"Urban waterfalls" protect metro access, resist truck collisions
April 4, 2014
Exposed street escalators in Bochum, Germany, have been given a new lease of life with clever shelter designs by Despang Architekten. Described by the architects as "urban waterfalls," the seemingly simple shelters had to be tough enough to withstand the impact of a large truck, while presenting an elegant glass entrance to the underground metro. A series of metal supports covered in glass sheets allow rainwater to cascade over the sides, producing the waterfall effect. The ribbed steel structure also protects against vandalism.
The escalators were installed on either side of a busy street in the 1970s and, as in many European cities, they were left open to the elements. A recent look at repair bills inspired a re-think of all the metro-stop escalators.The brief called for some protection against bad weather but any structure had to have a barrier to guard against traffic accidents, including the maximum impact of haulage vehicles.
Instead of resorting to massive concrete walls or bollards, the architects designed a low concrete barrier, covering a network of steel rebars. However, the roof and street-side wall of the shelter are glass sheets. These were fitted over a structure of thin steel ribs that look rather delicate but actually provide significant protection from impact. The structures were completed by Despang partners based in Germany and Honolulu, Hawaii.
Vandalism and maintenance
The ribs also allow for transparency, but glass on a public structure is always susceptible to vandalism. As a solution, the glass wall was placed behind the steel ribs so it is only accessible in narrow sections from the outside, making it unlikely that it could be easily damaged. The exposed side of the glass panel faces the upward-moving escalator, so travelers only have contact with a small section of glass as they arrive at street level.
The other key aspect of any urban street project is maintenance. Rather than include gutters that could become clogged, the simple sheet-glass design allows rainwater to flow over the roof and down the side wall. As much as it makes the structure almost maintenance-free, the resulting "waterfall" was something the architects felt added to the positive aesthetic . As the project architect lives mostly in Hawaii, he also compares the effect to "being inside a wave," not an experience many of us have had on urban streets.
The architects felt that the structure should do more than meet a functional requirement, which is why the combination of fine steel ribs and glass was chosen over a more solid or simply open form. In addition, the ribs are painted blue on one side, which adds dimension to the design and changes the effect of the lighting at night. The 50/50 transparency and opacity effect created by the alternating ribs and glass eases travelers from the dark underground to the bright street in daytime. The lighting scheme was likewise calibrated to help users transition from the brightly-lit underground to the darkened street, without blinding them.
The city of Bochum is likened to Detroit in the US. Formerly the home of large-scale automobile manufacturing and steel works, it has been in decline since the car industry moved elsewhere. The new, steel-based, metro shelters are part of a larger scheme to improve the urban fabric of the city.
Source: Despang Architekten