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

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Temperature ( o C) 1400 1200 1000 800 600 400 200 0 ECCS SAFIR 1 NZS 3404 SAFIR 2 0 10 20 30 40 50 60 70 time (min) SAFIR 1 SAFIR 2 NZS 3404 ECCS Temperature ( o C) 1400 1200 1000 800 600 400 200 0 0 10 20 30 40 50 60 70 time (min) SAFIR 1 SAFIR 2 NZS 3404 ECCS Temperature ( o C) 1400 1200 1000 800 600 400 200 0 0 10 20 30 40 50 60 70 time (min) SAFIR 1 SAFIR 2 NZS 3404 ECCS Figure 4.12 a-c: Comparison of the linear equations provided by NZS 3404 and ECCS with the temperatures obtained from SAFIR with three sided exposure to an ISO 834 fire for a. 180 UB 16, b. 310 UB 40.4 and c.530 UB 82.0 73
The temperature range that equation 4.3 is valid for is non conservative, when comparing the line with the time temperature curve from SAFIR 1. Neglecting the results from Figure 4.12 a, due to the section factor for this beam size being out of range, the upper limit for the temperature based on the results of Figure 4.12 b and c, should be closer to 750 °C than the present 850 °C in the New Zealand Steel Code. This is the upper temperature limit in the Australian Code. The ECCS equation temperature limitations could be modified, by increasing the upper limit, but by a lesser amount than suggested for four sided exposure in Section 0. The temperature range for equation 4.2 could be raised to at least 700 °C for three sided exposure, with a linear interpolation region added to the method here for temperatures below 400 °C. Since the formula for equation 4.3 is modified for three sided exposure from equation 4.1, the line from equation 4.3 fits better with the SAFIR 2 curve with a slab. This is because the data that the line is formulated to fit to is from results of three sided exposure with a slab present, from British Steel Institute tests, SNZ, (1997). Equation 4.3, therefore, appears to give a more realistic prediction of the average temperature of steel beams with three sided exposure, but again equation 4.2 is more conservative, by giving higher temperatures. The designer may wish to choose a more economical design by using the estimations of the NZS formulas, but the factor of safety in design is less than when using alternative methods of temperature estimation. Although the average temperature of steel beams is best predicted by equation 4.3, the ECCS formula, equation 4.2, gives a temperature estimation closer to the maximum likely temperature that will be reached in the steel, which is unaffected by fire exposure conditions, see Section Figure 4.10. Using the maximum temperature instead of the average temperature for three sided exposure is more conservative, as it gives higher temperatures and will give a more likely failure time for simply supported members. The temperature of the steel section is 74
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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
Page 37 and 38: insulation has on the rise of the s
Page 39 and 40: ( T − T ) k H p f s ∆t ∆T
Page 41 and 42: spreadsheet method very closely, wi
Page 43 and 44: protection, and for user defined fi
Page 45 and 46: This equation originates from the y
Page 47 and 48: 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 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 132 and 133: 6 COMPARISON OF METHODS USING OTHER
Page 136 and 137: 6.2.4 Results for protected steel:
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Figures 6.2 b shows the comparison
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Figure 6.3 a shows that the average
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The fire that the test beams were e
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7 ADDITIONAL MATERIAL IN EUROCODE 3
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For thermal analysis in Eurocode 3,
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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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