FIRE SAFETY DESIGN
AND SPECIFICATIONS
Fire resistance is the most important way in which a structure can withstand collapse in a fire event. It is dependent on many factors, including the applied load, member type (column, beam, wall etc.), member dimensions, type of construction materials, heat flux from the fire on the member and rate of temperature rise.
At LB Fire Protection we provide a tailored design and specification service for your project or building, covering the following aspects for passive fire protection:
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fire protection for structural steelwork, including dry board and intumescent coatings,
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fire protection for metal framed non-load bearing wall systems,
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penetration seals, linear joint seals and cavity barriers,
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fire door sets, including essential hardware such as hinges, closers and smoke seals,
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fire resisting partitions (internally framed and non-load bearing).
FIRE RESISTANCE
Fire resistance is usually assessed against three criteria of failure, until one occurs:
Insulation
The ability of an element of construction to withstand fire exposure on one side only, without significant transfer of heat to the unexposed side, as measured in standard fire resistance test methods that measure surface temperature on the unexposed side of the element (as defined
by BS EN 13501-2).
Integrity
The ability of a separating element, when exposed to fire on one side, to prevent the passage of flames and hot gases or the occurrence of flames on the unexposed
side, for a stated period of time in a standard fire resistance test (i.e. the
relevant part of BS EN 13501).
Load bearing capacity
The ability of a load-bearing element of a structure to withstand the effects of fire to an appropriate degree without loss of load-bearing capacity.
Effect of fire on steel
At temperatures above 400°C steel starts to lose its yield strength. Approximately 80% of yield strength is lost at 700°C.
Due to the inherent vulnerability of steel to fire, it is necessary to limit the temperature rise of the material so that sufficient strength remains for the structural frame to continue to be able to provide a load bearing function. The insulation of steel is a common method which limits its rise in temperature during a fire and can be achieved by covering exposed members with gypsum based boards. In recent years the use of reactive coatings (intumescent paints) has also become widespread, particularly for construction of new buildings.
At LB Fire Protection we can specify fire protection for new structural steelwork and also survey and design improvements to existing exposed structural steelwork in order to provide protection and increase resistance to fire.
Effect of fire on concrete
Certain characteristics of concrete can make it vulnerable to fire when acting as a structural element. Exposure of concrete to high temperatures introduces a ‘temperature gradient’ within the material. The hotter surface layers tend to separate and spall from the body of concrete and cracks often form at joints and towards any unrestrained edges.
A loss of surface layer protection to the steel reinforcement and cracks within the concrete compromise the structural integrity of the element and can lead to failure. The concrete mix design, constituent materials and quality of placement all affect the ability of concrete to resist the effects of high temperatures.
At LB Fire Protection we can provide specialist advice for concrete mix designs and quality control which ensure that the resistance of structural elements to fire is increased.