Construction Technology Flashcards
When would you use pile foundations?
In weak or water baring soil.
Where the structure is heavy.
When would you use strip foundations?
In houses or buildings where the perimeter walls transfer load to the ground.
What is substructure?
All elements of work that are undertaken below the damp proof course that provides the basis for the superstructure to be constructed upon.
Transmits the loads of the building to the ground.
What is the external envelope?
The materials and components that form the external shell or enclosure of a building.
These may be load or non-load bearing.
What are the Building Regulations?
Statutory instruments that set out the minimum performance standards for the design and construction of buildings.
Supported by the Approved Documents and other codes of practice.
What are the approved documents?
A. Structure.
B. Fire safety.
C. Site preparation and damp proofing.
D. Toxic substances.
E. Sound proofing.
F. Ventilation.
G. Hygiene.
H. Drainage and waste disposal.
I. Not in use.
J. Combustion appliances and fuel storage systems.
K. Protection from falling, collision and impact.
L. Conservation of fuel and power.
M. Access to and use of buildings.
O. Overheating.
P. Electrical safety.
Q. Security in dwellings
R. Infrastructure for electronic communications
S. Infrastructure for electric charging vehicles
What are British Standards?
Publications issued by the British Standards Institution prefixed BS.
They give recommended minimum standards for materials, components, design and construction practices.
What are international standards?
Publications issued by the International Organisation for Standardisation – prefixed ISO.
They are compatible with and complement the British Standards.
What is superstructure?
The structural components of a building constructed above ground level.
What are the typical components of site investigations?
Their objective is to collect and record data to help with the design and construction process. This should include matters in relation to the site that may impact the development for example:-
Boundary hedges & fencing.
Existing trees.
Size, depth and location of services including gas, telephone, electricity, water & drains.
Existing buildings.
Ground water conditions.
Soil investigations.
Trial pit information.
What is the purpose of soil investigations?
Their purpose is to determine the suitability of the site for the proposed works and determine adequate and economic foundation design.
The investigation should determine the potential difficulties associated with the ground conditions and assist with identifying a suitable foundation solution.
What is a retained façade?
The facade of the building is retained whilst everything behind the front wall is demolished.
Allowances needs to be made for a temporary support structure and also cleaning & restoration works to the retained façade.
Retained facades are often required as a result of listed building requirements.
What are temporary works?
Are needed to enable the permanent works to be built and are usually required for safety or access reasons.
Propping
Scaffolding
Formwork
Excavation support
What is buildability?
Buildability is harnessing the contractor’s expertise and knowledge during the design stage to generate ideas for effective and efficient methods of construction.
What are the benefits of off-site construction over in situ?
Safety - Hazards such as falling from height is more likely to happen on site.
Efficiency & quality - Construction takes place in a controlled environment.
Sustainability - Reduction in waste.
Speed - Shorter build time as factory work can run concurrently with on site works.
What is a tower crane and what are some considerations during its
erection and operation?
A tower crane is a tall crane used for lifting objects into high places.
The boom allows a longer reach with 360° access.
You would usually use a smaller crane to erect a tower crane.
Weather conditions could prevent it from working, in particular high, strong winds.
What is a scaffold?
Scaffold is a temporary working platform erected around the perimeter of a building or structure to provide a safe working place at a convenient height.
Scaffold is usually required for work 1.5m above ground level.
What are hoists?
Designed for the vertical transportation of people and/or materials.
What is shoring?
Shoring is a form of temporary support given to existing buildings.
Its purpose is to provide a precaution against damage or injury due to collapse of the structure.
What are the main components of concrete?
Cement.
Aggregate (natural rock, crushed stone, gravel).
Water.
What is a borehole?
A borehole can be used for soil investigation
Boreholes are the most suitable method of soil investigation when foundations are over 3m deep.
What is a culvert?
A culvert is a tunnel-like structure that is constructed to allow water to flow under a road, railway or similar obstruction.
What is the purpose of a drainage headwall?
A small retaining structure built at the inlet/outlet of a storm water drain.
They protect the end of the drain, as well as protecting the embankment from erosion.
What is ground heave?
Usually associated with clay soil which swells when wet, causing upward movement of the ground.
What are some of the techniques available for ground improvement?
Vibro compaction
Vibro stone columns
Dynamic compaction
Dynamic replacement
What are the key factors the contractor should consider when excavating?
Nature of the soil and moisture content of the ground.
Method of excavation.
Are ground support systems required?
Proximity of existing buildings.
Depth of excavation.
Underground services and drainage.
Can you explain some of the techniques to waterproof a basement?
Tanking - Materials such as asphalt, polythene sheeting, bitumen etc are applied internally or externally to provide a continuous membrane to the slab and walls.
Drained cavity - Accepts that a small amount of water seepage will occur. Cavity walls are formed, the water seepage is collected and the cavity is drained and pumped away.
What is the purpose of a foundation?
To provide support for the structure, transferring their load to the ground to avoid excessive settlement.
What are the typical considerations when selcting the type and size of foundations?
The load of the building.
Nature and load bearing capacity of the ground.
Type of structure.
Cost.
Construction constraints.
What are the different types of foundation?
Strip foundation
Pile foundation
Raft foundation
Pad foundation
What is a raft foundation?
A continuous slab that extends over the entire footprint of the building.
Load of the building is spread over a larger area, thus reducing stress on the ground below.
What is a pad foundation?
Typically used to support individual columns, spreading the load to the ground below.
What are strip foundations?
In houses or buildings where the perimeter walls transfer load to the ground.
What are pile foundations?
A pile is a column that extends deep into the ground.
Typically used where the bearing capacity of the soil is poo.
When would you use pad foundations?
For lighter structures such as warehouses.
Wide span, light weight buildings.
When would you use raft foundations?
A raft can be used for lightly loaded buildings, or on soils with good bearing capacity.
What types of piles are you aware of?
Pre-Cast - Piles are and hammered into the ground. This is not often favoured due to the high noise levels associated with installation and the lack of flexibility in terms of depth required.
Sheet - A deep trench is excavated and concrete is poured in situ.
The piles can be used to form basement walls or act as retaining walls.
Bored - An auger is used to excavate the soil and then concrete is poured in once complete.
CFA - Are drilled and concreted in one continuous operation enabling much faster installation time than for bored piles.
Secant - Interlocking piles (male and female, often different diameters and hardness) are bored to provide a combination of foundations and basement walls. Free of gaps.
What are the main piling construction methods?
Bored
Driven
What are the main types of piles?
End bearing - the base of the pile transfers load through low bearing capacity soil to a strong stratum such as rock or very dense sand.
Friction - they bear on frictional resistance between their outer surface and the soil in contact.
What is the difference between bored vs. pre-cast (driven) piles?
Bored piles are defined when the process for removing the spoil to form the hole for the pile is carried out by a boring technique.
Pre-cast Concrete piles are generally used where soft soil deposits overlie firmer strata. These piles are usually driven using a drop or single action hammer.
What are retaining walls?
They act as an earth retaining structure for the whole or part of their heights.
They are used to support and retain soils laterally so that it can be retained at different levels on the two sides.
What are the advantages and disadvantages of driven piles?
Advantages:-
Piles can be pre-cast to the required spec.
Piles of any size, shape and length can be made in advance.
Fast, neat and clean installation.
Disadvantages:-
Requires heavy equipment.
Increased noise and vibrations.
Can be costly if piles are short.
What are the advantages and disadvantages of bored piles?
Advantages:-
Any size or shape can be formed on site.
No risk of damage upon delivery.
Reduced vibrations and noise.
Disadvantages:-
Significant spoil generated.
Reliance on multiple trades.
Do not improve the bearing capacity of the ground.
What is underpinning and why might it be required?
A method for repair and strengthening the foundations.
Used to:-
Stabilise foundations undergoing settlement.
Stabilise foundations that have moved.
To increase the load capacity of existing foundations.
To accommodate a new building, basement etc.
What are standard brick dimensions in the UK?
Standard bricks are 215mm x 102.5mm x 65mm.
How many standard bricks per m2?
60 bricks per m2.
How many standard blocks per m2?
10 blocks per m2.
What are weep holes?
Small openings in the outer skin of the masonry.
Provide ventilation to the cavity and allow moisture to drain.
Can you name 2 types of brick bond?
English bond
Stretcher bond
What is a basement?
A storey constructed below ground level.
What are the 3 different types of basement construction?
Retaining wall and raft which consists of a slab raft foundation to serve as the basement floor that distributes the building load. The basement walls serve as the retaining walls.
Piled solution where the main superstructure loads are carried to the basement floor by columns and transmitted to the ground via pile caps and bearing piles. In this example the basement has numerous columns passing through it.
What is a curtain walling system?
Comprises a lightweight aluminium frame onto which glazed or opaque infill panels are fixed.
What is scabbling?
Scabbling utilises piston driven carbide tipped heads which impact the surface material at a rapid rate.
This pulverises concrete or brittle coatings and can be very effective in the removal of slightly bonded coatings or where the coatings are impossible to be removed by the shot blasting process.
What is a movement joint?
Designed to safely absorb the expansion and contraction of construction materials.
What is the difference between dead and live loads?
Dead loads are static forces that are relatively constant for an extended period of time i.e. immovable fixtures.
Live loads are dynamic forces from occupancy and intended use i.e. weight of people.
What is pre-tensioned concrete?
In pre tensioning, the reinforcement, tendons or cables, are stretched across the concrete formwork before the concrete is cast.
After the concrete is hardened, the cables are released.
What is post-tensioned concrete?
The concrete is cast around tubes or ducts that will contain the reinforcing cables.
One the concrete has been strengthened, the cables are fed through the ducts and put into tension using jacks.
Can you explain what reinforced concrete is?
A combination of concrete and reinforcements.
Made to use the compressive strength of concrete and tensile strength of steel at the same time.
Can you explain what a glulam beam is?
Glue laminated timber.
Made of multiple layers of solid wood bonded together with high strength adhesive.
What are the technical advantages of steel frames?
Steel frames are often quicker to assemble in comparison to alternative methods.
Recyclable.
Can span longer distances.
Steel frames are lighter in comparison to concrete frames and will often benefit from a cheaper foundation solution.
What are the technical disadvantages of steel frames?
Steel frames require fire protection to be retrospectively installed.
The price of steel often fluctuates and can result in a lack of cost certainty.
Steel does not have the same acoustic and thermal properties of concrete frames.
What are the technical advantages of concrete frames?
Fire protection is often provided inherently as part of the structure.
High compressive strength.
Concrete frames often provide good sound and heat insulation.
