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

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Temperature ( o C) 1200 1000 800 600 400 200 0 SAFIR Spreadsheet 0 50 100 150 200 250 300 Time (min) SAFIR Spreadsheet Fire Temp Temperature ( o C) 1400 1200 1000 800 600 400 200 0 0 50 100 150 200 Time (min) SAFIR Spreadsheet Fire Temp Temperature ( o C) 1400 1200 1000 800 600 400 200 0 0 50 100 150 200 Time (min) SAFIR Spreadsheet Fire Temp Figure 6.1 a-c: Comparison between SAFIR and spreadsheet results for an unprotected steel beam with four sided exposure to a parametric fire, from top to bottom: a. 0.04-800, b. 0.08-800 c.0.12- 800 fires 119
This time-temperature curve shows the results from the spreadsheet method and the SAFIR programme. The curve of the fire is also shown, which remains at 20 °C once the fire decays to this temperature. This Eurocode parametric fire has a ventilation factor of 0.04,0.08 and 0.12 from top to bottom respectively; a fuel load of 800; and a thermal capacity of wall linings (√kρc) of 1160. See Section 2.3.2 for more details regarding the Eurocode fires. Figure 6.1a-c shows that the temperatures of the steel from both the SAFIR simulation and the spreadsheet analysis reach a temperature close to the temperature of the fire and that the temperature of the steel begins to decrease immediately after the temperature of the fire begins to decay. At the peak fire temperature, the steel temperature is less than 2 °C lower than the fire. The rate of temperature decrease is slower in the steel than the rate of decrease of the fire because the temperature decrease is based on the difference of temperatures. When the temperature difference between the fire and the steel is small, the decreasing rate of temperature of the steel is small because the steel can not lose as much heat energy to its surroundings if the surroundings are at a similar temperature. As in Section 4 and 5 with the ISO fire, the curve from the SAFIR analysis reaches a plateau when the temperature is around 650 –750 °C. The curve from the spreadsheet calculations continues with a steady increase of temperature, until the steel temperature nears the temperature of the fire. This occurs during the decay region also when the steel is cooling down. This is due to the specific heat of steel changing in the SAFIR programme, and remaining constant in the spreadsheet analysis. As with the heating of the steel, when the beam can absorb more energy before the temperature increases, when the steel temperature is between 650 – 800 °C, the steel must lose more heat energy before it can cool down in this temperature range. Figure 6.1 a-c confirms the results seen with the ISO fire in Section 4, that the spreadsheet method gives very close results to those found in SAFIR for unprotected steel with four sided exposure. 120
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Fire Design of Steel Members K R Le
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ABSTRACT: The New Zealand Steel Cod
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TABLE OF CONTENTS: ABSTRACT:.......
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5.4 RESULTS FOR FOUR SIDED EXPOSURE
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LIST OF FIGURES: FIGURE 1.1: VARIAT
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FIGURE 5.11: TEMPERATURE CONTOUR LI
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designed with confidence. Full scal
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eams and struts when subjected to a
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Gilvery and Dexter, (1997), prepare
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with conditions specified to ensure
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1.6 BACKGROUND INFORMATION: 1.6.1 F
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experienced in fire situations, but
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The thermal conductivity is not imp
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[ The heated perimeter of the steel
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The advantages of board systems are
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The values for the thermal properti
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insulation has on the rise of the s
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( T − T ) k H p f s ∆t ∆T
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spreadsheet method very closely, wi
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protection, and for user defined fi
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This equation originates from the y
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1400 1200 1000 800 600 400 200 0 0.
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time. The value of the wall lining
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The Eurocode does not define a meth
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f f y y ( T ) (20) = 1.0 0 < T < 21
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temperature is chosen because it is
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The variation of yield stress data
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15 m -1 < H p /A < 275 m -1 in NZS
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= H p A (m -1 ) 7.85 The cons
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Connections: NZS 3404 requires that
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4 CALCULATION OF STEEL TEMPERATURES
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4.1.2 Analysis Between Methods of T
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Figure 4.2 shows the variation of t
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Minimum temperatures Maximum temper
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For all three sizes of beam, the sp
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Temperature ( o C) 1200 1000 800 60
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The ECCS equation has a time period
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4.3.1 Results from simulations with
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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
Page 98 and 99: calculations made by the spreadshee
Page 100 and 101: susceptible to heating, heat up mor
Page 102 and 103: Figure 5.3 a-c show the results fro
Page 104 and 105: 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
Page 112 and 113: 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 122 and 123: Thermal conductivity, k i = 0.19 W/
Page 126 and 127: the slab except to reduce the secti
Page 128 and 129: Figure 5.14 shows the correlation b
Page 130 and 131: 5.8 CONCLUSIONS: The thermal behavi
Page 132 and 133: 6 COMPARISON OF METHODS USING OTHER
Page 136 and 137: 6.2.4 Results for protected steel:
Page 138 and 139: Figures 6.2 b shows the comparison
Page 140 and 141: 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
Page 146 and 147: 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
Page 159 and 160: 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
Page 165 and 166: 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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