MARIBOR ISLAND BRIDGE, SLOVENIA

Abstract

The new footbridge at the Maribor Island crosses over the Drava River in the most minimal way and attempts to preserve the natural landscape of the riverside area as much as possible.

It seeks a subordinate position next to the cultural monument of the Maribor Island Power Plant. The footbridge is designed as a three-span inverted Fink's truss, with spans of 164 m + 117 m + 13 m and with bearings and dilatations at the end abutments.

The footbridge design would become the longest span of its kind in the world.

Architectural Concept

The design of the footbridge attempts to preserve as much as possible the natural riverside landscape and minimise visual intrusion into it. Its light form, which almost blends in with its surroundings, is not impotent and emphasises the importance of the historical hydroelectric power plant.

In designing the new footbridge, we sought to find a balance between efficiency, economy and elegance by using an inverted Fink truss. The combination of the three represents an alternative to many anonymous, often uninteresting designs, which frequently take into account purely technical and economic criteria.

Based on the given circumstances and the requirements of the terrain, the inverted Fink's truss was carefully designed and positioned. A triangular structure dominates the entire length of the footbridge, which is spanned between three supports, on both banks of the Drava river and on Maribor Island.

Materiality, durability and rationality

A steel structure is foreseen - a box girder to which are attached steel crossbeams, under each mast, made of polished stainless steel. The crossbeams are connected by pre-tensioned turnbuckles. The flooring is made of aluminium profiles with a ribbed walking surface. The steel profiles of the railing are connected by stainless steel rope. The handrail is in bleached heat-treated wood and a linear led light is installed underneath.

The choice of materials is dominated by the consideration to make the components of the new footbridge as discreet as possible in space.

Landscape

Although the competition area extends over the semi-urban part of north-western Maribor, both banks are predominantly natural and wooded. The banks are covered by a mixture of classical riparian vegetation and mixed riparian forests. The typical riparian vegetation consists mainly of numerous willows and alders, in some places also dodder alder. The mixed riparian forest consists of oak, hornbeam, sycamore, blackberry and other characteristic species.

The bridge minimally disturbs the existing riparian area. On the left bank A small viewing platform is provided along the footbridge. In all three locations where the new the footbridge meets the existing terrain (left bank, right bank, island), as part of the construction of the footbridge and the viewing platform, the area will be landscaped by planting native peripheral shrub and tree vegetation.

This consists of the following species:

• White willow Salix alba;

• Willow Salix caprea;

• Black alder Alnus glutinosa;

• Populus tremula.

Due to the natural riparian nature of the site and the abundance of native pioneer plants, the site will be after the intervention, will develop in a very short period of time into the climacteric phase of the current bypass community.

Optimal management of pedestrian links and cycle traffic

Cycle and pedestrian traffic shall follow the shortest route across the river and the longitudinal gradient of the traffic surface. Cycle traffic is positioned on the downstream side, giving pedestrians an unobstructed view of the power plant facility. Due to the levels of the access angles, the access ramp is designed 3.5% in the embankment on the right bank and 3.5% in the embankment on the left bank. On the right bank, an out-of-level crossing of the footbridge and the existing riverside path is designed, thus almost equalising the height difference between the left and right banks. The elevation of the footbridge junction on the right bank suggests the possibility of a shorter connection from Limbus to the Drava cycle path.

The functional management of cycling and pedestrian traffic is partly organised by the central arrangement of the masts and the longitudinal grid in contact with the walkway surfaces.