Pedestrian bridge with cycle path over the oil terminal harbour, Raunheim
The new white oil terminal bridge is an elegant, curved structure. It spans the 70m wide entrance to the oil terminal harbour in Raunheim with a spiralling access ramp. This sculptural bridge design stems from Frankfurt architects schneider+schumacher. The clients for the bridge appointed Schüßler-Plan as structural engineers.
The bridge’s location is, on one hand, influenced by the industrial character of the harbour, and on the other, by the River Main that runs parallel to it, with its attractive embankment and mature trees. The bridge will primarily be used by cyclists and pedestrians. The location of the bridge so close to the harbour’s storage tanks was of particular concern at the design stage. The oil depot is used for the transfer and storage of highly flammable substances. For this reason, the bridge had to be designed to prevent people on the bridge gaining access to the passing tankers, or at least to make it difficult.
In view of these exacting circumstances, a solution was developed that not only fulfils all the safety requirements, but also takes into account the specific location of the bridge on the River Main. The objective was to emphasize the bridge’s leisure use, and above all to provide unobstructed river views from the bridge despite all the safety issues. “A swiftly-rendered stroke of a paintbrush, connecting the two sides of the Raunheim oil terminal harbour” is how Prof. Michael Schumacher (architect and owner of the practice) describes the design approach. The combination of design strategy and safety requirements has resulted in a bridge with an elegant, curved and sculptural form.
The construction, with a total length of approximately 170m, consists of a continuous five-part girder, which allows some 70m to be spanned at the harbour entrance. Viewed from above, the bridge appears as a lightly undulating S-shape, which, at its north end, culminates in a circular access ramp: a 14-metre spiral, constructed of white concrete. On the side facing the oil terminal harbour, for security reasons, the ramp becomes a gently curving white wall, thus fulfilling the stringent safety requirements. By contrast, towards the River Main, the bridge opens up to allow unobstructed views of the river.
The lower semi-circle of the spiral consists of a modified retaining wall that develops effortlessly from the geometry of the steel structure above. The double axial curvature of the steel bridge is continued into the adjacent concrete wall. The crossed steel tube supports carrying the bridge are firmly connected both to the bridge and to the foundations, forming a monolithic structural entity. These load-bearing bracing elements are designed as stiff, forked components. The real clue of the design however lies in the cross-section chosen for the bridge: an L-shaped hollow steel box. On one side the vertical wall rises up to a height of 2.8m above the walkway, providing the required shielding towards the oil terminal. On the other side, facing the river Main, the bridge structure extends horizontally up to 2.5m beyond the line of the parapet, serving as protection. Additionally, the parapet arrangement, with its filigree netting made of stainless steel, slopes inwards in order to keep pedestrians away from the bridge edge. These measures are regarded as adequate to minimise the risk of a source of ignition occurring over the oil terminal harbour entrance.
The bridge fits elegantly into its surroundings. Both its colour and shape create a subtle connection to the harbour context: the white edifice matches the white of the tankers hulls lying in the oil terminal harbour. Moreover, the homogeneous white gloss paint reflects the water under the bridge, visually anchoring the bridge in place. The bridge’s surface material is derived from the dark asphalt leading to it, making the transition to the bridge clearly visible, and emphasising the contrast of light and dark of its curved form. The oil terminal harbour bridge was opened to pedestrians and cyclists in May 2013, a year after building work commenced.