A series of alternative designs for steel frame floor construction subject to fire, are used to demonstrate the significant benefits that can be generated from a close working relationship between the designer and the researcher. The paper describes the structural fire design strategy, the modelling and detailed analysis that support the chosen designs for a recent prestigious project in central London.

1. By
A.M.Allam1, M.G.Green3, I.W.Burgess1 and R.J.Plank2
1Department of Civil and Structural Engineering
2School of Architectural Studies
3Buro Happold Ltd
University of
Sheffield
http://www.shef.ac.uk/uni/academic/A-C/cse/groups/fire/group.html

2. •A series of alternative designs are used to demonstrate
the benefits that can be generated from a close working
relationship between the designer and the researcher.
•An intensive study has been carried out to illustrate the
benefits of implementing the fire limit state into the
design procedure.
•The analyses were conducted utilising a finite element
program called VULCAN.
2
3D

3. •A general fire example has been used to illustrate the
significance of careful arrangement of a structure.
(a)
Case 1Case 3
Case 2
(b)
10 x 6m = 60m
5 x 3m = 15m
3

4. The effect of the
load ratio, Case 1
Mid-span slab
deflections, Case 1,2
4
-800
-600
-400
-200
0
0 200 400 600 800 1000
Temperature (o
C)
Deflection(mm)
No-Shaft (Case 2)
No Shaft - Wind-bracing
With Shaft (Case 1)
-1200
-900
-600
-300
0
0 200 400 600 800 1000
Temperature (
o
C)
Deflection(mm)
Load ratio 0.44
Load ratio 0.41

5. • The building is 30m high
above ground level, 56m
long and 30m wide.
• Lines of symmetry have been
used to simulate the repetitive
structural layout.
• The effect of the secondary
structural actions in the
performance of the building,
have been considered.
5

6. Edge beam
Secondary beam
Parallel beamColumn
Slab shell element
CL
3m
3m
3m
Fin plate
CL CL 6

7. 130mm r.c. slab on
"Super Holorib"
Protected Cellular beams
12m long
Unprotected Secondary
beams 6m long
Concrete-filled
steel columns
130 thick R.C. slab
on “Super Holorib”
Main beams
435mm 435mm
CL
Shear Studs
Additional steel
T12@600 c/c
7

8. Deflection at mid-
span of main beam
-400
-250
-100
50
-400
-250
-100
50
Deflection Profile
8
-250
-200
-150
-100
-50
0
0 200 400 600 800 1000
Temperature (
o
C)
Deflection(mm)
80%
90%
100%
105%
110%
115%
Load level

9. •The results indicate that the flooring system survives
fire to extremely high steel temperatures.
•Depending on the support conditions, the action of
the slab can affect the load-paths considerably.
•The membrane action of the slab, caused by restraint
against thermal expansion, should be considered.
•It is inadequate to place reliance on predictions of
behaviour based on furnace tests or numerical
modelling of isolated members.
9