Positioning pile cap concrete deck

Situation

The Peljesac bridge is a bridge currently under construction in Croatia. The purpose of the bridge is to achieve territorial continuity of the Republic of Croatia; namely, by connecting the southern exclave comprising the bulk of Dubrovnik-Neretva County with the remainder of the Croatian mainland. It will be a Cable-stayed bridge with a total length of 2,404 meters, a width of 21 meters and a clearance below 55 meters. The longest span will be 568 meters. The two pylons would be 115 meters above the road deck, 170 meters above sea level, and 240 meters above the seabed. The beam part of the bridge will consist of 14 smaller pylons (7 from Brijesta on Pelješac side and 7 from Komarna on Croatian mainland side), each built 180 meters apart, with a span of 180 meters. Longest pylons are 128 meters.

Challenge

The construction of the bridge was assigned to China Road and Bridge Corporation. After installation of the bridge pylons, CRBC needed to position the pile cap concrete deck 2.5 meters under sea level. In order to do that, the complete seabed construction had to be lifted with 1000 barge crane lifting steel platform above pylons equipped with Holmatro hollow plunger cylinders to create final positioning of the concrete deck to ensure vertical and horizontal leveling. Total lowering done by Holmatro hollow plunger cylinders is 6.5 meter.

Solution

To support the pile cap concrete deck, Holmatro developed 40 double-acting hollow plunger cylinders, each with a capacity of 100 tonnes. The stroke of cylinders was used to position and lower the concrete deck 2.5 meters under sea level. All cylinders were controlled simultaneously by a 230V Vari pump equipped with Holmatro Flow panels. The accurate needle valves of the Flow panels allowed the customer to control each lifting point consisting of 4 – 6  cylinders - with a maximum tolerance of a few mm between 40 lifting points. To put each Pyle into the center of pile cap CRBC is using 10 pcs Holmatro general purpose cylinders HGC series with a PA 09 H2 hand pumps equipped with pressure gauge and needle valve.

How does it work?

1. The prefabricated concrete deck will be onshore prepared, this is the bottom part of the bridge pile cap. 
2. The working platform (blue steel construction) will be placed on top of the concrete deck in combination with the foam work.
3. The steel platform is equipped with Holmatro hollow plunger cylinders (HHJ100H20) which have a steel bar going through the cylinder. They connect the concrete deck with 40 connection points between the steel platform and concrete.
4. The construction will be placed with a 1000t. crane on a barge over the drilled steel piles in the seabed.
5. The final lowering of 6,5 meters is done by using Holmatro hollow plunger cylinders which are equipped with the steel bar and two nuts. The plunger will be extended and upper nut will be fixed on top, the lower nut we will release from underneath support frame to lowering can start. After the plunger is completely in the underneath nut it will be fixated and the next lowering step can start.
6. When they reach the final position of the bottom part of the pile cap they take out the crane steel platform with cylinders and build up formwork around the pile cap to make something like a dry pool that they are able to fill with additional construction steel and concrete. When the steel platform is free they go forward with the next pile cap and make the same operation from the beginning.