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

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Figures 6.2 b shows the comparison of the results from the spreadsheet method with those from SAFIR. The curves are much closer to each other than those in Figures 6.2a when the changing specific heat of steel is not taken into account by the spreadsheet method. The maximum temperature reached in the modified spreadsheet analysis is 825 °C, which is only 25 °C higher than the maximum temperature reached from the SAFIR simulation. The decay region of the simulation in Figures 6.2 a and b shows differences between the results from SAFIR and the spreadsheet method. In Figures 6.2 a this can be explained by the differences in specific heat, but Figures 6.2 b should have a closer decay rate than that that appears on the graph. The rate of temperature increase is very similar in Figures 6.2 b, so it is expected that the rate of decrease should be more similar also. The SAFIR curve appears to be slightly translated to the right from the spreadsheet method curve, which suggests that the steel from the SAFIR simulation takes longer before it begins to heat up. The rate of decrease from the SAFIR simulation is quite substantially slower than the decrease rate with the spreadsheet method, so the steel is losing heat to its surroundings more slowly than the spreadsheet method suggests. The SAFIR programme also has variations of specific heat, density and thermal conductivity for its insulation. This could contribute to the difference in the results, although it does not explain why the difference occurs only in the decay stage and not in the heating stage at temperatures below 700 °C. 6.3 REAL FIRES: To confirm the results and conclusions found in Sections 4 and 5 of this report, the temperatures of steel beams and fires from experimental test data has been compared with calculations performed by the spreadsheet method, and simulations in SAFIR with the same fire temperature data. The beam sizes used in the unprotected and protected tests have been used in the computer analysis where possible, and where not the closest beam size by dimensions and mass per unit length has been used. 123
6.3.1 Unprotected Steel: The experimental data comes from a ‘Compendium of UK Standard Fire Test Data, Unprotected Structural Steel – 1’ (Wainman and Kirby, 1988). The beam is sized according to British Standards, and is a 203 x 133 mm beam, with mass of 30 kg/m length. The steel temperatures from the experimental data is measured at four locations on top flange, four locations on the web, and five locations on the lower flange. The beam was exposed to an ISO 834 fire and the mean furnace gas temperature is recorded. All temperatures have been measured at three minute intervals. The beam has a 132 mm concrete slab protecting the top flange, resulting in three sided exposure conditions for the beam. To perform simulations in SAFIR with a concrete slab, the pre-processor wizard developed by Ionica and Vanderseipan, must be used because the pre-processor developed by John Mason does not have these capabilities, see Section 2.3.1. The elevated temperature conditions were exposed to three sides of the beam and to the under side of the concrete slab. 1000 Temperature ( o C) 800 600 400 200 Spreadsheet Real steel Temp SAFIR 0 0 10 20 30 40 50 60 Time (min) Spreadsheet Fire Real Steel Temp SAFIR ave Figure 6.3: Comparison between the average temperature from experimental data for three sided unprotected steel with results from the spreadsheet method and average temperature of a SAFIR simulation The average temperature for the top and lower flange, and the web are shown in Figure 6.3. This figure also shows the results from a calculation by the spreadsheet method and from the simulation in SAFIR using the same sized beam and exposure conditions. 124
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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
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Temperature ( o C) 1000 800 600 400
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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 134 and 135: Temperature ( o C) 1200 1000 800 60
Page 136 and 137: 6.2.4 Results for protected steel:
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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