Construction Technology Flashcards
Under what conditions would expect a raft foundation to be used for a substructure?
- Lightly loaded buildings on poor soils
- Where underground services i:e train lines dictate the use
- Where it may be impractical to create individual strip or pad foundations for a large number of individual loads. In very general terms, if strip or pad foundations would cover 50% or more of the floor area, then a raft may be appropriate.
What are the different types of piling and when would you expect them to be used?
- Sheet piles – These are interlocking sheets (normally steel) that are driven into the ground and are used to form basement walls or act as retaining walls.
- Secant piles – interlocking piles (male and female, often different diameters and hardness) are bored to provide a combination of foundations and retaining walls. They can be used to provide a waterproof structure.
- Rotary Bored Piles (Replacement) – an auger is used to excavate the soil and then concrete is poured in once complete. The reinforced steel is then inserted. CFA (Continuous Flight Augured) is where the boring and pouring takes place simultaneously. Support casing can also be used.
- Pre-cast piles (Displacement) – pre-cast piles are brought to site and hammered into the ground. Not often favoured due to the high noise levels associated with installation and the lack of flexibility in terms of depth required.
- Contiguous piles - A row of successive cast-in-situ concrete piles constructed with unconnected small gaps formed using CFA or rotary bored piles. Quick and easy method for retaining walls.
What is the difference between Bored and Pre-cast piles?
Pre-cast piles are hammered into the ground. Advantages:
• Piles of any size, length and shape can be made in advance and used at the site. As a result, the progress of the work will be rapid.
• A pile driven into granular soil compacts the adjacent soil mass and as a result the bearing capacity of the pile is increased.
Bored uses a rotary auger to remove the soil and then replace it with concrete pour in-situ followed by steel reinforcement. Advantages:
• Low noise/impact when working near other buildings
• CFA version is quickest version
What are the typical components of site investigations?
Objective is to systematically collect and record data to help in design / construction. Should include:
• Boundary hedges / fencing
• Existing trees
• Size, depth and location of services – gas, telephone, electricity, water, drains
• Existing buildings
• Ground water conditions
• Soil investigations – trial pits etc
What are grade 1 basements?
Some leakages and damp areas tolerable. Local drainage may be required. Used in Car parking Plant rooms (excluding electrical equipment)
What are grade 2 basements?
No water penetration but damp areas tolerable dependent on the intended use. Ventilation may be required to control condensation.
Used in Workshops and Plant rooms requiring drier environment than Grade 1 storage
What are grade 3 basements?
Dry environment. No water penetration. Additional ventilation, dehumidification or air conditioning appropriate to intended use Ventilated residential and commercial areas including offices, restaurants, and leisure centres etc
What are grade 4 basements?
Totally dry environment. Requires ventilation, dehumidification, or air conditioning appropriate to intended use. Used in Archives, Landmark buildings, and stores requiring a controlled environment
What are British Standards?
- Publications issued by the British Standards Institution – (prefixed with ‘BS’)
- They give recommended min standards for materials, components, design and construction practices
- Manufacturers have to pay to have their products and manufacturing processes tested in order to receive BSI Kitemark
What are international standards?
- Prepared by the International Organisation for Standardisation – (prefixed ‘ISO’ or ‘EN’ or both)
- Compatible with and complement BS’s using noted with ‘EN’
- In June 2018, it was announced that the UK would apply to stay in the European Standards system for industry products and services after Brexit.
Name some forms of modern construction methods?
- Cross Laminated Timber (CLT) – Pre-fabricated boards made of dried timber glued at 90 degrees to the previous layer which reduces movement.
o High strength to weight ratio
o Acoustic performance and airtightness performance - Modular construction – Prefabricated units
o Speed of supply and installation
o Reduced cost (labour, waste, economies of scale)
o Quality control
o Improved safety
o Reduced storage requirements - 3D Printing – Computer-controlled sequential layering of materials to create complex three-dimensional shapes
What are the main site considerations?
- Access – approach roads etc
- Storage
- Accommodation
- Temporary services
- Plant
- Site security
- Safety and health
What is TM59 (CIBSE Guidance) 2017?
• Standardised assessment method for dynamic thermal modelling of overheating in homes.
To comply with the CIBSE TM59 Overheating Methodology there are criteria thresholds for mechanically and naturally ventilated homes.
• Not compulsory but widely adopted
What is a green roof?
Green roofs are roofs that are purposely fitted or cultivated with vegetation. They are also be known as living roofs or eco-roofs.
Extensive – low maintenance
Intensive – More intensive like a garden. May required additional loading capacity
- Decreased surface water runoff
- Decreased heating and cooling demands for the building
- Increased local biodiversity
- Improved local air quality
- Disadvantage - Higher capital cost
What is a blue roof?
A blue roof is a roof designed for the retention of rainwater above the waterproofing element of the roof. This is as opposed to more conventional roofs which allow for rainwater to drain from the roof.
• Can be used to reduced water runoff and therefore flooding
• Can be used for rainwater harvesting which can be used to supplement the mains water supply, WC flushing or irrigation of a green roof.
