1. Definition:
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cl. 1.4.1 & 2.2.3.1
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2. Requirement for fire resistance
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cl. 2.1.1
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Adequate structural resistance for the required fire
resistance period.
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cl. 2.2.4.7
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Durability and fire resistant
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cl. 4.1.2
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Appropriate degree of fire resistance
(a) flame penetration;
(b) heat transmission; and
(c) collapse.
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cl. 4.3
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Requirement for
fire resistance
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cl. 4.3.1 for high strength concrete
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1. Prevention of spalling in high strength concrete
-
content of silica fume not exceed 6% by weight
of total cementitious content
-
Pfa and ggbs comply with cl 4.2.5.5 for normal
strength concrete
2. Method to reduce risk of concrete spalling. At least
one of the following method
(a) Method A: A reinforcement mesh with a
nominal cover of 15mm. This mesh shall have wires with a diameter ≥ 2mm with
a pitch ≤ 50 x 50mm. The nominal cover to the main reinforcement shall be ≥
40mm;
(b) Method B: Include in the
concrete mix not less than 1.5 kg/m3 of monofilament propylene fibres. The
fibres shall be 6 – 12 mm long and 18 – 32 μm in diameter, and shall have a
melting point less than 180°C;
(c) Method C: Protective layers
for which it is demonstrated by local experience or fire testing that no
spalling of concrete occurs under fire exposure; or
(d) Method D: A design concrete
mix for which it has been demonstrated by local experience or fire testing
that no spalling of concrete occurs under fire exposure.
3. For high strength concrete exceeding C80, at least one
fire test should be carried out to demonstrate that the main reinforcing bars
of a structural member shall not be exposed.
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3. Design parameters:
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cl. 2.2.3.2, 3.6, Table 3.5 to 3.7
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Strength reduction factors
Elevated temperature see BS EN 1992-1-2
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cl. 2.3.2.7 & Table 2.2
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Partial safety factors for loads:
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cl. 2.4.3.2 & Table 2.3
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Partial safety factors for materials:
Effects of exceptional loads or localised damage. γm may
betaken as 1.3 for concrete in flexure and 1.0 for steel.
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Reference:
3. BS EN 1992-1-2 Eurocode 2 Design of concrete structures –
Part 1-2 General rules: Structural fire
design
4. The Effect of Elevated Temperature on Concrete Material and Structures - A Literature Review by US Nuclear Regulatory Research
