ITH in Istanbul
Secure bolt connection of the cable clamps of the Bosphorus bridges
The Bosphorus bridges in Istanbul are central traffic hubs with over 400,000 vehicles a day. Their stability depends largely on the high-strength support cables, which are secured with precise pre-tensioned cable clamps.
During a comprehensive maintenance project, the bolt connections of the cable clamps were bolted quickly, securely and efficiently using the latest ITH Bolting Technology.
Industry
Bridge building
Technology
ITH Multi-Tensioning
Year
2015
ITH multi-tensioning process for maximum precision
The Bosphorus bridges in Istanbul are essential traffic arteries between Europe and Asia and carry over 400,000 vehicles every day. Their stability depends largely on the supporting cables, which are made of high-strength steel and secured with specialized cable clamps. As part of a comprehensive maintenance project, the bolted connections of these cable clamps were checked and optimized using the latest ITH Bolting Technology. The aim was to ensure uniform pre-tensioning of the bolts and thus ensure the long-term stability of the bridges.
The cable clamps are fastened with high-strength M36x734 reduced shaft bolts / reduced-shank bolts, which require precise and even tension. This is necessary to ensure optimum load distribution and avoid unwanted settling of the connections. To meet these requirements, the ITH Multi-Tensioning method was used. This method makes it possible to pre-tension several bolts simultaneously with a defined force, resulting in parallel and uniform pre-tensioning.
Ten ITH ES 36-470 Bolt Tensioning Cylinders were used, which generate hydraulic, frictionless tension and thus ensure an exact tightening torque. The use of cardanic pulleys also made it possible to compensate for structural tolerances and achieve optimum power transmission.
This maintenance project required close cooperation between international partners from Germany, Japan and Turkey. The Turkish Ministry of Transport commissioned a leading Japanese company with the maintenance of the bridges, which in turn set its sights on the bolting technology expertise of ITH.
The entire maintenance process was carried out in strict compliance with international safety standards. Timely implementation was crucial in order not to disrupt the flow of traffic on the bridges. ITH met these requirements through the use of efficient bolting technology and close coordination with all project participants.
Thanks to precise and efficient assembling using the ITH Multi-Tensioning process, it was possible to ensure uniform and permanent pre-tensioning of all cable clamps. The main advantages of the technology used include
Reduction of assembly tolerances through parallel pre-tensioning
Longer service life of bolt connections due to even load distribution
Efficient and time-saving assembling
High level of safety thanks to controlled screw tension
These measures helped to secure the structural integrity of the Bosphorus bridges in the long term and significantly extend their service life.
The successful maintenance project on the Bosphorus bridges shows how innovative bolting technology contributes to the maintenance of critical infrastructure. Close cooperation between international partners, coupled with ITH’s precise and efficient technology, resulted in a safe and durable bolt connection of the cable clamps. ITH thus underlines its expertise as a leading supplier in the field of bolting technology for bridge and steel construction.
Type ES 36-470
Before assembling the cable clamps, the individual steel wires were hydraulically pressed together. All the bolt connections of a cable clamp were then pretensioned in parallel using single-stage ITH bolt tensioning cylinders type ES 36-470 for precise tensioning. The “ITH Multi Tensioning” system was used here, in which all Bolt Tensioning Cylinders used are connected together in one hydraulic circuit. This
the preloads were applied to the bolt connections in a precise, uniform and parallel manner with a high system accuracy of ± 2.0%.
M36x734
In the course of the project, around 700 bolt connections M36x734 were screwed together precisely and securely.
Internal radii r > 280 or r > 290
In order to efficiently absorb the loads occurring in bridges (e.g. dead weight, live load, dynamic loads), the suspension cables often consist of numerous individual steel wires (e.g. on the Golden Gate Bridge in San Franciso, USA). The high-strength steel wires end in anchor blocks (concrete foundation) on both sides of the bank and are pressed together by cable clamps as they pass over the pylons (bridge piers).
Two versions are used on the Bosphorus bridges:
- Cable clamp, double-shell, inner radius r > 280 mm with 10 x reduced shaft bolts M36x734 with cardanic washers
- Cable clamp, double-shell, inner radius r > 290 mm with 4 x reduced shaft bolts M36x734 with cardanic washers
Products used
Bolt Tensioning Cylinder
Consulting
Get in touch with us
Contact us for an individual consultation with our experts
Further projects
You might also be interested in
