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Week 3: Footings and Foundations eLearnings • Centre of mass • Equilibrium • Foundation systems • Subsidence • Foundation types Independent Site Survey • Board pier Auguring • Cassion foundations


ENVS 10003 CONSTRUCTION LOG BOOK eLearning’s Foundations and Footings Centre of Mass -The center of mass is the point about which an object is balanced. -Point where the entire weight of the object is concentrated. -Location of the center of mass depends on the object’s geometry. -Referred to as Centre of Gravity.

Equilibrium Equilibrium-state of balance or rest resulting from the equal action of opposing forces. -As each structural element is loaded, its supporting elements must react with equal but opposite forces. -Applied forces must be resisted by equal and opposite forces-reaction forces. -In a building structure, the reaction forces are developed in the supporting elements.


ENVS 10003 CONSTRUCTION LOG BOOK Equilibrium and Free Body Diagrams -Objects or systems in equilibrium can be represented in diagram form called free body diagrams. -Real life appearance of elements is replaced by a combination of simple lines with symbols showing the types of structural connections used (roller, pin and fixed joints). -The applied forces (F) and reaction forces (R) are represented by arrows

-Allow the system to be analysed so that the amount of load distributed to each support can be determined. Equilibrium-Object or System at Rest -Sum of the applied and reaction forces must be zero in order for equilibrium to exist. -We need to consider: 1. The sum of the vertical forces must be equal to zero. ∑V=0

2. The sum of the horizontal forces must be equal to zero. ∑H=0

3. The sum of the movements must be equal to zero. ∑ M = 0 27

ENVS 10003 CONSTRUCTION LOG BOOK Foundation Systems Overview -Foundations are the substructure that are constructed party or wholly below the surface of the ground -Primary function-to support and anchor the super structure above and transmit its loads safely to the earth -Must accommodate the form and layout of the superstructure and respond to the varying conditions of soil. rock and water below -The principle loads acting on the foundations are a combination of dead loads and live loads that act vertically -It must also compensate for Horizontal loads such as wind induced sling, uplifting or overturning, sudden rotund movements and resist the surrounding pressure of the mass of soil and groundwater -May also have to counter the thrust imposed by tensile structures


ENVS 10003 CONSTRUCTION LOG BOOK Subsidence -The gradual settlement of a structure as the soil beneath the foundation consolidates under loading -Increase of structure loads causes a reduction in the volume of soil voids containing air or water -Subsidence occurs relatively quickly in dense, granular soils such as course sand or gravel -Clay soils have a large percentage of voiles therefore subsidence can be quite large and occur over a longer period of time

-A proper designed foundation system ensures that all loads are evenly distributed so subsidence is uniformly distributed -A uniform foundation system should have an equal load per unit area without exceeding the bearing capacity -Differential settlements is caused when there is uneven consolidation of the foundation system, causing the building to partially subside, crack and warp -this can often lead to the failure of the structural integrity of the building

DRAW fig pg. 2.08


ENVS 10003 CONSTRUCTION LOG BOOK In Construction: Classification of foundation systems of two broad categories-shallow and deep Factors when deciding foundation systems -Pattern and magnitude and building loads -Subsurface and groundwater infrastructure -Topography of the site -Impact on the adjacent properties -Building code requirements -Construction method and risk

Shallow -Employed when stable soil of adequate bearing capacity occur near the ground surface -Transfer loads by direct vertical pressure n/resistantstructures.html

Factor to Consider in selecting, assigning and designing the type of foundation system -Pattern and magnitude of building loads -Subsurface and groundwater conditions -Topography of the site -Impact on adjacent properties -Building code requirements -Construction method and risk Deep -Employed when underlying soil is unstable or of inadequate bearing capacity -Go through the unsuitable soil down to the appropriate load brewing platform or stratum of rock/dense sands/gravel week below the superstructure


ENVS 10003 CONSTRUCTION LOG BOOK Types Underpinning -Rebuilding or strengthening the foundation of an existing building Excavating -Constructing sheet piling, tie backs, soil anchors, slurry walls and dewatering the water table


ENVS 10003 CONSTRUCTION LOG BOOK Shallow Foundations -Spread footings-extend laterally to distribute their load-must be placed below the death of frost penetrating to avoid freezing the expanding -Most common forms are strip, isolated, stepped and mat footings Foundation Walls -Extend below the surface-must resist pressure form the dead and live loads of the super structure and all the pressure form the earth below ground 32

ENVS 10003 CONSTRUCTION LOG BOOK Column Footings -Reinforced concrete, wood, steel

Concrete Slabs-mat/Raft -Serve as combined floor and foundation system, depends on site characteristics and design of the superstructure


ENVS 10003 CONSTRUCTION LOG BOOK Pole Foundations -Elevate timber structures, preserve natures system and aesthetic features, particular useful for steep gradients

Pile Foundations -Transfer loads to a more appropriate stratum-timber, H steel, pre-cast reinforced concrete -Composed of tie beams, pile caps and friction piles


ENVS 10003 CONSTRUCTION LOG BOOK Caisson Foundations/Board Piers -Cast in place foundations dug by a large auger filled with ‘cages’ of steel to reinforce the concrete

DRAW fig pg. 3.26

Key Terms: Moment: the critical change point between structural integrity and collapse-can also be a critical point in load bearing capacity. Retaining Wall: A foundation system that resists horizontal mass forces and ‘retains’ landmass Pad Footing: A shallow foundation system commonly led by a column with a square area underneath to equally distribute loads Strip Footing: A series of pad footings interconnected by reinforced concrete Slab on Ground: A solid mass of concrete on gradient Substructure: The name for the foundation system


ENVS 10003 CONSTRUCTION LOG BOOK Independent Site Study Palmerston Place construction site (13/3/2014)

Board Pier Auguring -Pier auguring provides extra strength to foundations, as there is an underground cellar in the construction -Alternate to an edge-beam-cannot be used as it would undermine the adjacent house

-Adjacent house was incrementally reinforced prior to the board pier installation

-Sink ‘cages’ into 6m holes -Fill with concrete-reinforced concrete







Week 4: Floor Systems and Horizontal Elements eLearnings • Floor systems: Timber, Steel and Concrete


ENVS 10003 CONSTRUCTION LOG BOOK eLearnings Floor Systems and Horizontal Elements Overview -Floor system are the horizontal floor planes that must support both live and dead loads -Must transfer their load horizontally across space to their beams and columns or to load bearing walls -Composed of a series of linear load bearing beams and joists over laid with a plane of sheeting or decking, or a nearly homogenous slab of reinforced concrete -Depth is directly rested to the size and proportion of the structural bays it must span and the strength of the material used -As it must support various live loads, floor systems should be relatively stiff whilst maintaining its elasticity -Deflection rather than bending become a critical factor when assessing human comfort and integrity -Depth and cavities of the floor system need to be considered in real tin to the various mechanical services throughout the construction -Purpose, maintenance, repair and durability are all factor that must be considered when choosing and designing floor system


ENVS 10003 CONSTRUCTION LOG BOOK The 3 Main Floor Systems 1. Concrete -Precast or in-situ -Fresh concrete must be shaped ands supported by formwork until it cures and can support itself. this formwork is often designed as a separate structural system-can sometime be included in the structure-sacrificial formwork -Beam: Reinforced concrete beams are designed to act together with longitudinal and web reinforcement in resisting applied forces -Slabs: Concrete slabs are plate structure that are reinforced to span wither one or both directions of a structural bay

2. Steel -Support steel decking or precast cornet planks -Beams may be supported by girders, columns or load bearing walls -Beam framing is typically an integral part of a steel skeleton frame system -May use solid steel beam or web joists (truss structure) -Steel decking or wood planks have relatively short spans due to their low compression rate -Joist have limited overhand potential -Normally cut, shaped and drilled in fabrication workshop Example 1.



3. Timber -Timber beams support structural planking or decking -Beams may be supported by girders, posts or load bearing walls -Concentrated loads or floor openings may require additional framing -Underside of floor structure may be left exposed; an applied ceiling is optional -Sub flooring, underlayment and applied ceiling finished have relatively short spans -Joist framing is flexible is shape and form -manipulative structural diaphragm to transfer lateral loads to shear walls


ENVS 10003 CONSTRUCTION LOG BOOK Key terms: Span: A space between two or more load bearing joists or girders Spacing: The distance between two floor system elements Girder: The primary load bearing member or a floor constructions system Joist: The secondary load being member of a floor construction system and onto of which the flooring is placed Steel Decking: Decking constructed from steel-often corrected and with concrete poured onto of it-reinforced steel flooring Concrete plank: A pre-fabricated plank of concrete to fill a span of construction flooring




Construction Logbook: Weeks 3-4  
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