A glowing future.pdf - British Stainless Steel Association

Stainless Steel: A glowing future in
Construction by Paul Snelgrove
the Puerta de Europa twin towers in Madrid, among
others. The choice of stainless steel is due to its natural
corrosion-resistant properties, ease of fabrication,
resistance to surface damage, and to the variety of
available surface finishes. The Eurostar Terminal at
Waterloo, London, in the UK, uses stainless steel for
roofing panels, gutters and supports, to meet long-life
design criteria of 125 years with a first maintenance
requirement of 25 years. Stainless steel surfaces are
generally easy to keep clean, although they do require
some attention to maintain their original beauty. On
buildings, depending on the grade of steel and where
it is used, cleaning need only take place, on average,
once every six to twelve months.
The first all-stainless steel bridge in Bilbao, Spain
(Picture: Courtesy of AvestaPolarit)
A
s Bilbao residents watch construction
progress on the world’s first all-stainless
steel bridge, developments across Europe
confirm the growing interest in a host of
architectural applications for the metal.
Designed by the late Jose Antonio Fernandez Ordonez,
Bilbao’s Abandoibarra Bridge will span the
Nervion River, linking the University of Deustro to the
famous Guggenheim museum, itself clad in titanium.
When finished, the bridge will be 143 meters long and
7.6 meters wide, its all-stainless exterior made of 500
Mt of 20mm-thick hot-rolled quarto plate, in a highstrength
duplex grade (international standard:
EN10088 1.4362). Completion is scheduled for December
2001. The microstructure of duplex stainless
steel gives it even better exterior corrosion resistance
than standard austenitic stainless steels, and superior
tensile strength, allowing the use of lighter gauges.
Supplier AvestaPolarit has given the material on the
bridge a life-cycle guarantee of 50 years.
Functional and aesthetically pleasing
"Over the past 10 years, some of the most striking architectural
designs in the world have been made, not
out of bricks and mortar, but stainless steel," reads a
recent AvestaPolarit
press release. The text
goes on to cite the finishes
on the Lloyds
Building in London, The
Petronas Towers in
Kuala Lumpur, the European
Court of Human
Rights in Strasbourg and
Duplex and austenitic materials
The duplex grades now available create entirely new
possibilities in stainless steel architecture and construction.
Partly austenitic and partly ferritic in structure,
they combine the strength of the one with the
ductility of the other. Market observers describe architecture
as an exciting growth area in the use of these
grades, citing the UK examples of the Lowry Centre in
Salford, and the Dockland Boating Centre in London,
both partly roofed in duplex. Further afield, the
stainless-steel roof of the Conference and Exhibition
Centre in Hong Kong is light yet strong - and corrosion-resistant,
which is a vital factor in a coastal environment.
Standard austenitic grades (most commonly the 316
family) are ideal for many exterior uses, such as a
new glass and stainless steel building in the La
Défense business district and the new Charles De
Gaulle airport (see front cover picture), both near
Paris, France. Corrosion resistance is greatly affected
by the presence of molybdenum in this material, only
a slight raising of which, say from the usual 2 to 2.5
percent up to 3 percent, dramatically improves performance.
Above 3 percent, you move into the 317
range, or into duplexes if structural properties are required.
Also concerning corrosion, in Sweden, the UK and
elsewhere, street lighting columns, traditionally made
of reinforced concrete or galvanised steel, are a big
Internal stainless steelwork of the La Défense Tower, Paris
(Picture courtesy of AvestaPolarit)
A new glass and stainless
steel building in the La
Defense area of Paris
designed by architect IM
Pei (picture courtesy of
AvestaPolarit)
December 2001 STAINLESS STEEL INDUSTRY 13

issue today for many city councils. Concrete can crack
and drop off as the inner metal reinforcement rusts
and expands, while steel columns corrode both below
ground and above ground when water seeps inside
posts and damages the galvanising. In the UK alone,
it is estimated that about 3 million outdoor lampposts
will need replacing in the next ten years. Many are urgent.
The industry is promoting the proposition of
stainless steel columns that should last 70 years at
the very least.
Stainless steel seeks acceptance as a structural
material
Explaining that the industry is working hard to increase
the structural use of stainless steel, experts
affirm that the physical forming of a stainless steel
tube enhances the material's mechanical properties
(work-hardening), making it actually stronger than carbon
steel. The result requires no coating, painting or
maintenance, so stainless steel can be doubly advantageous
as a strong, lightweight structural member.
Already widely used in door- and window-frames, the
metal can be folded and shaped into elaborate sections,
and ground or brushed for an attractive finish. In
The exterior at North Greenwhich Station (picture courtesy
of EuroInox)
addition, the advantages of stainless steel in terms of
fire resistance are not yet fully exploited, and further
research is needed to assess the material's true potential
here.
Extensive R&D, centred on the behaviour of stainless
steel members and connections, has been carried out
in Europe since 1991. The work culminated in the
publication of the ENV for Eurocode 3 Design of Steel
Structures - Supplementary Rules for Stainless Steels
(EC3: Part 1.4). These rules were, however, adapted
from carbon steel rules. Since the load-bearing capacity
of stainless steel members differs from that of carbon
steel members, further research was required to
define a new design approach and maximise the costeffectiveness
of stainless steel’s desirable properties
in structural uses. A recently completed, partially ECfunded,
three-year research project, involving major
producers and other organisations from six European
countries, is now being followed up by a valorisation
project that updates the old design manual for
stainless steel. The project will also ensure wide dissemination
of the latest findings (partly through electronic
media) among architects and structural engineers.
Wall cladding at Souhwark
station (picture courtesy of
EuroInox)
Stainless steel for architects
"Handrails and parapets
were rare 20 years ago,
but have become almost
standard nowadays," explains
Thomas Pauly of
Euro-Inox, the European
stainless steel market
development association.
"Interior cladding is a big
growth area as well, being
easily maintained and
attractive. The extension
to London’s Jubilee Line
subway, for example,
uses it extensively," he
adds. Architects tend to
worry about fingerprint
soiling, but very robust embossed
and pattern-rolled finishes exist which are less
sensitive to fingerprints. These are much used for elevators
and escalators in stations, hotels and airports.
"Stainless steel has both practical and decorative
merits and elevators and escalators are amongst the
biggest markets for flat products," says Mr. Pauly.
Stainless steel facades in architecture go back to the
1950s. The electricity substation at the Elephant and
Castle traffic circle in London dates from that time
and, despite pollution, is still in fine condition. “Now
we can make stainless steel facades at the same cost
as with other materials, so there is huge development
potential,” Mr. Pauly points out. Stainless steel roofing
has been around for 30 years, but is set to grow.
There is an obvious trend towards metallic materials
on buildings, especially for decorative purposes, and a
swing back from the “disposable architecture” philosophy
to greater construction quality and durability.
“With stainless steel you don’t get corrosion, even under
difficult circumstances, and whatever you combine
it with it won’t corrode, so its durability is exceptional,”
says Mr. Pauly. Ecologists like it, too, since stainless
steel is neutral to the environment and does not result
in noxious substances getting into the water table.
Switzerland, Austria and parts of France and Germany
have a long tradition of metallic roofing, and the
architects in these Alpine areas readily use stainless
steel. There are two approaches. One is the welded
stainless steel roof, which is a 100-percent watertight
solution, useable on a flat roof, and the other is the
conventional standing seam roof, which can be built
by any roofing contractor. “This is now a very large,
potential market throughout Europe, which we are trying
hard to promote,” underlines Mr. Pauly.
Stainless steel in tunnel and road applications
Tunnel linings are an interesting growth area. Alpine
countries use it a lot, often in short tunnels, which can
use up to 300 metric tons of stainless steel. An interesting
projection could be made from this about the
quantities of stainless steel involved in the new tunnel
just agreed between France and Italy, which will be
one of the longest in Europe. The most popular grade
for tunnels would be 316, but there is potential for
higher alloy grades, depending on the corrosion conditions.
Road tunnels have the problem of exhaust
gases and de-icing salt, so high chromium and nickel
14 STAINLESS STEEL INDUSTRY December 2001

grades, maybe with up to 25 percent chromium, are
needed.
Another important growth area is in reinforcement
bars for concrete structures, like bridges and lighting
columns. Everywhere you see the need for expensive
refurbishment work on structures often only 30 years
old. Carbon steel in concrete tends to corrode, especially
if the concrete coverage is under 5 cm. Exhaust
gases and de-icing salt get in. In the U.S., highway
authorities automatically specify stainless steel for
certain applications in bridges and tunnels. Their highways
are privatised, so they look at a 40-year or more
lifetime horizon. The extra cost of stainless steel bars
is vastly outweighed by lower maintenance costs over
the complete lifetime. "Gradually, life-cycle costing
awareness is gaining ground in Europe, and that, plus
a growing ecological orientation, is making people
more conscious of long-term benefits," Mr. Pauly
says. "Reinforcement bars are standard products and
have huge potential in these applications," he adds.
Where there’s fire or water, there's stainless steel
Repair and relining of chimneys is also a fairly big
market, especially in countries and at times when a
major move from solid fuel to oil or gas is afoot. The
necessary reduction in chimney diameter, to avoid
condensation, is quickly and cheaply achieved by installing
a thin stainless steel inner sleeve in the existing
chimney. This was a big German market after reunification,
and there is still constant demand for refurbishment
solutions.
Another growth area for stainless steel, related to construction,
is plumbing, for which there are now new
regulations in Europe, where the use of other metallic
materials can be restricted. In some areas, such as
parts of Scotland, northern France, Germany and
Sweden, for example, there have been corrosion
problems due to a lowering of pH values in the water
down to about 6.5. Above 7 it is alkaline, below 7 it is
acid. European bodies, laboratories and regulators
now have a program to approve a different material,
and stainless steel is the only metallic material that
can be used unconditionally.
Stainless swimming pool at a health club in Holmes Place,
Kingston, manufactured and installed by Invarmex (UK)
Nottingham.
crete cracks to patch in the case of leakage, and old
pool tiles can be left under the stainless steel skin.
"Many pools built in the 1960s and 1970s are nearing
the end of their lifetime, and we are trying to carry this
technology to France, the UK and elsewhere," Mr.
Pauly says.
Growth on two fronts
The inexorable growth in the use of stainless steel
falls, it seems, into two categories. One is that of applications
where stainless steel substitutes for other
materials. Domestic chimneys, formerly with mainly
ceramic or plastic solutions, are an example of the
first case, as are railings. The other growth category is
through increased demand for finished products that
use stainless steel. Stainless steel cladding in elevators,
for example, has grown due to refurbishment of
subway stations and the increasing number of highrise
buildings and shopping malls. Of the two categories,
Euro-Inox predicts that promoting “substitution”
applications is the principal opportunity for what will
surely be a bright future for stainless steel.
Swimming pool linings
Again according to Mr. Pauly, today, about 150 large,
public pools in Europe are lined with stainless steel,
using a technology developed in Austria. In fact, the
two market leaders for this are Austrian companies.
The idea spread quickly in Germany, and between the
two countries there are about 120 to 130 such lined
pools. This is a very interesting repair solution, especially
outdoors, since you can leave water in the pool,
or make repairs during the winter. You have no con-
Copyright British Stainless Steel Association, December 2001
December 2001 STAINLESS STEEL INDUSTRY 15