Reinforcement of Bosphorus Bridge

Project Details
ClientGeneral Directorate of Highways
ContractorMakyol & IHI J.V.
Tonnage500 ton
Project Period24 month
Completion Date2016
LocationIstanbul, Turkiye

Project Brief

In 2014, Nunteknik undertook the part of Bosphorus Bridge’s 40th Year Maintenance and Reinforcement Project. In scope of this project, Nunteknik handled following works:

  • Latitudinal and longitudinal reinforcement of bridge tower legs
  • Repairment of orthotropic cracks on bridge deck
  • Erection of four viscose dumpers on the areas where deck and tower legs are approaching each other

For reinforcement works, more than 100 ton IPE500 profiles were used per tower leg. These profiles were erected within the tower legs which are 5x7m wide. Towers were reinforced longitudinally from +3 to +27 elevation. Latitudinal reinforcements were done in five different elevations from +42,5 to +149. For erection on +149 elevation, materials were lifted by crane inside the tower, countersunk bolts were screwed by mountaineers from outside tower legs; totally 200 pcs of M22x120 bolts were screwed on each tower legs.

More than half of the otrhotropic cracks on the deck, ribs were reinfored by stell plates. In project general, bolts were screwed with using turn-of-nut method. After measuring and determining optimum angle required for bolts ensuring 18KN by using Skidmore-Wilhelm test device, required angle was adjusted with torque machines and all bolts were screwed with this angle. Thus, reinforcement was done by friction force stemmed from pressure between plates and rib.

Bosphorus Bridge is one of the first suspension bridges in the world. At the time of construction of the Bridge, mostly cross suspension cables were used in this type of bridges throughout the world. However, in the course of time, it has been found out that vertical suspension cables are much more efficient with regards to carrying bridges. Therefore, in 40th Year Maintenance of Bosphorus Bridge, cables were replaced vertically. Due to a fact that vertical cables are not taking horizontal burden on the bridge, viscose dumpers were erected where the deck and tower legs are approaching each other. Nunteknik lifted these -2,5 ton- dumpers to 60 mt height by platforms and erected dumpers while the bridge is working.