The Aim: A Compact Auditorium

Designing the Bridge Theatre in London

Whenever we argue about what makes the perfect theatre, we can usually agree that its primary purpose is to conjure the best possible relationship between actors and audience. What makes some better than others in conducting energy and generating atmosphere is more debatable, but I would argue that irrespective of scale or style, chief amongst the essential qualities for a great theatre is density: that is, the number of closely packed human faces that an actor can absorb from the stage and with whom an audience member can feel complicit in the room.

For any given audience size, actors know that a more compressed, encompassing crowd will mean that they will need to energise a smaller volume of space with their voices and gestures, and if the audience is physically closer to the performers it will be far easier for them to become properly involved with each other. Density is the key, without which comfort, good sightlines, technical sophistication or even great acoustics – important thought they are – can never entirely camou age a room that feels too di use and therefore theatrically inert. 

Density was a commercial imperative for historic theatres, but expectations of comfort and unimpeded views, expanded human frame sizes and the welcome advances in re safety and accessibility have made it harder for designers to aspire to the intensity of those (originally) more cramped and incendiary playhouses. The problem becomes more acute as the scale of the audience expands and the natural limits of human contact become strained. With this conundrum in mind, and without a commission, in the autumn of 2014 Roger Watts and I set out to explore what an ‘ideal’ larger scale 21st century auditorium might look like. We discussed a room that could aspire to the density of an Elizabethan playhouse or a deep-galleried West End theatre and yet could match the adaptability and democracy of the best contemporary spaces. 

The Prototype 

As a benchmark we settled on the physical footprint of our personal favourite auditorium, Frank Dunlop and Bill Howell’s 1970 Young Vic. The manually adaptable, chamfered seating space of 16m x 16m, surrounded by shallow seating galleries on four sides but with the fourth side removable, has proved itself capable of an almost limitless series of di erent formats, and yet it remains a room in which everyone feels connected to one other, and so are encouraged to behave like active participants rather than passive consumers. Keeping the 16m gallery to gallery width of the (normally) 420 seat Young Vic, we experimented with a more vertical, three-tiered system of perimeter seating galleries to target a capacity nearer the Lyttelton’s 890. 

To get anywhere near this capacity with decent sightline angles would mean compressing the height between each gallery as far as possible so that the audience would be vertically closer to each other and to the stage. We designed three-row deep galleries made of laser cut steel to reduce weight and structural depth, minimising the need for columns by means of torsion beams and bespoke cantilevered supports. Three layers of xed galleries would form three sides of the space, surrounding a modular stage and stalls zone that could be manually but quickly transformed to end on, at oor, apron stage, traverse or thrust stage variations. A fourth, demountable seating gallery would enable in the round con gurations. The technical infrastructures of lighting, ventilation, heating and cooling (so often the downfall of new theatre construction and cost planning) would be incorporated into the primary fabric of the structure as a single, coordinated, pre- designed and pre-fabricated object. 

Production designers have rightly criticised architects for completing too much of the design story around the playing area, so that the auditorium becomes ‘a locked-o camera’. Mindful of this, we designed the upstage edge of the auditorium room as open to a clear playing (or seating) area, so that designers and directors would have the option of a fully end on format and maximum freedom to dovetail the design of each production with the xed gallery elements. Thus, in end-on con guration, a ‘proscenium’ width of up to 15.5m might be achieved, or stopped down to narrower openings. This would place a greater burden on the show designer to complete the architectural identity of room for any given production, but achieve a di erent quantum of adaptability for, say, promenade or in the round con gurations. 

The Chance of Realisation

As Roger and I were developing these strands of thought in early 2105, we were asked by Nick Hytner and Nick Starr, our former clients at the NT Future and NT Studio projects, to design the rst theatre of their new, non-subsidised venture, the London Theatre Company. On seeing the sketches for our experimental modular auditorium, they immediately understood the theatrical possibilities and were happy with the likely capacity, so we agreed to develop the design together as a working prototype. Searching for possible sites, we visited a ground oor and basement plot at No 1 Tower Bridge, set aside by Southwark Council for cultural use as a planning condition for a soon-to-be completed residential building. Even the empty space felt great, and the riverside location onto Potters Field Park was extraordinary. The 10m total headroom was tight, however, by coincidence demanding the sort of compressed structural design that we had already been mapping out for theatrical density. We calculated that our three tier, 900 capacity room would t, but with only millimetres to spare. On that basis the Nicks negotiated the lease in the summer of 2015 and o cially appointed us as architects, with the aim of fully designing, manufacturing, assembling, commissioning and opening the theatre to the public in 2 years. 

New Ways in the Design 

Once the project was real, we knew we would need to collaborate with a specialist fabricator to develop and build the modular auditorium. Nick Starr introduced us to Tait Towers in the USA, a company more used to making theatre machinery and rock staging. Working with design engineer Ewart Richardson, together we developed the basic auditorium design into what was, for us as architects, an extraordinarily detailed 3D digital engineering model that could both be tested for weld joint stresses and interrogated for individual sightlines. With the London Theatre Company team, we digitally ‘sat’ in every seat in the house, in all formats, to verify the quality of the sightlines and set up the various ticket pricing bands. Likewise we ‘stood’ on every part of every stage con guration in order to experience an actor’s relationship with the audience and identify the points of command to inform the various stage geometry options. 

Wiring, lighting, sound and emergency systems were all coordinated within the design, including the surrounding steel diaphragm wall which doubled as the air supply plenum, with integrated duct routes and grilles at each level around the seating galleries. Our regular collaborators Skelly and Couch (environmental engineering) and Gillieron Scott (acoustics) worked with Tait and ourselves to design and calibrate the systems, whilst theatre practitioners were enlisted to advise on the infrastructure for sound and light. 

Gillieron Scott built a detailed digital sound model of the space, enabling the client team to experience and tune the audibility of performers from every seat and in every format. We made a number of bespoke seat prototypes with manufacturer Kirwin and Simpson, which were tested by the client team before we settled on the nal design, which can swivel to improve side gallery sightlines in more end on configurations. The hundreds of small adjustments and recalibrations at the design development stage have resulted in a nished space with consistently good sightlines and a lovely natural acoustic for spoken word. 

Once the base design had been realised, the digital model was used directly for steel fabrication. As a nal testing of the digital design prior to site operations, the team built a full-sized prototype of the three-tier side and corner components in a hanger in Norfolk, allowing us to experience the relationship of actor and audience, tweak the ergonomics of steps, seating and handrails, and to rehearse the site erection methodology. The auditorium was made in lorry-sized modules, bolted together on site, allowing easy transport and erection with only a mobile tele-handler and a small, skilled site crew. The entire stalls pit and stage area consist of a bespoke, innovative modular staging system developed by Tait to allow quick manual adaptation for di erent formats. 

A Prototype consisting of modules 

For this firsrst auditorium we chose a simple, warm material palate of deep brown painted steel for the main auditorium structure, natural oak slats for the tier fronts, black recycled rubber ooring and a rich burnt orange woollen cloth and tan leather upholstery for the seats. The semi-transparency of the tier fronts, tested in detail by Gillieron Scott, seeks to balance acoustic feedback with visual continuity of human bodies around the space, reinforcing a perception of the whole audience actively sharing the room together. Final seating capacity varies from 900 to 1075 depending on format. 

Our collaborative experiment in density has given us unexpected new insights to the detailed technical world of engineering product design, has smudged the usual demarcations between the design and making processes, and all but dissolved the traditional supplier and consumer relationship between consultant team and client. As a model for future experiment and re nement, the Bridge has been well received by actors, audience and critics for its rst end-on, and second in-the-round promenade productions (the current, third production is in thrust) but we are actively gathering feedback from the technical team running the venue to inform the next version. London Theatre Company are currently looking at different capacity variations of the modular auditorium with us, which will be visually transformed not only by scale but by di erent material and colour choices. More widely, we hope this will be the prototype model for a family of dense, adaptable, prefabricated modular auditoria around the world. 

 

Engineering the Bridge 

By Ewart Richardson and Mark Ager 

The key challenge presented to TAIT by Nick Starr, Steve Tompkins and Roger Watts from Haworth Tompkins was how to minimize the vertical height of the balcony structure, such that 3 balconies could be tted within the existing found space. This was both a practical requirement – the economics of The Bridge (a commercial theatre) would only work with a 900 seat capacity house, but also to realise the intent to pack the auditorium with a ‘sea of faces’. 

The traditional way of designing a balcony structure would be to start with the primary steelwork, add secondary supporting steelwork, then allow space for the building services, and sound cladding, before adding the architectural ‘skin’. At The Bridge Steve gave us the challenge of reducing the thickness – in some cases to 20mm – between the statutory headroom for a balcony and the feet of the audience on the balcony above. Clearly a more dynamic approach was required. 

The key to achieving this has been to pack all these various elements into a single conjoined whole that both acts as the structure, and surfaces, and carries within it the various service routes. Whilst the key component of the balcony – steel – has been available for nearly 4,000 years, there are 3 modern technologies that have enabled this approach at The Bridge. 

The first is the use of sophisticated 3D mechanical design package CATIA (first developed to allow the design of the Dassault Mirage fighter – and subsequently used by most major aerospace, automotive and shipbuilding manufacturers all over the world). Catia is a tool that facilitates the design of complex structures – structures that importantly combine multiple functions in compact space. Such structures could be (and have been) designed using earlier 2D methodologies but such techniques would, for example, typically involve data transfer to di erent packages for nite element analysis (FEA), Catia allows a designer to carry out near-constant FEA cycles to prove the design as it develops – all in native Catia le format and usually on the same desktop machine. Catia assists a designer to explore the ‘what’s possible’ – while looking for the design solution – without involving often time-constrained (and potentially costly) third parties. 

From Design to Production 

In the case of The Bridge all the steel elements contribute to the structural strength of the balconies. The e ect of loads can be analysed using the FEA tool to determine not only whether it’s strong enough (there are codes to limit the ‘utilization’ of the material – what percentage of the material’s yield stress we should use) but also what sort of de ection we might see in the structure under such loading conditions.. In the case of The Bridge Theatre, de ection-limiting was more restricting than stress-limiting. We were very much aware that an audience member’s perception of ‘wobble’ in the structure could affect their comfort just as much as their amount of personal space. 

The screenshot below shows a typical in- process analysis of one of the balcony units. It shows individual loads on each seat base, both vertical and horizontal loads on the front balcony handrail, gravity loads due to self- weight and ‘virtual parts’ mounted onto the balcony front stanchions that allow us to load up the ‘cantilevered’ lighting bars than could be mounted on the front of the balconies: 

Catia has various ways of sharing information for collaboration during the design process. We were able to screen-share with Haworth Tompkins and LTC, and also export ‘dumb’ lightweight 3D models that can be viewed independently in multiple platforms (including iPads). 

Further down the line, Catia was able to import the builder’s 3D BIM model so that we were able to devise (often tortuous) methods to get the structure into the building: 

Thirdly, modern CNC pressing and folding techniques enabled our designers to send a 3D le of the required element to the manufacturer rather than create costly multiple annotated 2D drawings of a pro le – then folded part (the straight from Catia technique also avoids the complication of di erent manufacturers using di erent bend allowances). 

This particular element I’d suggest would have been di cult to make in a traditional manner (see last image): 

The challenge of this approach is that the theatre systems needed to be completely speci ed before the design is complete in order that the various cable ways/air ducts and other elements can be designed into the system. There was little or no exibility in adding new cable and ducting routes late in the process. 

Production and Installation 

The next challenge was how to fabricate the structure and introduce it in to the venue. It was clear to the team that the various elements needed to be prefabricated o site and then delivered and installed. The Bridge gallery structure consists of around 50 main components (galleries and towers) each weighing from 2 to 4 tonnes, total weight around 200 tonnes. Each component was fully fabricated off site, painted and with nal nishes installed, then prewired, so that when it was brought into the building it was substantially complete, and just need to be bolted into position. 

The elements were then transported into the building via an overhead crane rig and then manoeuvred into position with a 20 ton tele- handler. This again required detailed planning as sometimes the clearances were around 20mm (or in some cases even less as the building was out of tolerance). The complete structure was assembled in around 14 weeks. 

Also, point-cloud laser scan surveys of the building can be easily imported into Catia and were instrumental in validating the accuracy of the as-built structure handed over to us. 

And during installation, by aligning our model with the co-ordinates used by on-site Electronic Distance Measuring (EDM) equipment (Total Station) we were able to accurately position and level elements as they were installed. 

The second is the extensive use of pro le- cutting technology to allow complex shapes to be cut from sheet steel. In all, the Bridge contains over 3,000 separate laser and water- jet cut components, allowing a structure to be designed which would not have been possible without this technique. 


BTR Ausgabe 5 2018
Rubrik: English texts, Seite 278
von Steve Tompkind