L2 oct22 struct-retard Flashcards
a) Identify three factors that affect the fire resistance of concrete frames. (3 marks)
b) Explain the difference between cast-in concrete and precast concrete.(2 marks)
For part a) , many candidates failed to identify three of the four factors – thickness of the
concrete; mixture/content of the concrete; the load applied to it; or the amount of
cover/protection.
Cast in is poured in to shuttering on site. Pre cast is formed and poured away from site.
One option for enhancing the fire resistance of timber is sacrificial timber. Name and describe
two other options. (6 marks)
Fire resisting boards can be mechanicaly fixed to a timber structure to provide insulation from the effects of a fire. Board types are gypsum, calcium silicate or mineral wool.
Explain how steel behaves in fire and the way that this determines the fire protection required.
(5 marks)
Steel loses its design safety margin at around 550oC
This means it can buckle and collapse
The thicker and heavier steel, the longer it takes to heat up
Issued: 01/2023 Page 4 of 10
This means it takes longer to collapse
The need to protect steel from heat to limit loss of strength to prevent collapse
Thinner section needs more protection as it is more vulnerable
Identify three types of fire resisting materials that can be applied to structural designs to protect
them from fire. (3 marks)
Intumescent (reactive) coatings
Boards/casing systems
Non-reactive (cementitious) sprays
In relation to materials used to enhance the structural resistance of steel, describe each of
the following methods of application:
a) Profile (2 marks)
b) Box (2 marks)
c) Solid (2 marks)
Profile the perimeter of the steel is followed when applying reactive and non reactive coatings
Box Boards are fixed in a box like structure around the steel section. lath can also be applied to recieve non reactive coatings.
Solid - box like structure completely filled with fire resistant materials such as non reactive coatings or concrete
a) Explain why minor damage to intumescent coating systems should repaired at the
earliest opportunity. (2 marks)
b) State the process to follow when repairing damage to intumescent coating systems
(3 marks)
Damage may allow moisture ingress which would lead to degradation of the intumescent
Fire performance may be affected
It may promote corrosion
The area treated may become inaccessible as the construction progresses/at a later date
so it is important to carry out the repair at the earliest opportunity
