Technical
NSC 41
October 18
deck or slab geometry falls outside of the scope of the codes or
PN005c, FE analysis is an accurate alternative for determining an
appropriate temperature distribution through a composite slab
and is especially useful for profiles of unusual geometry.
Conclusions
1. BS 5950-8 and BS EN 1994-1-2 provide tabulated data
for temperature profiles which in some cases can be unconservative.
The two codes produce very similar temperature
profiles but the UK National Annex does not allow the use of
the profiles provided in BS EN 1994-1-2.
2. PN005c provides a set of calibrated quadratic equations to
describe the temperature profile in different locations within a
composite slab. It takes account of a range of deck geometries
to provide safe temperature profiles.
3. FE analysis is a suitable alternative to the curves presented here
and is particularly suited to unusual deck profiles which may
fall outside the scope of the codes and NCCI document.
A future article will consider how the temperature profile
through the slab can be used in the design of composite beams
in fire.
References
1 BS 5950-8:2003
Structural use of steelwork in building - Part 8: Code of practice
for fire resistant design
BSI, 2003
2 BS EN 1994-1-2:2005
Eurocode 4 - Design of composite steel and concrete structures -
Part 1-2: General rules - Structural fire design
BSI, 2005
3 PN005c-GB
NCCI: Fire resistance design of composite slabs
The Steel Construction Institute
4 NA to BS EN 1994-1-2:2005
UK National Annex to Eurocode 4: Design of composite steel and
concrete structures - Part 1-2: General rules - Structural fire design
BSI, 2008
Figure 4: Comparison of temperature profiles for a 90 minute fire (using normal weight concrete)
Figure 5: Comparison of temperature profiles for a 120 minute fire (using normal weight concrete)
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