Structure and Analysis Bridge Design brief
Moh-993
CSB-MM-Sustainability-2010.pdf
Steel bridges – Material matters
Corus
Sustainability
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Contents
1 Introduction 2 Economic Priorities 2.1 Efficient use of resources 2.2 Minimum disruption 2.3 Durability 2.4 Adaptability 3 Environmental Priorities 3.1 Recycling and re-use 3.2 Minimum CO2 and energy burdens 3.3 Minimum waste 3.4 Lightweight construction 4 Social Priorities 4.1 Sustainable communities 4.2 Health and safety 4.3 Minimum impact 4.4 Aesthetic bridges 5 Corporate Responsibility
River Kelvin Bridge
Structural Engineer – Atkins
Steelwork Contractor – Fairfield-Mabey Ltd
Main Contractor – Farrans
Client – Glasgow Harbour
The original plan for this crossing was a
two-span bridge similar to an existing
adjacent structure. However, the high
strength-to-weight ratio of steel meant that a
single span was feasible. Avoiding the
construction of a pier in the fast flowing tidal
river minimised the cost and environmental
impact as well as the health and safety risks
for the workforce. The lightweight nature of
steel minimised the loads on the piled
foundations, and also facilitated erection
using readily available cranage.
This 61.5m single span steel composite
bridge is a key part of the regeneration of
Glasgow's waterfront, and is believed to be
the longest of its type ever built in the UK.
Economic A steel composite deck was the most cost effective solution
Environmental A single clear span over the river minimised the environmental impact
Social Avoiding the construction of a pier in fast flowing tidal water minimised the health and safety risks for the workforce
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Introduction
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1. Introduction
Steel is widely used around the world for the construction of bridges from the very large to the very small. It is a versatile and effective material that provides efficient and sustainable solutions.
Steel scores well on all the sustainability measures, and offers a broad range of benefits addressing the economic, environmental, and social priorities of the ‘triple bottom line’ of sustainability.
The basic raw material (iron) is the most abundant of all the earth’s elements, and steel can be recycled indefinitely without any loss of property or performance.
Sustainability is built into steel products all along the supply chain, from responsible sourcing of raw materials through a manufacturing process dedicated to continuous improvement to the production of modern and efficient bridges.
En vir
onm ental Priorities
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riorities So ci
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Economic priorities • Efficient use of resources • Minimum disruption • Durability • Adaptability
Social priorities • Sustainable communities • Health and safety • Minimum impact • Aesthetically pleasing bridges
Environmental priorities • Recycling and re-use • Minimum CO2 and energy burdens • Minimum waste • Lightweight construction
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Hunslett Viaduct
Structural Engineer – Mouchel Parkman
Steelwork Contractor – Fairfield-Mabey Ltd
Main Contractor – Alfred McAlpine
Client – Leeds City Council
This 12-span 510m long viaduct carries
a dual two-lane carriageway through a
sweeping S-shaped curve, and is part of
the final stage of the Leeds Inner Ring
Road. Weathering steel was chosen
because the girders will never need to
be painted leading to long-term
environmental and economic benefits for
the local population. The decision to use
weathering steel was supported by the
client, who liked the idea of reflecting
the industrial heritage of Hunslett, an
area that was once known as the
workshop of Leeds.
Economic Weathering steel provided an economic, durable solution with minimum whole life cost
Environmental Offsite production in a modern fabrication plant using state-of-the-art CNC machinery integrated with CAD software ensured that waste was minimised
Social Weathering steel chosen to celebrate the industrial heritage of the area
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Introduction
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Economic priorities
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2. Economic priorities
Steel has long been recognised as the economic option for a range of bridges. It dominates the markets for long span bridges, railway bridges, footbridges, and medium span highway bridges. It is now increasingly the choice for shorter span highway structures as well.
2.1 Efficient use of resources Structural steel is a high-quality material that is readily available worldwide in certified grades, in products of various shapes and sizes. Prefabrication of steelwork in controlled factory conditions leads to high quality work at minimum cost. The excellent quality control is achieved through a thorough testing regime at the steel mills and during the construction processes of cutting, drilling, welding, fit-up and painting. The quality assurance that is attained should give confidence to all clients and engineers who specify steel for their bridge project.
The high strength-to-weight ratio of steel minimises the structural weight of superstructures and thus minimises the substructure costs, which is particularly beneficial in poor ground conditions. Minimum self-weight is also an important factor in the cost of transporting and handling components. Use of steel facilitates shallow construction depths, which overcomes problems with headroom and flood clearances, and minimises the length and cost of approach embankments.
2.2 Minimum disruption Offsite prefabrication of steel components means that construction time on site, often in hostile environments, is minimised. The speed of bridge construction made possible by steel allows disruption to road and rail users to be kept to a minimum, if not eliminated, with significant positive knock-on effects for the UK economy. The relatively low weight of structural steel components permits the erection of large sections; in some circumstances complete bridges can be moved into position overnight.
A wide range of construction methods and sequences are available for steel bridges. They can be lifted, piece-by-piece, by cranes; they can be launched by sliding or rolling from the abutment; or they can be slid or transported into position. Steel offers flexibility in terms of erection sequence and certainty in terms of the programme. Components can be sized to suit access restrictions at the site and, once erected, the steel girders provide platforms for subsequent operations.
Sheppey Crossing
Below: Fabrication factory Below Right: A2/A282 Viaduct, Dartford
Architect – Yee Associates
Structural Engineer – Cass Hayward LLP
Steelwork Contractor – Fairfield-Mabey Ltd
Main Contractor – Carillion
Client – Highways Agency and Sheppey Route Ltd
This 1270m long steel composite
viaduct with 19 spans rises to 30m over
the River Swale to allow ship passage,
yet the sweeping curved low profile
deck minimises intrusion into the flat
landscape. By using modern fabrication
facilities and forging a team of the
designers, main contractor and
steelwork contractor, the high level
bridge was fabricated and erected within
programme and budget. Opened in
2006, the Sheppey Crossing provides
the first fixed link from mainland Kent to
the Isle of Sheppey.
Economic Cost effective solution under a major DBFO contract
Environmental Deck launched over the River Swale to minimise the impact on the river
Social Provides much needed easy access to the Isle of Sheppey
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2.3 Durability Bridge owners increasingly value steel for its durability and low maintenance advantages.
Steel bridges now have a proven life span extending to well over 100 years. Steel has a predictable fatigue life and the structural elements are visible and accessible. Any signs of deterioration are readily apparent, without the need for extensive investigations. Corrosion is a surface effect, which rarely compromises the structural integrity of a bridge, and any problems may be swiftly addressed by repainting the affected areas.
Advances in coating technology and an industry commitment to the training of coating applicators mean that the latest protective systems are expected to last well beyond 30 years before requiring maintenance. Furthermore, the use of unpainted weathering steel, which requires almost no maintenance, is increasingly popular, as it is recognised as the ultimate low maintenance option for bridge construction.
2.4 Adaptability Steel bridges are readily adaptable to changes in road configuration and increased loading that would render other types of structure obsolete ahead of their original design lives.
One notable example is the Tamar suspension bridge in Plymouth, which needed widening and strengthening due to increased traffic loads and volumes. The solution was to replace the concrete deck with a new lightweight steel one, and add steel cantilever sections.
Left: Weathering steel bridge, (Haydon Bridge Bypass)
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Economic priorities
The result was that the widened 5-lane bridge was only 25 tonnes heavier than the old 3-lane structure, and was able to accommodate 44 tonne trucks.
Steel bridges also lend themselves to easy and rapid strengthening or repair in the event of accidents, with well proven techniques like heat straightening ensuring that damaged structures are soon back in use.
Above: Tamar bridge, Plymouth
River Usk Crossing
Architect – Yee Associates
Structural Engineer – Faber Maunsell Ltd
Steelwork Contractor – Fairfield-Mabey Ltd
Main Contractor – Morgan-Vinci
Client – Newport City Council
This landmark bowstring arch with a
clear span of 187m combines elegant
design, high quality fabrication and
innovative construction. Durability was a
key issue from the outset and external
surfaces of all steelwork were treated
with a high performance epoxy-based
paint system. The box section arch
members were fabricated from
weathering steel and left unpainted
internally, which avoided the significant
safety issues associated with the initial
painting and future maintenance painting
inside confined spaces. A further
innovation was the use of full depth
precast slab units to form the steel
composite deck. This assisted in
controlling the steelwork geometry
during construction, and minimised
cracking of the slab.
Economic Efficient, cost effective solution
Environmental Single clear span avoiding permanent supports in the River Usk
Social Landmark bridge providing relief to congested local roads, enhanced cross river links for residents, and a key catalyst to local regeneration
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Environmental priorities
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3. Environmental priorities
Nothing could be more natural or sustainable than to build our world with steel. Iron, the basic raw material, is the most abundant element on Earth.
3.1 Recycling and re-use A compass points north because the iron content of the planet gives it polarity like a magnet.This virtually inexhaustible natural resource can be recycled indefinitely without loss of property or performance.
Steel is the most recycled construction material and choosing it for bridges represents a sustainable management of natural resources. When a steel bridge reaches the end of its useful life, the girders can be cut into manageable sizes to facilitate demolition, and returned to steelworks for recycling.
Some 99% of structural steel either finds its way back into the steelmaking process where it is used to create new steel products or is reused. There is no degradation in the performance of recycled steel. Alternatively, component parts of steel bridges can be reused in other structures; entire bridges have been relocated and bridges can be designed with ease of future relocation in mind.
Use in Construction projects
P
Steel production
Raw material supply
Post-construction scrap
End of life phase
Refurbishment
Re-use
Pre-construction scrap
Manufacture of steel construction products
Above: Recycling route diagram
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Newark Dyke
Structural Engineer – Cass Hayward & Partners
Steelwork Contractor – Cleveland Bridge UK Ltd
Main Contractor – Skanska Construction UK Ltd
Client – Railtrack plc
This railway bridge comprises a 77m span
bowstring truss which replaced two 1890
steel truss decks that were unable to cope
with the planned increase in line speed.
Nevertheless, the old steel truss decks had
stood the test of time, and the replacement
scheme included their removal for recycling
into new steel products.
Steel was selected for the new bridge
because of its high strength-to-weight ratio,
which permitted a shallow construction depth
and minimised the total weight to be slid into
position. The low self-weight also minimised
foundation works adjacent to the existing rail
line. This bridge was the first UK steel bridge
to be designed for the next generation of
225 Km/hr trains, and was completed in 2000.
Economic Erected adjacent to the old bridge and slid in to position during a 72-hour possession, minimising disruption to the East Coast Main Line
Environmental Innovative use of steel needle beams as part of the substructures will assist with the future removal of this bridge
Social Offsite fabrication and partial assembly on land adjacent to the site minimised the health and safety risks for the workforce
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Environmental priorities
3.2 Minimum CO2 and energy burdens Selecting steel for bridges is a good way of reducing energy consumption and the level of CO2 emissions.
The World Steel Association, which speaks for the world steel production community, advocates the use of the system expansion, or substitution, method for calculation of the carbon and energy burdens associated with steel production. This approach treats steel manufactured both from virgin materials and from recovered scrap as being essentially part of the same process, with credits for production from scrap being allocated to production from virgin materials.
The figures in the table opposite calculated using the World Steel Association method and data, which take account of a 99% recycling rate, are recommended for use in comparative studies.
3.3 Minimum waste Offsite production in modern fabrication plants using state-of-the-art CNC machinery integrated with CAD software ensures that waste is minimised, both during manufacture of steel elements and on site. Waste minimisation is promoted by good designs that minimise use of materials; the steel bridge industry provides a full range of technical back-up for designers to promote this aim.
Above: CAD model of a bridge
Embodied CO2 and energy figures for steel products
Embodied CO2 Embodied Energy Steel plates 0.919 tCO2/t 17.37 GJ/t
Steel sections 0.762 tCO2/t 13.12 GJ/t
Newport City Footbridge
Architect – Grimshaw
Structural Engineer – Atkins
Steelwork Contractor – Rowecord Engineering Ltd
Main Contractor – Alfred McAlpine
Client – Newport Unlimited and Welsh Assembly Government
Drawing inspiration from the City’s historic
wharves, this crane-like structure supports a
145m span footbridge/cycleway across the
River Usk, and is a magnificent landmark in
the heart of a regeneration area. The bridge
deck loads are transferred to ground level by
two 120mm diameter cables, which also act
as stays for two pairs of masts. Fabrication of
the 850 tonne structure began in August
2005, with pre-assembly and erection in early
2006. The completed structure plays a critical
part in the City’s accessibility strategy, and is
powerful evidence that regeneration is
underway.
Economic Landmark structure delivered within tight cost and time constraints
Environmental Lightweight steel deck avoided any works in the tidal river to minimise the impact on the local river ecology
Social Location of major support structure on the west bank kept work away from nearby dwellings on the East side
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3.4 Lightweight construction The lightweight nature of a steel bridge means that it leaves the lightest possible footprint. Minimum foundation works are desirable not only for cost reasons, but also to minimise the environmental impact. The excavation, transportation and disposal of arisings for substructures requires energy, creates CO2, and lorry movements are a nuisance for the local community. It is better to create minimum ground disturbance where possible and steel helps to achieve this aim.
Above: Lightweight Footbridge, A38 North of A5, Lichfield
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Social priorities
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Swansea Sail Bridge
Architect – Wilkinson Eyre Architects
Structural Engineer – Flint & Neill Partnership
Steelwork Contractor – Rowecord Engineering Ltd
Main Contractor – Balfour Beatty Civil Engineering Ltd
Client – Welsh Development Agency
This exciting structure comprises a
140m long steel deck supported by
70mm diameter spiral strand stay cables
connected to a 42m high steel mast.
Steel was key to the success of the very
short programme (concept to
completion in 15 months), and the
formal clarity and final surface finish.
Opened in June 2003 for the inaugural
‘Great West Wales Triathlon’, this bridge
has become a popular icon for the
region and a destination in its own right
as well as an essential link between the
Port Tawe Innovation Village and the
City Centre.
Economic Lightweight steel structure with minimum foundation works
Environmental Single pier and long spans minimises the impact on the River Tawe
Social Landmark structure forming an essential link in the regeneration of Swansea Docks
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4.1 Sustainable communities The offsite fabrication of steel bridges in a factory environment provides jobs for a workforce close to where they live. This benefits family life and promotes stable communities. Continuous investment in new plant and machinery and the stable long-term nature of jobs in a steel fabrication factory, assist in the training of a specialist workforce. Such skills development both motivates the workforce and increases the efficiency of steel bridge construction.
4.2 Health and safety Steel bridges represent the superior option when health and safety is considered. Offsite fabrication means steel is safely manufactured in factory conditions. Automated production, using robotic welders, makes for safer working environments. Because the majority of construction work is offsite, the steel erection work on site is inherently safer, with far fewer trades and operatives involved and is faster, thus minimising time working at height in hostile environments.
The steelwork contractor’s trade group, the British Constructional Steelwork Association (BCSA), has a continuous programme of research, education and publications aimed at improving the already highly creditable safety performance of the steel construction industry. The BCSA’s Safe Site Handover Certificate is an outstanding example of a modern safe-working practice, and its Sustainability Charter, to which all Member companies can sign up, represents another best practice initiative from the steel construction sector.
4. Social priorities
Society gains in many ways from the benefits delivered by steel bridge solutions. Landmark steel bridges embody good design. They are economical and fast to build, and have stimulated the regeneration of many former industrial, dock and canalside areas.
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Gateshead Millennium Bridge
Architect – Wilkinson Eyre Architects
Structural Engineer – Gifford and Partners
Steelwork Contractor – Watson Steel Ltd
Main Contractor – Harbour & General
Client – Gateshead Council
This iconic steel bridge spans 105m across
the River Tyne, and comprises a parabolic
fabricated box section deck supported by
spiral strand stay cables from an inclined
parabolic steel arch. The fundamentally
simple concept comes to life as the pair of
arches pivot around their common springing
point to allow shipping to pass beneath. The
steel components were fabricated in Bolton
and fully assembled on the bank of the Tyne
at Wallsend. The entire superstructure was
then transported six miles to its final
position in November 2000 using the Asian
Hercules II floating crane, and lowered into
position to a tolerance of +/- 2mm.
Economic Offsite construction minimised disruption to river traffic
Environmental Bridge fabricated and assembled offsite, and floated in to position with minimum impact of construction on the local community
Social Landmark structure linking Newcastle and Gateshead, and a key feature of the regeneration and development of East Gateshead
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Social priorities
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Social priorities
4.3 Minimum impact The lightweight nature of steel bridges, and the fact that the components are manufactured offsite means far fewer site visits from heavy vehicles, benefiting local communities. The typically rapid construction period for a steel bridge means that impacts on local people and businesses can be minimised.
4.4 Aesthetically pleasing bridges Steel has broad architectural possibilities. Steel bridges can be made to look light or reassuringly solid, and can be sculptured to any shape or form. The high surface quality of steel creates clean sharp lines and allows attention to detail. Modern fabrication methods can easily provide curvature in both plan and elevation. The painting of steelwork introduces colour and contrast, and repainting can change or refresh the appearance of the bridge.
Steel bridges are an essential feature of a country’s infrastructure and landscape. Few man-made structures combine the technical with the aesthetics in such an evocative way. Look closely at the next ‘landmark’ bridge you see; the chances are that it is made of steel.
Above: Fabricated steelwork being delivered Below: Renaissance Bridge, Bedford
(Photo courtesy of Angle Ring Co Ltd.)
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River Tame Crossing
Structural Engineer – Scott Wilson
Steelwork Contractor – Fairfield-Mabey Ltd
Main Contractor – Birse Rail
Client – Network Rail
The River Tame Crossing comprises a pair of
identical half-through girder decks, each
carrying two tracks, and was part of the major
upgrade of the West Coast Main Line in 2007.
The decks replaced an existing 100-year old
bridge, and the lightweight nature of steel
permitted the existing substructures to be
re-used.
Investment in the latest robotic welders helped
the steelwork contractor to produce the girders
more cost effectively, and faster than before,
with the confidence that the finished product
would be right first time. The robots were used
to weld stiffeners on girders and are directly
linked to the CAD 3D modeling system.
Economic Lightweight steel enabled the re-use of existing piers
Environmental Offsite fabrication with modern plant leading to high quality, and minimum waste
Social Factory production promotes family life and stable communities
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The Tata Steel Group vision is to be the world steel benchmark for value creation and corporate citizenship. We are proud of our workforce and it is their involvement that will help us deliver this vision. The aim is to become an employer of choice and to build a reputation that is globally respected and admired.
Value creation means becoming supplier of choice, by offering premium products and services, backed up with an unrivalled service package as well as differentiating through innovation and delivering leading edge solutions in technology, processes and products.
As a corporate citizen Corus acts with a sense of responsibility, integrity and respect. It is about providing a safe workplace, respecting the environment, and caring for communities and demonstrating high ethical standards.
As the sustainability debate moves on, it involves more than simply addressing the environmental impact of steelmaking, it is about achieving a balance between the economic, social and environmental aspects of our activities.
Corus manages its corporate responsibility performance against clear and objective criteria, and strives to improve in all areas of environmental performance through the adoption of sustainable practices and continuous improvement. Corus works proactively to reduce the targets adopted and minimise the impact on the environment. We set targets for improvement and then monitor, review and report against these targets.
Corus is highly proactive in ensuring that sustainable practices are adopted all along the supply chain, from an environmentally responsible approach to the sourcing of materials, through manufacturing processes that have a continuous improvement culture built-in, to the production of steel construction products that are modern and efficient.
All Corus manufacturing sites are certified to ISO 14001, which is the international standard for environmental management systems.
Far Left: Scunthorpe Community Gala Left: Salmon returning to the River Don Opposite: Bottesford Beck, Scunthorpe
5. Corporate responsibility
As a responsible supplier, Corus is committed to fulfilling the duty of care that is owed to the environment, our suppliers and customers, our workforce and the communities in which we operate.
Corporate responsibility
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A2/A282 Viaducts
Structural Engineer – Jacobs
Steelwork Contractor – Fairfield-Mabey Ltd
Main Contractor – Costain
Client – Highways Agency
This major road improvement scheme
alleviates congestion on the A2/A282
intersection in north Kent and includes
four new major steel bridges. The nature
of the junction is such that access for
future maintenance would be very
difficult, which was the prime reason for
selecting weathering steel for the bridges.
The low maintenance characteristics of
the material offered environmental and
health and safety benefits, as well as
minimising future disruption to road
users, and the whole life cost of the
improvement scheme. With a total of
4000 tonnes, this project represents one
of the largest uses of weathering steel in
the UK to date.
Economic Lightweight steel lifted into position during night closures to minimise disruption to road traffic during construction
Environmental Reduced site traffic minimised the impact of construction on local communities
Social Use of weathering steel minimises future maintenance requirements, and the associated traffic disruption
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Corporate responsibility
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www.corusgroup.com
Care has been taken to ensure that this information is accurate, but Tata Steel Europe Limited, and its subsidiaries, does not accept responsibility or liability for errors or information which is found to be misleading.
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