Bridging the continental divide: monitoring construction of a landmark bridge in Turkey

Authors: Özgür Avci & T/F/D

When finished, the 1915Çanakkale Bridge in Turkey will be the longest mid-span suspension bridge in the world. At just over 4.6 km, it will span the Çanakkale Strait and complete a new southerly motorway route between Turkey and the rest of the European continent. Four partner companies are working on the complex build as a joint venture, Limak and Yapı Merkezi from Turkey, Daelim and SK E&C from South Korea (DLSY JV). The partners contribute global technical expertise and experience to each phase of the project, started in 2017. Kwangsoon Hwang is the Survey Manager at DLSY JV, overseeing the survey aspects of the construction and monitoring geometry control. During the tower building phase, Hwang’s challenge was to gather reliable data on the real-time positioning and long-term monitoring of the pylon towers. Using Leica Geosystems equipment, installed by Leica’s distribution partner SISTEM A.S., Hwang and his team completed the survey works on time, with maximum precision. After the initial construction, the equipment will serve as the permanent monitoring system for the bridge.

A bridge of national and international significance

The 1915Çanakkale Bridge and Malkara-Çanakkale Motorway Project is a mega-scale investment in transportation and infrastructure set to make a significant contribution to Turkey’s economy. This new route will take the pressure off the current motorway link, which travels through Istanbul. It will make commercial and tourist travel easier, bringing Turkey closer to Europe and the Balkans. As well as its substantial commercial importance, the symbolic importance of the bridge is honoured by some of its design elements. The 2,023 metres-long mid-span between the tower legs of the bridge symbolises the 100th year of the foundation of the Turkish Republic. In contrast, the tower height of 318 meters above sea level symbolises the 18th of March 1915 Çanakkale Victory, one of the most important dates in the history of Turkey’s struggle for independence.

Accurate positioning data was critical to constructing the towers

Accurate positioning of the caissons (watertight retaining structures used in the towers’ foundations) and the towers themselves are critical in the construction of the bridge. The sections of the towers are manufactured off-site, and the design tolerances are exceptionally tight so fractions of a millimetre matter in piecing the structure together. To monitor the real-time positioning of the fabricated blocks during the build, Hwang and his team used 16 Leica GM30 GNSS receivers for monitoring with 16 Leica AS10 GNSS Compact GNSS Antennas, four on each tower.

Each pylon consists of two towers. Leica GNSS Spider software was used to calculate the positions of each receiver, employing three units of Leica GR30 reference servers with three Leica AR10 GNSS Antennas. Hwang explains that they received data in “real-time, 15 minutes, 30 minutes, one hour and two hours baseline processing from the Spider software. The Leica GeoMoS monitoring software calculates the average position of baselines which are calculated from three references. The data collected was used for geometry control of the Towers in order to install the towers within specified tolerances.” The Leica Geosystems monitoring solution provides easy access to all available data from all GNSS units in one convenient location, helping the users in the field and their colleagues in the office to be most efficient. Real-time positions were used by the Bridge Fabrication teams to monitor the positions and verticality of the towers, making sure that they were safely and accurately slotted into place.

Regular reports on weather conditions are crucial in suspension bridge construction

In addition to the positioning data, wind speed and direction data, as well as temperature sensor data, were assimilated by the Leica GeoMoS software. Up-to-date graphics and regular reports were quickly generated by the GeoMoS Now! monitoring web-service,saving time for Hwang’s team: “The possibility to combine all data collected on site in real-time and display the accurate results in GeoMoS Now! speeded up our processes at the office and the operations on site.” Leica GeoMoS Now! is a web-based application that provides round the clock access to monitoring project data via any web-based device. Dashboards can be customised to provide easy-to-read reports for different users and job functions, for example, engineers or fabrication teams. Being able to give instant access to data allows for early detection – and resolution – of any problems.

Easy to use system saved time on data collection, processing and training 

After accuracy, the main benefit of the solution to Hwang and his team was the ability to save time and work faster. This included the training, which was a quick process because the Leica Geosystems equipment is intuitive to use. Hwang explains, “We needed to train all the personnel who will be using this solution. It took almost no time to easily adapt to the solution with the help of manuals and training provided by Leica’s authorised dealer SISTEM A.S. During the project they also provided 24/7 on-site and remote support related to any problem faced at the construction site.”

Ongoing monitoring to keep bridge passengers safe

“Since the towers have been completed, the product will be used for the cable installation and after the full completion of the project, it will serve as the permanent monitoring system for the whole bridge,” explains Hwang. Leica GNSS Spider was configured to calculate baselines in post-processing mode, and the high-accuracy results are archived in the GeoMoS database, from where periodic reports are generated. Leica GM30 GNSS monitoring receivers, as well as Leica AS10 GNSS antennas, are designed for continuous operations with low energy consumption and are rugged enough for challenging weather conditions – ideal for a bridge at altitude, exposed to the elements. Because installation on large and sensitive structures is difficult and expensive, they are also designed to be future-proof by exceeding the signal needs required today. They will still be in place when the 1915Çanakkale Bridge and Malkara-Çanakkale Motorway is completed in 2022/2023, watching over commuters and travellers for many years to come.

For more information contact the monitoring solutions specialists at Leica Geosystems.