The Franjo Tudjman Bridge in Dubrovnik is a cable-stayed bridge at the western approach to Dubrovnik, Croatia. The original bridge design was developed in 1989, however construction was stopped at the onset of the Croatian War of Independence, during which Dubrovnik was significantly destroyed. The bridge was finally opened in 2002 and named after the 1st President of Croatia. As one of the symbols of Dubrovnik and Croatian Independence, it is also one of the first tourist attractions which tourists can see when approaching Dubrovnik by the road, sea or air.
The bridge is 518 metre long, measured between the abutments. Substructure of the bridge consists of the abutments, a pier on the western shore supporting a pretensioned girder and an anchoring pier on the eastern shore. Supported structure on the cable-stayed portion of the bridge consists of a composite girder, an A-shaped pylon and the cable stays. Overall span of the girder is 324.7 m. A total of 38 cable stays have been executed, comprising 27 to 61 steel wire cables. The pylon is 141.5 m tall, measured from the top surface of the foundations. The cable stays are anchored to the top of the pylon.
During light design development, there were numerous and very specific challenges that needed to be resolved. The first to was to fulfill all the requirements of the current and very strict law on protection from light pollution in Croatia (many experts define it as one of the most strict laws against light pollution in Europe), which included requests to protect sea flora and fauna of the Adriatic sea, therefore no light should be aimed neither reflected towards the sea, but also to not to have a light pollution towards the sky. The second was to avoid any glare towards drivers, but since the bridge is visible from all directions, even from the above (where the main passenger port for cruise ships is situated), the request was also to not to have any glare from any view direction. Therefore, a very narrow optics was used for the pylon lighting, while the horizontal line of light has a specific optics without visible dots that can cause the glare. Moreover, the specific request was to develop very powerful fixing details resistant to vibrations due to a very high level of wind in the Dubrovnik area. Dubrovnik is also in the high level thunderstorm zone, therefore it needed to be taken into account as well. Finally, the bridge occasionally has very powerful vibrations during simultaneous wind and rain conditions due to specific cables angles and structure, therefore fixing details needed to be developed and tested according to that request as well, specifically for this project. All above mentioned requests were finally resolved successfully.
Since the bridge is situated in a high level of wind and thunderstorm, a specific mounting detail is developed allowing engineers to mount and maintain the light fixtures from the walking area of the bridge. To be more specific, a custom made bracket for light fixtures which can bend like a door hinge enables mounting and maintenance by lifting up the bracket and easily handling light fixtures from the walking area on the bridge. As a result, 1011 RGBW LED light fixtures are mounted on the bridge without causing any glare towards the drivers or people for any view direction, including from the sea.
This challenging project realized by the client “Hrvatske ceste” (operator of the state roads) was finalized and opened in May 2023. Although the standard light scenario is in white colour, the complete system allows the Client City of Dubrovnik to be actively visually involved in celebrating holidays, cultural events, sport games and various events.
