Puente de Vidin-Calafat

Overview of the New Danube Bridge Project

Introduction to the Project

• The new bridge over the Danube between Bulgaria and Romania was selected in 2006 by Bulgaria's Ministry of Transport through an international tender.

• FCC Construcción was awarded the design and construction contract, which included two railway stations for passengers and goods.

Importance of the Bridge

• The bridge connects Vidin (Bulgaria) and Calafat (Romania), playing a crucial role in linking the Pan-European transport corridor from Germany to Turkey.

• It is notable as the second bridge over a 650-kilometer border between Romania and Bulgaria.

Construction Timeline

• The contract was signed in March 2007, with construction starting in November 2008 and completion by late 2012.

Technical Specifications of the Bridge

Design Features

• The bridge spans 1,791 meters with a unique asymmetric deck design featuring two outer lanes for vehicles totaling 15 meters wide.

• A central railway platform measures 6 meters wide, accommodating pedestrian traffic and bicycles, resulting in an overall width of approximately 31.35 meters.

Structural Components

• The structure is divided into three distinct parts: access bridges for railways totaling 772 meters, non-navigable river sections at 646 meters, and navigable canal sections at 745 meters.

Engineering Details

Materials and Construction Techniques

• Non-navigable section features a central box girder made from prefabricated concrete segments measuring up to 215 meters long.

• Each segment is supported by eight concrete piles with variable heights up to 20 meters.

Navigable Canal Section

• This section includes three main spans with lengths varying from 115 to 180 meters, supported by four concrete piles ranging from heights of 39 to 45 meters.

Safety Measures and Equipment

Impact Protection Systems

• Each pile incorporates protective elements against ship impacts using precast concrete pieces weighing between 85 to135 tons secured through pre-tensioning methods.

Construction Infrastructure

• FCC established a machinery park three kilometers downstream for efficient production including five lines for manufacturing segments necessary for construction.

Construction Challenges of the Danube Bridge

Geotechnical and Environmental Considerations

• The concrete used for the bridge has a resistance between 50 and 80 megapascals, varying by location, particularly in the foundation over the Danube, which posed significant challenges due to incomplete geotechnical information.

• A major issue was the water level variation of up to 11 meters between low and high flow periods, necessitating extensive surveys for explosives or sunken ships in the area.

• Pile drilling utilized bentonite mud with a casing thickness of 12 mm and variable lengths from 12 to 35 meters; excavation involved a recirculation process lasting 2 to 3 hours depending on pile length.

Foundation Construction Techniques

• The foundations for non-navigable piles were constructed within a circular cofferdam measuring 25 meters in diameter, requiring prior construction of an access peninsula.

• Deep navigable piles (up to 80 meters) were installed using pontoon-mounted equipment, complicating execution maneuvers significantly.

Concrete Formulation and Pouring Process

• A notable achievement was developing concrete formulas with 450 kg of cement that maintained workability for up to 34 hours, ensuring optimal conditions during pouring.

• Non-navigable channel piles were poured in one phase with a volume of 640 cubic meters; navigable channel piles required two phases totaling approximately 2,350 cubic meters.

Impact Resistance Features

• Defenses against ship impacts were prefabricated nearby and transported via river using heavy lifting equipment designed specifically for this purpose.

• The defense system included three levels of concrete spikes created on-site, forming a robust impact-resistant block structure.

Structural Innovations

• Navigable channel heads feature solid caps supporting spherical bearings; lateral solid pilots (22 meters tall), crucial for tension support systems developed by BBR, are integrated into this design.

• An innovative aspect is that pre-tensioned tubes prevent typical tension oscillations when cables pull in opposing directions—critical for elements difficult to replace.

Assembly Techniques

• Connections between struts and deck sections involve complex on-site cast diaphragms requiring precise formwork assembly due to their intricate nature.

• Dovetails arrived via road transport and were positioned using self-launching equipment; each weighed up to 100 tons with about 300 units placed sequentially over each pile.

Final Assembly Steps

• After placing dovetails on each pile, hydraulic jacks repositioned complete segments before executing closure pours on-site followed by final internal pre-tensioning.

• Exterior deck sections were also constructed on-site using sliding carts supported by the central box girder across two phases extending from central connections outwards.

Engineering Complexity

Construction Process of a Major Bridge

Assembly and Installation of Structural Elements

• The assembly process involved pre-tensioning the vertical head of the pile after placing eight additional elements, followed by repositioning the entire structure using four 1700-ton jacks.

• A mobile lifting cart was installed to handle the remaining segments, with each pair of segments taking approximately 16 hours to lift, while the complete cycle for placement took between 3 to 4 days.

• The installation process included anchoring one side of a segment, applying resin on the previous segment's surface, and temporarily joining them with pre-tensioned bars before finalizing connections.

• Once concrete reached sufficient strength, tensioning was performed from within the deck using independent wing cars to ensure stability and alignment during construction.

• A prefabricated element measuring 318 meters was suspended between two sections for closure, with in-situ work done to ensure proper geometry and connection.

Finalization and Quality Control

• The completed section measured 52 meters in length and utilized a jack system for controlled descent to connect with prefabricated deck segments.

• Complex expansion joints were designed for both road and rail sides due to high-speed train requirements (160 km/h), particularly challenging on the Bulgarian side.

• This bridge is noted as one of the largest globally, showcasing impressive dimensions alongside functionality, robustness, quality, and aesthetic appeal.

Engineering Excellence by FCC Construction

• FCC Construction has successfully maintained a strategic transport route exceeding 2000 kilometers from Germany to Turkey through this project.