School of the Built Environment Construction Technology D19SC Unit 3 SUBSTRUCTURE DESIGN -...
-
Upload
bethany-moody -
Category
Documents
-
view
225 -
download
1
Transcript of School of the Built Environment Construction Technology D19SC Unit 3 SUBSTRUCTURE DESIGN -...
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 1
School of the Built Environment
Construction Technology D19SC
Unit 3
SUBSTRUCTURE DESIGN -
FOUNDATIONS
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 2
School of the Built Environment
Construction Technology D19SC
In any building
• the superstructure
• the substructure (foundations)
• the supporting soil
act together to give the building structural stability
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 3
School of the Built Environment
Construction Technology D19SC
Foundations are the vital link between the superstructure and the ground.
The criteria for a successful foundation are:
• it should be at a minimum depth and size, without exceeding the allowable bearing capacity of any soil layer below the foundation.
• it should have settlement consistent with the supporting structure
• it should be able to withstand natural ground movements from frost, moisture and heat
• regard is given to buildability
• it should be economical
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 4
School of the Built Environment
Construction Technology D19SC
The principles of foundations.
The basic function of a foundation is to intercept the load exerted by a building structure and transfer this load to the supporting soil in such a way that the building will not sink into the ground (subside)
Structural stability is normally achieved in either of two ways, or indeed a combination of both.
– Spread the load exerted by the building over a sufficiently wide area to prevent the supporting ground being overstressed
– Divert or transfer the load to a strata, deep in the ground, which is capable of supporting the imposed load without failure
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 5
School of the Built Environment
Construction Technology D19SC
When a building is placed on the ground it exerts a force on the soil. Safe foundations place that load such that the soil is not overloaded.The ability of the ground or soil to “bear” a load varies with types of soil and ground depth
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 6
School of the Built Environment
Construction Technology D19SC
Type of subsoil Bearing Capacity
(kN/M2)
Rocks, granites and chalk 600 – 10000
Non-cohesive soils
Compact sands
Loose uniform sands
100 - 600
Cohesive soils
Hard clays
Soft clays and silts
0 – 600
Peats and made-up ground To be determined by investigation
Typical subsoil bearing capacities
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 7
School of the Built Environment
Construction Technology D19SC
• Be constructed of materials that will not be degraded by chemicals found in the soil around the foundation. Normally foundations are composed of concrete and when conditions demand, the specification of the concrete will need to be altered to avoid corrosive elements in the soil.
• Able to withstand the effect of frost (also applies to services buried in ground)
To achieve this basic function the foundation must be:
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 8
School of the Built Environment
Construction Technology D19SC
TYPES OF SOIL
RockThe hardest rock is igneous e.g. granite and basalt. Normally they have a high safe bearing capacity, 2-3 times that of sedimentary rocks and 25-30 times that of clays and sands. Generally bedrock is an excellent base to build on but unfortunately the cost of levelling and the cost of excavating service trenches outweighs the initial advantage of a good natural base.
Course grained non-cohesive soilsGravels and sands come under this heading. When loaded they shear if unconfined. The particles slide over each other at an angle known as the angle of internal friction .
Fine grained cohesive soilsThese include clays and silts. The major problem with these types of soil is that their nature changes with the level of moisture in the soil. When the soil drys out they shrink, but when the moisture content is increased the soil swells. When water trapped in the soil freezes it can cause vertical heave
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 9
School of the Built Environment
Construction Technology D19SC
Types of soil
Organic soilsThese include peat, loam and mud. Generally unsuitable for building on. Normally 150-200 mm thick. Such soil (top soil) is usually removed before building begins.
Made up soilAs the stock of quality building land diminishes, poorer ground is often used. Today made up ground is being utilised. Extreme care should be taken to ensure that such land is properly investigated.
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 10
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 11
School of the Built Environment
Construction Technology D19SC
Working out imposed loads
C1 C4 C4 C4 C4 C1
C2 C5 C5 C5 C5 C2
C6 C3 C3 C3 C3 C6
B1 B1 B1 B1 B1
B1 B1 B1 B1 B1
B1 B1 B1 B1 B1
B1
B1
B1
B1
B1
B1
B2
B2
B2
B2
B2
B2
A B C D E F
1
2
3
6.000 6.000 6.000 6.000 6.000
6.000
9.000
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
B3
SD1
SD1
SD1
SD1
SD1
SD1
SD1
SD1
SD1
SD1
B1 = 406 x 130 x 39 Universal Beam C1 = 254 x 254 x 71 Universal Column Note that this building has 3 storeys
B2 = 457 x 152 x 74 Universal Beam C2 = 305 x 305 x 88 Universal Column above ground level + a concrete roof
B3 = 305 x 127 x 37 Universal Beam C3 = 305 x 305 x 149 Universal Column having the same construction as the
C4 = 305 x 305 x 79 Universal Column floors. The ground floor slab is ground
SD1 = Structural Concrete Composite Floor C5 = 305 x 305 x 186 Universal Column supported and is to be disregarded in
using Corus ComFlor 80 Composite Floor C6 = 254 x 254 x 85 Universal Column foundation assessments.
Decking- depth of slab = 150mm.
Load imposed by ComFloor Deck = 0.75kN/m2
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 12
School of the Built Environment
Construction Technology D19SC
QUESTION FOR DISCUSSION IN CLASS
The loads exerted by the building vary according to the size, use and form of construction used.
What loads are exerted by a building on to the ground below the building?
As discussed in unit 2, the building is exposed to both dead and live loads
Permanent or dead loads: the weight of the structure, cladding and fixed equipmentTemporary or live loads : imposed loads – people furniture, non-fixed equipment. environmental or dynamic loads - snow or wind.thermal loads – temperature changes causing load on structure
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 13
School of the Built Environment
Construction Technology D19SC
To achieve this basic function the foundation must be:
Strong enough to prevent downward vertical loads shearing through the foundation
Stable so that it will not overturn .Whenever possible loads on foundations should be placed centrically.
Capable of withstanding the opposing forces, the weight of the building and the resistance of the soil, such that the foundation will not bend
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 14
School of the Built Environment
Construction Technology D19SC
• Capable of withstanding changing conditions in the ground if they occur, e.g. movement caused by shrinking and swelling, water pressure, etc.
• Accommodate initial settlement of the structure. It is especially important that uneven settlement does not occur.
• That the installation of foundations does not overstress the ground such that adjacent existing foundations and services are damaged. It should be noted that the installation of new ground based services can undermine existing foundations. It should also be noted that where services pass under or adjacent to foundations the load exerted on them by the foundations may cause failure. In such situations, such as a sewer collapse this may in turn undermine the foundation.
To achieve this basic function the foundation must be:
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 15
School of the Built Environment
Construction Technology D19SC
BUILDING NEAR TREES
The combination of shrinkable soils and trees, hedgerows or shrubs represents a hazard to structures that requires special consideration. Trees, hedgerows and shrubs take moisture from the ground and, in cohesive soils such asclay, this can cause significant volume changes resulting in ground movement. This has the potential to affect foundations and damage the supported structure. In order to minimise this risk, foundations should be designed to accommodate the movement or be taken to a depth where the likelihood of damaging movement is low.
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 16
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 17
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 18
School of the Built Environment
Construction Technology D19SC
Water requirements for different types of trees
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 19
School of the Built Environment
Construction Technology D19SC
Near Surface Foundations - spread foundations– Strip Foundations– Pad Foundations– Continuous Column Founds– Balanced Footings– Rafts:
• Plain Slabs• Stiffened Edge• Downstand Raft• Upstand Raft• Cellular Raft• Buoyancy tanks
Deep Foundations– Piled Foundations
• Bored Piles• Driven Piles
Main types of foundations
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 20
School of the Built Environment
Construction Technology D19SC
Main types of foundations
Spread foundations Piled foundations
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 21
School of the Built Environment
Construction Technology D19SC
SPREAD FOUNDATIONS
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 22
School of the Built Environment
Construction Technology D19SC
Simplest form of foundation is the strip foundation, used to support a load bearing wall
Main types of strip foundations
Conventional strip Deep strip Wide strip
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 23
School of the Built Environment
Construction Technology D19SC
CONVENTIONAL STRIP FOUNDATIONS
Spread the load exerted by the building over a sufficiently wide area to prevent the supporting ground being overstressed
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 24
School of the Built Environment
Construction Technology D19SC
A good quality ‘freehand’ sketch of a simple strip foundation
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 25
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 26
School of the Built Environment
Construction Technology D19SC
Deep strip foundations
Tend to be used at depths greater than 1.2 m deep
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 27
School of the Built Environment
Construction Technology D19SC
A good quality ‘freehand’ sketch of a deep strip or trench fill foundation
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 28
School of the Built Environment
Construction Technology D19SC
Pad foundation
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 29
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 30
School of the Built Environment
Construction Technology D19SC
GROUND BEAMS
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 31
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 32
School of the Built Environment
Construction Technology D19SC
RAFT FOUNDATIONS
Spread the load over a wider area
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 33
School of the Built Environment
Construction Technology D19SC
RAFT FOUNDATIONS
Spread the load over a wider area
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 34
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 35
School of the Built Environment
Construction Technology D19SC
Raft foundation
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 36
School of the Built Environment
Construction Technology D19SC
PILE FOUNDATIONS
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 37
School of the Built Environment
Construction Technology D19SC
Divert or transfer the load to a strata, deep in the ground, which is capable of supporting the imposed load without failure
Pile Foundations
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 38
School of the Built Environment
Construction Technology D19SC
Pile foundations Two main types displacement & replacement
Typical displacement or driven pile
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 39
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 40
School of the Built Environment
Construction Technology D19SC
Displacement or percussive piles being installed
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 41
School of the Built Environment
Construction Technology D19SCTypical replacement or bored pile
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 42
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 43
School of the Built Environment
Construction Technology D19SC
Pile cap
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 44
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 45
School of the Built Environment
Construction Technology D19SC
BASEMENTS
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 46
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 47
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 48
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 49
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 50
School of the Built Environment
Construction Technology D19SC
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 51
School of the Built Environment
Construction Technology D19SC
What type of foundation would you use in the assignment?
Where would you locate the foundations?
Is there a role for a basement?
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 52
School of the Built Environment
Construction Technology D19SC
Stairs & Lifts
Entrance Reception
Area A
Toilets
Stairs & Lifts
Area B
Toilets
GROUND FLOOR PLANGrid 3 m
Unit 3 SUBSTRUCTURE DESIGN - FOUNDATIONS 53
School of the Built Environment
Construction Technology D19SC
ATRIA
Stairs & Lifts
ReceptionArea C
Stairs & Lifts
Toilets
Area D Area E
Toilets
UPPER FLOOR PLANGrid 3 m