Fire protection to the structural frame of the building and fire retardant coatings Flashcards
Question 9 Describe the factors that affect the fire resistance of concrete frames and describe two methods to add additional fire protection. (5 marks)
1 Thickness of concrete
2 The mixture and ratios of the concrete, cement and agregate types overall density
3 The load applied to the concrete
4 The amount of concrete cover over the enacased steel reinforcement.
B by adding insulation
Intumescent Coatings – These are specially designed fire-resistant paints that expand when exposed to heat, forming an insulating char layer that protects the concrete from high temperatures.
Fireproof Cladding or Board Systems – Fire-resistant boards, such as calcium silicate or gypsum-based panels, can be installed over concrete surfaces to enhance fire protection.
Fire-Resistant (non-reactive)Sprays and Coatings – Cementitious or fibrous fireproofing sprays can be applied to concrete to improve its thermal resistance and prevent spalling under fire conditions.
Question 10 Describe three passive fire protection measures that may be considered to improve the fire resistance of timber frames. (6 marks)
Three methods of improving the fire resistance of timber frames are:
Sacrificial timber can be added to a timber frame to protect the inner material from fire damage. The sacrificial timber will char at a slow predictable rate.
Fire resisting boards can be added to protect/insulate the timber structure and mechanical fasteners from the effects of fire. The boards are manufactured from fire resisting materials such as gypsum or calcium silicate.
Flame retardant treatments by impregnation or surface treatments. Impregnation takes place off site, surface treatments can be appled on or off site. Used to prevent heat release and surface spread of flame, delaying the time within a compartment for flashover to take place.
??!!Intumescent coatings can be applied to the surface of a timber structure. When exposed to heat these coatings swell and provide insulation to the structure protecting it from the effects of fire.??!!
Question 11 a) Explain how the thickness of a steel structure affects its fire resistance and the amount of structural fire protection required. (2 marks)
b) Explain, using examples, how the shape of a steel structure can affect the performance of fire protection systems. (3 marks)
A thicker heavier steel section takes longer to heat up and reach its limiting/critical temperature than that of a thinner lighter weight section. The thickness of fire protection required is calculated using A/V (area/volume) increasing the thickness of a steel structure increases its volume and mass giving a lower section factor. Lower section factors require less fire protection for a given configuration. Different configurations of fire protection required can result in section factors of different values, i.e. 3-sided vs 4-sided protection.
The shape of a steel structure can affect the performance of fire protection system as intumescent coatings can crack when expanding exposing the steel to high temperatures. This can occur, for example, at the web post of a cellular beam which is a common point of failure in this type of beam. This also affect circular hollow beams. I, H and hollow square sections are less affected with this type of performance failure.
Question 12 Explain why it is considered best practice for sections of steel or structural elements to be protected by the same fire protection intumescent paint system. (4 marks)
It is best practice to use the same type of intumescent paint system for sections of steel or structural elements as different manufacturers, generally do not test their systems with a competitor. Fire protection systems should not be mixed as they are not tested together. The behaviour of different systems is unknown and could behave in a detrimental way at the point they butt up to each other or sprayed on top of one and other. The chemical make-up of one system could have a detrimental effect on the other causing it not to react as intended/tested.
Question 13 One of the factors to be taken into account when determining the choice of fire protection system for different purposes is the level of fire rating required. State four other factors that would be taken into account. (4 marks)
Guidance from manufacturers
Robustness required
Aesthetics
Enviromental exposure, humidity, temperature changes
Regulatory requirements
Correct installation
