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Page 1







The timber roof of Alfriston School’s new swimming pool
appears to float over the water’s surface

The fl agship publication of The Institution of Structural Engineers

December 2015
Volume 93 | Issue 12



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34 TheStructuralEngineer Professional guidance

CROSSDecember 2015

This 40th CROSS Newsletter1 marks 10
years since the introduction of Confi dential
Reporting on Structural Safety by SCOSS –
the Standing Committee on Structural Safety.

Since 1976 SCOSS had been collecting
data on structural safety from publically
available sources. At fi rst the Comm ittee
reported its fi ndings every two years to the
Presidents of The Institution of Structural
Engineers and the Institution of Civil
Engineers. Later the Health and Safety
Executive joined as a sponsor and these
three bodies continue to fund the operation
in the interests of Institution members, the
construction industry and the public. Biennial
reports and alerts were produced.

In the early 2000s the Committee
recognised that there were many events and
concerns that were not published anywhere
from which lessons could be learned. A
system used by the aviation industry served
as a model and in 2005 CROSS was formed.

Since then the number of subscribers
has risen to 8500 and over 500 reports
have been received, of which many have
been published in the quarterly newsletters.
Where particular risks are identifi ed, SCOSS
alerts are published. CROSS and SCOSS
were more recently merged into a new
organisation: Structural-Safety.

Fundamental to the scheme have been
the unstinting contributions from the SCOSS
Committee and the CROSS Expert Panel.
Also key to the operations have been the
contributions by executives and staff at The
Institution of Structural Engineers. Of course,
CROSS also could not exist without the
reports submitted so that experiences can be
shared for the benefi t of us all.

More reports are always needed and
readers are asked to help by contributing
their experiences in complete confi dence
at dential-

We look forward to the next decade and to
enhancing and expanding the programme.

Confi dential Reporting on
Structural Safety (CROSS)

In this article, we summarise

the latest CROSS newsletter

from Structural-Safety.


1) (2015) CROSS
Newsletter No. 40 – November 2015 [Online]

Available at:


(Accessed: November 2015)

Newsletter No. 40
The fi rst two reports are signifi cant in that
they come from major bridge owners who
are willing to share their experiences of
in-service issues. Both illustrate the value
of inspections in assessing safety and it is
hoped that other infrastructure owners will
be encouraged to follow suit and report

Next is a concern about falling objects
that may become increasingly signifi cant as
more tall domestic buildings are constructed
in urban locations. In addition to new-build,
many buildings are altered, which gives rise
to numerous problems, and sometimes to
collapse, so the next report which describes
a near-miss is relevant.

Next are reports of components being
blown off buildings and the design of fi xings
for photovoltaic (PV) panels. Finally there are
concerns about the costs of some design
standards and about gallows brackets.

Spalling concrete falling from
motorway bridge
An incident occurred at a motorway
overbridge resulting in a piece of spalling
concrete falling onto the carriageway and
striking a vehicle. This resulted in minor
injuries to the driver. It is understood that
the concrete which fell was no greater than
50–60mm in size and had spalled from an
area of previously repaired concrete.

Failure of stainless steel tie bars
In 2002 the footways of an important
estuary bridge were widened, says a report
from the owner. The works replaced the
cantilevered footways of the structure with
footways supported on steel girders, which
in turn were supported on steel columns.
The strengthened footways and the original
structure are connected through a keyed
concrete joint and pairs of 32mm diameter
stainless steel tie bars.

Open balustrade balconies over a
public highway
A reporter has watched the construction of
a large residential development adjacent to a
public highway where the balconies oversail
the footpath. He is concerned that nobody
has fully considered the risk to the public of
small – but heavy – objects falling from these
balconies onto pedestrians below.

Dangerous alterations
The structure of an existing building is being
replaced, but the facade retained. The
construction method was to create a new frame
within the existing, with columns punching
through the existing slab. An existing beam had
been left simply supported, with no continuity
over the columns.

Cladding panel blown o�
This reporter has become aware of an incident
where a decorative cladding panel fell from
height when it became detached from an upper
level of a multistorey building in high winds.

PV panels blown o� roof
This report is about PV panels being blown off
of a fl at roof; luckily nobody got hurt. The fi xing
method is simple, but relies on panels being
perfectly installed 100% of the time.

PV panels on domestic roof
The building is traditional, domestic in scale and
executed with a duo-pitched roof of concrete
tiles on battens on membrane on factory
trusses. The roof supports a large area of PV
panels whose attachments are supported on
every third truss. The reporter asked the design-
and-build roof contractor if this was suffi cient to
support wind and snow loads.

Cost of design standard for sca� olding
The design standard for access scaff olding,
TG20, produced by the National Access and
Scaff olding Association (NASC), costs £1206.
The reporter is concerned that designers will
not use the latest information at this price.

Gallows brackets for supporting
chimney breasts
A reporter has seen suggestions that gallows
brackets are suitable for support after the
removal of internal chimney breasts.

Further details and comments on these reports
from the CROSS panel can be found online at where readers can
also register to receive the newsletter.

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dislodges the load and permits it to drop, the
consequences can be catastrophic.

Dropped objects
Dropping items is a foreseeable event that
has potential to kill or maim. A dropped
object (even a nut, tool or helmet) will
not fall vertically, so the zone of potential
ground impact can be very large. It is
normal practice to cocoon whole buildings
in fabric wrapping to control the fall of
dropped objects. In other cases, temporary
sterilisation of zones below, building crash
decks or erecting scaff olding fans or net
systems to catch dropped objects might be
alternatives. Tethering of workers’ tools and
equipment will be a suitable precaution.

Working conditions
Screening-off has double benefi ts. At
height, winds can be gusty and fearsome
and rain drives horizontally. Providing better
weather protection will aid productivity. The
same fi erce wind can strip temporary works
off the structure being constructed if proper
anchorage is not eff ected.

Tall buildings make it harder to get to
welfare facilities on the ground in any
reasonable time. Hence, portable facilities
(toilets, washroom, drinks etc.) are required
at height.


1) The Institution of Structural Engineers

(2013) ‘Managing Health & Safety Risks No.

17: Working at height’, The Structural Engineer, 91 (6),

p. 18

2) The Institution of Structural Engineers (2014)

‘Managing Health & Safety Risks No. 30: Fires on

construction sites’, The Structural Engineer, 92 (8),

pp. 24–25

3) The Institution of Structural Engineers (2014)

‘Managing Health & Safety Risks No. 29: Industrial

rope access’, The Structural Engineer, 92 (7), p. 30

4) BBC (2013) London helicopter crash: Two die in

Vauxhall crane accident [Online] Available at: www. (Accessed:

November 2015)


BBC (2005) Madrid skyscraper faces collapse

[Online] Available at:

world/europe/4261315.stm (Accessed: November


The Institution of Structural Engineers (2013)

‘Managing Health & Safety Risks No. 15: Using

cranes’, The Structural Engineer, 91 (4), pp. 32–33

shafts, and there is a risk of falling down
them by accident. Access to such voids
must be closed off with highly controlled
access for services installation (the danger
of opening a door and stepping into a void
is obvious). All fl oor penetrations need to be
covered with covers secured down.

Any work near a free edge should be
avoided and there will be a need for guard
rails, boundary netting and the like. The
use of safety harnesses will be appropriate
in some circumstances. Rope access is
to be avoided, but might be essential for
some activities, so should be planned with
specialist input3.

Invariably, tall cranes are required – and
often embedded within the structure being
built. Stability against strong winds at
height is needed, as well as consideration
of jib clash if multiple cranes are used.
Consideration has to be given to dismantling
cranes as well as progressing them upwards
as building heights increase. In high-rise
construction, visibility is a problem, meaning
that crane operators may well be unable
to see the ground and loading area below.
Adequate communication is vital, with
emergency provision to stop lifting if loads
become trapped.

Cranes on very tall buildings also need
aircraft warning lights. In 2013 a helicopter
collided with a crane in London4.

Lifting loads is generally hazardous, but
on very tall structures it becomes even
harder to control the swing of suspended
items; wind regimes might be extremely
gusty, leading to a risk of loads swinging and
impacting the structure. Such impacts are
undesirable due to damage, but if an impact

Working at height is always hazardous
and article No. 17 in this series described
some of the potential issues1. When very tall
buildings are being designed, constructed
or modifi ed, a number of standard hazards
become exaggerated and require special

In terms of layout, access is inherently more
restricted in high-rise than on large low-rise
sites. Moreover, during the construction
phase, egress routes planned for the
completed structure may be absent (or
blocked off ). To compound the generic
hazards, there will be potential confusion
on location: fl oor levels may all look the
same and there might be a lack of familiarity
with routes. This generates dangers for
workers and for any of the emergency
services who may be called in (article No.
30 describes how common site fi res can be
and the need to progress fi re precautions in
line with building advancement2). To guard
against these dangers, routing signs and
guidance to exits must be clear and keep
up with structural height progression. Site
evacuation plans need to be kept under
surveillance, regularly updated and workers
briefed. The reverse is also true: emergency
services will need up-to-date plans to fi nd
their way around.

Access to upper levels will be required
for constructors, for lifting material and for
removal of waste. Routes should be planned
taking account of the evolving build state to
avoid ad hoc and potentially unsafe fi xes. A
number of proprietary external lift systems
and mast-climbing platforms are available
and these depend on stabilisation off the
rising structure; again, advance planning is

Avoiding falls
All tall buildings naturally have fl oor
penetrations, open service ducts and lift

No. 46: Safety issues in high-

rise construction

Managing Health & Safety Risks



Professional guidance

Health and safety December 2015




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Page 67

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Up to £47,500 + Benefits

Niche consultancy based in Southwark has

a requirement for a Structural Project Engineer

to join the expanding London studio working on

exciting new commissions with top Architects

and helping to develop the brand. Candidates

will need to be a Graduate or just

Chartered member of IStructE and/or

ICE as well as being educated to

MEng/MSc in Civil, Structural or

Architectural Engineering.

T 020 8408 9971
E [email protected]

knowledge based
recruitment in
structural engineering


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Large mainstream consultancy has a

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Candidates will need to Chartered with IStructE

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design, project and team-running experience

in the UK and should be capable of

undertaking a 360 role encompassing

recruitment, client development

and management of teams.

Chartered Senior
Structural Engineer

Central London Ref: 50565
Up to £47,500 + Benefits

No 1 Structural Engineers in the UK has a

requirement for a Chartered Senior Structural

Engineer to join the London studio to working

on a number of new dynamic, cutting-edge

international commissions. Candidates will

need to be recently Chartered with IStructE

and will have worked for another

premier London consultancy on

high-profile, challenging, design-

focused projects



2 Structural Design

Central London Ref: 50694
Up to £37,500 + Benefits

Premier consultancy based in London’s

West End has a requirement for 2 Structural

Design Engineers to join different teams within the

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have a MEng/MSc in Civil, Structural or

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Central London Ref: 50637
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2 Chartered
Structural Engineers

Central London Ref: 50653
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Premier consultancy based in Islington

has a requirement for 2 Chartered Structural

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combined with an affinity with

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For the fifth year running
we were a proud sponsor of

The Structural Awards by IStructE
and this year we sponsored the

“Award for Community or Residential
Structures”. Well done to all the winners

and see featured iconic projects by some
of this year’s successful nominees and

clients of Walker Dendle Technical


Walker Dendle Technical
Recruitment would like to congrat-

ulate Expedition on their two winning
projects featured with a W and Elliott

Wood, Engenuiti & Webb Yates Engineers
for their commended projects with a C in their
categories at the Structural Awards 2015. For

the 9th year running we had a table for
the night with guests from Conisbee,

Eckersley O’Callaghan, Engenuiti,
Expedition, Price & Myers,

Sinclair Johnston, Techniker &
Webb Yates Engineers.





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