The long-awaited complete reconstruction of the busiest traffic artery in the Czech Republic - the Barrandov Bridge - began on 16 May. Over the next few years, it will be repaired by workers from the Bridge Construction Division at PORR a.s. From the very first day, the work has been in full swing and in the past weeks it has been possible to mill the roadway, demolish the entrance ramp from Strakonická Street or remove the bridge ledges.
The work is proceeding as it should for the time being; however, as with any demanding construction, there were several significant changes awaiting the workers. For example, when milling the bridge deck, the workers had to mill off up to 30 centimetres of the roadway instead of the planned thirteen centimetres. "It was therefore necessary to update the bridge deck leveling and composition with ultra-high-performance concrete. All related works, especially the bridge equipment, had to be redesigned," explains Martin Ředina, Director of the Bridge Construction Division at PORR.
In addition, when drilling the pier crossbars for the new prestressing cables, the workers discovered that the shear reinforcement was partially routed in a different position compared to the design specification. They had to adjust the drilling procedure quickly and proceed with great care.
It cannot be ruled out that these changes will have an impact on the traffic-limiting works on the bridge, and intensive negotiations with the construction investor are currently underway.
Concrete that will last for centuries
At the moment, the bridge is undergoing the replacement of the bridge bearings, while at the same time concrete is being poured for the deviators in the chamber of the superstructure and the crossbars are being drilled for the routing of the prestressing cables. "A new feature is the use of ultra-high-performance concrete with dispersed reinforcement, which we are using in the bridge deck levelling layer. We use it to further extend the life of the bridge - in fact, the durability of this special concrete is well over 200 years. It is extremely strong and is therefore ideal for very heavy-duty structures, which the Barrandov Bridge undoubtedly is," says Martin Ředina about the special material.
Ultra high performance concrete was developed in the 1990s with the aim of creating a material that is characterised by high strength and durability. On the Barrandov Bridge, PORR is using a modified version (UHPFRC or Ultra High-Performance Fibre Reinforced Concrete), which contains special fibres that contribute to greater tensile strength.
So, in the near future, the bridge will be levelled with the aforementioned high-performance concrete, after which PORR workers will return its equipment, i.e. insulation, abutments, ledges, drainage, railings, etc.
Work on the Strakonická ramp in full swing
Work on the Strakonice ramp is also an integral part of the reconstruction. Here, the new pillar heads have already been concreted, new bearings have been fitted, the planking wall has been concreted and the bridge deck support structure and formwork have been installed. Here, too, work is in full swing and is proceeding according to schedule. In the next few days, the ramp will undergo the concreting of the supporting structure, followed by the construction of the cornices and bridge equipment, i.e., as with the bridge itself, the insulation, drainage, roadway structure, abutments and railings will be delivered.
