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

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the slab except to reduce the section factor for a reduced heated perimeter. Reducing the section factor in effect increases the effective width, making the temperature rise of the steel decrease to a slower rate. The difference is very small however so a substantial difference in the temperature results from the spreadsheet method is hard to distinguish when comparisons are made between the spreadsheet method and SAFIR. The maximum temperatures found in the beam are not affected by changing the fire exposure conditions. For conservative results for the temperatures reached in the member, analysis of the member as if exposed on four sides to the fire by the spreadsheet method gives results close to the maximum temperatures as found by the SAFIR programme. Even though the average temperature is much lower when a concrete slab is present as found in SAFIR, this only because a small percentage of elements are at a much cooler temperature which subsequently lowers the average temperature of the steel. Throughout the section of the steel however, only the cooling effects of the concrete affect the top flange that is in contact with the slab. Since it is the lower flange that yields and forms a plastic hinge, this cooling effect does not affect the failure temperature of the beam. 5.6.3 Comparison with the ECCS Formula: The ECCS equations for three sided exposure are the same as for four sided exposure but with a reduced section factor. The equation for protected steel beams with heavy insulation is equation 5.1 in Section 5.2.3, and is below: 40( 140) d = − i A c + i ρid t T i l 2 ki H p cs ρ s 0.77 The properties of the insulation are listed in Section 5.6, and are of Fendolite by Firepro. Figure 5.14 shows the comparison of the ECCS formulas with three sided exposure compared with the results from the spreadsheet method and SAFIR. 111
1000 Temperature ( o C) 800 600 400 200 ECCS Ave SAFIR Max SAFIR Spreadsheet 0 0 20 40 60 80 100 120 Time (min) ave max Spreadsheet ECCS 1000 Temperature ( o C) 800 600 400 200 0 0 20 40 60 80 100 120 Time (min) ave max Series4 ECCS 1000 Temperature ( o C) 800 600 400 200 0 0 20 40 60 80 100 120 140 Time (min) ave max Spreadsheet ECCS Figure 5.14: Comparison between the results from SAFIR and the spreadsheet method with the ECCS equation for protected steel members with three sided exposure to the ISO 834 fire. From top to bottom a. 180 UB 16, b. 310 UB 40.4 and c.530 UB 82.0 112
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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
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 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 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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