Doka enables a record breaking Eyiste Viaduct project in Turkey
Formwork expertise from Doka is much in demand right now for construction of the country’s highest viaduct. With piers up to 155 metres tall, the Eyiste Viaduct will be the connecting link between Central Anatolia and Turkey’s Mediterranean region, shortening travel time between the cities of Konya and Alanya. Cantilever forming travellers and Automatic climbing formwork Xclimb 60 from Doka are in use on this major bridge project.
1,372 metres in length and carried by 2 abutments and 8 piers, the viaduct will span the Göksu River near Bağbaşı District. The superstructure of the balanced cantilever bridge has 9 spans, the longest of which is 170 metres. The piers vary in height from 31 to 155 metres. Work started in March 2017 and the structure is scheduled to be opened for traffic in June 2020.
The bridge’s superstructure is being constructed by the balanced cantilever method, which is ideal for long spans and has established itself as the method of choice for bridge-building projects in Turkey. A total of 130,000 m³ of concrete and 28,000 metric tons of steel (excluding pre-stressing cables) will be used in construction of this viaduct.
3D model tried and tested under extreme conditions
Differing pier heights and the long deck cause differences in the way external influences affect the structure. The CSiBridge software was used to model the viaduct in 3D so that the bridge’s ability to handle vertical and lateral forces could be assessed and the results incorporated into planning.
The simulations indicated that the shortest pier (31 metres) would be most affected by seismic forces. The long bridge deck and the tallest pier (155 metres), by contrast, would be more susceptible to creep, shrinkage and temperature effects (CST) and to wind loads. Based on these results, only the four tallest piers are being cast monolithically with the deck sections. The deck remains supported on longitudinally sliding bearings, providing flexibility and reducing seismic effects.
High-performing cantilever forming travellers
The balanced cantilevering superstructure sections of the new Eyiste Viaduct are constructed toward each other from pier head to pier head. The four cantilever forming travellers (CFTs) work in pairs, so that the horizontal forces acting on the bridge piers are always in equilibrium.
The travellers can handle varying section lengths from 3,00 to 5,00 metres and concrete weights up to 250 metric tons. The forming carriages speed up progress on the build and allow for variations in segment geometry. Slide bearings secure the CFTs against unwanted travelling on longitudinal gradients.
Fully enclosed working platforms on all levels and hydraulic test loading of the rear carriage anchorages prior to each pouring operation help ensure safety at work. 6 paired sets of Automatic climbing formwork Xclimb 60 are in use for forming the bridge piers. The system climbs hydraulically, anchored to the structure at all times by guiding shoes. Because it is guided on the structure at all times, the system can still be climbed even in windy conditions.