An Elegant Lighting Design for the World's First "Tipping" Bridge
Everyone is familiar with the concept of the bascule bridge, a structure that splits open in the middle, with both halves raised in order to allow ships to pass through. It's a standard engineering concept that has not changed much in decades. Now take a look at the Gateshead Millennium Bridge, a cable-stayed structure that spans 126m (416') across the River Tyne in the north of England. The Gateshead is the world's first “tipping” bridge. This elegantly arched structure literally tips on its side to make way for maritime traffic.
As designed by Wilkinson Eyre Architects (WEA), the tipping movement of the two curves that make up the bridge's structure has been compared to the opening of an eyelid. The action is powered by six hydraulic rams; the effect is notably silent.
The firm of Jonathan Speirs and Associates (JSA) was assigned the task of lighting this unique public monument. (Speirs worked closely with LD Carrie Bremner; the latter was responsible for much of the liaison work with the client and the final focus.) Working with a budget of £190,000, about US$305,000 (out of an overall budget of £22 million, or over US$35 million), Speirs and his team created a complex design that aimed to fully illuminate the bridge without causing light pollution (this was a major issue, as a recently completed bridge in Scotland had been criticized by astronomers for significant light pollution).
The bridge's lighting design breaks down into several elements: the arch, the underside of the deck, the pedestrian walkway and cycle deck, the dividing hedge, and the caissons, which contain the hydraulic system. The arch is lit with a series of Irideon AR500 units from ETC, a choice made partly because it was decided that a color-changing option was integral to the design. To sell this point to the client, says Speirs, “A series of Photoshop images were created based on a daytime color rendering provided by WEA. These included the white light option as well as differing colors, with a wipe of color drifting from side to side, graphically demonstrated with a PowerPoint demonstration. This proved to be very helpful for the client to visualize and appreciate the lighting proposals.”
Nevertheless, the arch was lit selectively, says Speirs. “The structural stays that connect the arch to the bridge deck are almost non-existent. It was decided that they should not be lit, as there was so little physical material to reflect the light that, as a result, we would have spilled a considerable amount of light into the sky.”
Lighting the underside of the bridge deck was a different sort of challenge, as it is not seen directly most of the time, then is exposed when the bridge is open. Also, says Speirs, “The River Tyne flows incredibly slowly, resulting in an almost mirror-like appearance of the water surface. We were interested primarily in the reflections and then how the bridge would appear when it was in the open position.” However, the local harbormaster ruled that no light should be visible on the bridge when opened, so as not to distract ships passing through.
Therefore, says Speirs, “The intention was to use a narrow beam source to light along the structural rib and also then to illuminate the belly of the pedestrian deck.” The solution proved to be a 35W CDB-T PAR-20 10° lamp in a custom IP65 cylindrical housing from UK-based LB Lighting that was painted to match the rest of the deck underside. For ease of maintenance, the units are reached through a removable plate in the deck; a special mounting bracket allows the unit's housing to swivel through 90° to face upwards. The front glass of the unit is removed with captive screws and is tethered by a short length of stainless steel wire to ensure the glass is not dropped. When relamped, the housing is rotated back until it hits a focusing stop. “The reflections are so good that any faulty lamps can be spotted by looking at the reflections in the water,” says Speirs.
The key to lighting the pedestrian walkway and cycle deck, says the designer, was the fact that “we wanted people inhabiting the bridge after dark to feel comfortable and want to linger.” Indeed, a series of linear benches in the central hedge that separates the pedestrian and cycle zones allows one to linger and admire the view from the bridge. Complicating matters is the pedestrian deck surface, a black, non-slip material that doesn't reflect well. Thus, says the LD, “it was felt that a string of white LED luminaires recessed into the deck would define and delineate the route as well as give some illumination to the balustrading. These marker lights were paired at every second balustrade. Each of these luminaires draws three watts.” A similar approach was taken with the cycle deck; because it is an open aluminum grating, the paired LEDs were placed in the same access panel as the underside deck lights.
The central hedge of the bridge is constructed from stainless steel sheets with linear perforated slots. “The lighting idea was a simple one, to make this form glow from within,” says Speirs, who placed linear white cold-cathode tubes at the bottom of the hedge structure. “By adding a linear white acrylic diffuser at the low level on the cycle deck,” he adds, “light was pushed out onto the surface of the aluminum deck; this clearly highlights the step between the levels.”
Also, “at the center of the bridge is a series of upside-down U-shaped balustrades. These demarcate the change in level and aid people in stepping from one level to the other. We located more white LED luminaires in the deck to define these handrails. The undersides of the handrails catch light from these sources in a way that we had not truly appreciated at the design stage.”
The two caissons, containing the machine that controls the bridge's hydraulic system, were designed to be washed in blue light. Says the LD, “The idea occurred that, just before the bridge opens, the hydraulic rams would be lit with white light — and this would signal the impending opening. This developed into the idea that the floor in the caisson would have glass lenses and the blue illumination would continue to signify the lighting ‘below deck.’” The blue light is created with 150W CDM-TD metal-halide units by German-based Meyer, supplied by CLS in the UK, with blue glass lamps. “The white light on the [hydraulic] rams is also 150W CDM-TD metal-halide, the slow buildup of intensity adding to the drama.” Also, recessed into the low walls are a series of brick-shaped units with custom silver louvers to blend with the concrete.
Finally, in order to alert pedestrians and cyclists to the bridge's opening and closing, recessed in-ground units were custom-designed; green LEDs feed into a fiber-optic shape of a “go” arrow symbol. Red LEDs feed into a no-entry symbol.
With its unusual design, unique engineering, and distinctive lighting, the Gateshead Millennium Bridge has won a number of awards, including an IALD Award of Excellence, International Illumination Design Awards Award of Distinction, a UK National Lighting Award in the Exterior Lighting category, and the inaugural ELEC European Lighting Design Award for Exterior Lighting. It is now a landmark on the River Tyne. Speirs calls the project “a genuine pleasure,” adding that it was “an exemplary project that demonstrates yet again that, when a design team works together with a common vision for a forward-looking and supportive client, the results speak for themselves.”
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