Option 2: Fire resisting walls, floors and ceilings and fire resistant glazing Flashcards
Describe how composite floors are constructed and explain how this affects how they behave
in fire.
(4 marks)
Composite floors generally consist of a profiled metal deck with a poured concrete topping which can
perform differently in fire, because the metal base will conduct heat from fire laterally, and in so doing
the metal face will attempt to expand.
The rate of temperature increase in the critical parts of the floor may be lessened compared to
concrete alone, however the composite floor will also be fixed through shear connectors to the
supporting steel structure.
During the fire, steam formed in the concrete may force out the metal decking, distorting it and
causing gaps and subsequent failure, and whilst the steel reinforcement will transfer the load and the
heat from fire, the composite structure may ultimately deform under the heat and sag under the load
of the concrete.
The fire performance of all floors can be enhanced through the use of added passive fire protection
systems, appropriate to the floor type.
a) State two factors to be taken into account when determining the degree of fire resistance
required of compartment walls.
(2 marks)
b) State four locations in a building where compartmentation would be installed.
(4 marks)
A
Compartmentation fire performance
The degree of fire resistance required will depend on several factors including:
* The specified fire resistance period
* The height of the top floor above ground and the intended use known as the purpose group
of the building
* Whether fire resistance is expected from one side or both sides of the barrier
* The type of fire performance required i.e. stability, integrity and insulation
B
Between Different Occupancies – To separate areas with different uses, such as residential and commercial spaces in a mixed-use building, to prevent fire spread between them.
Stairwells and Escape Routes – To protect exit routes, ensuring safe evacuation by preventing fire and smoke from spreading into these critical areas.
Plant Rooms and Service Areas – To contain potential fires in high-risk areas like boiler rooms, electrical rooms, and generator spaces.
Basements and Parking Garages – To prevent fire from spreading to upper floors and to contain fires in areas with high fire loads, such as vehicles and stored materials.
Explain the purpose of fire resisting suspended ceilings and state how they are constructed.
(4 marks)
The purpose of fire resisting suspended ceilings is to provide compartmentation to protect the floor or service void above.
A fire resistant suspended ceiling is constructed using a grid system made of specially designed fire-resistant metal components, combined with fire-rated ceiling tiles that are specifically manufactured to withstand high temperatures for a set period, ensuring the ceiling can contain flames and smoke spread during a fire, all while adhering to building codes and fire safety regulations; essentially, both the grid and tiles must be fire-rated and installed according to manufacturer specifications to achieve the desired fire resistance rating
a) One type of active fire curtain is Vertical Fire Curtains. Describe this type of active fire
curtain and explain how it operates.
(4 marks)
b) State two places where active fire curtain barriers may be found.
(2 marks)
Vertical Fire Curtains typically comprise a fire-resistant fabric wound onto a roller enclosed within a head
box fixed above the opening to be protected. They are usually powered by an electric motor. A weighted
bar is fitted to the bottom edge of the fabric curtain and each side is retained within a vertical channel
which is fixed to the sides of the opening to be protected. The electric motor is connected via a power
supply to a control panel which is in turn connected to a local detector or fire alarm panel. Deployment of
the Fire Curtain is usually initiated by the fire alarm but shall fail-safe by gravity.
Found in
- Atriums
- Lobbies and receptions
- Boundary protection (external)
- Openings in walls
- Compartmentation
- Stair wells
- Lifts
- Escalators
Describe each of the following types of glass and state how each behaves in fire including the
type of fire resistance provided:
a) wired glass
(3 marks)
b) laminated intumescent glass
(3 marks)
Wired Glass
Wire mesh glass, sometimes referred to as Georgian wired glass, is the oldest form of fire resisting
glazing systems available, formulated with a grid or mesh of thin metal, wire embedded within the
glass in the manufacturing process.
The wire prevents the glass from falling out of the frame even if it cracks under thermal stress, and
applications include visual panels within fire doors, as screens, overhead glazing and fanlights. Such
glazing can maintain integrity when subject to thermal shock, i.e. when sprayed with water.
Laminated composites combining a hard intumescent interlayer between annealed glass
Typically, this glazing system is formed with a sodium silicate based interlayer, which in the event of a
fire will turn opaque and swell, and in the process will ensure that, as the glass layers crack, they will
remain bonded to the interlayer.
This is a progressive process depending on the number of sheets of glass and interlayers bonded
together, which enables this system to offer extended fire insulation performance.
The way that a glazing system is supported is critical to its performance in fire. Explain the
purpose of glazing seals and describe the factors to be taken into account to ensure that they
are effective in supporting glazing.
(4 marks)
- glazing seals seal the gap between the glass, the bead and the edge of the frame to
prevent the penetration of hot gases and flame. - in the case of intumescent seals, the seals provide additional protection to the top of a
timber bead to lower the risk of bead ignition. - the seals bed the glass against the retaining bead and minimise the probability of uneven
point loading or edge stresses.
