This design for a series of foot, cycle and equestrian birdges over the HS2 railway is based around a carefully composed and detailed warren truss: an efficient and well understood structural approach that in this case has been developed with a close appreciation of detail, material quality and visual transparency.
The key considerations of user safety and structural efficiency coincide in this design: the cross-sectional height of the truss has been determined in response to the requirements for bridge user protection and containment. With the truss structure predominantly located above deck level also forming the containment provision the overall height of the bridge, and hence impact on the wider landscape, has been minimised. Minimising the structural height in this way leads in turn to a maximum span of just over 40m, matching the requirements for spanning many of the HS2 cuttings.
A slender ‘blade’ form to the primary members ensures that they present a narrow face to the deck and maximise the opportunity for views from the structure and along railway cuttings. The articulation also serves to give the bridge a distinctive and elegant appearance from the footpath approaches: the alternating thick and thin lines of the diagonal members combine with the tilted top and bottom chords to animate its appearance, especially in oblique views where the appearance of the truss is similar to a zig-zag line drawn with a chisel pointed calligraphy pen.
“Safety is always paramount, however accessibility and transparency were also the key design drivers for these bridges – characteristics one wouldn’t always associate with railway overbridges. The design team looked at how we could make the bridge approaches and the landscape around them completely accessible to create a seamless user experience for all, whether travelling on foot, on bike, on horseback or with any type of mobility aid.
With a simple but crafted structure, we combined contrasting materials such as oak and steel, giving a warm aesthetic and creating a tactile surface for people on their journey.”