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

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Thermal conductivity, k i = 0.19 W/m K Density, ρ i = 775 kg/m 3 Thickness, d i = 0.02 m 5.6.1 Results from a Simulation with the SAFIR Programme: When analysing the unprotected steel sections with a concrete slab on the top flange, the wizard pre processor was used to set up the data and structural files required by SAFIR for the simulation. However, difficulties were experienced when this was attempted with protected steel. To overcome this problem and attempt to model the effect of having a concrete slab supported by the steel beam, the pre processor by John Mason was used. This pre-processor does not have the option of having a slab on top of the beam, but by protecting the beam with spray on protection on four sides, and then changing the properties of the protection to those of concrete for the elements on the top face of the beam, a concrete slab can be modelled. The problems with this method is that the thickness of the concrete slab is 20 mm rather than 150 mm, and the width of the concrete slab only extrudes to the edge of the insulation, or 20 mm further on either side of the width of the beam. Making the assumption that this models the effect of a concrete slab is conservative as using a thicker slab that extrudes further from the faces than shown here will give lower temperatures than those found using this method. Figure 5.11 shows the layout of the protected steel beam as inserted into SAFIR, and the resulting contour lines of temperature after 10 minutes of exposure to the ISO 834 fire. In Figure 5.11, the contour lines can be seen to follow the perimeter of the beam through the insulation, but not through the concrete slab. This is because there is no fire exposed to the outer face of the concrete slab. The temperature of the slab increases due to conduction from the steel, but the temperature of the concrete is much lower than that of the insulation and the steel. The temperature of the coolest contour line is 84 °C but this is at the steel-insulation interface. It can be seen from Figure 5.11 that this contour does not extend around to the concrete- 107
steel interface even though the temperature of the flange is close to 84 °C. The temperature of the nodes at the steel concrete interface along the top flange range from 58 °C to 60 °C at this time, which is significantly lower than that of the equivalent nodes on the bottom flange which at are temperatures between 110 °C and 120 °C. Concrete slab Fendolite protection Minimum temperatures Steel beam Figure 5.11: Temperature contour lines for a 180UB16.1 beam protected with Fendolite and with a 20 mm concrete slab, exposed to the ISO 834 fire on three sides. The temperature variation across the cross section is shown below in Figure 5.12. The maximum temperatures occur through the web and the lower flange and the minimum temperatures occur midway along the flange overhang, as shown in Figure 5.11 108
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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
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 116 and 117: 800 Temperature ( o C) 600 400 200
Page 118 and 119: To examine the limits of the thickn
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
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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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