CT Questions Flashcards
How does the soil type affect the design of strip foundations?
Different soil types have different bearing capacities. Clay is particularly susceptible to ground movement on a cylical basis due to expansion and contraction due to water levels.
Describe the build up of a typical concrete slab floor
Compacted hardcore, sand blinding layer, insulation, DPM, concrete floor slab, floor screed, floor finish. Insulation can be above or below floor slab dependant on manufacturers details.
Describe the build up of a typical timber floor
Sleeper walls (in honeycomb pattern) support timber joists, damp proof course, insulation, floor finish
What are piles?
Series of columns constructed or inserted into the ground to transfer the load to a lower level of subsoil.
What types of piling methods do you know of?
Driven piles, Cast in-situ piles
What type of piling materials do you know of?
Concrete, steel and timber
What are the different ways that piles transfer load to the surrounding ground?
End bearing piles - piles transfer load to harder strata,
Friction piles - load is taken by the friction developed between side of the pile and surrounding ground,
Settlement reducing piles - usually incorporated below the central part of a raft foundation, in order to reduce differential settlement to an acceptable level.,
Tension piles - piles constructed to reduce uplift by hydrostatic pressure, ground movement, or turning moment forces.
Why would you use augured pile over displacement ?
Vibration and disturbing ground conditions, in relation to nearby buildings.
How do you connect pile to pile cap?
Breakout pile, construct pile cap tying in reinforcement
How do you link pile caps to ground floor slab?
Construct ground beam with slab on top
When would you use strip foundations?
When soil has relatively good bearing capacity and building has light structural load. Good for supporting a linear structure like a wall.
What soils would you use strip foundations on?
Bedrock/Gravels/some sands
How can you test the bearing capacity of soil?
The plate load test.
When would you use pad foundations?
When soil has relatively good bearing capacity and building has light structural load. Good for supporting columns.
What soils would you use pad foundations on?
Bedrock/Gravels/some sands
When would you use raft foundations?
When differing soil types with poor bearing capacity, need to spread load over a wide area.
When would you use piled foundations?
When you need to reach significant depths to find good bearing capacity. In soils such as clay or made ground. When you have a high structural load.
How are piles installed?
Either driven (displacement) or bored (replacement)
Describe pile retaining walls
Piles placed next to each other to form a retaining wall.
What is a geothermal pile?
Contains a ground source heat pump
What are shallow foundations?
Strip, pad and raft
What are deep foundations?
Piles
What are the factors that influence choice of foundations?
Ground conditions and superstructure load– depth of solid ground, tree roots etc.
How does a displacement pile work?
Like a nail/screw – displacing ground
How does a replacement pile work?
Replacing ground/concrete poured in situ.
Describe ground breams?
Beams that span either pad or pile caps and can be used to support brick/block work.
What is ground heave?
Ground heave is the upward movement of the ground usually associated with the expansion of clay soils which swell when wet.
What impact my trees have on foundations?
May have to consider tree roots or if removing may cause ground heave changing make up of ground condition.
What are sheet piles.
Commonly steel with interlocking edges that are driven into ground to provide earth retention.
What is a piling mat?
A solid working platform for a piling rig, usually timber.
Name some types of retaining wall.
Gabions, Brick/Block, pile wall, sheet pile
Describe basement construction
A basement is part of a building that is either partially or completely below ground level. Excavation, Masonry/concrete/prefab panels and then waterproofing.
Describe types of basement waterproofing
Drained Cavity, Common on existing old buildings where external wall constantly wet so build false wall in front (egg crates) then water in cavity is drained by gravity or pumped, Tanked , Better as substructure walls are not wet and membrane is put on ground facing wall, must be careful not to damage when backfilling.
What are the advantages and disadvantages of using timber frame construction?
Advantages: Thermal insulation, Speed of build, Environmental impact
Disadvantages: Risk of rot and infestation , Timber frame constructions must include carefully designed vapour barrier detailing to prevent vapour passing through
What are the advantages and disadvantages of steel frame construction?
Advantages: 1) Quick to assemble, 2) Highest strength to weight ratio of any building material, 3) Lighter so can be used in poorer soils than concrete
Disadvantages: 1) Need additional fire protection to maintain structural integrity, 2) Price of steel is variable, 3) Steel is thermally conductive so thermal bridges can form if not carefully detailed
What are the advantages and disadvantages of concrete frame construction?
Advantages: 1) Fire protection as part of the structure, 2) Provides good sound and heat insulation, 3) Can contend with complex geometry better than steelwork
Disadvantages: 1) More time consuming, 2) Need for steel reinforcement due to concrete being weak in tension, 3) Heavy so larger/deeper foundations required
What are the main pieces of legislation and standards that govern electrical safety?
Building Regulations Approved Document P, Electricity at Work Regulations 1989, Electricity, Safety, Quality and Continuity Regulations 2002, British Standard 7671
