FIRE DESIGN OF STEEL MEMBERS - Civil and Natural Resources ...

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where the temperature of the steel, T s is in °C, (Purkiss, 1996, BSI, 1990, EC3 1995). This value can vary as Harmathy, (1993), uses a value of 1.14 rather than 1.4. ENV 1993-1-2 also adopts a more variable approach to the thermal elongation of steel, with the following relationship between thermal elongation and temperature: ∆l l ∆l l ∆l l = 1.2x10 = 1.1x10 = 2x10 −5 −5 −2 T T −8 2 −4 s + 0.4x10 Ts − 2.416x10 20 < T s < 750 ° 1.8a 750 < T s < 860 °C 1.8b −3 s − 6.2x10 860 < T s < 1200 °C 1.8c The variation of these formulas with temperature are shown in Figure 1.3. 0.02 Thermal expansion of steel 0.016 0.012 0.008 0.004 0 0 200 400 600 800 1000 1200 1400 Temperature ( o C) Equation 1.8 Equation 1.7 Figure 1.3: Variation of thermal expansion of steel with temperature 1.6.3 Section Factor, H p /A: The ratio of the heated perimeter to the cross sectional area gives the inverse of the effective width of the steel member. This term is called the Section Factor (SNZ, 1991). Throughout this report the notation used is H p for the heated perimeter and A for the cross sectional area. Other notations include F for the heated perimeter, or the same ratio can be achieved in a three dimensional sense with the heated area per unit length to the volume per unit length used instead, A/V. Here A for heated surface area should not be confused with A of cross sectional area used in this report. 15
[ The heated perimeter of the steel member varies depending on the protection applied to the member, ie sprayed protection which has the section profile or board protection which boxes the section. When the member is exposed to the fire on less than four sides the ration can be calculated according to the table below. The cross sectional area is always the area of the steel section. The UK and international practice is also to use these values. An alternative method of giving the general size of the beam with a single value is the Australian method of the ratio if exposed surface area to mass per unit length. This value gives the same information as the H p /A value, with a constant factor of 7.85, which is the density of steel in tonnes/kg 3 . Figure 1.4: Variations of Hp/A for different methods of protection, (EC3 1995). Many publications give the H p /A value for a range of beam sizes, but the calculation is not difficult using the width and depth of the beam, if the radii and fillets of the section are ignored. 16
Page 1 and 2: Fire Design of Steel Members K R Le
Page 4: ABSTRACT: The New Zealand Steel Cod
Page 8 and 9: TABLE OF CONTENTS: ABSTRACT:.......
Page 10 and 11: 5.4 RESULTS FOR FOUR SIDED EXPOSURE
Page 12 and 13: LIST OF FIGURES: FIGURE 1.1: VARIAT
Page 14: FIGURE 5.11: TEMPERATURE CONTOUR LI
Page 17 and 18: designed with confidence. Full scal
Page 19 and 20: eams and struts when subjected to a
Page 21 and 22: Gilvery and Dexter, (1997), prepare
Page 23 and 24: with conditions specified to ensure
Page 25 and 26: 1.6 BACKGROUND INFORMATION: 1.6.1 F
Page 27 and 28: experienced in fire situations, but
Page 29: The thermal conductivity is not imp
Page 33 and 34: The advantages of board systems are
Page 35 and 36: The values for the thermal properti
Page 37 and 38: insulation has on the rise of the s
Page 39 and 40: ( T − T ) k H p f s ∆t ∆T
Page 41 and 42: spreadsheet method very closely, wi
Page 43 and 44: protection, and for user defined fi
Page 45 and 46: This equation originates from the y
Page 47 and 48: 1400 1200 1000 800 600 400 200 0 0.
Page 49 and 50: time. The value of the wall lining
Page 51 and 52: The Eurocode does not define a meth
Page 53 and 54: f f y y ( T ) (20) = 1.0 0 < T < 21
Page 55 and 56: temperature is chosen because it is
Page 57 and 58: The variation of yield stress data
Page 59 and 60: 15 m -1 < H p /A < 275 m -1 in NZS
Page 61 and 62: = H p A (m -1 ) 7.85 The cons
Page 63 and 64: Connections: NZS 3404 requires that
Page 66 and 67: 4 CALCULATION OF STEEL TEMPERATURES
Page 68 and 69: 4.1.2 Analysis Between Methods of T
Page 70 and 71: Figure 4.2 shows the variation of t
Page 72 and 73: Minimum temperatures Maximum temper
Page 74 and 75: For all three sizes of beam, the sp
Page 76 and 77: Temperature ( o C) 1200 1000 800 60
Page 78 and 79: The ECCS equation has a time period
Page 80 and 81:
4.3.1 Results from simulations with
Page 82 and 83:
From Figure 4.5 a-c, the formula ra
Page 84 and 85:
Temperature ( o C) 1000 800 600 400
Page 86 and 87:
average temperature of the beam, be
Page 88 and 89:
Temperature ( o C) 1400 1200 1000 8
Page 90 and 91:
significantly decreased from a cool
Page 92 and 93:
Since both programmes use the same
Page 94 and 95:
Therefore, the ECCS equations provi
Page 96 and 97:
5 CALCULATION OF STEEL TEMPERATURES
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calculations made by the spreadshee
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susceptible to heating, heat up mor
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Figure 5.3 a-c show the results fro
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7850*600*10500 > 2*775*1100*(1869*2
Page 106 and 107:
As can be seen from Figure 5.4 a-c,
Page 108 and 109:
310 UB 40.4 beam H p /A = 241 m -1
Page 110 and 111:
The SAFIR results fit between the t
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constant specific heat being used i
Page 114 and 115:
From Figure 5.7 a-c, it appears tha
Page 116 and 117:
800 Temperature ( o C) 600 400 200
Page 118 and 119:
To examine the limits of the thickn
Page 120 and 121:
1000 Temperature ( o C) 800 600 400
Page 122 and 123:
Thermal conductivity, k i = 0.19 W/
Page 124 and 125:
1000 Temperature ( o C) 800 600 400
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the slab except to reduce the secti
Page 128 and 129:
Figure 5.14 shows the correlation b
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5.8 CONCLUSIONS: The thermal behavi
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6 COMPARISON OF METHODS USING OTHER
Page 134 and 135:
Temperature ( o C) 1200 1000 800 60
Page 136 and 137:
6.2.4 Results for protected steel:
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Figures 6.2 b shows the comparison
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Figure 6.3 a shows that the average
Page 142 and 143:
The fire that the test beams were e
Page 144 and 145:
7 ADDITIONAL MATERIAL IN EUROCODE 3
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For thermal analysis in Eurocode 3,
Page 148 and 149:
To determine the performance of a s
Page 150 and 151:
The plastic neutral axis is located
Page 152 and 153:
It is therefore recommended that th
Page 154 and 155:
These methods may be used to provid
Page 156:
Eurocode has a large annex with gui
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8.3 CHANGES TO NZS 3404: The follow
Page 161 and 162:
H v height of the ventilation (m) I
Page 163 and 164:
EC3, 1995. Eurocode 3: Design of St
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Temperature Conditions. National Re
Page 168 and 169:
APPENDIX A - SPREADSHEET METHOD: Be
Page 170 and 171:
APPENDIX B - SAFIR: In Figure B.2 i
Page 172 and 173:
*.str file developed by the pre pro
Page 174 and 175:
22 FISO 23 FISO FISO 24 FISO FISO 2
Page 176:
APPENDIX C - FIRECALC Below in Figu
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