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

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1.6.4 Methods of steel protection: There are many passive fire protection means available to reduce the temperature rise of steel members when exposed to elevated temperatures. The fire resistance of these are often calculated using heat transfer principles and properties of the protection but these should be backed up with test results to determine the actual behaviour of the product in place Some common forms of protection for steel, and methods to increase the fire resistance of steel members are listed below. The methods used in this report are the spray on and board protection. Spray-on Insulative Protection: This method of protecting steel is usually the cheapest form of passive fire protection for steel members. These materials are usually cement based with some form of glass or cellulosic fibrous reinforcing to hold the material together, (Buchanan, 1999). The disadvantages of spray on materials are that the application is wet and messy and the finish is not architecturally attractive. However this is not usually a problem for structural members that are hidden with suspended ceilings and partitions. The other important aspect of this insulation is the ‘stickability’ of the material, or how well the material stays in contact with the steel member at normal and elevated temperatures. If the insulation falls off the steel it obviously no longer is protecting the steel so the cohesion and adhesion of spray on protection must be thoroughly tested. Board Systems: Most board systems that are used to increase the fire resistance of steel members are made out of calcium silicate or gypsum plaster. Calcium silicate boards are made of an inert material and the board can remain in place for the duration of the fire. Gypsum plaster board has good insulating properties, and its resistance to elevated temperatures is improved with the high moisture content present in the board, which must be evaporated at 100 °C before the board further increases in temperature. This gives a time delay when the board reaches 100 °C, but reduces the available strength in the board after the water has evaporated. 17
The advantages of board systems are that they are easy to install and can be attractively finished. The boards can be fixed hard against the steel member or with a void between the inner face of the board and the steel section, See Figure 1.4. Other Protection Methods: Other protection systems that are often used in construction to increase the fire resistance rating of steel members include concrete encasement, intumescent paint, concrete filling, water filling and flame shields for external steelwork. Concrete encasement, concrete filling and water filling protection systems are based on the same protection principles. They decrease the rate of the temperature rise of steel by absorbing heat energy from the steel. Concrete and water filling are used for hollow steel sections, while concrete encasement has an I-beam surrounded by concrete. Intumescent paint is a special paint that swells into a thick char when it is exposed to higher temperature, providing protection to the steel beneath. This allows the structural members to be attractively exposed but is more expensive than other systems. 18
Page 1 and 2: Fire Design of Steel Members K R Le
Page 4: ABSTRACT: The New Zealand Steel Cod
Page 8 and 9: TABLE OF CONTENTS: ABSTRACT:.......
Page 10 and 11: 5.4 RESULTS FOR FOUR SIDED EXPOSURE
Page 12 and 13: LIST OF FIGURES: FIGURE 1.1: VARIAT
Page 14: FIGURE 5.11: TEMPERATURE CONTOUR LI
Page 17 and 18: designed with confidence. Full scal
Page 19 and 20: eams and struts when subjected to a
Page 21 and 22: Gilvery and Dexter, (1997), prepare
Page 23 and 24: with conditions specified to ensure
Page 25 and 26: 1.6 BACKGROUND INFORMATION: 1.6.1 F
Page 27 and 28: experienced in fire situations, but
Page 29 and 30: The thermal conductivity is not imp
Page 31: [ The heated perimeter of the steel
Page 35 and 36: 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 84 and 85:
Temperature ( o C) 1000 800 600 400
Page 86 and 87:
average temperature of the beam, be
Page 88 and 89:
Temperature ( o C) 1400 1200 1000 8
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significantly decreased from a cool
Page 92 and 93:
Since both programmes use the same
Page 94 and 95:
Therefore, the ECCS equations provi
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5 CALCULATION OF STEEL TEMPERATURES
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calculations made by the spreadshee
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susceptible to heating, heat up mor
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Figure 5.3 a-c show the results fro
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7850*600*10500 > 2*775*1100*(1869*2
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As can be seen from Figure 5.4 a-c,
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310 UB 40.4 beam H p /A = 241 m -1
Page 110 and 111:
The SAFIR results fit between the t
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constant specific heat being used i
Page 114 and 115:
From Figure 5.7 a-c, it appears tha
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800 Temperature ( o C) 600 400 200
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To examine the limits of the thickn
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1000 Temperature ( o C) 800 600 400
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Thermal conductivity, k i = 0.19 W/
Page 124 and 125:
1000 Temperature ( o C) 800 600 400
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the slab except to reduce the secti
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Figure 5.14 shows the correlation b
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5.8 CONCLUSIONS: The thermal behavi
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6 COMPARISON OF METHODS USING OTHER
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Temperature ( o C) 1200 1000 800 60
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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
Page 156:
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
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
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22 FISO 23 FISO FISO 24 FISO FISO 2
Page 176:
APPENDIX C - FIRECALC Below in Figu
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