Foundation, Superstructure, Structural & Frames

Question 1

627 What is a foundation?

Answer 1

A foundation is a method of transferring the loads of a building into the ground.

Question 2

628 What are the typical considerations when selecting the size and type of foundations used?

Answer 2

• Type of building and how many floors. Live and dead loads that will be imposed
• Soil bearing capacity and water table height
• Is there likely to be any future increase load on the foundation (is there going to be an extension)
• Cost
• Location to existing buildings/structures and or historic mines.

Question 3

629 What are the different types of foundation?

Answer 3

• Strip foundation
• Pad foundation
• Raft
• Pilled foundation
• Steel sheet piles
• Contiguous piles
• Secant piles
• Precast concrete/ prefabricated steel
• Vibro piling
• CFA

Question 4

630 What is a raft foundation?

Answer 4

Is a continuous pad that sits under the entire footprint of the building and spreads the load out over a wider area.

Question 5

631 What is a pad foundation?

Answer 5

A pad foundation is where one or more columns enter into a mass volume of concrete which in turns spreads those loads over a wider area.

Question 6

632 What is a strip foundation?

Answer 6

A strip foundation is a shallow and narrow concrete foundation that is placed under masonry walls to bear the load. It is usually used with house construction.

Question 7

633 What are piled foundations?

Answer 7

These are foundations that allow the load of the building to be directly transferred into the ground either by end or load bearing piles and also friction piles. Two main construction methods are used, bored and driven.

Question 8

634 In what situation might a piled foundation be the best solution for the project?

Answer 8

• Where the structure is heavy and the underlying soil is weak
• Where settlement might be a problem
• Where the water table is high
• Where the load level of the structure is not uniform
• In the presence of horizontal forces

Question 9

635 Can you explain how end bearing and friction bearing piles transfer the load of the building?

Answer 9

• Friction piles get most of their strength from sheer stress from the side of the pile. The surface of the pile works to transfer the forces into the surrounding soil.
• End bearing piles transfer their load directly into the rock layer below the pile.

Question 10

636 What is the difference between bored and driven piles?

Answer 10

• Driven piles are hammered or vibrated into the ground and generally are quicker to install but this method is more susceptible to delays if there are obstructions in the ground.
• Whereas bored piles are driven into the ground. This can be done using a CFA rig. It is generally a slower method with more wastage but deals better with obstruction in the ground.
• The main difference is their point of manufacture. Driven piles are manufactured offsite whereas bored piles a manufactured in situ

Question 11

637 What are the key advantages and disadvantages of driven piles?

Answer 11

Advantage:
* Speed of installation is generally quicker
* Less arisings
* Less wastage of material
* Driven piles can compact the soil around them and make the bearing capacity greater
Disadvantage:
* Heavy equipment needed for handling and delivery
* Method doesn’t deal with will obstructions
* Noise and vibration are high compared to bored
* Can be costly if the piles are too short

Question 12

638 What are the key advantages and disadvantages of bored piles?

Answer 12

Advantages:
* Less noise and vibration
* Deals better with obstructions
* Flexibility of size and shape as they are constructed onsite.

Disadvantages:
* Slower
* Causes more waste in materials and arisings
* More people required to install
* Do not improve the bearing capacity of the soil

Question 13

639 What are secant piled walls?

Answer 13

These are bored piled walls that form a continuous pilled wall which can be beneficial for both structural stability and water ingress. They are constructed by:
1. Forming a guide wall either side of the desired wall location.
2. Female/primary piles are then drilled between the guide walls. These can then bill filled with soft or hard concrete depending on the spec.
3. Next male/secondary piles are drilled between the female piles which causes the piles to overlap and provides strength and a continuous wall.
4. These are then filled with steel reinforcement and strong concrete

Question 14

640 What is underpinning and why might it be required?

Answer 14

Underpinning is a method of strengthening foundations. Might be used for:
* Stabilising foundations undergoing settlement
* Stabilising foundations that have moved because of landslips or unstable slopes
* Stabilising foundations that might be affected by subsidence, heave or erosion
* Stabilising foundations that might be affected by vibration damage
* To increase the loadbearing capacity of the existing foundations
* To accommodate a new adjoining building, new basement or a deep sewer.

Question 15

640 What is underpinning and why might it be required?

Answer 15

Underpinning is a method of strengthening foundations. Might be used for:
* Stabilising foundations undergoing settlement
* Stabilising foundations that have moved because of landslips or unstable slopes
* Stabilising foundations that might be affected by subsidence, heave or erosion
* Stabilising foundations that might be affected by vibration damage
* To increase the loadbearing capacity of the existing foundations
* To accommodate a new adjoining building, new basement or a deep sewer.

Question 16

641 What is a superstructure?

Answer 16

Superstructure is the part of the building that is above the ground floor slab and includes the frame, roof, walls/windows/facade.

Question 17

643 what are the key considerations when designing building envelope?

Answer 17

Weather protection, fire resistance, acoustic and thermal performance, structural performance, aesthetics, expected life span and maintenance cost.

Question 18

644 What is a retained facade?

Answer 18

This is when the facade is retained and the rest of the building remodelled or a new structure built behind it. Is often used when restoring listed buildings.

Question 19

645 What is a standard Brick Dimension in the UK?

Answer 19

215mm x 102.5 x 65mm which gives 60 bricks per m2
10 Blocks per m2

Question 20

648 What are weep holes?

Answer 20

Small openings in the outer skin of a masonry wall that provide ventilation and to allow moisture to drain away.

Question 21

649 Name some brick bonds

Answer 21

• Stretcher – Most common where vertical joints are staggered by half a brick width.
• English – Alternating courses of headers and stretchers
• Flemish – Alternating headers and stretchers in each course
• Garden Wall – Course of headers every 4th course

Question 22

651 What is a movement joint and why are they used?

Answer 22

This is a flexible material between to harder materials it allows for expansion and contraction of the hard materials without allowing the materials to crush each other or pulling apart and leaving a significant gap. Can also allow for some settlement and or seismic activity.

Question 23

652 What are the main components of concrete?

Answer 23

Cement, aggregate and water. Different mixtures give different strength. Additives can be used to help it go off quicker/underwater. Warm water can be used a cold temperature to ensure it can still be poured.

Question 24

653 What are the difference between live and deal loads?

Answer 24

Dead loads refer to static loads that are relatively constant like the structure itself, fixed elements within the building such as internal walls, kitchens, bathrooms and stairs.
Live loads are dynamic from occupancy and use. This also includes loads from weather which can also impose loading on a structure.

Question 25

654 What is a retaining wall?

Answer 25

A structure that is used to hold back large volumes of earth. Resists the lateral pressure where there is a change in elevation.

Question 26

655 What is pretensioned concrete? (165)

Answer 26

This is a form of pouring concrete slabs were instead of using large volumes of rebar high tensile steel is laid in the slab instead. Before pouring the concrete, the cables are pulled taught. After the concrete has gone off the cables are relaxed. The cables attempt to shorten and transfer the energy into the slab which gives it compressive strength.

Question 27

656 What is post tensioned concrete?

Answer 27

This is where the ducts are inserted into the slab. Post pour when the concrete has reached a desired strength cables are threaded through and tensioned with hydraulic jacks.

Question 28

658 Can you explain what reinforced concrete is?

Answer 28

This is concrete that has steel reinforcement bars cast inside. Concrete is good compressive strength but poor tensile strength. Steel has good tensile strength. When we you add steel to concrete the reinforced concrete will have good compressive and tensile strength.

Question 29

659 What are the key advantages of timber frames?

Answer 29

• Timber is a sustainable material
• Relatively quick construction
• Arrives to site already made (modular) but can be altered on site with ease.
• Can be astatically pleasing

Question 30

660 What are the disadvantages of a timber frame?

Answer 30

• Is limited in terms of what loads can be placed upon it
• Needs specialist trades to install
• Fire protection is required

Question 31

661 What are the key advantages of a steel frame?

Answer 31

• Can be quick to erect on site compared to concrete frames
• Can be built extremely high. Can give large open plan floor plates
• High strength and weight ratio
• Can be recycled

Question 32

662 What are the key advantages of a steel frame?

Answer 32

• Subject to fluctuations in market rates for materials
• Typically steel frames have a lower load bearing capacity than concrete
• Does not have the same acoustic and thermal properties as concrete
• Requires fire protection

Question 33

664 What are the key advantages of concrete frames?

Answer 33

• Good thermal and acoustic properties
• No fire protection required
• Better load bearing capacity than steel frames. High compressive strength
• Cladding and other finishes can be fixed directly to the frame

Question 34

665 What are the key disadvantages of concrete frames? (174)

Answer 34

• Slow to construct (concrete needs time to cure)
• Requires a larger volume of material. Doesn’t span as well as steel
• Requires temporary works formwork and propping
• Requires more trades to erect

Question 35

667 What key factors should be considered when selecting frames?

Answer 35

• Programme. Steel, timber and concrete frames take different times to construct.
• Height of the building. Timber frames can only be used up to a certain height
• Ground conditions and effect the foundation
• Current cost of materials and scarcity of trades and cost in use
• Thermal, acoustic and fire performance
• Sustainability requirement and carbon footprint
• End user requirements. Are big open spaces required
• Future expansion requirements

Question 36

670 What factors should be considered when designing internal partitions?

Answer 36

• Thermal, acoustic and fire requirements
• Flexibility. Are demountable partitions required
• Requirements for doors and windows
• Strength and structural requirements
• Robustness
• Height of partition

Question 37

671 Category fit outs

Answer 37

• Cat A – Basic level of fit out, may include raised floors, suspended ceilings and partition walls. Can have basic M & E services
• Cat B – Ready to move into, partitions and doors, floor finishes, specialist lighting and facilities, kitchens, furniture and company branding.

Question 38

673 Name some common plasterboard types?

Answer 38

• Standard – White/ light grey
• Fireboard – Pink
• Acoustic – Blue
• Moisture resistant – Green