SPECIAL REINFORCEMENT STEEL FOR BRIDGES AND TUNNELS

How the Top12-500 from Swiss Steel increases the service life of civil engineering structures

Corrosion is the enemy of any steel reinforcement. It endangers the safety of buildings and, in the worst case, leads to failure of the entire construction. The result is usually a costly repair. In many countries, bridge rehabilitation is therefore one of the most urgent challenges to ensure that traffic volumes and goods flows continue to be maintained. For example, thousands of bridges in Germany urgently need to be restored. More than 2,500 bridges, which makes up 5% of all road bridges, have been assessed as insufficient or inadequate. In the worst case scenario, you're in danger of being blocked. And since large bridges with heavy traffic are particularly affected, as much as 12% of bridge areas in Germany are in acute need of rehabilitation.


External attack – corrosion on steel

Civil engineering structures are exposed to the attack of chlorides which, depending on their concentration, have an extremely corrosive effect and cause pitting on the reinforcing steel.

Chloride corrosion leads to high material removal and reduces the cross-section of the steel. This process is not visible from the outside and poses a major threat to the stability of the structure: The reduction of the steel cross-section reduces the load-bearing capacity of the reinforcement and in extreme cases there is a risk of collapse for the entire construction. When using conventionally reinforcing steel, the calculated service life of components is often undercut in many cases, depending on the chloride concentration - therefore construction costs are often far from being amortized.

Reinforcement corrosion is often the cause of complex and costly rehabilitation work. With the additional expenditure, the repair costs also increase, especially in places that are difficult to access. The economic damage caused by traffic jams, closed lanes of roads, bridges or tunnels is enormous. 

NEED FOR REDEVELOPMENT OF ROAD BRIDGES IN GERMANY

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TOP12-500: THE IDEAL SOLUTION AS REINFORCEMENT

Stainless reinforcing steel leads to lower costs

The lifecycle costs of a building must already be calculated in the project planning of reinforced concrete structures. With the Top12-500, Swiss Steel offers the optimum steel solution to meet the highest demands for durability in civil engineering. The Top12-500 is a high-alloyed, stainless reinforcing steel with the material number 1.4003. In contrast to the standard reinforcing steel, this special steel has up to five times higher corrosion resistance against chlorides.

Top 12-500: available from 6 mm to 28 mm

The Top12-500 has been proven to comply with DIN EN 488, EN 10088, SIA 262 and SIA 2029 standards, while the Top12-500 rebar is available in Switzerland in diameters from 6 to 20 mm. In Germany, the German Institute of Structural Engineering has been approved Top 12-500 for dimensions from 8 to 28 mm.

PROJECT REFERENCES WITH THE TOP12-500

Motorway intersection Munich-East: bridge replacement


At the München-Ost motorway junction, the A 94 motorway from Munich to Simbach crosses the Munich ring motorway (A 99).

More than 40 years after commissioning, major defects in the structure of the bridge structure due to chloride ions penetrated were discovered during the main inspection and further investigations.

As part of the project, various measures will be taken to increase the durability of chloride-containing components: In addition to optimizing the concrete composition, the connection reinforcement of the foundations, the pillars themselves and the bearing pedestals are made of Top12-500 steel. The superstructures are supported lengthwise in the middle row of pillars. The dimensions of these pillar cross-sections are based on Top12-500 steel with diameters up to 14 mm. In total, approx. 41 tons of Top12-500 steel with nominal diameters of 10 mm, 12 mm and 14 mm are used in the pillars.

Motorway A96: Modernisation of the Etterschlag and Eching tunnels



As part of the safety retrofitting of the Eching and Etterschlag tunnels on the A96 Lindau-Munich motorway, the existing corrosion damage meant that the slotted gutters and emergency walkways had to be replaced or repaired. After almost 20 years of operation, measurements within the framework of condition assessment of the structures revealed chloride contents at the level of the reinforcement, which were well above the corrosion-inducing limit values.

The exposed reinforcement bars already showed considerable local cross section losses. In order to avoid reinforcement corrosion in the future, the emergency walkways were equipped with an optimized concrete technology and the low-corrosion Top12-500 rebar.

Download project folder here (German)

BACKGROUND KNOWLEDGE: HOW WE PRODUCE THE TOP12-500

Top12-500 is five times more corrosion resistant

The secret of the excellent mechanical-technological material properties and high corrosion resistance lies in the production of steel: a decisive factor is the selective addition of alloys in the steel melt, including more than 12 % chromium. The ribbed reinforcing steel is manufactured using a patented rolling process. After rolling, the steel is controlled and specifically cooled down to obtain its very good mechanical properties. In order to increase corrosion resistance in line with requirements, Swiss Steel pickles the Top12-500 after hot rolling - a further step to increase corrosion resistance by a factor of five. Pickling removes the so-called rolling skin. As a result, the bar surface is smoother and more homogeneous and the ribbed steel is protected against surface corrosion and pitting. Whereas the conventional, unalloyed reinforcing steel B500B withstands a chloride content of approx. 0.5% by weight in concrete, this value is up to five times higher in the Top12-500.

The result: less rehabilitation intervals

Therefore, the formula for achieving the calculated service life in civil engineering is made up of the following components: Concrete + adequate reinforcement cover + Top12-500. the example of bridge piers shows that users save up to two rehabilitation intervals, replacing the standard reinforcing steel with Swiss Steel's steel product.

FURTHER INFORMATION AND DOWNLOADS

The SCHMOLZ + BICKENBACH Business Unit Swiss Steel offers you comprehensive information and technical data sheets on the stainless reinforcing steels Top12-500 and Top700:

(Contact details also available in the brochure)

 

 

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