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

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6 COMPARISON OF METHODS USING OTHER FIRE CURVES: 6.1 INTRODUCTION: To ensure that the results found by comparing methods of calculating the thermal response of steel beams exposed to the ISO 834 fire gives reasonable and accurate results, the same comparisons have been repeated with other fire curves. As described in Section 2.4.2, there are five Eurocode Parametric curves being studied in this report with varying fuel loads and ventilation factors and a constant wall lining value. These variations are to provide a range of fires and demonstrate that the methods here can be applied to many cases. Since each parametric curve is different, only one beam size has been used in this section to reduce the repetitiveness of the results and reduce the time to analyse the same procedure many times. Real fire experimental data has also been used to verify the thermal response methods used in this report. 6.2 EUROCODE PARAMETRIC FIRES: 6.2.1 Introduction: The Eurocode Parametric curves are more realistic curves than the ISO 834 fire as the temperature depends on the ventilation, the fuel load present and the thermal properties of the wall linings of the compartment. The duration of heating of the parametric curve is dependent on the amount of fuel available and it has a decay phase that occurs after the peak, which is also dependent on the fuel load and ventilation of the room. The SAFIR pre-processor developed by John Mason has a function allowing different fires to be analysed with the SAFIR programme that could not be analysed before. The Eurocode Parametric fire is one of these, and by entering appropriate values for the opening factor, wall lining properties and fuel load the fire can be defined. 117
6.2.2 Assumptions: When using the Eurocode fire formula, the value for √kρc of the wall linings is used, not the individual components of the factor. When inputting data into the SAFIR , values for each component were required to be entered. To achieve a value of 1160 for √kρc, values of k, ρ and c were adjusted to get an exact value of 1160 for the square root of the product of the three thermal properties. The other assumptions as stated in Section 4 and 5 referring to the temperature of the surrounding air and constant temperature throughout the cross section of the beam are valid in this section also. The pre-processor displays the information concerning the fire such as the time to peak temperature, peak temperature and decay rate and these corresponded with those calculated for the spreadsheet analysis for all parametric fires used in this report. The Eurocode fires were simulated in the SAFIR programme with only one beam size to reduce the number of iterations performed. This beam is the BHP 310-UB-40.4, and is the medium sized beam that was used in the ISO standard fire comparisons. It is assumed that the results that are found in this section with this beam will provide the same conclusions as with other sized beams. The results found in Sections 4 and 5 suggest that the analysis of one beam size is relevant, and the method transferable to other beam sizes. 6.2.3 Results for unprotected steel exposed to the Eurocode Parametric fire: A comparison between the spreadsheet method and the results from the SAFIR analysis show that the spreadsheet method can be an effective and accurate way to model the behaviour of unprotected steel for both heating and cooling stages of a real fire. 118
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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
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 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 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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