Post on 12-Apr-2017
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VERSATILE MATERIAL
Uses of steel in bridge construction
What is SteelSteel:- Steels are alloys of iron and other elements, primarily carbon high tensile strengths and low costs. Widely used in construction and other applications.
Uses of steel in bridge constructionIndustrial importance on steel: More than 1.3 billion tons produced annually
Mild steel replaced wrought iron
Hardness, ductility, and tensile strength of the resulting steel is controlled
Various grades defined by assorted standards organizations
Why we Uses steel in bridge construction??
The following are some of the advantages that steel can offer;
Long steel
High quality material
Speed of construction
Versatility
Modification and repair
Recycling
Durability
Aesthetics
Why we Uses steel in bridge construction??
Long steel
As reinforcing bars and mesh in reinforced concrete
Railroad tracks
Structural steel in modern buildings and bridges
Wires
Why we Uses steel in bridge construction??
High Strength to Weight Ratio
strength to weight ratio of is particularly beneficial in poor
ground conditions
Minimum self-weight is also an important factor in transporting
and handling components
shallow construction depths overcome problems with headroom
and flood clearances, and minimize the length of approach ramps
For example………
The Newark Dyke rail bridgeComprises a 77m span
bowstring truss
820 tones of S355 steel
The selection of steel was made
because of its high strength to
weight ratio,
The low self-weight also
minimized foundation works
adjacent to the existing rail line.
First UK steel bridge to be
designed for the next generation
of 225 Km/hr trains
Why we Uses steel in bridge construction??
Quality Steel is a high quality material grades, shapes sizes The testing regime carried out at the steel mills properly Pre-fabrication in controlled shop conditions leads to high
quality work at minimum cost. cutting, drilling, welding, fit-up and painting is easily
permitted
Readily available
Why we Uses steel in bridge construction??
Speed of ConstructionThe prefabrication of components time on site in hostile environments is minimized. The speed of steel bridge construction reduces the
durations of rail possessions and road closures,public disruption to those networks are minimizedThe light-weight nature of steel permits the erection
of large componentsFor example…..
The Hallen Bridge
A 500T truss bridge near Bristol(England)Carries a single-track railwaySections were shop-fabricated and transported to site where the bridge was fully assembled off line.Transported into position using multi-wheeled Econofreight vehicles
Why we Uses steel in bridge construction??
VersatilitySteel suits a range of construction methods and
sequences. Installation by cranes, launching, slide-in
techniques or transporters.Steel gives the Contractor flexibility in terms of
erection sequence and programs.Components can be sized to suit access
restrictions at the site
Why we Uses steel in bridge construction??
Once erected the steel girders provide a platform for subsequent operations.
Why we Uses steel in bridge construction??
Modification & Repair
Steel bridges are adaptable And can readily be altered for a change in use They can be widened to accommodate extra lanes of traffic,
and strengthened to carry heavier traffic loads. Steel bridges can readily be repaired after accidental damage. A heat treatment technique, based on the theory of restrained
expansion, was proposed by a UK fabricator as a more economic and less disruptive solution
Tamar suspension bridge (Plymouth)The 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
The result was that the
widened 5-lane bridge was only
25 tones heavier than the old 3-
lane structure, and was able to
accommodate 44 tone trucks
Why we Uses steel in bridge construction??
Recycling Steel is a ‘sustainable’ material. 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.
Why we Uses steel in bridge construction??
Durability Steel bridges now have a proven life span extending
to well over 100 years. The potential durability of steel may be summarized
in the following quote by a Mr. J. A . Waddell in 1921:
“The life of a metal bridge that is scientifically designed, honestly and carefully built, and not seriously overloaded, if properly maintained, is indefinitely long.”
Why we Uses steel in bridge construction??
Durability
Steel has a predictable life, as the structural elements are visible and accessible
Signs of deterioration are readily apparent Corrosion is a surface effects are removed by
repainting the affected areas Alternative form of corrosion protection is the use of
weathering steel
Why we Uses steel in bridge construction??
Aesthetics Steel has broad architectural possibilities
Could be sculptured to any shape or form
The high surface quality of steel creates clean sharp lines and
allows attention to detail
The painting of steelwork introduces color and contrast, and
repainting can change or refresh the appearance of the bridge to
appear as new one
Truss Bridge (Incheon international airport)
This arch-truss bridge connects incheon international airport to seoul in korea (above), and has a main span of 540m. Steel was considered the only option for such a high profile site.
Examples of steel bridgesMILLAW VIADUCT Location:- Millau-Creissels, France Total length:- 2460 m Longest span:- 342 m Concrete used:- about 127,000 cubic meter Steel used:- 19,000 tones of for the reinforced concrete Required 5,000 tones steel of pre-stressed steel for the cables
and shrouds
lifetime of the bridge will be at least 120 years
Preference of steel for Millau viaduct
The advantages of the steel against the original concrete design are: • light-weight and slenderness of the beam (36 t against 120 t)• reduction of the depth of the beam to 4.2 m, meaning smaller wind loads• improved safety: less work at great height due to pre-assembly on ground
and incremental launching construction• minimizing the number of stay cables and the size of foundations• reduction in total costs – the over-riding advantage. • Within two and a half years nearly 43 t of steel were fabricated for the
beam, the towers and the auxiliary piers.
Examples of steel bridges
Sydney harbour bridge:-Made of steel the bridge contains 6 million hand
driven rivets The Bridge has huge hinges to absorb the
expansion caused by the hot Sydney sun. You will see them on either side of the bridge at the footings of the Pylons
Six million hand driven rivets and 53,000 tonnes of steel were used in its construction
• Golden gate bridge• Structural Steel Quantities
• Tons• Kg• Main Towers• 44,400• 40,280,000• Suspended Structure• 24,000• 21,772,000• Anchorages• 4,400• 3,991,000• Approaches• 10,200• 9,250,000• Total• 83,000• 75,293,000