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Eurocode 4: Design of composite steel and concrete structures– EN1994-1-2:2003 www.structuralfiresafety.org Part 1–2: General rules – Structural fire design Annex F [informative]: Calculation of moment resistances of partially encased steel beams connected to concrete slabs

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Content Design Procedures Annex A Stress-strain relationships for structural steel Basis of Design Basic requirements Actions Material design values Verification methods Simple Models General aspects Thermal response Mechanical response Validation Tabulated data Partially encased beams Composite columns Material Properties Mechanical & thermal properties Structural steel Concrete Reinforcing steel General Advanced Models Constructional Details Composite beams Composite columns Connections www.structuralfiresafety.org Annex B Stress-strain relationships for siliceous concrete Annex C Stress-strain relationships for concrete adapted to natural fires Unprotected / protected composite slabs Composite beams Composite columns Annex E Moment resistance of unprotected beams Annex D Fire resistance of unprotected slabs Annex F Moment resistance of partially encased beams Annex G Simple models for partially encased columns Annex H Simple models for concrete filled columns Annex I Planning & evaluation of experimental models

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F.1(1) Flat slab system www.structuralfiresafety.org h hchc ewew bcbc b efef b eff + - x Compressive stress in concrete Tensile stress in steel h c,h h c,fi f c / γ M,fi,c f ay / γ M,fi,a f ay,x / γ M,fi,a k r f ry / γ M,fi,s k a f ay / γ M,fi,a The section of concrete slab is reduced as follows: regardless fire classes Standard fire resistanceR30R60R90R120R180 Slab reduction h c,fi (mm)1020304055 Table F.1

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F.1(2-3) Other slab systems www.structuralfiresafety.org applies Joint between precast elements which is unable to transmit compression stress trapezoidal profiles transverse to beam Table F.1 re-entrant profiles transverse to beam h c,fi h c,fi,min h c,fi ≥ h c,fi,min prefabricated concrete planks h c,fi h c,fi,min h c,fi ≥ h c,fi,min h c,fi trapezoidal profiles parallel to beam h eff Annex D For calculation refer to

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F.1(4) Active width of upper flange (b - 2b fi ) www.structuralfiresafety.org ewew bcbc b efef f ay / γ M,fi,a (b – 2b fi ) varies with fire classes. Yield strength of steel is taken equal to f ay / γ M,fi,a. Standard fire resistance Width reduction b fi of upper flange R30(e f / 2) + (b – b c ) / 2 R60(e f / 2) + (b – b c ) / 2 + 10 R90(e f / 2) + (b – b c ) / 2 + 30 R120(e f / 2) + (b – b c ) / 2 + 40 R180(e f / 2) + (b – b c ) / 2 + 60 Table F.2 b fi

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F.1(5) Web division www.structuralfiresafety.org ewew bcbc b Web is divided into two parts: h x Top part Bottom part hlhl h h l are given for different fire classes: For h/b c ≤ 1 or h/b c ≥ 2 For 1< h/b c < 2 h l is given directly in Table F.3 Parameters a 1 & a 2 are given in Table F.3 Next

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Table F.3 Bottom part of web: h l www.structuralfiresafety.org Standard fire resistance h/b c ≤ 1h/b c ≥ 2 a 1 [mm 2 ] a 2 [mm 2 ] h l,min [mm] a 1 [mm 2 ] a 2 [mm 2 ] h l,min [mm] R303 6000203 600020 R609 50020 000309 500030 R9014 000160 0004014 00075 00040 R12023 000180 0004523 000110 00045 R18035 000400 0005535 000250 00055 = h – 2e f h l,min ≤ h l ≤ h l,max ewew bcbc b h x hlhl h efef

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Table F.3 Bottom part of web: h l www.structuralfiresafety.org Standard fire resistance 1< h/b c < 2 h l,min [mm] R3020 R6030 R9040 R12045 R18055 = h – 2e f h l,min ≤ h l ≤ h l,max

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F.1(7-8) Section yield strength www.structuralfiresafety.org ewew bcbc h x hlhl h The reduced yield strength depends on distance x: Bottom web Top web f ay / γ M,fi,a Standard fire resistance Reduction factor k a k a,min k a,max R30[1.12 – 84 / b c + h / 22b c ] a 0 0.50.8 R60[0.21 – 26 / b c + h / 24b c ] a 0 0.120.4 R90[0.12 – 17 / b c + h / 38b c ] a 0 0.060.12 R120[0.1 – 15 / b c + h / 40b c ] a 0 0.050.10 R180[0.03 – 3 / b c + h / 50b c ] a 0 0.030.06 a 0 = 0.018 e f + 0.7 efef k a f ay / γ M,fi,a Bottom flange

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F.1(9) Yield strength of rebars www.structuralfiresafety.org ewew bcbc h Standard fire resistance a3a3 a4a4 a5a5 k r,min k r,max R300.0620.160.126 0.11 R600.034-0.040.101 R900.026-0.1540.090 R1200.026-0.2840.082 R1800.024-0.5620.076 u 1,3 Yield strength decreases with temperature. Reduction factor k r depends on fire class & position of rebar: h b c 2h + b c 12 u2u2 3 usus

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F.1(11) Shear resistance of web www.structuralfiresafety.org May be verified using the distribution of the design yield strength according to (7) Resistance of reinforced concrete may be considered If V fi,d ≥ 0.5V fi,pl,Rd

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Fire classes Position of rebars F.2 Yield strength of rebars www.structuralfiresafety.org Reduction factor k s depends on: h bcbc b efef 3 b + Stress in concrete Stress in steel h fi - - - uhuh ulul hchc Standard fire resistance Reduction factor k s k s,min k s,max R301 01 R600.022 u + 0.34 R900.0275 u – 0.1 R1200.022 u – 0.2 R1800.018 u – 0.26 u = u i Bottom bars Top bars u = h c - u h Table F.6

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F.2(2) Upper flange www.structuralfiresafety.org f ay / γ M,fi,a Active width of upper flange: (b – 2b fi ) varies with fire classes. Yield strength of steel is taken equal to f ay / γ M,fi,a. Standard fire resistance Width reduction b fi of upper flange R30(e f / 2) + (b – b c ) / 2 R60(e f / 2) + (b – b c ) / 2 + 10 R90(e f / 2) + (b – b c ) / 2 + 30 R120(e f / 2) + (b – b c ) / 2 + 40 R180(e f / 2) + (b – b c ) / 2 + 60 F.1(4) applies as follows: h bcbc b efef h fi

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F.2(3) Reduced concrete section www.structuralfiresafety.org f c / γ M,fi,c Section is reduced as shown. Compressive strength: Standard fire resistance h fi [mm] b c,fi [mm] R30≥ 25 R60165 – 0.4b c – 8(h / b c ) ≥ 2560 – 0.15b c ≥ 30 R90220 – 0.5b c – 8(h / b c ) ≥ 4570 – 0.1b c ≥ 35 R120290 – 0.6b c – 10(h / b c ) ≥ 5575 – 0.1b c ≥ 45 R180360 – 0.7b c – 10(h / b c ) ≥ 6585 – 0.1b c ≥ 55 h bcbc b h fi 3 b b c,fi not varying with fire classes Table F.7

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F.2(4-5) Yield strength of rebars www.structuralfiresafety.org Standard fire resistance a3a3 a4a4 a5a5 k r,min k r,max R300.0620.160.126 0.11 R600.034-0.040.101 R900.026-0.1540.090 R1200.026-0.2840.082 R1800.024-0.5620.076 Reduction factor k r depends on fire class & position of rebar: h b c 2h + b c F.1(9) applies as follows: h bcbc b 3 b u 1,3 1 u2u2 3 usus 2 ewew

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F.2(6-7) Shear resistance www.structuralfiresafety.org Assumptions: Shear force is transmitted by steel web, which is neglected when calculating the hogging bending moment resistance. Resistance of reinforced concrete may be considered If V fi,d ≥ 0.5V fi,pl,Rd

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