St Philips Footbridge
The design of this 50m-span and 4m-wide footbridge provides an appropriate solution to a complex crossing problem in central Bristol: the connection of two river banks of the River Avon with a significant difference in elevation, appearance and architectural quality. One of them has a Victorian masonry wall as a boundary and the other a green slope. The former will be immediately developed to high architectural standards while the latter is expected to be a linear river path constrained by an industrial area for some years.
The bridge is steel beam with a forked geometry, hosting a ramp for disabled users and cyclists and a staircase as part of its own structure to maximise functionality. The design approach to generate its shape was at the same time structural, aesthetical and functional. The bridge is compact, simple, elegant, innovative and clearly legible for both footbridge and river path users.
Knight Architects’ scope included the alternatives analysis, conceptual design and architectural input during developed design, planning application, detailed design and construction stages. Construction started in August 2017 and was completed in May 2019.
PREMIER CONSTRUCTION MAGAZINE spoke to Project Architect Héctor Beade from Knight Architects to find out a bit more about the project.
Was there a brief for the project?
“The brief provided by Bristol City Council defined an approximate location for the bridge and requested an accessible shared pedestrian and cyclist route with a width of 4m. Design was fully free and we developed it in close communication with the council. It was clear from the early stages that the common design aspiration was for a simple and elegant bridge that, when it is seen in front of the other two bridges in the area, is clean and legible.”
The design is quite different to what you would imagine a bridge to be. Was that done on purpose?
“The design is a consequence of the numerous constraints that we were presented with and our aspirations regarding the appearance of the bridge. It is very different to any of the bridges we have designed before and a result of the combination of functional, structural and aesthetic requirements and aspirations.”
Can you tell us about the design in a bit more detail?
“The bridge character comes, to a great extent, from the Y shape geometry of the bridge, probably its most unusual aspect. This was a consequence of the very limited space available on the eastern bank, both in terms of design arrangement and accessibility for construction. This site is expected to change over time, as is the space availability. We aimed for a design that is appropriate in the current context but can also take advantage of the improvement of the public space when the site changes. The bridge ramp that creates one of the fork branches is positioned where the river path widens, the most convenient location in the current scenario. The other branch is a staircase, as part of the bridge structure that is functional nowadays to go north and, moreover, will become fundamental when the area is redeveloped to provide a useful east-west connection. We wanted for the bridge geometry to be clean and bold because it is located near two other bridges so if it was transparent, it would get lost between the other bridges.”
Were there any special requirements taken into account during the construction of the bridge?
“We couldn’t have any supports in the river, temporary or definitive, to avoid environmental impact, so we had to be able to do everything in a single span. Also, we had to take in to account what materials could be used, because the maximum weight of the bridge was limited so it could be installed in a single crane lift. Steel was the natural choice to have a lightweight and structurally robust structure.”
What was the project like for you to work on?
“I have been working in this industry for 20 years and, although this is a project of a relatively small scale, it has been one the most complex designs I have been involved in, due to the number and nature of the constraints that we needed to meet at the same time.”