame, bracings are included on each side to help withstand forces.
At each of the four sections that made up the main body of the tower, bracings are placed in different directions.
After the main body of the tower is done, a final addition to the top of the structure is a pyramid tip with a long vertical pole extending out to reinforce the height.
The width of each side is half the height of the section. The diagonal bracing is slightly longer than the height.
Week 3 – Structural Elements Key structural elements: -
Strut: a compression element Tie: a tension element Beam: top will be in compression while bottom in tension Slab/Plate: transferring load in two directions Wall panels: carry or transport vertical loads Shear wall: acts as a shear diaphragm to carry horizontal load and prevent overturning.
Week 3 – Footings and Foundations The function of buildings is to stay still and not move or overturn. This requires transferring of loads to the ground. Foundations are found at the bottom of buildings where the building meets the ground. They are the substructure of the building and their function is to transfer all loads acting on the structure to the ground. Over time, buildings compress the earth beneath them and they tend to sink a little into the earth. This is called settlement. Footings and foundations need to be designed to ensure that this settlement occurs evenly and that the bearing capacity of the soil is not exceeded. Differential settlement causes cracks in a building. Shallow footings are used where soil condition is stable and where the required soil bearing capacity is adequately close to the surface of the ground. Load is transferred vertically from the foundation to the ground. Deep foundations are used where soil conditions are unstable or where the soil bearing capacity is inadequate. Load is transferred from the foundations, through the unsuitable soil and down to levels where bed rock, stiff clay, dense sand or gravel is located. Types of shallow footings: -
Pad footings: footings that spread a point load over a wider area of ground. Strip footings: used when load from a wall or a series of columns is spread in a linear manner. Raft foundation (raft slab): provides increased stability by joining individual strips together as a single mat.
Types of deep foundations: End bearing piles and friction piles. Retaining walls and foundation walls are used when sites are excavated to create basements or where changes in site levels need to be stabilised. The pressure load of the earth behind the wall needs to be considered to prevent the wall from overturning.
Week 3: Masonry Masonry refers to building with units of various natural or manufactured products, usually with use of mortar as a banding agent. Terms: -
Bond: the pattern or arrangement of units Course: horizontal row of masonry units Joint: the way units are connected Mortar: mixture of cement or lime, sand and water used as a banding agent
Masonry units together make a monolithic whole. Masonry construction: -
Vertical elements: Walls, Columns or Piers Horizontal and curved spanning elements: Beams, Lintels or Arches Spanning or enclosing elements: Vaults or Domes
Week 3: Geometry and Equilibrium Centre of mass or centre of gravity is the point about which an object is balanced. The location of the centre of mass depends on the object’s geometry. For a structure to be stable, the centre of mass must be above its base. Equilibrium is a state of balance or rest resulting from the equal action of opposing forces. In other words, as each structural element is loaded, its supporting elements must react with equal but opposite forces. For an object to be in equilibrium, any applied forces must be resisted by equal and opposite forces. These forces are called reaction forces. In a building structure, the reaction forces are developed in the supporting elements. In order to achieve equilibrium, we need to consider: 1. If the object is not moving up or down, then the sum of the vertical forces must be equal to zero. 2. If the object is not moving sideways, then the sum of the horizontal forces must be equal to zero. 3. If the object is not rotating, then the sum of the moments must be equal to zero. The moment of a force is the tendency to make an object or a point rotate. A force will only produce a moment about a point if it is applied at a distance from that point along a line of action that does not pass through the point. Moments are measured by the product of the force magnitude and the perpendicular distance between the line of the action of the force and the point (this distance is called the moment arm). Moments also have magnitude and sense. Since moments are the product of force and distance, the units are expressed in Newton-meter (Nm) or Kilonewton-meter (kNm).
Week 3: Bricks Bricks are manufactured from clay or shale which is shaped and then hardened by a firing process in a kiln. The standard size of a brick is 230 long, 76 high and 110 wide. Clay is a natural material so there is a wide variation in colour of bricks. Bricks are mainly used in walls, arches and paving. They can be arranged in a series of different ways: -
Stretcher course Header course Brick on edge course Soldier course
Mortar joints for brickwork are usually 10mm (vertical joints are called perpends and horizontal joints are called bed joints). There are a range of joint finishing profiles which are selected depending on the type of brick, weather exposure and aesthetics. Advantages of using bricks are that they can be joined with water based mortar and will not deteriorate if adequately ventilated. However, they absorb moisture and expand over time, therefore expansion joints are required. Salts and lime from the soil can be drawn up through the bricks when in contact with the ground, causing pathologies or aesthetic problems such as efflorescence. Week 3: Concrete Blocks The most common size is 390 long, 90 wide and 190 high and fractions of such. They typically have holes in them to reduce weight, increases insulation and allows for reinforcement. They are manufactured from cement, sand, gravel and water. The manufacturing process involves mixing, moulding and curing. Concrete blocks can be classified as load-bearing (Concrete Masonry Unit- CMU) or non-load bearing. The face shell refers to the outside face of the block while the web refers to the interior portions between the hollow cells. They are mainly used in the construction of walls and CMU can be strengthened with steel reinforcing bars and filled with grout. Concrete blocks tend to shrink over time due to hydration and drying, therefore requiring movement joints. Week 3: Stone Igneous stone is formed when molten rock cools. Granite, basalt and bluestone are examples of igneous stone. They are dense, hard and dark in colour. Igneous stone is often used in footings due to their imperviousness to water. Sedimentary stone is formed when accumulated particles are subjected to moderate power. Limestone and sandstone are examples of sedimentary stone. They are much softer than igneous stone and less dense. They are also prone to water and wind damage. An advantage of sedimentary stone is that they can be carved easily.
Metamorphic stones are formed when igneous or sedimentary stone is subjected to high pressure, high temperatures or chemical process. Marble and slate are examples of metamorphic stones. They are expensive and used as flooring and bench top. Other types of stones are monolithic stones, rubble and ashlar. Ashlar stones are stones that have been carved into smaller modules. They are used like bricks before the use of bricks.
Hardness
Fragility Ductility Flexibility Porosity Density Conductivity Durability Reusability
Sustainability
Cost effectiveness
Stone Varies. Igneous is hardest, then metamorphic then sedimentary. Geometry dependant. Very Low Rigid. Varies. Depending on type but generally dense. Poor Extremely Very high. Can be reused without change or re-worked. Transport energy is the main factor. Stone sourcing has a high environmental cost. Depends on labour and scarcity.
Concrete Medium-High
Brick Medium-High
Medium
Medium
Very Low Very Low Medium Medium
Very Low Very Low Medium-low Medium
Poor Very Durable Medium. Can be crushed to be used as aggregate. Inclusion of recycled and waste products allows a positive reduction in carbon footprint. Generally cost effective.
Poor Very Durable High. Can be reused or crushed to be used as aggregate. Firing process adds to its carbon footprint.
Generally cost effective.
Week 3: Glossary Moment The moment of a force is the tendency to make an object or a point rotate. A force will only produce a moment about a point if it is applied at a distance from that point along a line of action that does not pass through the point. Moments are measured by the product of the force magnitude and the perpendicular distance between the line of the action of the force and the point. Slab on ground Slab on ground is a concrete slab place at or near ground level to serve as a combined floor and foundation system.
Retaining Wall Foundation walls provide support for the superstructure above and enclose a basement or crawlspace partly or wholly below grade. (CHING, “Building Construction Illustrated” p 3.10)
CHING, “Building Construction Illustrated” p 3.10
Pad Footing Pad footing is a type of footing used to spread a point load over a wider area and transfer the load to the ground.
CHING, “Building Construction Illustrated” p 3.09
Strip Footing Strip footing a type of footing that is used when load from a wall or a series of columns is spread in a linear manner.
CHING, “Building Construction Illustrated” p 3.09
Substructure The substructure is the underlying structure forming the foundation of a building.
WEEK 3 STUDIO ACTIVITY REPORT Sidney Myer Asia Centre The floor in Sidney Myer Asia Centre is made of polished concrete. The photo to the left shows cracks on the ground. This is due to the concrete ground contracting and tension creates these cracks.
Sidney Myer Asia Centre is structurally supported by these angled pre-cast concrete columns. This is a compression structure where the load from above is transferred through these columns to the ground. As there is a theatre hall below ground, there are no vertical columns that stretch down to the foundation but rather concrete load bearing walls surround the hall. There is also a cantilever that extends outwards from the wall. This is only supported at one end where the top of the angled columns are.
Frank Tate Pavilion The photo to the left shows the floor structure of the study shed in Frank Tate Pavilion. The structure here consists of steel bearings as the primary member spanning the longest distance and timber joists. The primary and secondary members are bolted together with metal plates. Stained timber flooring material sits above this frame structure.
The photo to the right shows a cantilevered floor made of pre-cast concrete with a rough finish. This is sandwiched between two in situ concrete slabs. The load of this cantilever is transferred through the concrete supports to the column and then to the ground.
Underground Car Park and South Lawn This photo shows one of the columns that hold up the car park below South Lawn. These columns are made of concrete that is cast in situ. The columns are shaped this way to accommodate the roots of the trees grown above at South Lawn. Evidences of efflorescence can be seen from columns and walls in this car park. This is due to the lack of moisture control as it is a car park and aesthetic quality is less of a concern.
Arts West Centre This large metal truss is seen at Art West Centre. While the metal frame itself is mainly aesthetic, the transfer of its load to the ground can be observed. The truss is supported at one end by a stone sculpture and load bearing wall at the other end. The timber beam seen in the photo is not structurally supporting the metal truss.
This is part of the outer wall of a building opposite the Arts West Centre. The outer wall seems to be made of concrete blocks but through an opening the main material of the load bearing wall is seen to be made of bricks. This is a brick masonry wall with a concrete skin.
Stairs at the West End of Union House The photo to the left shows a set of stairs at the west end of Union House. It is constructed out of a steel frame made of steel UC beams and steel plates bolted onto the beams that make up the steps. The load of the stairs and users walking on it is transferred through the horizontal spanning beams to their points of support.
David Caro Building This is a photo of the brick wall of David Caro building. Bricks tend to absorb water and expand over time. Originally, expansion joints were not included for this building’s walls and therefore cuts have to be made on the brick wall to allow for expansion. This can be seen from the vertical and horizontal lines on the wall in the photo.
North Court Union House The north court of Union House provides a shaded resting place. A membrane structure is used here to provide shade from the sun. This structure is a tension structure and it is supported by metal wires attached to metal poles that surround the structure. It is a cheap and efficient way to cover a large area with little materials.
Beaurepaire Centre Pool This is the exterior of the Beaurepaire Centre pool. Here the connection from the structural walls and columns to the ground can be seen. A stretch of strip footing underlies the stone wall while a pad footing can be seen under the column. Glass panels are used instead of walls to allow sunlight into the building.
Weep holes can be seen in brick cavity wall construction. They are place at the same height as the level of the ground. The photo to the right shows weep holes along the brick wall which are the same height level as the floor seen through the glass.
Lot 6 The structure of the Lot 6 building consists of precast concrete columns and glass panels. The columns are made off site and transported to the site. Glass panels separate the interior of the building from the outside, acting as walls for this column-and-wall structure.
Week 4: Floor Systems and Framing Systems Concrete systems: Slabs of various types are used to span between structural supports. These can be one-way or two-way. Steel systems: Steel framing systems can take various forms, with some utilising heavy gauge structural steel members and others using light gauge steel framing. This system uses steel girders (steel bearers) and joists. They sometimes combine with concrete slab systems. Timber systems: Traditional timber floor framing systems use a combination of bearers and joists. Bearers are the primary members of the floor system and span the longest system. Joists span perpendicular to joists and are the secondary members of the floor system.
http://1.bp.blogspot.com/-0ykvMM31rr0/T6Nh6AtM9cI/AAAAAAAAAHM/zpKl9AkWubA/s320/Joist.jpg
Week 4: Span and Spacing Span is the distance between two structural supports. It can be measured between vertical supports or between horizontal supports. The span is not necessarily the same as the length of a member. Spacing is the repeating distance between a series of like or similar elements. Spacing is often associated with supporting elements such as beams or columns and can be measured horizontally or vertically. It is generally measured centre-line to centre-line. Week 4: Concrete The common concrete mix is 1 part cement: 2 parts fine aggregate: 4 parts coarse aggregate: 0.4/0.5 parts water. When cement powder and water are mixed, hydration occurs. In this process crystals are formed that interlock and bind the sand, crushed rock and cement paste together. If too much water is added, the final concrete will not be strong enough. If too little water is added, the concrete mixture will be too stiff and it will be very difficult to work with. Formwork is the temporary support or moulds used to hold the liquid concrete in place until it becomes hard. Sacrificial formworks are supports that stay in place after the concrete hardens. Formwork can be built in situ or in a factory out of a range of different materials.
During the curing process the formwork needs to be supported as the weight of the wet concrete is very heavy. This is achieved by using props and bracings. Finishes can be applied on concrete surfaces. Concrete is very strong in compression but weak in tension. Reinforcement is used to improve its tension strength in the form of mesh or bars. The result is reinforced concrete. Concrete is permeable and if the steel bars are too close to the surface it will experience oxidisation and lead to structural degradation of the concrete. Week 4: Precast concrete Precast concrete refers to any concrete fabricated in a controlled environment and transported to site. They are more standardised and better in quality, they also allows work on site to be done at a faster rate. Precast concrete are limited in size due to the need for them to be transported to site. Changes on site are also hard to incorporate. Precast concrete is often associated with the structures of buildings. Precast concrete are rarely used in footings, and more commonly used in retaining walls, walls and columns. Week 4: In Situ Concrete In situ concrete is concrete that is cast in place instead of fabricated elsewhere. The process includes the fabrication and assembly of the framework, placing any required reinforcement, the pouring, vibration and the curing of the concrete. In situ concrete is used in many applications. It is generally used for structural purposes and is widely used in footings, retaining walls and all bespoke structural elements. Sometimes concrete is sprayed into place using a pressure hose. (SHOTCRETE) This is useful for landscapes, swimming pools, basement walls, etc. Week 4: Beams and Cantilevers A beam is a horizontal structural element. The function of a beam is to carry loads along the length of the beam and transfer these loads to vertical supports. It can be supported at both ends, supported at numerous points, supported at points away from the end or supported at only one end. A cantilever is created when a structural element is supported at only one end. The function of a cantilever is to carry loads along the length of the member and transfer these loads to the support. A cantilever can be horizontal, vertical and angled.
Week 4: Glossary Joist A joist is the horizontal secondary member of frame construction spanning perpendicular to bearers. They can be made of steel or timber depending on the type of frame construction. Steel Decking Steel decking serves as a working platform during construction and as a formwork for in situ concrete slab casting. They are corrugated to increase their stiffness and spanning capability. Concrete Plank Concrete plank is a precast, prestressed, hollow-core slab, usually relatively lightweight; used for floor and roof decking. Girder Girders are steel beams that serve as the primary member of steel frame construction. Spacing Spacing is the repeating distance between a series of like or similar elements. Spacing is often associated with supporting elements such as beams or columns and can be measured horizontally or vertically. It is generally measured centre-line to centre-line. Span Span is the distance between two structural supports. It can be measured between vertical supports or between horizontal supports.
http://stratco.com.au/Products/Steel_Framing/Types/Tuffloor/Images/joists.gif
Week 5: 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 short or long. Short columns are shorter in length and have thicker cross-sectional area. Long columns are taller and slimmer. Columns are considered short if the ratio of effective column length to the smallest cross section dimension is less than 12:1. Short columns fail by crushing when the compressive load applied exceeds their compressive strength. Columns are considered long if the ratio of effective column length to the smallest cross section dimension is greater than 12:1. Long columns become unstable and fail by buckling. The length of the column and how they are fixed determines how they will buckle and how much they can carry. Week 5: Walls, Grids and Columns Walls are used to enclose and separate spaces, moderate climate, filter out light and insulate the interior. Walls can also be a major structural component to carry loads. Structural frames: -
Concrete frames use a grid of columns with concrete beams connecting the columns together. Steel frames typically use a grid of steel columns connected to steel girders and beams. They may be braced with diagonal members. Timber frame uses a grid of timber posts or poles connected to timber beams. Bracing is required at the corners of junctions in order to stabilise the structure.
Load bearing: -
-
-
Concrete load bearing walls can be achieved using in situ or precast elements. Reinforced masonry load bearing walls are constructed from core filled hollow concrete blocks or grout filled cavity masonry. Bond beams over openings can be created using special concrete blocks which are filled with concrete to bond the individual units together. They 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 brick or metal wall ties placed within the mortar bed. Steel lintels are commonly used over opening. Cavity masonry walls are typically formed from two skins of masonry. Damp proof course and weep holes exist to prevent moisture from entering the interior of the building.
Brick Cavity Wall Detail (http://buildingtechnology.files.wordpress.com/2011/01/newpicture252872529.png)
Stud framing: -
-
Metal and timber stud framed walls use smaller sections of framing timber or light gauge framing steel. Noggings are used to prevent the long members from buckling. Stud framing generally consists of top plates, bottom plates, vertical studs, noggings, cross bracing and ply bracing. Brick veneer construction is a combination of a skin of non-structural masonry and a skin of structural frame wall. (E.g. structural stud wall with brick skin) They are widely used in the construction industry.
(http://www.carpentry-tips-and-tricks.com/images/Studwork.jpg)
Week 5: From Wood to Timber Wood is a natural material and not useful for construction. They have to be processed and made into timber which is suited for construction. Grain direction helps us understand the structural performance of the wood. The timber is strong and stiff parallel to the grain while weak perpendicular to the grain. Timber is seasoned to remove moisture content so that the timber is appropriate for intended use (<15% moisture). Timber is generally seasoned through air seasoning, kiln seasoning and solar kiln seasoning. Different woods have different properties and we group them based on their biological provenance.
Softwoods: pine, cypress, fir Hardwoods: ash, gum, oak Week 5: Timber Considerations Design detailing can and should minimise exposure to hazards. Always specify timber for a particular use/ scenario. Consider: -
Size Strength guide Moisture Content Species of wood Treatment Availability
Knots are weak points in timber. They can cause slope of grain. Knots should be used in positions of compression so that it is not a point of weakness. When used in tension it may break. Week 5: Engineered Timber Products Solid products: -
-
-
LVL- Laminated Veneer Lumber is made from laminating thin sheets of timber with grain aligned to longitudinal direction. It is possible to create very deep and long sections with LVL. It is mainly used in structural components. GLULAN- Glue Laminated Timber is made from gluing pieces of dressed sawn timber together to form a deep member. It is mostly laminated with grain aligned to longitudinal direction and mainly used for structural components. CLT- Cross Laminated Timber is made by gluing and pressing thin laminates together to form a sheet. It laminates with grains laid in alternate directions to provide strength in two directions. It is used in horizontal and vertical structural panels.
Sheet Products: -
-
-
Plywood is made by gluing and pressing thin laminates together to form a sheet. The grains in laminates are laid in alternate directions to provide strength in two directions. Plywoods are used for structural bracing and flooring, formworks, joinery and marine applications. MDF- Medium Density Fibreboard is 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 denser than plywood. It is used for nonstructural applications. Chipboards and strandboards are made by layering hardwood or softwood residuals in specific orientations with wax and a resin binder and applying high temperature and pressure. They are used for flooring and cladding finish.
Week 5: Glossary Stud Stud is the vertical member of a stud frame wall construction. Nogging Noggings are included in stud walls to prevent long members from buckling. Lintel A lintel is a structural horizontal member that spans the space or opening between two vertical supports. Buckling Buckling occurs when long and thin members fail through bending. Seasoned Timber Seasoned timber is timber that has been naturally or kiln-dried to remove most of its moisture content so that it can be used in construction. Timber is typically considered seasoned if it has less than 15% of its initial moisture content.
Week 6: Roof Systems Roof is the primary sheltering element of the interior. Roofs can be classified as Flat Roofs or Pitched/ Sloping Roofs. Flat roofs have a pitch of 1 to 3 degrees. Tile roofs tend to have a pitch of 15 degrees or higher while sheet metal roofs can be much lower. Concrete roofs are generally flat plates of reinforced concrete. The top surface is sloped towards drainage points and the entire roof surface is finished with applied waterproof membrane. Flat structural steel framed roofs consist of a combination of primary and secondary roof beams for heavier roof finishes such as a metal deck or concrete slab. Sloping structural steel roofs consist of roof beams and purlins with lighter sheet metal roofing. Portal frames consist of a series of braced rigid frames with purlins for the roof and girts for the walls. These are usually finished with sheet metal. Space frames are three-dimensional plate type structures that are long spanning in two directions. Linear steel sections of various cross section types are welded, bolted or threaded together to form matrix like structures. Gable roofs are characterised by a vertical, triangular section of wall at one or both ends of the roof. The roof consists of common rafters, ridge beams and ceiling joists. They can be timber, cold-formed steel sections or heavier steel. Where the roof overhangs the gable end wall outriggers are used.
RIDGE RAFTER PLATE
COMMON RAFTER RAFTER PLATE
RAFTER PLATE GABLE-END STUDS COMMON RAFTER Hip roofs are characterised by a vertical, triangular section of wall at one or both ends of the roof. The roof consists of common rafters, hip rafters, valley rafters, jack rafters, ridge beams and ceiling joists. They can be timber of cold-formed steel sections.
Truss roofs are framed roofs constructed from a series of open web type steel or timber elements. They are efficient and able to span long distances with little material. They are increasingly used for roofing.
(http://www.trusscorp.com.au/Assets/Images/Common-Roof-Truss.jpg)
Week 6: Introduction to Metals Pure metals can be found naturally although it is more commonly found in minerals. Metals are malleable, ductile and not brittle. Metals can be ferrous metals (iron) or non-ferrous metals (all others). Alloys are combinations of two or more metals and are ferrous if they contain iron and non-ferrous otherwise. Metal Properties Hardness Fragility Ductility Flexibility Porosity Density Conductivity Durability Reusability Sustainability Cost
Depends on type. Lead is not as hard as gold. Low High Medium-high. High when heated. Impermeable High Very good conductors of heat and electricity Can be durable if protected High Very high embodied energy. Recyclable and renewable Generally cost effective and economic
Metals will react with other metals by giving up or taking on another metalâ&#x20AC;&#x2122;s ions. The galvanic series lists the metals in order of their tendency to give up ions to other metals and corrode. Ion transfer will happen when metals are directly in contact with each other or they are in an environment that facilitates the transmission of the ions. To reduce the risk of corrosion metals can be separated by an insulator such as rubber gasket or kept away from moisture. Galvanised steel is steel coated with a thin layer of zinc to protect the steel from rusting.
Week 6: Ferrous Metals and Alloys Iron is magnetic, very chemically reactive and has good compressive strength. Wrought iron is formed when iron is heated and hammered into desired shape. It was widely used in bars for windows and doors and other decorative elements. It is still used today but is expensive and labour intensive. Cast iron is formed when iron is melted and the molten metal is poured into moulds to cool. It has a very high compressive strength. It is rarely used in contemporary construction due to its weight and brittleness and generally only used for compression elements. Steel is an alloy of iron with carbon being the primary addition element. Other alloying elements include manganese, chromium, boron and titanium. It is very strong and resistant to fracture. It can transfer heat and electricity and can be formed in to many different shapes. Steel is commonly used in framing. Hot rolled steel are elements shaped while the metal is hot. They are generally used as primary structural elements and protected with coating (paint or galvanising). Joints are welded or bolted together. Cold formed steel are elements folded from sheets that have been previously produced and cooled down. They are used as secondary structures and protected by galvanising. Joints are bolted or screwed together. Steel is also used as reinforcing bars due to its good tensile resistance. Deformation in the bars assists bonding with concrete. Steel sheeting is used in cladding and roofing and must be protected. Stainless steel alloy has chromium as the main alloying element. Wall ties in cavity walls are often made from stainless steel due to its corrosion resistance. Stainless steel is very rarely used as primary structure due to its cost. Week 6: Non Ferrous Metals and Alloys Aluminium is very light compared to other metals. They are non-magnetic and non-sparking. Aluminium can be easily formed, machined and cast. Pure aluminium is soft and lacks strength but alloys of them can have useful properties. They are used in extruded sections which are common for window frames and other glazed structures. Aluminium reacts with air creating a very fine later of oxide that keeps it from further oxidation, giving it a matte natural finish. Copper is reddish with a bright metallic lustre when polished and turns green from oxidation. It is very malleable and ductile, and is a good conductor of heat and electricity. It is traditionally used as roofing material and natural weather causes it to develop a green patina over time. It is also used in pipework and electrical cabling.
Zinc is a bluish-white, lustrous metal. It is brittle at ambient temperatures but malleable at high temperatures. Zinc is mainly used in galvanising to help protect iron from corrosion. It can also be used on its own as a cladding material for both roof and walls. Lead is a bluish-white lustrous metal. It is very soft, highly malleable, ductile and a relatively poor conductor of electricity. Lead was used frequently for roofs, cornices, tank linings and flashing strips but is less commonly used today because it is now known to be toxic to humans. Tin is a silvery-white metal, is malleable, somewhat ductile and has a highly crystalline structure. It is very rarely used today and generally only for decorative purposes. Titanium is well known for its excellent corrosion resistance and for its high strength-toweight ratio. It is light, strong, easily fabricated with low density. Titanium is presently used in strong light weight alloys, making an attractive and durable cladding material. It is prohibitively expensive. Bronze is an alloy of copper and tin. It is resistant to corrosion and is much harder than copper. Bronze is presently used in construction for bearings, clips, electrical connectors and springs. Brass is an alloy of copper and zinc. Brass is malleable and has a relatively low melting point and is easy to cast. It is not ferromagnetic. They are tough and typically used in elements where friction is required such as locks, gears, screws and valves. It is also commonly found in fittings.
Photo: Copper roof of a dome in Edinburgh. It shows a feature of copper creating a green coating from oxidisation. (http://www.builderbill-diy-help.com/copper-roofing.html)
Week 6: Glossary Rafter Rafters are sloped timber beams that extend from the ridge to roof beams or load bearing walls. Purlin Purlin is a horizontal structural member of the roof system that support roof loads and transfer them to roof beams. They span perpendicular to the direction of roof beams. Cantilever A cantilever is a beam that is anchored only at one end. Portal Frame Portal frame is a rigid structural frame system consisting essentially of two members connected at the top by a third member. Eave An eave is the bottom edge of the roof that projects out beyond the side of a building. Alloy Alloys are combinations of two or more metals. An alloy is ferrous if it contains iron and nonferrous it if doesnâ&#x20AC;&#x2122;t. Soffit Soffit is described as the underside of any construction element such as ceilings of the outer edge of a roof. Top chord A top chord is the highest longitudinal member of a truss.
Week 7: Rubber Rubber can be naturally sourced from Rubber trees (tree sap) or it can be synthesised in a laboratory generating a range of variations (plastic). Natural rubber is most commonly used as seats, gaskets, control joints, flooring, insulation, hosing and piping. Hardness Fragility Ductility Flexibility Porosity Density Conductivity Durability Reusability Sustainability Cost
Harder rubbers resist abrasion. Softer rubbers provide better seals Low High when heated but varies in cold state Highly flexible All rubbers are waterproof 1.5x of water Very poor (used as insulators) Can be very durable High Natural rubber has low embodied energy and medium for synthetic rubbers Generally cost effective
Week 7: Plastics Plastics are made from elements such as carbon, silicon, hydrogen, nitrogen, oxygen and chloride combined by chemical reactions into monomers. Monomers combine with each other to form polymers, which makes the substances we call plastics. Thermoplastics are mouldable when heated and become solid again when cooled. They can be recycled. (Polyethylene, Polycarbonate, Perspex, PVC) Thermosetting plastics can only be moulded once. Melamide Formaldehyde (laminex) is widely used for finishing surfaces. Polystyrene is mostly used in insulation panels. Elastomers (synthetic rubbers): EPDM, Neoprene, Silicone. Hardness Fragility
Medium-low Low-medium. Generally will not shatter or break but can be fragile in degraded state. Ductility High when in heated state and varies in cold state Flexibility High Porosity Many plastics are waterproof Density Low Conductivity Poor Durability Can be very durable depending on type, finishing and fixing. Reusability High for thermoplastics and elastomers, very limited for thermosetting plastics. Sustainability Embodied energy varies. Not renewable. Cost Generally cost effective Plastics degrade when exposed to weather, especially sunlight, and need to be checked and maintained.
Week 7: Paints Paints are liquid until they are applied on a surface forming a film that becomes solid when in contact with air. Their main purpose is to protect an element and give aesthetic properties. Clear paints are called lacquers or varnishes. Components: -
Binder: the film-forming component of the paint Diluent: dissolves the paint and adjusts its viscosity Pigment: gives the paint its colour and opacity. Can be natural or synthetic.
Types: -
Oil based: used prior to plastic paints. It can achieve very good high gloss finishes. It is not water soluble and therefore brushes have to be cleaned with turpentine. Water based: most commonly used today, it is durable and flexible. Tools and brushes can be cleaned with water.
Paint properties: -
Colour consistency: the colour of the paint should resist fading. Durability: paint needs to resist chipping, cracking and peeling. Exterior painted surfaces have to resist the effect of rain, air pollution and ultra-violet in sunlight. Gloss: surface finishes can range from matte to gloss. Flexibility: water based latex paint is more flexible than oil based paint.
Week 7: Detailing for Heat and Moisture Design and construction experts need to understand how to make sure that water doesnâ&#x20AC;&#x2122;t penetrate buildings and that heat flow is controlled according to climate. Tanking is the placement of a waterproof membrane, typically artificial rubber, around the construction. This is often used in basements. For water to penetrate into a building, all three following conditions must occur: -
An opening Water present at the opening A force to move water through the opening
Removing any one of the conditions and water will not enter. Three different strategies to prevent water from penetrating into a building: -
Remove openings Keep water away from openings Neutralise the forces that move water through the opening
One strategy is sufficient but two or more is pursued to increase security.
Openings can be planned elements such as windows, doors or skylights; or unplanned such as poor construction workmanship or deterioration of materials. Common techniques used to remove openings are sealants and gaskets. They are not as durable as buildings and therefore need to be updated over time. Keeping water away from openings is a commonly used strategy. This is done by: -
Grading/ sloping roofs so that water is collected in gutters which then discharge the water to downpipes and stormwater systems. Overlapping cladding and roofing elements. (Weatherboards and Roof tiles) Sloping window and door sills and roof or wall flashings Sloping the ground surface away from the walls at the base to buildings
Neutralising the forces is another strategy to keep water away from openings. These forces include gravity, surface tension, momentum and air pressure differential. Slopes and overlaps are used to carry water away from the building using the force of gravity (flashings). A drip or a break between surfaces prevents water clinging to the underside of surfaces such as a window sill or parapet capping. These gaps and breaks prevent water reaching and entering openings because the surface tension of the water is broken at the drip location. Instead, the water drops down. Windblown rain, moisture and snow can move through simple gaps. To inhibit this movement, gaps are often constructed in more complex shapes. The complex shape slows the momentum of the moisture and helps to deflect the water away from the gap entry. Water can still move through gaps if there is a difference in air pressure. An air barrier is introduced in the internal side of the gap to create a pressure equalisation chamber (PEC) so that water is not â&#x20AC;&#x2DC;pumpedâ&#x20AC;&#x2122; through the gap. Heat gain and heat loss occurs when: -
Heat is conducted through the building envelope. The building envelope and building elements are subjected to radiant heart sources. Thermal mass is used to regulate the flow of heart through the building envelope.
Effective control of heat gain and heat loss saves energy, saves money and increases comfort levels for occupants. Controlling heat through conduction can be done by using: -
-
Thermal insulation to reduce heat conduction Thermal breaks made from low conductive materials like rubbers and plastics to reduce heat transfer from outside to inside when using highly conductive materials like metals Double glazing or triple glazing so that the air spaces between glass panes reduces the flow of heat through the glazed elements
Controlling heat through radiation is done by using reflective surfaces and shading systems that prevent radiation striking the building envelope (blinds, screens, vegetation).
Large areas of exposed thermal mass can be used to absorb and store heat over a period of time. When temperatures drop, the stored heat is released. This system works well when there are large differences in temperatures between day and night (not in tropical areas). Materials used for thermal mass include masonry, concrete and water bodies. Air leakage occurs if a building has: -
An opening Air present at the opening A force to move air through the opening
Strategies to stop air leakage include: -
Eliminating any of the causes Wrapping the building in polyethylene or reflective sarking to provide air barrier Weather stripping around doors, windows and other openings
Week 7: Arches, Domes and Shells (CHING, “Building Construction Illustrated” p 2.25-2.27) Arches are curved structure for spanning an opening, designed to support a vertical load primarily by axial compression. They transform the vertical forces of a supported load into inclined components and transmit them down the sides of the archway. Vaults are arched structures of stone, brick or reinforced concrete, forming a ceiling or roof over a hall, room or other wholly or partially enclosed space.
(CHING, “Building Construction Illustrated” p 2.25)
A dome is a spherical surface structure having a circular plan and constructed of stacked blocks, a continuous rigid material like reinforced concrete, or of short, linear elements, as in the case of a geodesic dome. A dome is similar to a rotated arch.
(CHING, “Building Construction Illustrated” p 2.26)
Shells are thin, curved plate structures typically constructed of reinforced concrete. They are shaped to transmit applied forces by membrane stresses â&#x20AC;&#x201C; the compressive, tensile, and shear stresses acting in the plane of their surfaces. Week 7: Glossary Drip A drip is a metal strip that extends beyond the other parts of the roof and is used to direct rainwater off the wall of the building. Vapour Barrier A vapour barrier is any material used for damp proofing, typically a plastic or foil sheet, that resists diffusion of moisture through wall, ceiling and floor Gutter Gutter is a narrow trough or duct which collects rainwater from the roof of a building and diverts it away from the building structure. Parapet A parapet is a barrier which is an extension of the wall at the edge of a roof. Down pipe Downpipe is a pipe that carries water from the gutter to the drain or to ground level. Insulation Insulation is any material used to reduce or control the effects of heat or sound; or protects against transfer of heat and electricity. Sealant Sealant is a waterproof material used for sealing gaps between elements to make it airtight and watertight. Flashing Flashing is a thin, impervious sheet of material placed in construction to prevent water penetration or direct the flow of water. Flashing is used especially at roof hips and valleys, roof penetrations, joints between a roof and a vertical wall, and in masonry walls to direct the flow of water and moisture.
(http://www.dictionaryofconstruction.com/definition/flashing.html)
Week 8: Glass Glass components: -
Formers are the basic ingredient used to produce glass. Any chemical compound that can be melted and cooled into a glass is a former. (silicon sand) Fluxes help formers to melt at a lower temperature. (soda) Stabilizers combine with formers and fluxes to keep the finished glass from dissolving or crumbling. (lime)
Glass is non-porous and waterproof. The density of glass is medium high and it is able to transmit light and heat but not electricity. Hardness Fragility Ductility Flexibility Durability Reusability Sustainability Cost
High High Very Low Very high when molten but very low when cooled. Very durable Very High Typically high embodied energy Generally expensive to produce and transport
Two main types of glass: -
Flat glass Shaped glass
Float glass is now the most common glass production process in the world. Clear float glass is the simplest and cheapest glass product available in the market. It breaks into very sharp shards. A tough plastic interlayer is bonded together between two glass panes to create laminated glass. Laminated glass improves the safety and security of glass products as even though the glass can still crack, the sharp fragments tend to adhere to the plastic rather than falling apart. Tempered glass is produced by heating annealed glass to approximately 650 degrees Celsius at which point it begins to soften. The surfaces of this glass are then cooled rapidly creating a state of high compression in the outer surfaces of the glass. As a result the bonding strength is increased; making it break into small, pellet shaped pieces rather than sharp shards, improving the safety of the product. Other types of glass: -
Tinted glass: useful in sun-exposed situations to reduce visible light transfer Wired glass: similar to laminated glass but a steel wire mesh is used instead of plastic film. Patterned glass
-
Curved glass Photovoltaic glass Glass channels: used in façade systems Slumped and formed glass: used as design features Glass fibres: hair-like strands used in telecommunications.
Week 8: Glass Skins – John Sadar “The role of the glass has shifted from allowing light to penetrate the building enclosure to being the building enclosure.” Glass is material – Glass is invisible rock; it is visibly light but physically dense. Glass is technology – Glass has advanced from mouth blown glass to float glass. It has diffused into a wide range of products. (E.g. holographic, dichroic, photovoltaic, double-skin, laminated, fritted, angle-selective.) Glass has advanced from being framed as a window to becoming a glazing system. Glass is cultural artefact – Humans have a relationship to the sun and the natural world. Glass is the interface between the building and the sun. It is seen as having the potential of bringing our ideal picture of balance with the natural world into fruition due to its invisible effects. Week 8: Openings: Doors and Windows
WINDOWS AND WINDOW TERMINOLOGY
http://www.1stwindows.com/terminology.htm
Week 8: Glossary Window sash A window sash is the secondary frame of a glass panel that is movable. Inertia Inertia is the resistance of any physical object to any change in its state of motion, including changes to its speed and direction. Door Furniture Door furniture refers to fixtures on a door which include handles, locks, door stops, hinges, etc. Stress Stress is the load per unit area applied onto a system that would tend to deform the body on which it applies. CHING, â&#x20AC;&#x153;Building Construction Illustratedâ&#x20AC;? p 8.23
Shear force Shear force is the force in the beam acting perpendicular to its longitudinal axis.
WEEK 8 STUDIO ACTIVITY REPORT INSULATION
TIMBER STUD
STEEL FRAME
BRICK MORTAR INSULATION DOUBLE GLAZED GLASS PANEL
TIMBER STUD
CAULK JUNCTION STEEL FRAME FIXING STEEL
WINDOW SILL REVEAL DETAIL
Above: Photo of actual building. The detail allocated is a pop up window extending out from a brick wall. The window is composed of a steel frame and double glazed glass panels.
Above: The steel frame of the window is welded together as seen from the mark.
Above: The outer fabricated steel is screwed into steel frames underneath. The junction between the steel window sill and the glass can be seen here as well.
Week 9: Construction Detailing Detailing is about how materials are put together in any construction project. It may be based on tradition or innovative. One element of construction detailing is movement joints. Movement joints accommodate for materials moving, expanding and contracting. These include expansion joints, contraction joints and movement joints. Health and safety is also an important consideration for construction. Detailing for stairs is an example of this. Material selection is limited based on legislations and risks such as fire. Buildings age over time. Some materials tend to deteriorate quickly with water damage. Therefore coating of materials is an important detail especially in harsh environments such as coast side and industrial areas. A matte surface will age more gracefully than a glossy surface. Some materials improve their appearance with age. Copper creates a green coat as it oxidises. Another area of detailing is how easily surfaces can be repaired. Plasterboard is commonly used in housing and it can easily be patched or painted. Corners are particularly vulnerable to damage and a metal piece is often attached to corners to protect them from damage. Cleanable surfaces are important, especially for places like restaurants or hospitals. Curved corners can avoid trapped dirt and therefore detailing and material selection to accommodate this is important. Providing maintenance access such as suspended ceiling allows for ventilation and ductwork to be hidden, and if damage occurs the tiles can be replaced and there is also access into this space for cleaning. Three general principles for constructability are: -
Easy to assemble (e.g. assemble points) Detail should be forgiving Detail should be based on efficient use of construction facilities, tools and labour.
Week 9: Composite Materials Monolithic materials are a single material or materials combined so that components are indistinguishable. Composite materials are created when two or more materials are combined in such a way that the individual materials remain easily distinguishable. They are formed from different materials that are bonded together and retain their identities and properties. They act together to provide improved specific or synergistic characteristics not obtainable by any of the original components acting alone. They can be fibrous, laminar, particulate or hybrid. Fibre Reinforced Cement (FRC) is made from cellulose fibres, Portland cement, sand and water. They are commonly found in sheet and board products but can also be in shaped
products such as pipes and roof tiles. It is used in cladding for exterior or interior walls and floor panels. Fibre cement building materials will not burn, are resistant to permanent water and termite damage and resistant to rotting and warping. It is reasonably inexpensive material. Fibreglass is a mixture of glass fibres and epoxy resins. It is commonly found in flat and profiled sheet products and shaped products. It is used as transparent or translucent roof or wall cladding and for preformed shaped products such as water tanks, baths and swimming pools. The benefits of fibreglass products is that they are fire resistant, weatherproof, relatively light weight and strong. Aluminium sheet composites are made from aluminium and plastic. It is commonly used as a feature cladding material in interior and exterior applications. Reduced amount of aluminium are required for making and lighter weight, less expensive sheets can be produced. They are weather resistant, unbreakable and shock resistant. Timber composites are combinations of solid timber, engineered timber and galvanised pressed steel. It is commonly found with timber top and bottom chords with galvanised steel or engineered plywood webs. They are used as beams and trusses. Minimum amount of material is used in timber composites to achieve maximum efficiency. They are also cost effective, easy to install and easy to accommodate services. Fibre reinforced polymers are made from polymers with timber, glass or carbon fibres. They are often associated with moulded products. They are commonly used for decking and structural elements. Some FRP materials can provide a strength-to-weight ratio greater than steel and they are corrosion resistant. Week 9: Movement Joints (CHING, â&#x20AC;&#x153;Building Construction Illustratedâ&#x20AC;? p 7.48-7.50) Expansion Joints Expansion joints are continuous, unobstructed slots constructed between two parts of a building or structure permitting thermal or moisture expansion to occur without damage to either part. Control Joints Control joints are continuous grooves or separations formed in concrete ground slabs and concrete masonry walls to form a plane of weakness and thus regulate the location and amount of cracking resulting from drying shrinkage, thermal stresses or structural movement. Isolation Joints Isolation joints divide a large or geometrically complex structure into sections so that differential movement or settlement can occur between parts. At a smaller scale, an isolation joint can also protect a non-structural element from the deflection or movement of an abutting structural member.
Week 9: Joints (CHING, “Building Construction Illustrated” p 2.30)
Week 9: Glossary Sandwich Panel Sandwich panel/ Aluminium composite panel (ACP) is a type of flat panel that consists of two thin aluminium sheets bonded to a non-aluminium core. They are frequently used for external cladding or facades of buildings, insulation, and signage. Skirting Skirting/ Base board is a board covering the lowest part of an interior wall. Its purpose is to cover the joint between the wall surface and the floor. Composite Beam Composite beam is a beam combining different materials to work as a single unit, such as structural steel and concrete or in situ and precast concrete. Cornice The cornice is the uppermost section of mouldings along the top of a wall or just below a roof.
Week 10: Lateral Loads Wind and earthquake forces are dynamic lateral loads. Wind and earthquake forces have different effects on buildings. Wind forces are a function of the exposed surface area to wind while earthquake forces are a function of the amount of building mass above the foundation. Resisting lateral forces: Structures that respond properly to lateral forces must have resistive elements in both the horizontal and vertical planes. Diaphragms are structural elements that resist and collect lateral forces in the horizontal planes of a structure and transfer them to the vertical bearing elements. Roofs and floors can be considered diaphragms. Braced frames are essentially truss structures that provide diagonal paths for moving the lateral loads through the structure in the vertical planes. Shear walls are structural elements made of rigid materials that resist lateral loads in the vertical planes. Shear walls collect the lateral loads from the horizontal resisting elements and transfer them to the foundation. Moment resisting frames are structural systems that are constructed with rigidly connected joints. The joints of these frames provide a continuous interface between the horizontal and vertical elements and make the frame rigid enough to act as a monolithic unit under the impact of lateral loads. Seismic base isolators are connections placed between the foundation and the substructure that allow the substructure and superstructure to move independently of the foundation during earthquakes. Area of weakness: A soft story exists in a building when one or more floors are significantly weaker or more flexible than those above and/or below. They result in uneven load distributions and nonuniform deflections in response to lateral loads. Re-entrant corners occur in irregular geometries such as L, T, H, U or + shapes. The most critical problem with these plans is the differential stiffness throughout the structure that leads to various degrees of resistance to lateral forces. Discontinuous structural members such as window or door openings in shear walls, split floor levels, column offsets and sharply changing roof profiles can result in weakness and areas of stress concentration. In an earthquake, loads are applied to each floor at the center of mass. If the center of mass of the floor does not coincide with its center of rigidity, then there will be a moment applied to the floor, producing torsion and deflection.
Week 10: Collapses and Failures â&#x20AC;&#x201C; Peter Ashford Flat steel sheeting on plywood considerations: -
Thermal differences Corrosion of cut edges Glue failures Galvanised exposed nails to fix sheeting Reclad with exterior grade plywood Fixing method
Materials selection critical considerations: -
Suitability of material for the application (exposure, compatibility, strength and deflection) Long term performance Maintenance Construction and detailing
Week 10: Heroes and Villains, a framework for selecting materials â&#x20AC;&#x201C; Dr Dominique Hes Issues to consider when selecting materials: -
Health Waste, recycling, recycled Energy use and embodied energy Pollution Life cycle
Health considerations: -
Reduced VOCs (water paints, sealers, adhesives, particleboard, carpets) Reduced particles/ dust (horizontal shelves, floor coverings, loose fibre products) Green cleaning practices (vacuuming, chemicals)
Source and waste considerations: -
Renewable/ Abundant resources (agricultural products, timber) Timber (recycled, plantation) Waste (reduce, reuse, recycle, minimise use of composites)
Energy considerations: -
Minimise embodied energy Optimise lighting Optimise appliances
Pollution considerations: -
Minimise waste
-
Choose materials that donâ&#x20AC;&#x2122;t contain toxins Choose natural materials Choose organic
Life cycle: -
A way of looking for the best solution Consider the longevity of materials Consider the timelessness of the materials Design for reuse, recyclability, maintenance Design for purpose Design for durability
Week 10: A Tale of Corrosion Statue of Liberty: Galvanic Corrosion The Statue of Liberty was designed by Auguste Bartholdi. The copper skin is supported on an iron skeleton designed by Gustave Eiffel. When copper is exposed to the atmosphere, it reacts with oxygen. The copper starts to dull, first becoming a darker brown colour and then forming a green copper oxide patina. The first solution to stop corrosion of the copper and iron was to separate them at their junctions by a layer of shellac-impregnated asbestos cloth. However, over time the cloth became porous and actually held moisture at the joint between the two metals. This provided good conditions for galvanic corrosion and the iron begins to corrode. The connection system started to fail as the build-up of rust expanded and pulled the rivets away from the copper skin. The second solution was to replace the original iron armature frame with Teflon-coated stainless steel.
Week 10: Glossary Shear wall Shear wall is a wall portion of a structural frame intended to resist lateral forces, such as earthquake, wind, and blast, acting in the plane or parallel to the plane of the wall. Soft storey A soft story exists in a building when one or more floors are significantly weaker or more flexible than those above and/or below. Braced frame Braced frame is a structural system which is designed primarily to resist wind and earthquake forces. Life cycle Life cycle refers to the period of time that a building (or material) can be expected to actively and adequately serve its intended function. Defect A defect is any condition or characteristic that detracts from the appearance, strength, or durability of an object. Fascia Fascia is a board or flat piece of material covering the ends of rafters or other fittings. Corrosion Corrosion is the gradual destruction of metals through chemical reactions to its environment. IEQ Indoor Environmental Quality (IEQ) is an important criterion for green, or sustainable, building design. It refers to general overall building occupant comfort. This includes humidity, ventilation and air circulation, acoustics, and lighting.
CONSTRUCTION WORKSHOP REPORT The aim of the construction workshop was to create a beam that can hold the greatest load before structural failure. Each of the four groups was given specific types of material and quantity to construct their beams. The product of each group’s work is shown below: Group 1 The first group’s product was a timber frame structure. It consists of timber flanges with hardwood sheets used as bracings spanning in between to create trusses. The hardwood sheets are nailed onto the timber. Both vertical and angled bracings are used in the beam.
Group 2
The second group’s beam was a simple product of nailing three timber products together to form a beam. As the largest load will be a single point coming from above, this beam can be placed standing so that the load can be transferred across all three timber layers.
Group 3 The third group’s product is a triangular timber truss. This is made of two long softwood products angled to meet at a point and nailed to two hardwood sheets at the base to form a triangular truss. When a force is applied at the top, the two softwood members will be in compression while the hardwood base will be in tension.
Group 4 Group 4’s product is quite unique. The beam is constructed from two pieces of hardwood sheets sandwiched between two long softwood timber products. Another piece of softwood is added at the bottom to hold everything in place. All members of the beam are nailed together. The reason for the group’s decision to construct the beam in this way is unknown.
Testing for structural performance When the construction of the beams is complete, the products are tested for structural performance and failure. A point load is applied at the highest centre point of each beam and their strength is tested to see how much weight they can withstand before failure.
Group 1
The first groupâ&#x20AC;&#x2122;s beam did not experience structural failure but rather material failure. As seen in the left image above, there is a knot where the timber flange cracked under compression. Although this has been placed in compression, the knot still caused material failure as it covers most of the width of the timber member. The right photo above shows the crack in the timber where the beam failed.
Group 2 The second groupâ&#x20AC;&#x2122;s beam was able to hold a weight of 680kg before failure. With three layers of softwood attached together, the beam bended under the large force and failed when the tension at the bottom is too high causing the timber to crack and break. The maximum deflection for this beam is 33mm.
Group 3
The third groupâ&#x20AC;&#x2122;s beam was successful in holding up a large weight before failing. The load is divided between the two softwood members and transferred down to the base. The beam was able to hold a load of up to 690kg before failing. The structure failed when one of the bracings broke under too much compression. The maximum deflection for this beam is 75mm.
Group 4 The fourth groupâ&#x20AC;&#x2122;s beam was the least effective in supporting the point load applied. The beam failed when the softwood pieces bended too much and broke. The maximum load was 550kg and the maximum deflection was 65mm.