Logbook week 3

LOGBOOK WEEK 3 FOOTINGS AND FOUNDATIONS          

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Looking for buildings to be in equilibrium.

This is achieved by transferring loads to the ground.

Foundations found at bottom of building where it meets the ground, part of the substructure.

Must also resist force of soil pressing against walls.

Soils move and cause movement of foundations and footings, resulting in structure moving, cracking.

In unstable soil, foundations may go right down to the bedrock.

Pad footings or isolated footings: spread a point load over larger area.

Strip footings: used when loads from a wall or columns spread in linear manner.

Raft foundation: sometimes also called raft slab, provides increased stability by joining individual strips together as single mat.

End bearing piles: extends foundations to bedrock or soil that provide support for structure.

Friction piles: rely on resistance of surrounding earth to support structure. (Drilling along timber, steel or concrete members into ground) or (drilling into ground and then filling hole with concrete and reinforcements are sometimes put into the hole first.

Retaining walls and foundation walls to resist earth pushing against foundations.

STRUCTURAL ELEMENTS      

Structures rely on structural elements for loads to be carried, the materials the elements are composed of and shape of the element.

Struts: compression element. Column or element in truss.

Ties: vertical members used as tension elements.

Beam: partly in tension, partly in compression, horizontal member across spans. Made from timber, steel, reinforced concrete.

Slab/plate: transferring weight in two direction or just one if thickened in one crucial direction. Horizontal.

Walls: carries and transfers loads to footing or slab below, as well as bracing system to prevent rotation (shear diaphragm).

MASS MATERIALS         

Materials used in mass construction: stone, earth, steel and concrete.

Stone: pyramids, great wall, Earth: mud brick walls, compacted in form work as a wall.

Bricks: clay products fired in ovens at high temp, earliest examples from china.

Concrete: reinforced form used more commonly today.

Main properties: strong in compression, weak in tension, hard, strong, good thermal mass and durable.

Mass construction can be modular or non-modular.

Modular: clay brick, mud brick, concrete block, ashlar stone Non modular: concrete, rammed earth, monolithic stone (columns and beams).

MASONRY          

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Mass construction made from smaller units of stone, earth, clay or concrete.

Stone: slabs, ashlar blocks, rubble stone.

Earth: mud bricks.

Clay: Bricks, honeycomb blocks.

Concrete: Blocks, commons (smaller).

Bond: the pattern or arrangement of the units.

Course: a horizontal row of masonry units.

Joint: the way units are connected to each other.

Mortar: mixture of cement or lime, sand and water used as a bonding agent.

Masonry properties: the properties of the unit (part) are to a degree applicable to the built element. The units together act as a monolithic whole.

Stone can be used to create arches and beams.

Arches can be rotated three dimensionally to create a dome.

GEOMETRY AND EQUILIBRIUM 

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Centre of mass of an object is point about which that object is balanced and where the entire mass of the object is concentrated. The location of the centre of mass (AKA centre of gravity) depends on an objects geometry.

Equilibrium is a state of balance as a result of equal and opposite forces. Applied forces must be resisted by equal reaction forces from structural members for equilibrium to occur.

A body in equilibrium can be represented by a free body diagram, which involve simplified forces and joints.

For an object to be in equilibrium, the net horizontal, vertical and moment must = 0.

Moment is the rotation of an object when a force is applied along a line of action that doesn’t pass through the point.

M = Force x Distance, the positive direction is anticlockwise and distance is measured perpendicular to the point.

(Measured in newton metres NM).

CONCRETE BLOCKS   

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Dimensions: 90 long by 90 wide and 190 high.

Standard masonry unit made from concrete. Large range of sizes and proportions available for different purposes.

Generally have holes in them, useful to reduce weight, increase insulation ability and allows for steel reinforcement to be placed inside.

Made from sand, cement, gravel and water. Manufacturing process involves mixing, moulding and curing.

Used for walls both load bearing and non-load bearing walls.

Properties: medium to high hardness, medium fragility, low ductility very low flexibility.

Medium permeability sealed to reduce water absorption. Medium density and poor conductors of heat and electricity.

Very durable, recycled medium and also crushed as aggregate.

Positive reduction in carbon footprint as inclusion of recycled materials.

Generally cost effective however labour must be considered.

Can have unique, bespoke designs (can be expensive).

CONCRETE BLOCKS vs CLAY BRICKS:

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Concrete shrinks over time while bricks expand.

Blocks shrink due to cement paste reducing in volume as it hydrates and drying shrinkage occurs as water lost to atmosphere.

Bricks tend to absorb moisture from atmosphere and expand.

Both require movement joints.

BRICKS      

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Standard sized masonry unit made out of clay which is then shaped and hardened by heating in a kiln oven. Proportions vary slightly from types and countries, however always a similar size.

Standard size is 230 long 76 high 110 wide. The dimensions are as such to account for the mortar placed in between bricks.

The top part of the brick is the bed, the front face is the stretcher and the side face is the header.

Wide range of colours as clay is natural material.

Three main types of bricks; extruded and wire cut, machine pressed and handmade (convictmade).

Laid in different ways, stretcher course is the usual horizontal form, header course is the vertical positioning, brick on edge course is bricks vertically laid thin side facing out while soldier course the horizontal with thin side facing out.

Mortar joints are normally 10mm wide. Vertical joints are called perpends, horizontal joints are named bed joints.

There is a wide range of finishes that can be applied which depends on the brick type, weather conditions and aesthetic choices.

The properties include hardness (medium – high), fragility (medium), ductility (very low) and flexibility (very low).

Bricks have low permeability, medium density and is a poor conductor of heat and electricity.

Very durable material with high recyclability, generally locally produced however firing process adds to carbon footprint. Bricks are fairly cost effective but labour and transport costs need to be considered.

ADVANTAGES: Bricks can be joined with water based mortar and will not deteriorate if properly ventilated.

DISADVANTAGES: Absorb moisture and expand over time (require expansion joints), salts and lime from soil can be brought up if in contact with earth which causes aesthetic problems and pathologies.

Require expansion joints or cracking can result.

STONE     

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Type and technique of construction varies with location.

Stone can be categorised into three different types: igneous, sedimentary and metamorphic.

Igneous formed when molten lava cools, very dense and hard stone. Used in footings of buildings.

Sedimentary such as limestone is much softer and less dense, favoured for easy carving.

Metamorphic stone such as marble formed when sedimentary or igneous is subjected to pressure, high temperature or chemical processes.

Typically used as flooring, cladding or bench top uses.

Gabion wall is stones in cage mesh, screening or retaining walls typically.

Retaining walls where earth is being held back.

Monolithic stones not used anymore, due to difficulty transporting.

Ashlar, stones carved into smaller units, usually flat faced. Can be seen in Great Wall of China.

Rubble, stones used as found, or worked minimally. Require skilled labour to sort and place stones.

Properties of stone including wide ranging permeability, high density, poor conductors of heat and electricity.

Hard, igneous > metamorphic > sedimentary Fragility depends on geometry, have low ductility, and have low flexibility.

Very durable, high recyclability, transport energy is main factor of carbon footprint.

Cost dependent on labour and rarity of the stone used.

TUTORIAL ACTIVITY   

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The tutorial involved a tour of the university campus with close analysis of key buildings.

This resulted in a number of observations of features of structures.

The David Caro Physics building was constructed without expansion joints for bricks, which has resulted in extensive cracking of the building as they have no room. To counter this, large vertical cuts have been made into the structure.

The Beaurepaire Building is a steel framed brick building with no bracing; a portal frame creating a rigid joint has been used. The steel has not been galvanized and corrosion is visible.

The tent on the north side of Union House covering the bbq and stage area is a membrane structure which is pulled into tension by mass concrete.

The carpark under the Sth lawn features two way curved columns in situ concrete evenly distributed to account for car spaces.

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The undercover study/leisure area adjacent to the Sydney Myer Asia Centre and Alice Hoy has steel and concrete footings and columns, timber joists made of pine and hardwood decoration with galvanized zinc cladding for protection.

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Old Arts features a 3.5 metre deep steel truss spanning 25 – 30 + metres which is also the depth of the floor of the 2nd level. The truss is supported by the Old Arts building and a concrete column.

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The Sports Pavilion contains in situ concrete for the race from clubrooms to the oval, evident from the spacers in the concrete where reinforcement was placed during pouring.

The Architecture Building and Planning Building has in situ concrete columns and slab as part of the substructure. A pad footing takes load of all columns in building.

Combination of in situ and pre cast concrete to save time and labour and extruded aluminium window frames are a feature of the structure.

KEY TERMS 

Moment: The tendency of a force to produce rotation of a body about a point, equal in magnitude to the product of the force and the lever arm (perpendicular distance) in a clockwise or anticlockwise direction.

Strip footing: continuous spread footings of foundation walls.

Retaining wall: A wall that resists lateral loads of earth, with the load assumed to be acting 1/3 above base of wall. Used in basements, on hills to prevent soil shifting downslope.

Slab on ground: concrete slabs on the ground plain and is in two types; conventional slabs that have deep excavated beams and waffle slabs which have Pad footing: Simple, cost effective, stump footings used for vertical load support for timber frames.

Substructure: underlying structure forming the foundation of the building.

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REFERENCE LIST           

“Structural Elements” Retrieved from: https://www.youtube.com/watch?v=wQIa1O6fp98&feature=youtu.be “Footings and Foundations” Retrieved from: https://www.youtube.com/watch?v=PAcuwrecIz8&feature=youtu.be “Mass Construction” Retrieved from: https://www.youtube.com/watch?v=8Au2upE9JN8&feature=youtu.be “Masonry” retrieved from: https://www.youtube.com/watch?v=DC8Hv8AKQ8A&feature=youtu.be “Geometry and Equilibrium” Retrieved from: https://app.lms.unimelb.edu.au/bbcswebdav/courses/ENVS10003_2014_SM2/WEEK%2003/GEOMETRY%20AND%20EQUILIBRIUM.pdf “Bricks” Retrieved from: https://www.youtube.com/watch?v=4lYlQhkMYmE&feature=youtu.be “Concrete Blocks” Retrieved from: https://www.youtube.com/watch?v=geJv5wZQtRQ&feature=youtu.be “Stone” Retrieved from: https://www.youtube.com/watch?v=2Vn5_dk4RtQ&feature=youtu.be “Concrete Slab Floors” Retrieved from: http://www.yourhome.gov.au/materials/concrete-slab-floors Ching, F. (2014). Building Construction Illustrated. (5th ed.). Hoboken, New Jersey: John Wiley & Sons.

“Stump Pad Footings” (2014). Retrieved from: https://www.dlsweb.rmit.edu.au/toolbox/buildright/content/bcgbc4010a/09_footing_systems/03_stump_pad/page_001.htm