Special profiles
Special profiles are tailor made hot rolled steel shapes, designed to meet individual customer requirements. The main products used in bridge construction are bulb flats for plate stiffening, and expansion joint profiles.
Bulb Flats
Bulb flats are an asymmetric plate stiffening section manufactured in a wide range of sizes and grades. They fulfill a range of applications in bridges including the stiffening of box girders, plate girders and steel decks. The advantages that bulb flats offer assist both in the initial construction phase and throughout the working life of the bridge. Recognition of the benefits which bulb flats provide is resulting in increased usage in bridges around the world, both large and small.
Weight and Cost Savings
The unique shape of the bulb flat distributes the steel to maximise its resistance to buckling. This results in a more efficient strength to weight ratio than other forms of stiffener, and may allow a weight saving of up to 64%.
Reduced Painting Costs
Bulb flats reduce both initial and subsequent painting costs by having a smaller surface area than other equivalent stiffener arrangements.
Easier Access
The compact shape of a bulb flat provides easy access for welding, fabrication and painting. Similar benefits also apply to inspection and maintenance activities.
Enhanced Corrosion Protection
The rounded shape of bulb flats enables better coatings adherence, and provides inherent corrosion resistant features by enhancing drainage, and minimising dirt and moisture traps.
Grades
For bridge construction, grades are generally in accordance with EN 10025-2, with readily available yield strengths of 355N/mm2 and 235N/mm2. However, high yield strength steels to EN 10025-3/4 with yield strengths up to 420N/mm2 are available by agreement for thicknesses up to 12 mm.
| Bridge | Type | Use of Bulb Flats |
| Jiangyin, China | Suspension | Web stiffeners in the steel box deck units |
| Tsing Ma, Hong Kong | Suspension | Bulb flats used in the curved approach bridges |
| Oresund Bridges | Cable-stayed | Internal stiffening of the warren truss approach spans |
| Parkway Bridge, UK | Vertical lift | Longitudinal and transverse deck stiffeners |
| Humber Bridge, UK | Suspension | Stiffeners for steel box deck units |
Product Range
Tata Steel manufacturers bulb flats in a wide range of sizes and in lengths up to 18m. Additional sizes to DIN and JIS ranges may be available by agreement.
| Size | Width (b) mm | Thickness (f) mm | Mass Kg/m | Bulb height (c) mm | Bulb width (d) mm |
| Minimum | 120 | 6 | 7.31 | 17 | 17.7 |
| Maximum | 430 | 20 | 90.8 | 62.5 | 66.8 |
Dimensions
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Technical Support
Tata Steel is able to offer advice to consulting engineers and designers on the incorporation of bulb flats into bridge designs. New design software is also available for the rapid assessment of the strength of alternative bulb stiffener arrangements.
Expansion Joint Profiles
Special profiles have been supplied to manufacturers of expansion joint systems, and used in a large range of bridges, including the Storebaelt East bridge in Denmark, where the joint was designed for 2000mm of movement.
Special Profiles
Specially designed steel profiles may benefit particular bridge designs, or overcome unique problems. Tata Steel designers are always ready to work with client’s engineers to explore new opportunities for the development of special profiles.
