Construction Technology and Environmental Sciences Flashcards
1
Q
What is substructure?
A
All the elements of a building below the superstructure or damp proof course (DPC) level. Where there is no DPC level, then it is to the underside of the lowest floor finish.
2
Q
What are foundations and name the two types of foundations?
A
Foundations are the lowest part of a building that is in direct contact with the soil to transfer loads into the ground safely. The 2 types of foundations are:
- Shallow - Strip, Pad, Raft
- Deep - Pile, Pier, Diaphragm walls
3
Q
What are the factors that influence the choice of foundation?
A
- Nature of the load - low height buildings over a long area are suitable for shallow foundations as for high-rise buildings over a shorter area will require deeper foundations.
- Ground conditions - dependent on soil bearing capacity.
- Presence of water - this is to do with water table which is the presence of water in the ground. High water table could cause flooding and strain the foundations causing it to fracture or even collapse. Too low, then the foundation could be inadequately supported.
- Accessibility - If the space/area is restricted for specialist machinery/plant, this could affect the foundation type.
- Sensitivity to noise and vibration - Depending on the method of installation e.g. displacement or replacement could affect neighbouring structures.
- Cost.
4
Q
What is the typical method for installing a foundation?
A
- Excavate trench.
- Disposal of excavated material.
- Earthwork support.
- Compaction.
- Blinding.
- Hardcore.
- Formwork.
- Reinforcement.
- Concrete poured.
5
Q
What are the different grades of basement waterproofing?
A
- Grade 1a - Seepage and damp areas from internal and external sources are tolerable if the intended use of the space is not affected e.g. car parks.
- Grade 1b - Seepage is not tolerable but damp areas such as patches are tolerable with no need for management measures.
- Grade 2 - Seepage is not acceptable, damp is tolerable arising from condensation or moisture in the air - management measures may be necessary.
- Grade 3 - Seepage and damp is not tolerable and management measures are necessary e.g. residential use.
6
Q
What are the three types of basement construction?
A
- Retaining wall and raft monolithic.
- Box and cellular raft.
- Piled.
7
Q
What are the different types of waterproofing a basement?
A
- Tanking - use of bitumen stick on sheet to act as membrane/barrier. This can be applied both internally and externally.
- Dense monolithic - using high quality reinforced concrete that has been mixed with additives to make it waterproof.
- Drained cavity - cavities are formed both internally/externally to collect and drain water away through pump and sump action.
8
Q
What are the pros and cons of basement construction?
A
Pros:
- Additional space thereby maximising floor area.
- Ideal for metropolis areas where cost of land is expensive.
- Storage for plant equipment to be situated rather than roof.
Cons:
- Additional cost to construct basement e.g. additional ventilation requirements to prevent moisture and damp.
- Lack of lighting and other cost M&E elements resulting in higher costs.
9
Q
What are advantages of concrete frame construction?
A
- Highly economical - production cost of concrete is low compared to other materials as the ingredients are readily available in the market.
- Although it is a slower form of construction, this benefits the client from a cashflow perspective as there is reduced costs early on in the development.
- Energy efficient - Only small amounts of energy are needed to produce concrete compared to steel as it begins to cure even at room temperature.
- Flexible - Can be formed into shapes using formwork.
- Non-combustible - has the ability to withstand high temperatures therefore inherent fire protection is part of the structure.
- Water resistant.
- Acoustic and heat insulation - This is useful in residential construction as it can block out the sound from nearby apartments as well as being a good heat insulator.
- Low maintenance - Is able to withstand high temperatures and extreme weather conditions therefore requiring little to no maintenance.
10
Q
What are disadvantages of concrete frame construction?
A
- Low strength to weight ratio - Concrete is very high in compression due its ability to withstand a lot of weight however it is a heavy material which also requires extensive foundations to withstand the load.
- Slower to construct - This is due concrete’s curing time and depending on the quality of concrete needed it can take up to 28 days for it to reach its peak strength.
- Quality - As concrete is a mixture of different ingredients, many factors can affect the overall quality such as precise amounts and curing temperatures which can be an issue when constructing on site though this can be mitigated if prefabricated off site.
- Ability to span long distances - Due to low strength to weight ratio and because it’s a heavy material, additional supports and columns are needed to spread concrete over a longer area which can affect overall net area.
11
Q
What are the advantages of steel frame construction?
A
- Speed - Quick to assemble as parts are fabricated off site and then erected on site thereby reducing time on site.
- Recyclable - It is inorganic meaning it will not bend, warp, split or crack and is 100% recyclable.
- High strength to weight ratio.
- Ability to span long distances - Useful if constructing offices, stadiums, hangers etc., as a result it does not require many additional intermediary supports such as columns and etc.
- Rot and infestation proof - Not vulnerable to termites or fungi or other organisms.
- Consistently manufactured - Due to strict manufacturing controls, consistent material quality can be obtained leading to a more higher quality product.
- Economical foundation design - As steel is lighter than concrete, it can benefit from a cheaper foundation solution.
12
Q
What are the disadvantages of steel frame construction?
A
- Weak compressive strength - It can’t withstand heavy loads like concrete without buckling or bending.
- Lead time - As steel in manufactured off site there can be issues with deliveries not being scheduled on time which can have a knock on effect on other construction activities.
- Cost of steel - As steel prices fluctuate quite often, this can result in a lack of cost certainty.
- High maintenance - As steel is susceptible to corrosion, it therefore requires maintenance over time such as repairing/replacing of fixing components as they degrade over time.
- Fire protection - Steel frames require fire protection to prevent deformation/buckling when exposed to certain temperatures.
- Skilled labour - Requires experienced operatives which comes at a premium and sometimes resources can be difficult to acquire depending on market conditions.
13
Q
What are the advantages of timber frame construction?
A
- Speed of construction - As timber frames are pre-fabricated off-site, this can lead to rapid installation once on site.
- Cost effective - When compared to steel or concrete, timber is more cost effective due to the speed of construction which can reduce labour and overall project cost.
- Sustainability - Timber is a recyclable and environmentally friendly material. When sourced from sustainable managed forests, timber has lower carbon footprint compared to other materials. It also has good thermal properties which can contribute to energy efficiency and reducing a building’s operational carbon emissions.
- Design flexibility - Timber is a relatively versatile material thereby enabling designers to make open and innovative floor plans.
- Strength and durability - GLT or CLT can offer high strength to weight ratios and can withstand a variety of environmental conditions. If properly designed, timber frames can have a long life span with minimal maintenance.
- Energy efficient - Timber has inherent insulating properties which can add to a buildings thermal performance and minimise heat loss.
- Reduction in waste - As timber is pre-fabricated off-site it can contribute to reduced waste and sustainable construction.
14
Q
What are the disadvantages of timber frame construction?
A
- Fire risk - Timber is a combustible material therefore it has a higher fire risk compared to steel or concrete. Although this can be mitigated through use of fire protection measures such as sprinkler systems and fire-resistant cladding.
- Moisture and rot - If not properly protected timber is susceptible moisture absorption and rot.
- Pest infestation - Timber is vulnerable to termites and other insects which can compromise the structural integrity of the material.
- Acoustic performance - Timber has poor acoustic properties when compared to that of concrete or masonry.
- Initial cost - Whilst timber may cost effective overall, it does however have a high upfront cost, although this can be offset following construction time and reduced labour costs.
15
Q
How can BIM assist in the day to day works of quantity surveyor?
A
Through having access to detailed digital information, BIM can assist a QS in a number of ways such as:
- quantity take-off and estimation.
- cost planning and budgeting.
- collaboration and communication.
- procurement and tendering.
