Construction Technology Flashcards
What is substructure?
All structure below the superstructure i.e. all structure below the ground including the ground floor bed.
What is superstructure?
All internal and external structure above the substructure.
What is meant by primary superstructure?
External walls, stairs, structural walls, roofs
What is meant by secondary superstructure?
Raised floors, suspended ceilings, balustrades, doors
What is meant by internal finishes?
Paint, tiles, carpet, stair nosing
What is the external envelope of a building?
The materials and components that form the external shell or enclosure of a building.
May be structural or non structural
What are the building regulations?
Statutory instruments that set out the minimum performance standards for the design and construction of buildings.
Supported by approved documents A - R & regulation 7.
Name the approved documents.
A - Structure
B - Fire safety
C - Site preparation and resistance to contaminants and moisture
D - Toxic substances
E - Resistance to the passage of sound
F - Ventilation
G - Sanitation, hot water safety and water efficiency
H - Drainage and waste disposal
J - Combustion applications and fuel storage systems
K - Protection from falling, collision and impact
L - Conservation of fuel and power
M - Access to and use of building
N - Glazing safety (withdrawn, ss by park K)
P - Electrical safety
Q - Security
R - Physical infrastructure for high speed electronic communication networks
Regulation 7 - Materials and workmanship
What are British Standards?
- Publications issued by British Standard Institution (BS)
- Give recommended minimum standards for materials, components, design and construction practices
What are International Standards?
- Prepared by International Organisation of Standardisation (ISO)
- Compliment BS
What are the typical components of site investigation?
Objective - to collect and record data to help in design & construction
Should include info of adjacent sites that impact:
- Boundary hedges/fencing
- Existing trees
- Size, depth and location of services
- Existing buildings
- Ground water conditions
- Soil investigations (trial pits)
What are soil investigations?
Objective:
- Determine suitability of site for proposed works & adequate and economic foundation design
- Identify potential issues
What are the main site considerations for a contractor setting up on site?
- Access considerations, approach roads etc
- Storage considerations
- Accommodations
- Temporary services
- Plant
- Fencing/hoarding
- Health and safety
What is a retained facade?
Facade of the building is retained whilst everything behind the front wall is demolished.
Why are facades retained?
- Often listed
- Aesthetics
What considerations would you make if you were to retain a facade?
- Temporary support structure
- Cleaning/restoration requirements of facade
What are temporary works?
- May not appear on construction drawings
- Methods that are required to ensure safe construction, e.g. propping. These will be removed once permanent supports are in place.
What is landfill tax?
- Brought in by govt. in 1996
- To reduce landfill waste and promote recycling/reuse, & promote research into waste practices
- Applies to all waste disposed of at licenced landfill sites unless specifically exempt
- Administered by hm customs and excise
What are the landfill tax rates?
£94.15/ tonne for active waste
£3.00/tonne for inactive (inert) waste
(Rates from April 2020 - 2021)
What is active waste?
- Substances that either decay or contaminate land - which includes household waste.
- Expensive to dispose of.
What is inactive waste?
- Biologically or chemically inactive. Don’t give out harmful residue.
- Do cause problems with filling up areas.
- Cheap to dispose of.
What is a tower crane?
- A tower crane is a tall crane used for lifting objects into high places.
- The boom (arm) allows a longer reach with 360 degree access.
- A longer boom reduces the payload capability.
How would you erect a tower crane?
Using a smaller crane
What issues might cause a tower crane to suspend it’s use?
Adverse weather conditions, particularly high winds
What is a scaffold?
- Temporary working platform erected around the perimeter of a building or structure to provide a safe working place at a convenient height
- Usually required for working above 1.5m high
What is shoring?
- Form of support given to existing buildings.
- Precaution against damage or injury caused by collapse of structure.
What are hoists?
Designed for the vertical transportation of materials or people
What are foundations?
Foundations provide support for structures, transferring their load to layers of rock and soil that have sufficient bearing capacity.
What is a dead load?
- Permanent and static loads
- Predominately the structure itself
What are live/imposed loads?
- Usually temporary
- Changeable and dynamic
- Occupants, furniture, equipment, vehicles
What are wind loads?
- The movement of air against the structure
- Particularly important on tall buildings and buildings with a light-weight dead load
What are the main components of concrete?
Water, aggregate (rocks, sand etc), cement
What is aggregate?
Natural stone, crushed rock, gravel
What is a borehole?
- A borehole can be used for soil investigations or geothermal heating solutions
- Boreholes are the most effective solution for soil investigations where the foundations are to be over 3m deep
What are geothermal boreholes?
Permanent holes that use the earth’s natural heat energy to warm up circulated water.
This is a closed system that can be used to heat the building above.
What are piles?
A series of columns constructed or inserted into the ground to transfer the load of a structure into the soil
What are the different types of piles?
- Replacement/Bored piles (reinforced concrete insitu)
- Displacement/Driven piles (pre-cast, steel, composite)
- Basement walls (secant piles, sheet piles)
What are sheet piles?
- Sections of sheet materials with interlocking edges that are driven into the ground to provide earth retention or excavation support.
- Typically made of steel
- Often used for retaining walls and underground structures
What are secant piles?
- Intersecting steel reinforced concrete piles
- Primary female piles are installed first, with secondary male piles installed in between them. Overlap of roughly 3 inches creating a flush finish
- Useful in top-down construction and temporary waterproofing
What are bored piles?
- Auger is used to excavate soil, then concrete is poured in
- Variation of this is where a continuous flight auger is used to bore piles and fill core with bentonite slurry. Concrete is then poured into core, displacing the bentonite slurry due to it’s denser makeup. Rarely used now due to environmental impacts of bentonite
- Minimal vibration
What are pre-cast piles?
- Piles brought to site and hammered into the ground
- High noise levels associated with installation
- Lack of flexibility in terms of depth required
What are the different ways that piles transfer their load into the surrounding ground?
- End bearing piles: Pass through soft strata onto firm strata. Load transferred through toe of pile
- Friction piles: Through sheer stress against side of piles
- Tension piles: Through the length of the pile to reduce overturning moments on the building caused by uplift forces
- Laterally loaded piles: Horizontal forces in situations such as bridge piers. Similar to above.
When would you use bored piles?
- In cohesive subsoils for the formation of friction piles
- When close to existing buildings due to noise/vibration limitation
When would you use pre-cast concrete piles?
- When there is soft soil deposits lying on firmer strata
- When noise/vibration isn’t a concern
What are the risks for a PQS regarding cost control with piling?
End depth of piles are never a certainty, procurement route determines who takes the risk.
Traditional/D&B = Contractor
Management Contracts = Employer
What is a raft foundation?
Used to spread the load of superstructure over a large base and reduce load/m2 of area.
Generally reinforced concrete slabs.
When would you use raft foundations?
- In low bearing capacity soils
- Where settlement is likely
- Where floor areas are small and structural load low
What is a strip foundation?
Shallow foundations used to provide a continuous, level strip to support a linear structure such as a wall
When would you use a strip foundations?
- Most subsoils
- Light structural design
What are pad foundations?
A form of spread foundation formed by often square pads that support single-point structural loads such as columns
What are retaining walls?
They act as an earth retaining structure for the whole or part of their height
What considerations should a Contractor make when building a retaining wall?
Pressure of water/earth acting on wall
What are the main types of excavation?
- Open
- Perimeter Trench Excavation
- Complete excavation
What is open excavation?
- Use battered excavation technique which is excavating the soil with the sides left at a safe angle so as to not collapse
- Save money on temporary support work
- Extra excavation costs due to extra soil being removed to ensure sides are at a safe angle
- Requires free space on site for angled sides. Wouldn’t work on site boundary.
What is perimeter trench excavation?
Trenches are dug with required support around basement perimeter. Basement walls are formed, then inside of basement is excavated.
What is complete excavation?
- Centre of basement is excavated
- Basement slab is cased while sides of excavation are supported by struts
- Basement walls formed
- USED WHEN SUBSOILS ARE FIRM
What is a basement?
A storey below ground floor.
What are the 3 main types of basement construction?
a) Retaining wall and raft (monolithic) - slab raft foundation distributes building load. Basement walls are retaining.
b) Box and Cellular - similar to above but internal structural walls transfer and spread loads over raft, dividing basement into cells
c) Piled - superstructure load carried to basement floor by columns and treasferred into ground via pile caps & piles
What are the 3 main methods of waterproofing a basement?
a) Dense monolithic - basement designed to form watertight space
b) Tanking - asphalt or similar resin applied internally or externally to provide continuous membrane to base slab and walls. External better as it protects substructure.
c) Drained cavity - Accepts small about of water seepage, collects and drains this away. Inner non-load bearing wall forms cavity wall for water to drain into, CAN BE USED ON REFURB WORK
What is scabbling?
- Piston driven carbide tipped heads which impact surface at rapid rate
- Removes thin layer from surface of concrete
Why is scabbling used?
- Roughen surface of concrete for better grip
- Prepare surface for painting/sealing/coating
- Reduce levels/level surface
- Decoration
What are the technical advantages of steel frame construction?
- Quick to assemble
- Recyclable material
- High strength to weight ratio
- Not vulnerable to termites, fungi etc
- Consistent material quality as produced in strict accordance with national standards
- Non-combustible so won’t contribute to spread of fire
- Lighter than concrete
What are the technical disadvantages of steel frame construction?
- Needs fire protection
- Parts may need replacing
- Price of steel is variable, could be high market dependent
- Requires experienced builders
- Will fail (collapse) before wood in a fire in spite of not being combustible
What are the technical advantages of concrete frames?
- Could be cheaper than steel dependant on market price of steel
- Doesn’t require additional fire protection
- Slower construction will help cashflow
- Low maintenance with insitu concrete frames
- Cladding can be fixed to it and replaced easily
- Good sound and heat insulation
- Insitu allows alteration at later stages
- Can deal with complex geometry better than steelwork
What are the parts of an I Beam?
- Flange (top and bottom of the “I”)
- Web (the vertical steel, runs between the two flanges. Long part of the “I”)
- Root (where the flange and web meet)
What is a steel table?
Table that provides standard information on steel sections.
Different table for different beams/columns, e.g. UB and UC.
What is the weight of steel?
10mm3 steel = 0.0078kg
What is powder coating?
- A durable factory applied organic coating on metals available in many colours
- Polyester, acrylic, epoxy spray followed by heat curing
- Any holes made/cuttings should be done prior to application of coating