internal spans, the transfer structure
will also support 14-storeys of student
accommodation. In order to have sufficient
strength and robustness, the structure’s
columns are all plated 356 x 406 x 467
Bourne Steel completed the transfer
structure in September, allowing the project
team to start constructing the student
accommodation block above.
Summing up, Balfour Beatty Project
Manager Andy Cross says:
“Engaging Bourne at an early stage in
the project enabled us to create a robust
strategy for delivering this challenging
aspect of project works.
“Regular stakeholder consultation,
meticulous planning, and coordination of
programmed works, in collaboration with
our supply chain, ensured a well-executed
delivery, finishing ahead of schedule and
mitigating any disruptions to local residents
or businesses. The feedback has all been
The entire project is targeting a
BREEAM ‘Excellent’ rating upon scheduled
completion in 2021.
Transfer structures support one or more
columns from floors above. The structures
are clearly more critical elements than
normal floor beams simply in view of the
greater floor area that is supported by the
transfer structure. When designing structures to
resist accidental actions, transfer beams, their
connections and their supporting structures need
SCI publication P3911 suggests all transfer
beams should be subject to an assessment to
determine whether the standard approaches
for Class 1, Class 2a or Class 2b can be adopted.
An assessment is required for Class 3 buildings
anyway. Eurocode 1 Part 1-72 defines ways of
achieving appropriate levels of robustness to
mitigate the effects of accidental events.
In Class 1 and Class 2a buildings (lower risk
group) with low and medium consequences of
failure, transfer structures are recommended to
have at least the minimum level of horizontal tying
for Class 2a buildings. Enhanced tie forces are
recommended to take account of the additional
load supported by the transfer structure.
In Class 2b buildings, three alternative methods
of designing for robustness are available, tying,
notional removal and key element. Notional
removal is likely to be an unviable design approach
(although mentioned in BS EN 1991-1-7 in this
context) so tying and key element design are
expected to be most suitable.
If tying is adopted, increased horizontal tie
forces to account for the additional load from the
columns supported above are recommended
(as for Class 2a). Additionally, the connections of
the columns to the transfer structure should be
designed to resist tension.
If the key element approach is adopted, P391
suggests that both the transfer structure and its
supporting columns should be designed as key
Class 3 buildings require a specific risk
assessment to be undertaken. Transfer structures
should at least be designed following the Class
2b guidance. The risk assessment would identify
if additional measures should be undertaken to
achieve an appropriate level of risk.
The proportions of the transfer beams in the
Vine Street project: 1.8 m deep beams with 120
mm thick flanges and 45 mm thick webs underline
the significance of their function.
1. Structural robustness of steel framed buildings,
2. Eurocode 1 – Actions on structures Part-1-7:
General Actions – Accidental actions
The creation of large open spaces in the lower levels of buildings for
particular uses, or to display archaeological remains as at Vine Street,
involves the provision of transfer structures to carry the structures above.
Richard Henderson of the SCI discusses some of the issues.
Bourne Steel unload
the project's largest