Swedish 48-m Fast Bridge
Fast Bridge 48 is a 48-m single-span bridge system for loads up to Military Class 70 (MLC70, approximately 64 metric tonnes), according to North Atlantic Treaty Organization (NATO) standards. The bridge is made of extra high strength steels (HPS steels S960 and S 1100) and can be deployed in less than 90 minutes and retrieved in the same time from either side of a river or dry gap.
The bridge is the result of about eight years of research and development in cooperation mainly between the Swedish Defence Material Administration (FMV) and Karlskronavarvet AB. The design is patented.
Conceptual Design of Fast Bridge 48
The span length can range from 32 to 48 m, made up of four to six 8-m sections with a width of 4 m and depth of about 1.6 m (see Figure 1). The deck is made of a plate of S1100, thickness 5 mm, which is stiffened by cold-formed channel sections with web folds. Also, the bottom chord is made of cold-formed sections, whereas the diagonals in the truss are made of S460 rectangular hollow sections. The coupling plates are made of 50 mm S960 plates. The Fast Bridge 48 requires steel with a yield point of 1100 MPa and an impact toughness of 40 J at -40°C. Such steel is not covered in existing regulations, which is why it was necessary to verify whether existing criteria for the design and manufacturing methods were valid. Extensive tests were done on components concerning local and distortional buckling, and fatigue and static tests were done on welded components, in addition to examination of welding procedures. For instance, it turned out that the Swedish code for cold-formed structures was applicable, despite exceeding the strength and thickness limits in the code to a great extent.
Benefits of High Strength Steel in Bridge Construction
As there are no limitations on the deflections of military bridges, the strength of HPS steels can be fully utilized. This results in a lightweight structure that can compete with aluminum alloys and polymers. The benefits commonly gained with modern, improved-performance steel include:
- Reduced weight
- Increased life
- Reduced fabrication costs
Further development of the bridge makes it possible to span up to 200 m with intermediate supports dropped from the bridge during launching.
Fast Bridge 48 Reference Data
Owner: Swedish Armed Forces
Purchaser and project manager: Swedish Defense Material Administration
Steel designer: Kockums AB, Karlskronavarvet and Royal Institute of Technology, Stockholm
Swedish Hybrid Girder Bridge
The bridge in question is located in Mittådalen, in the middle of Sweden. It replaces an outdated existing bridge at the same site.
The bridge is simply supported, with a span of 25.6 m and a free width of 7 m. The girder height is 1245 mm, and the steel weight is 103 kg/m2 deck area. The cost of the steel contract was 43.4 kEUR, including bearings. Since the site is located far away from the nearest concrete plant, the deck of the bridge was prefabricated, with joints cast in situ. At the abutments, back-walls are connected to the end-plates of the bridge with headed shear connectors. The bridge rests on four steel roller bearings, with roller diameter of 180 mm. The use of S690 in the bottom flange meant that the following design criteria were met:
- The ultimate limit state
- The serviceability limit state (no yielding)
- The serviceability limit state (B<L/400)
Hybrid girders are now included in the Swedish bridge code. The limitation is mainly that the effective area of the web is based on the yield strength of the stronger flange plates, which must not exceed 1.5 times the strength of the web plate.
Benefits of High Strength Steel in Hybrid Girder Bridge
By using S690 in the bottom flange, the following advantages were obtained:
- Smaller butt weld volume
- Cheaper steel plates
- Easier handling and transport
- Smaller area to paint
One limitation of the concept with HPS is that the time for delivery of materials could be critical. Furthermore, on heavily trafficked roads, the fatigue strength may very well govern the dimensions of the flanges.
Hybrid Girder Bridge Reference Data
Owner: National Road Administration
Steel designer: Scandiaconsult, Lulea
Steel contractor: DEM-VERK MEK AB
Road Bridge over the Rhine River
The Rhine bridge at Düsseldorf-Ilverich is a cable-stayed road bridge on Highway A44. The bridge was built between 1998–2002. For the steel structure, 7180 t of steel grade 5355 and 520 t of grade S460 was used.
The main span of the bridge consists of two V-shaped steel pylons supporting the main girder with steel cables. The V-shaped pylons were necessary in order to keep the height of the towers small, due to the bridge’s proximity to the Düsseldorf airport. The approach bridges were made of pre-stressed concrete and the piers of reinforced concrete.
Benefits of High Strength Steels in Road Bridge at Düseldorf-Ilverich
In order to transmit the horizontal cable forces between the two sides of the V-shaped pylons, they were connected at the upper part by tension ties consisting of a welded hollow steel cross-section. A thermo-mechanical rolled steel grade S460ML was used for these tension ties for two reasons:
- Minimum plate thickness, to keep the weld volume small for the butt welds
- Welding without preheating
Both modifications helped to improve the economy and quality of the welds.
Road Bridge Düseldorf-Ilverich Reference Data
Owner: Federal Republic Germany, represented by Straβenbauverwaltung Nordrhein-Westfalen
Steel contractor and designer: Stahlbau Plauen
This composite highway bridge near Ingolstadt, Germany is a multi-span bridge with span lengths of 24.0, 5 X 30.0 m and 20.0 m, carrying a 15.0-m wide concrete slab (see Figure 5). The bridge is designed as an integral structure where the steel girders are directly connected to the columns by flexible steel plates, meaning that no bearings were needed.
Benefits of High Strength Steel in Composite Bridge Near Ingolstadt
For the semi-rigid connections between the composite piers and steel girders, lamellas of steel grade S690QL were used (see Figure 6). In order to ensure a semi-rigid connection the flexible steel, plates must be designed to the following stiffness and strength requirements:
- The plate thickness must be small enough to reduce restraints from translatory and rotatory movements of the structure at the columns.
- The plates must be thick enough to resist normal forces and restraining moments from movements safely.
These contradictory requirements lead to an optimization problem that is satisfactorily solved by using S690QL.
Composite Bridge Near Ingolstadt Reference Data
Owner: IFG Industrie-Forder-Gesellschaft, Ingolstadt, Germany
Steel designer: Hilzinger Bettcher-Zeitz Habisreutinger, Munchen, Germany
Steel construction: Max Bögl, Bauunternehmung GmbH&CoKG, Neumark, Germany
Roof Truss of the Sony Centre in Berlin, Germany
Various stories of a hotel building at the Sony Centre in Berlin are suspended from a roof truss to protect an old masonry building from overloading by the “Kaisersaal” integrated into the hotel building (see Figure 7).
Benefits of High Strength Steel in Sony Centre Roof Truss
The truss structure, composed of components with a solid rectangular shape, was made of steel grade 5460 and S690. High strength steel was used to keep the dimensions of the cross-sections small enough to fit standards for fire protection.
Avoiding Brittle Fracture
To avoid brittle fracture at low temperatures, verification was performed through calculation according to the European design code EN 1993-1-10, in addition to testing. The structural detailing and the dimensions of the “large-scale test specimens” are given in Figure 8.
Sony Centre Roof Truss Reference Data
Steel contractor: Waagner Biro Binder AG, Wien, Austria
Millau Viaduct, France
This 320 million Euro viaduct is the last link in the French Highway A75 between Clermont-Ferrand and Beziers, closing a gap across the valley of the River Tarn next to the city of Millau. The search for an aesthetic solution led to the adoption of a multi-span cable-stayed bridge with a light steel deck crossing the river at a height of 270 m. With a total construction height of 343 m, the bridge is the highest in the world.
The 2460-m deck is composed of six main spans of 342 m each and two side spans of 204 m each. The deck is composed of a steel girder with a total height of up to 4.20 m and a total width of 32.00 m in order to optimize resistance against high wind loads in the valley.
The cross-section consists of a central box (which is also linked to the steel pylons), lateral connecting panels, and lateral side boxes. Boxes and panels are stiffened by trapezoidal stiffeners. The seven steel pylons are erected in an inverted Y-shape and hold two times 11 cables each.
Benefits of High Strength Steel in Millau Viaduct
A total of 43,000 t of steel plates were applied for the deck and pylons. High strength steel grade S460ML (nominal yield stress of 460 MPa) was used for the entire central box and some connecting elements, with a thickness up to 80 mm, in order to:
- Resist high loads without increasing the amount of steel used
- Reduce cantilever bending movements during launching of the bridge
- Apply a more efficient welding process
- Reduce transport weights from the workshop to the site
Furthermore, the pylons were constructed of steel grade S460ML in a thickness of up to 120 mm.
Launch of the Bridge
The deck was launched from platforms on either side of the River Tarn. The deck was equipped with a launching nose and with one pylon at each end in order to increase stiffness during launching. With the use of auxiliary piles in the middle of each span, the launching cycle was 171 m. After connecting the two deck spans, the five remaining pylons were welded together, brought to their final position and erected. Then the cable stays were assembled and tightened and the auxiliary piles removed.
Millau Viaduct Reference Data
Owner: Eiffage Group, France
Steel designer: Greisch, Belgium
Steel contractor: Eiffel Construction Metallique, France
Verrand Viaduct, Italy
The Verrand Viaduct is an orthotropic deck bridge, part of the Mont Blanc-Aosta highway, located in the third building lot, Mont Blanc Tunnel-Morgex. More specifically, the viaduct is located at Prè Saint Didier (Aosta), near Courmayeur, alongside the existing S.S.26 (Mont Blanc Tunnel-Aosta). It was necessary to overpass a valley containing a country road and the Dora Baltea River. The viaduct was finished in August 2002 after two years of work, and utilized a total steel quantity of 6100 t.
The possible structural alternatives were all characterized by the decision to realize a unique motorway viaduct for all the roadways, with a width of around 20 m. It was decided to use an orthotropic deck bridge with two principal beams and interior bracing of five spans ( 97.5 m, 135 m, 135 m, 135 m and 97.5 m respectively), supported by four intermediate piers.
Benefits of High Strength Steel in Verrand Viaduct
A lattice launch girder with a length of 85 m was realized using high strength steel tubular sections of grade S690. In this way, the weight of the launch girder could be significantly reduced, which allowed a design process of the final steel-deck bridge that required no changes in cross-sectional dimensions for the launching process.
Verrand Viaduct Reference Data
Owner: R.A.V. (Valley of Aosta highway) S.p.A., Rome, Italy
Steel designer: SPEA S.p.A., Milan, Italy
Steel contractor: OMBA I.&E. S.p.A., Torri di Quartesolo, Vicenza, Italy