Introduction
In recent decades a series of spectacular structures have established the pedestrian bridge as a genre all of its own within the broader field of bridge construction. Built in the most diverse locations, in cities, parks and landscapes, across streets, railways, rivers or canyons, these bridges’ striking constructions, interesting trajectories, welcoming qualities and often sculptural appearance are astonishing. Pedestrian bridges have long led a marginal existence and we have only gradually become aware that they could be more than purely functional structures. Pedestrian bridges must of course primarily be functional, but they should also engage with a site’s unique features, its routes, topography and context. Their presence in public space offers not only the potential to connect separated spaces, but also to give a place its own identity. During 19th century industrialisation, rolled girders revolutionised bridge building and cost-effective serial structures were developed, meaning that other aspects faded more and more into the background. It was only later that increasing technical progress successfully counteracted this development. There are fewer restrictive functional and static demands on pedestrian bridges than there are on road and railway bridges. They therefore give designers the necessary freedom to react to a bridge’s site and uses and to develop bespoke solutions. Seating, niches, platforms or beautiful views on some bridges can thus be especially welcoming, inviting pedestrians to linger there. The master builders of the antiquity laid the foundations for bridge construction by developing the load-bearing round arch. They created audacious technical masterworks and succeeded in building imposing bridges with large spans, which 6
were funded by ambitious clients whose names remain inseparably linked with the bridges. The situation is no different today: an ambitious planner needs the backing of a committed client to achieve a successful result. Only then will they achieve their shared goal of creating something beautiful as well as useful. Highly complex projects in particular – whether structurally or organisationally complex – run an increased risk of encountering unexpected problems; they require a high degree of cohesion and the willingness of all involved to overcome very difficult phases of the project. Successful structures rarely result from the work of one individual; they require committed and motivated clients, planners and contractors. Interdisciplinary collaboration between architects and engineers is also important in bridge construction – to a different extent than is the case in other civil en gineering projects. Engineers need to engage intensively with the structure’s design as well as with the purely economic and structural aspects in developing support structures. They must think in terms of variations and justify decisions made from the complete range of possibilities, penetrating and understanding the context. These skills used to be – and still are – inadequately taught in engineering training; this inadequacy can be seen in some small and medium span bridges. Architects must engage with a bridge’s urban context, its formal language and the arrangement of its details. A high degree of sensitivity to design is essential in creating a good pedestrian bridge, especially if it is to be installed in a central urban area or special landscape. Architecture is indivisible, so it relies on a respectful and trusting discourse between the two disciplines; an approach
that is free of vanity and remains focused on the design, allowing everyone involved to join forces to develop good, beautiful solutions. Many outstanding structures – especially pedestrian bridges – prove that this discourse is already ongoing in some areas. Many of the pedestrian bridges portrayed in this book have been developed in competitions by architects and engineers working successfully together and complementing each other. The often daring constructions of the ntiquity did not rest on any particular a methods of calculation. Their construction was based on empiricism and painful experience and often cost many human lives. Only at the end of the 16th century did Galileo Galilei formulate the first principles of structural engineering and lay the foundations for scientific structural engineering, which was further developed by mathematicians such as Isaac Newton, Gottfried Wilhelm Leibniz, Jacob Bernoulli and Leonhard Euler. This represented a decisive step away from craftsmanly, empirical and intuitive bridge building to more precisely calculated engineering and technology-based construction. In today’s digital era, computer programmes can be used to very quickly carry out parameter studies, optimising a structure’s design so that ideas can be quickly confirmed or discarded. Computer programmes can also precisely calculate a structure’s dynamic behaviour. Synchronisation phenomena, which have recently occurred in various bridges, can be simulated, their causes and effects and the effectiveness of measures taken understood. This is an essential prerequisite for the construction of light and filigree pedestrian bridges. Furthermore, the computing capacity available today leads some planners to