Romania’s important bridge project

Romania’s important Braila Bridge project will deliver a key crossing spanning the Danube River
Road Structures / October 5, 2022
By Mike Woof
© Daniel Chetroni | Dreamstime.com
© Daniel Chetroni | Dreamstime.com

The new Braila Bridge link in Romania will provide a much-needed transport connection, replacing the current ferry service and reducing journey times for drivers.

The link has been discussed for some years, with the first studies for a bridge in the area having been carried out in 1986. The pre-feasibility study was carried out in 1996, with the final feasibility study having been completed in 2016 by ISPCF, EDIN, STE and Pegaso Ingegneria. The contract was awarded in 2017 to the Italian/Japanese joint-venture team Webuild (formerly Astaldi) - IHI Infrastructure Systems , with construction work commencing in 2018 by now renamed Webuild and its Japanese partner IHI,

An innovative anchor block design has been used for the bridge
An innovative anchor block design has been used for the bridge

Located close to Romania’s borders with Ukraine and Moldova, the new bridge runs approximately east-west and will provide an important connection for the E87 route, providing a key future link for passenger vehicles as well as heavy trucks. It will carry the planned Dobrogea Express (DX8) route, linking the town of Braila in Braila County at its western end with Smârdan in Tulcea County on the eastern side.

Construction of the bridge is costing around €400 million, with some 75% of the budget being provided by the EU while the Romanian Government is sourcing the remaining 25%. Meanwhile, the Romanian Road Authority (CNAIR) is the client for the project.

The location of the bridge spanning a busy waterway dictated the type and design of the structure to a large extent. Alessandro Minniti is project manager for Webuild on the Braila Bridge project and he explained that a suspension bridge was considered from the outset as being the most suitable solution for a number of reasons. The key issue was that the client requested to have a main span roughly equivalent to the width of the river to maximise the navigation channel.

The River Danube is the second longest river in Europe (after the River Volga) and is a busy waterway, being navigable for 2,415km of its 2,850km length and used for river vessels of all types.

No towers could be built in the middle of the river as they would have hindered traffic and been at risk of being struck by the many passing vessels. This ruled out the possibility of using a cable-stayed design for example, as the main span could not have been constructed with the necessary width of around 1km. Building a suspension bridge was the only solution and Minniti said, “It was a clear request from the client and it was not possible for the contractor to propose another kind of bridge.”

he anchor blocks are massive and will provide security for the structure during its working life
he anchor blocks are massive and will provide security for the structure during its working life

The contract was signed in late 2017, with work on the design commencing in the second quarter of 2018. Construction was to have taken three years, but the project was delayed for a number of reasons. Minniti commented, “In the meantime we delivered the design a bit earlier and we got the commencement for construction in December 2018.”

The bridge and some access roads should be ready for traffic by late 2022, with the remaining access road connections expected to be completed in 2023. However, the discussions over the terms of the agreement between the client and contractor have not yet been concluded so the actual completion date has still to be finalised.

On the west side of the River Danube where Braila lies, there are 4.5km of access roads being built to link with the bridge. On the east side of the river close to the town of Jijila, there will be 12.5km of access roads constructed and 4.5km of road will be a link heading immediately south to connect with the E87 route. Out of the total 23km of roads a section of approximatively 12km (including the suspension bridge) should be ready by the end of 2022. The remaining 11km will be for a new stretch of road heading eastwards and which will also link to the E87 route and this should be finished by the end of summer 2023. The bridge and link road project forms part of the Operational Programme for Large Infrastructure for Romania (POIM).

The suspension bridge is just short of 2km in length at 1,974m, while it features a main span of 1,120m. Minniti commented, “It’s not symmetrical.”

On the west side, there is a 490m side span leading to the main span while on the east side the side span measures 364m. Meanwhile, the tops of the towers are 192.64m above sea level.

The deck segments have been hoisted into place
The deck segments have been hoisted into place

Where the bridge is being built, the navigation channel is 180m wide. Allowing sufficient clearance for vessels to pass underneath was a key issue for the designers. But even at the highest river level recorded in the last 30 years, there would be around 39-40m of clearance according to Minniti and easily sufficient for the comparatively low profile river vessels.

Strong base

Although the eastern bridge tower sits at the edge of the river, it is well out of the navigation channel. Where it has been constructed, the river is very shallow and this means it is protected from impacts from any large vessel. However, the project team has ensured the safety of the structure and Minniti added, “It has been calculated to resist the impact of a boat, even though it’s outside of the navigation channel”.

Each tower sits on 76 piles measuring 1.8m in diameter, providing a very solid base for the structure. On the Braila side in the west, the cast in-situ piles have been bored to depths of 45m, while on the eastern Jijila side the piles have been driven to depths of 40m. A special high-resistance concrete developed for underwater conditions has been used for the construction of the bridge foundations.

Two segments have been delivered at a time from the shipyard on barges
Two segments have been delivered at a time from the shipyard on barges

A novel feature of the project has been the construction of a coffer dam around the base of the tower on the eastern side, allowing the contractor’s personnel to work in entirely dry conditions. This aided the construction operation considerably.

The diaphragm walls around the anchorage blockbases measured 35m deep and are now filled with 40,000m3 of concrete, weighing around 100,000tonnes each.

But during construction, the high water table even on the west side (a short distance from the riverside) presented a challenge, while the cofferdam on the east bank was located in the river. In all, 26 pumps were required to take water from the coffer dams, removing around 8,000litres/min of water from either side of the river, a total 16,000litres/min in total. However, this was an important factor according to Minniti and he said, “The big challenge was to work under safe conditions and that’s why we used this water pumping system.”

The pumps were powered by generator, with spare generator power ready on hand as a back-up system just in case.

Steel

Most of the steel used in the bridge has come from a local supplier in Romania and a high resistance steel with good weldability has been used for the deck sections. Only a small number of steel components for special tasks, such as the saddles for the cables or the reinforcement of the steel deck segments (U-ribs), have been manufactured in Italy. The wire for the cables meanwhile has come from  Japan.

Raising the deck segments into place has required careful precision working
Raising the deck segments into place has required careful precision working

The anchor blocks for the cables are massive according to Minniti and he said that a highly innovative design has been used for these. The upper side of the anchor blocks will form part of the carriageway. At the same time, there are separate expansion joints for the main span and the access viaducts, with these being located on either side of the anchor block. Minniti said, “We made the decision to use the concrete slab to separate the two expansion joints.”

The design of the anchor blocks features two chambers, with an upper and a lower area. Meanwhile, the cables are splayed into 16 strands and secured with anchorage plates. Each of the 16 strands in the cable is then composed of 544 galvanised wire strands, which measure 5.38mm in diameter. With nearly 9,000 wire strands for each cable, these measure up to 58cm in diameter. Webuild estimates that around 38,000km (almost earth’s circumference!)  of the 5.38mm diameter wire has gone into the cables for the bridge, while the design uses around 6,800tonnes of steel.

Special wheels ran back and forward to construct the cables, installing two strands at a time. The cables were then compacted to reduce the voids in between. Once this process was complete, more strands were then wrapped around the cables and these were galvanised again to provide additional protection against corrosion.

Working from the middle, two deck segments have been installed each day to ensure the load remains balanced
Working from the middle, two deck segments have been installed each day to ensure the load remains balanced

As it is not possible to access the internal wire strands, the joint venture team is installing a dehumidification system that will extract moisture and ensure that the humidity level inside the cables is less than 40%. Corrosion develops when moisture levels are between 50-60% and Minniti explained that this dehumidification system will ensure that it is impossible for corrosion to form in the cables. This will ensure that they retain their full strength for the life of the structure and the bridge is being built with a 120-year working life.

The design of the saddles used at the top of the towers is novel according to Minniti. The cables enter grooves cut into the saddles, which were machined from a special grade of steel. He said, “The cables cross the saddles and they basically transfer the load to the saddles and towers.”

The saddles were manufactured by a specialist firm in Italy from massive single pieces of steel, each weighing 5tonnes. Minniti commented “There are very few companies in the world that could manufacture the saddles.”

Deck design

The deck sections have been manufactured at a former shipyard facility close to Braila and located just 5km from the bridge construction site, providing employment for locals in the area. Most of the steel for the bridge has also come from a local works at Galati, just 25km to the north and again helping employment in the area. Minniti commented, “That made everyone happy, the client, the engineers and the Romanian Government.”

The cables are made of wire supplied by IHI © Cateyeperspective | Dreamstime.com
The cables are made of wire supplied by IHI © Cateyeperspective | Dreamstime.com

Having the deck sections and steel supplied locally has been a significant benefit for the joint-venture partners, allowing the engineering team to ensure quality standards have been optimised. “Inspections could be done easily,” Minniti said. With both the shipyard and the steel facility located on the river, this eased the transport of components and materials. Deck sections/segments could be transported by river.

The bridge deck is composed of 86 segments in total, of which 72 are standard units measuring 3.2m thick by 32m long and 25m wide. The largest sections weigh up to 360tonnes apiece, although the majority are in the 150-160tonne range. Minniti estimated that the bridge deck weighs around 21,000tonnes in total.

The segments for the bridge decks were transported along the river by barge from the shipyard to the bridge. To build the side spans of the suspension bridge, the sections were unloaded from the barge to the ground, moved to the lifting position and finally lifted. The special segments around the towers have been assembled on the ground and welded together, then raised into position in massive sections weighing over 1,000tonnes on both the west and east sides.

BridgeInstalling the deck segments for the main span was more complex however. These were raised one at a time from the barges and fixed in position, suspended from the cables. To balance out the structure, two segments were raised every day so as to ensure the weight was evenly distributed between the towers.

All of the segments have now been raised into position and the joint-venture team has been welding these together, a task that should be complete by the end of September 2022. Once this is complete, the waterproofing job for the deck can be carried out, followed by installing the asphalt running surface.

Dehumidification systems are installed for the steel deck sections also, as well as for the anchorage blocks. The bridge features two lanes in either direction, as well as a walkway on either side plus a maintenance walkway in between.

Once this landmark bridge is complete, it will make a major contribution to Romania’s transport network and will reduce journey times as well as transport costs. When complete, the bridge will allow journey times of just two minutes across the River Danube, compared with 45 minutes at present using the ferry service.

The suspension bridge and its connecting roads form part of the Rhine-Danube Corridor of the Trans-European Transport Network (TEN-T) and will form an important international link for Romania. The bridge is located around 95km from the River Danube Delta and around 8km from the centre of the city of Braila, which has a large commercial port handling medium-sized ocean-going vessels.

For more information on companies in this article
gradeWebuild