The Yavuz Sultan Selim Bridge, designed to ease Istanbul’s traffic congestion, is a gigantic feat of modern engineering supporting Istanbul’s commercial and financial growth. Built by ICA Construction, the bridge will provide the transcontinental city with additional rail and road transit capacity across the Bosphorus Strait, the waterway that separates Europe from Asia.
Key to the bridge’s design are four enormous pylons rising more than 1,000 feet (309 meters)—the tallest of any suspension bridge in the world. The construction schedule required 8.2 vertical feet (2.5 meters) of concrete to be added to the pylons each day while gradually decreasing the width between each pylon by decimeters to adhere to the structural design. Adding further complexity to the project was the harsh environment; cold north winds, haze and humidity challenged even the most rugged workers and equipment.
Project Demands Fast, Accurate Monitoring
One of the critical demands from the engineers was for the surveying team to check for deviations on the concrete surface of the pylons as they were constructed. Time was of the essence—the construction team could not afford delays—and accuracy was paramount since any tolerances out of specification would adversely affect the next level of pylon construction.
Innovation was imperative to meet the project requirements. ICA devised a solution using the Leica Nova MS50 MultiStation, which integrates long-range laser scanning in a high-precision total station, combined with Leica Viva GS15 GNSS receivers for tight control.
“We had complete confidence in the Leica Nova MS50 and Leica Viva GS15 GNSS receivers to deliver the accurate long range measurements required on this project,” said Surveying Manager Yasar Hacieyupoglu. “The Nova MS50 is the only instrument which can scan accurately and at speed over the range required.”
Innovative Approach Keeps Construction on Track
Most of the work was carried out from three ground control points that provided a clear line of sight to the pylons and construction site. The team first established control using Leica Viva GS15 GNSS static observations, which they processed in Leica GeoOffice.
They then set up the Nova MS50 over the control points, defined the scan window, and captured point clouds measured with a density of 1 centimeter every 100 meters over a distance of 492 feet (150 meters). After collecting scan data from all sides of the pylons, the team checked vertical slices, created in Leica MultiWorx, against the design (CAD) data.
The control was monitored weekly to check for any movement. In addition, the vertical alignment of the pylons was checked using several Leica TS30 total stations. To verify the accuracy for real time as-built comparison, measurements were taken from different positions during construction.
This cutting-edge approach kept the pylon construction work on track and gave the team confidence to keep the project moving forward.
“Leica Geosystems has been a collaborative partner on this project,” Hacieyupoglu said. “The construction company ICA, the main contractor, HYUNDAI Eng. and the surveying team, ENDEM Cons, all use Leica Geosystems’ products and know they can count on the support, training and service they receive from the manufacturer and market leader.”
For more ideas on how to apply innovation to benefit your construction project, please contact us.