Waldschlösschen Bridge

1. Task Definition

The construction of the Elbe bridge at the Waldschlösschen site is intended to pursue the goals of Dresden's transport policy to develop environmentally compatible, socially acceptable and locally compatible urban transport. In doing so, Dresden's urban traffic must fit into the historically grown as well as newly emerging urban structure, whereby it is itself involved in creating the structure. The bridge has the task of relieving the urban area of large-scale inland traffic. The bridge is not intended to accommodate regional through traffic.

The goal of the competition was to demonstrate innovative ideas for a new bridge structure in a landscape and urban planning sensitive environment. In addition, this competition was intended to illustrate that high architectural demands are to be placed on engineering structures and traffic structures, as essential design elements in the urban and landscape space.

The competition was also intended to demonstrate the importance of a new bridge structure in a sensitive urban environment.

Thus, the competition requires a feasible design that meets the functional, economic and construction requirements and deals in a convincing way with the future urban planning , architectural and landscape planning conditions as well as the existing important visual relationships.

2. Description of the Construction

The superstructure is a 636.10 m long composite bridge. The south and north foreshore spans rest on 4 and 3 pairs of V-columns, respectively, and one pair of rear struts each. The foreshore span over the Elbe River is suspended from steel arches by 2 x 8 double hangers. The spans of the foreland spans are between 30.38 and 80.16 m. The span of the arch (bearing spacing) is 140.17 m.

In elevation, the grade has its crest high point (121.901 m) exactly at the apex of the arch. It initially drops symmetrically to both sides at 0.707% and is rounded out in the crest area with H = 3550 m. In the foreland areas there are further changes of slope; the heights in the end points are 117.93 m (axis 10) and 116.66 m (axis 200).

In plan, the bridge is straight. The substructures are at right angles to the structural axis.

The headroom of the bridge increases linearly from 2.21 m at the ends of the bridge to 3.11 m at the bases of the arches (km 0+65.46 and 0-65.46). In the current field, it decreases parabolically to 2.21 m at the field center.

3. Choice of Construction Materials

Mainly structural steel S355 and higher-strength fine-grained structural steel S460 were used for the superstructure. S235 is used only for the stairs and railings. The superstructure is designed as a composite cross-section with a concrete deck slab in concrete grade C35/45 and is 37 cm thick in the deck area.

Four (south side) and three (north side) pairs of V-shaped columns are provided in the foreshore area. The stems and the short footing trusses are braced steel hollow boxes made of S355 with variable cross-sectional dimensions. In axes 65, 85, 145, 165 and 185, the hollow boxes of the V-columns are filled with unreinforced concrete C20/25 up to the lower edge of the main beams to avoid localized deformations due to ice pressure, ice impact or ship impact (at high water).

The two pairs of rear struts between the superstructure and the arch foundation (axis 100-105 and 125-130, respectively) are steel hollow boxes made of S355 with concrete filling C20/25 analogous to the V-columns. The external shape corresponds to a V- column stem.

4. Special Engineering Performance

As an engineering structure, the Waldschlößchen Bridge has to meet numerous requirements. Due to its exposed inner-city location, these are first of all an independent and pleasing design that does justice to the sensitive Elbe valley and the historic Dresden cityscape. This resulted in the requirement to design a very slender structure that, despite the large central span, still has appropriate proportions from a local point of view.

The requirement for the slender design contradicts the requirement from the point of view of shipping traffic to make the bridge crash-proof for damaged ships even in the event of flooding and also to ensure adequate safety against ice pressure. Furthermore, the structure must not have any damming effect during ice conditions.

This results in the particularly slim V-shaped supports, which had to be designed as composite cross-sections, i.e. with concrete filling, in order to be able to absorb the large loads from impact. This also results in the unusual and innovative arrangement of the bearings at the base of the V-pillars. This is the only way to ensure sufficient stability of the overall structure in the event of flooding. The specially developed spherical bearings are easy to maintain and simple to clean after a flood. They were manufactured exclusively with stainless steels.

Just like the V-shaped supports, the arch was also filled with concrete in the lower area to provide sufficient impact resistance. Only because of this and the use of higher-strength steel grades was it possible to make the arch very slender despite the large span.

The design of the arch with a V-shaped rear spur enables a particularly economical design of the structure. Here, form and function complement each other to form an optimal unit

Explanatory report by Kolb Ripke Architekten Planungsgesellschaft mbh for submission to the Ulrich Finsterwalder Ingenieurbaupreis 2015.