Developing a bridge proposal for a major Adriatic bay crossing rarely allows engineers to rethink structural typologies from first principles.
The Kaštela Bay Bridge competition in Split offered one of those rare opportunities.

The new bridge across Kaštela Bay represents one of the most ambitious infrastructure projects in the Split metropolitan area, creating a direct connection between Split and Kaštela while forming a new landmark across the Adriatic landscape.

After examining a wide range of conventionally applicable bridge typologies, we developed an alternative structural concept based on a sinusoidal wave of alternating arches integrated with a continuous multi-span girder bridge. One of the key constraints of the competition was the unusually high position of the bridge deck. With a navigation clearance of approximately 55 m, the structure inevitably becomes a dominant element not only in the skyline but also when viewed from below.

Many conventional bridge typologies leave this lower spatial experience largely unresolved. In our proposal, the alternating wave arches intentionally shape the underside of the bridge, creating a spatial rhythm that remains legible both from above and from the water. The wave-arch system combines the efficiency of a girder bridge with the stiffness of an arch. The orthotropic steel box girder carries the traffic loads, while the alternating arches act as upper and lower stiffening ribs, reducing stresses and enabling longer spans with a slender structural profile. The proposal extends structural ideas we have already tested in smaller realised bridges into a far larger metropolitan scale. The submitted scheme was developed as a 1,592 m crossing with 13 spans and a 280 m main span.

The concept was also supported by a clear construction strategy: the split pylons allow the two approach bridges to be incrementally launched from both shores, while the elements of the main span could be erected using a light temporary lifting structure.

The resulting silhouette forms a dynamic line across the water, echoing the rhythm of the Adriatic waves and the surrounding mountain ridges while maintaining structural clarity and efficiency. With its simple structural language and restrained elegance, the bridge could have become an integrated element of the landscape of Kaštela Bay.

We believe this structural idea deserves further exploration and look forward to advancing it further in future bridge projects.