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

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800 Temperature ( o C) 600 400 200 Spreadsheet SAFIR 0 0 10 20 30 40 50 60 70 Time (min) SAFIR Spreadsheet 800 Temperature ( o C) 600 400 200 0 0 10 20 30 40 50 60 70 Time (min) SAFIR Spreadsheet 800 Temperature ( o C) 600 400 200 0 0 10 20 30 40 50 60 70 Time (min) SAFIR Spreadsheet Figure 5.8 a-c: Comparison between the results from the spreadsheet method and SAFIR for protected steel beams with 20 mm board protection From top to bottom: a. 180 UB 16, b. 310 UB 40.4 and c.530 UB 82.0 101
The spreadsheet method gives temperatures greater than that of SAFIR even though SAFIR accounts for more heat transfer modes, because the spreadsheet method assumes that the insulation protection is in contact with the steel section for the whole perimeter, and transfers energy by conduction to the beam over the full perimeter. The H p /A value is smaller with box protection so the spreadsheet distinguishes that as a thicker beam. For a BHP-530 UB 82.0 steel beam, the H p /A value for spray on protection is 178 m -1 , which gives a effective width steel thickness of the inverse of this which is 5.6 mm. With box protection added to the same beam, the H p /A value changes to 140, giving an effective steel thickness of 7.1 mm. The thicker section should give lower temperatures for the beam, and when the H p /A value is decreased to those more equal to that of three-sided exposure, the results become closer to those found from SAFIR. With the spreadsheet ‘seeing’ the beam as a thicker section, it is assumed the temperatures would be lower than the results from SAFIR as thicker members take longer to heat up than thin members do. Since this does not occur this suggests that the energy received by the beam through conduction through the insulation as calculated in the spreadsheet, is much more than the radiation and convection components as modelled in the SAFIR programme. 5.5 RESULTS FOR FOUR SIDED EXPOSURE WITH THICK PROTECTION: In this section, the thickness of the insulation has been increased to 40 mm, rather than 20 mm as used in Sections 5.2-5.4. The one dimensional model which the spreadsheet equations are based on requires that the ratio of the outside perimeter to the inside perimeter is not too large, so that the one dimensional assumptions are valid. If the ratio becomes too large, the calculations will give temperatures that are too low, and a two dimensional heat flow analysis would be required. 102
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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
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 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 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
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
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APPENDIX A - SPREADSHEET METHOD: Be
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APPENDIX B - SAFIR: In Figure B.2 i
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*.str file developed by the pre pro
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22 FISO 23 FISO FISO 24 FISO FISO 2
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APPENDIX C - FIRECALC Below in Figu
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