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

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susceptible to heating, heat up more than those parts of the beam which are more protected due to the geometry of the beam, ie. the thickness or length of the segment, or the location of the point, ie. the centre of the web compared with the corner of the flange-web intersection. 5.2.2 Heavily Protected Beam with Four Sided Exposure: Four sided exposure is modelled in the SAFIR programme using insulation with the properties stated earlier in Section 5.2. The steel section is protected on all four sides, and an ISO 834 fire is subjected all sides of the protection. The temperature variation across the cross section of the element is small, and of similar proportions to that of four sided exposure for unprotected steel. The results from SAFIR and from the spreadsheet method are compared, and these are also graphed against the estimations from the ECCS equations in Section 5.2.3. There are no formulas provided in NZS 3404 for protected steel members. Figure 5.3 a-c show the results from four sided exposure to the standard ISO 834 fire, for 66 minutes. The graphs show a very close correlation between the temperatures predicted by the spreadsheet and the average temperatures found from the SAFIR simulation. The spreadsheet method gives higher temperatures than SAFIR at lower temperatures of the test, but the difference between the average SAFIR temperature and the spreadsheet temperature increases as the beam gets hotter, with the spreadsheet temperatures exceeding those determined from SAFIR. This is again due to the thermal properties of steel remaining constant with the spreadsheet method, but varying with SAFIR. The curves tend to separate more as the temperature increases, and the spread increases greatly at around 650 °C to 700 °C as this is where the thermal properties of SAFIR deviate most from the constant value of 600 J/kg K that is used in the spreadsheet. 85
Temp ( o C) 800 700 600 500 400 300 200 100 0 Spreadsheet SAFIR 0 20 40 Time (min) 60 80 spreadsheet safir 700 600 500 Temp ( o C) 400 300 200 100 0 0 10 20 30 40 50 60 70 Time (min) spreadsheet safir 600 500 Temp ( o C) 400 300 200 100 0 0 10 20 30 40 50 60 70 Time (min) spreadsheet safir Figure 5.3 a-c: Comparison between the results from SAFIR and the spreadsheet method for Fendolite protected steel beams with four sided exposure to the ISO standard fire. From top to bottom beam sizes a. 180 UB 16.1, b. 310 UB 40.4 and c. 530 UB 82.0 86
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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.
Page 49 and 50: time. The value of the wall lining
Page 51 and 52: The Eurocode does not define a meth
Page 53 and 54: f f y y ( T ) (20) = 1.0 0 < T < 21
Page 55 and 56: temperature is chosen because it is
Page 57 and 58: The variation of yield stress data
Page 59 and 60: 15 m -1 < H p /A < 275 m -1 in NZS
Page 61 and 62: = H p A (m -1 ) 7.85 The cons
Page 63 and 64: 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 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 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
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The plastic neutral axis is located
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It is therefore recommended that th
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These methods may be used to provid
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Eurocode has a large annex with gui
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8.3 CHANGES TO NZS 3404: The follow
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H v height of the ventilation (m) I
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EC3, 1995. Eurocode 3: Design of St
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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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