Temperature-time (T-t) curves and temperature contour plots due to the ISO 834 standard fire loading curve for typical New Zealand composite floors have been calculated and presented in tabulated format.

The temperatures in 10 minute intervals up to the requested fire resistance rating have been reported for the slab top face and along the thinnest and thickest region of the cross section.

The 2D cross sections of the following concrete slabs cast on a steel deck were analysed:

  • Comflor CF60, 0.75mm deck thickness – slab overall thicknesses 125, 140 and 170mm
  • Comflor CF80, 0.90mm deck thickness – slab overall thicknesses 135, 150 and 180mm
  • Flatdeck, 0.75mm deck thickness – slab overall thicknesses 110 and 140mm
  • Concrete Saver 60, 0.95mm deck thickness – slab overall thicknesses 110, 125, 140 and 170mm
  • Ultraspan 80, 1.2mm deck thickness – slab overall thicknesses 130, 150, and 180mm
  • Comflor 210, 1.25mm deck thickness – slab overall thicknesses 270, 305, 320 and 350mm
Flatdeck 110mm slab with temperature contours for 120 minutes of fire exposure.

The background to this work is summarised below:

  • NZS 3404 Parts 1 and 2:1997 Steel Structures Standard refers to HERA Report R4-82, Calculation of the design fire resistance of composite concrete slabs with profiled steel sheet under fire emergency conditions, which was published in 1994.
    • R4-82 based on ECCS Technical Note 32 (1984), which has subsequently implemented within EN 1994-1-2
    • EN 1994-1-2 rules (and ECCS publication) not permitted in UK as geometrical limits not satisfied by UK deck cross-sections and provide unsafe predictions.
    • HERA R4-82 does not give geometric limits to the rules. EN 1994-1-2 rules were amended in R4-82 to fit temperatures measured in 3 fire tests.
  • The new HERA work extends the number of composite slabs from the 3 considered in HERA R4-82 to 19 fire tests (simulated by FEA).
  • Calculated temperatures form basis of fire engineering design procedure developed by Master’s students from the University of Auckland for AS/NZS 2327 under the supervision of Associate Professor Dr Charles Clifton. Results from HERA simulations are reported in HERA R4-147, which is available free of charge.
  • HERA Report R4-82 has been withdrawn.

Update shared by our General Manager Structural Systems Dr Stephen Hicks