Spherical objects!

Of all the radical and inventive geometric shapes that buildings can assume, a sphere is arguably the most fantastical. There is no cosmic law stating that buildings must be rectilinear, and curves are as much a feature of architecture as angles. But the sphere unsettles the preconceived visual, functional and structural notions about what buildings should be, by allowing the natural organic form to triumph over the rational, orthogonal geometries we commonly associate with architecture. 

This is why spherical buildings are both beguiling and rare. And it is also why recently unveiled proposals for London’s newest entertainment venue have captured the imagination of many. The London MSG Sphere is set to be a colossal 23,000-capacity indoor music venue built on the Queen Elizabeth Olympic Park. It will be twinned with a sister MSG Sphere in Las Vegas, where construction is already set to begin this summer. Both venues will extend the template of New York City’s iconic Madison Square Garden, and are being developed by its owner, Madison Square Garden Company, known as MSG. The London version at least will seek to replicate the astonishing success of the nearby 20,000-capacity O2 Arena, which is the most popular music venue in the world in terms of ticket sales. 

The London project is in its conceptual design stages, with a planning application not expected until at least the end of the year. Therefore no details have been released about scale, structure or materials. But from an architectural point of view at least, what is already clearly evident – and what could well capture the popular imagination – is that this will be one of the largest spherical buildings in the world. 

Spherical buildings remain objects of fascination because of their geometric purity and technical complexity – as well as, on the face of it at least, their mind-boggling spatial impracticality. And yet the London MSG Sphere is among a new generation of spherical buildings addressing these challenges with fresh technological advances in structure, skin and construction that are potentially making this kind of building more practical to plan, design and construct. 

Challenges

According to Peter Chipchase, director and head of stadium design at engineer WSP and a veteran of a number of spherical buildings around the world, spheres present some very obvious challenges: “There’s a reason many office buildings aren’t shaped liked spheres: you’d have a succession of odd floorplates which were only realistically usable at the centre of the building. This would be hugely wasteful, expensive and inefficient. But for the kind of single-volume / minimised facade venue being proposed in London, a sphere has the potential to actually be hugely efficient. It’s about finding the right application.” 

James Law Cybertecture is a Hong Kong-based architecture practice renowned for its work with futuristic spherical or spherically inspired buildings, including Mumbai’s 62m-high Cybertecture Egg office building, which is due for completion in 2020. Founder James Law too cautions that designing spherical buildings presents some key challenges. “It is not easy to plan a spherical building well, and bad space planning in spheres can yield very inefficient buildings,” he says. 

“In terms of structural design, the challenge is finding the optimum balance between the internal structure and the surface structure, and how they can work with each other.”

However, once that “right application” has been found, Chipchase maintains that spheres may in fact offer some key efficiencies. 

“As an object a sphere actually has the optimum surface-area-to-volume ratio: despite what people may think, it’s very efficient. If you look at a bubble floating in the air, it’s a perfect sphere because that shape provides it with the optimum lightweight structure to support itself and withstand the forces around it. 

“The challenges begin when the sphere has to meet the ground and has to be supported, as obviously all buildings have to be. Then it becomes imperfect. Imagine a raindrop hitting the earth – it’s forced to change its form and behaviour because the forces acting against it change. Dealing with those forces and maintaining the form presents a unique challenge.” 

Structure 

Structure therefore emerges as one of the key considerations when designing spherical buildings, and its influence has already been evident in London’s fledgling MSG proposals. Early visualisations indicated a giant orb hoisted completely above the ground and precariously (not to say improbably) supported by an open cone of slender inclined struts. Yet later visualisations indicated the orb no longer suspended in the air but with approximately one-fifth of its volume more securely lodged beneath the earth.

The way most spherical buildings deal with the “forces” Chipchase also describes is by having a firmer, solid, normally concrete base which restrains the forces that might otherwise compel its curved surface to distort and spread outwards when interacting with an opposing horizontal plane. Accordingly, even in their infancy the latter London proposals seem to indicate some sort of restraining girdle structure at their base. 

For Law, the choice of structural materials is determined by size and complexity of the proposed sphere, as he explains: “As spheres can be built from repeating elements of geodesic geometries, materials ranging from timber to steel can be considered, with steel becoming more suitable the larger the building is.” 

While Chipchase also believes the steel diagrid frame probably offers “the default solution for the larger sphere”, he believes new technologies such as carbon fibre may present more progressive solutions. While expensive and not as yet applied to the spherical form on any large scale, carbon fibre combines huge strength and flexibility and is also lightweight and could therefore form a perfect material solution for a new generation of spherical buildings. 

Construction

How a sphere is built is as critical to its feasibility as what it is built from. As Law explains, new developments in modular construction could accrue efficiencies. “If a spherical building enjoys repeatable structural elements and easy connecting details, and if it can be based on a mass-produced and prefabricated set of structural components, it can be just as efficient and economical as a rectilinear building.”

The use of prefabrication is a strategy with which Chipchase agrees: “The key is to have the highest strength-to-weight ratio possible, with something that can be fabricated quickly with simple connections.” He also reveals another logistical area in which future spherical buildings can attain even greater efficiency: “The secret is to utilise the inherent self-supporting strength of the sphere’s components during construction. 

“If a building can be built up progressively with a modular frame whose components can resist all forces at every stage of construction, as was the case with the building of the glulam grid shell roof above Canary Wharf Crossrail station, then the need for temporary works – which is essentially a second, hugely wasteful and expensive structure that is simply discarded at the end of a project – can be eradicated.” 

Skin

The final key element to be considered is the sphere’s skin. For veteran engineer Ben Morris, co-founder of groundbreaking specialist Vector Foiltec, there is only one solution: ETFE. Morris’s firm developed the inflated translucent ETFE cushions that have revolutionised modern construction as the significantly cheaper and lighter alternative to glass. The company has used the material when designing the facades of dozens of iconic buildings around the world, including the Eden Project and the Water Cube at the 2008 Beijing Olympic Games. 

“ETFE is the ideal solution for spherical structures because it offers the most efficient area-to-frame ratio and is essentially floppy and flexible. In any building the majority of the structure is there to deal with deflection rather than stability; it’s about minimising differential movement. But because ETFE cushions are inherently flexible and elastic, that movement is taken away from the edges of the frame and spread across the entire surface. This means the skin as well as the structure can absorb movement without the need for movement joints which are always likely to fail over time.” 

Morris also points out that ETFE offers “high acoustic transparency”, rendering it particularly suited to music venues such as the MSG Sphere, so long “as a more solid external base structure is deployed to present sound being transmitted externally to surrounding areas”. He says it is also significantly cheaper and lighter than glass. 

However, James O’Callaghan of specialist engineer Eckersley O’Callaghan believes glass offers key advantages over ETFE for spherical buildings. “ETFE needs to be in tension, which is generally created by making a double curvature – hence its cushion form. However, this means the surface of the sphere would not be smooth and lead to an inconsistent spherical geometry.

“Glass, however, can be formed over moulds to achieve a double curvature or bent via toughening furnaces to precisely achieve any desired geometry. It is also a hardwearing material that has longevity and performance that is not replicable in polymers like ETFE. It also has greater transparency and acoustically avoids the drumming effect when it rains, which can be overwhelming with large roof ETFE roof structures.”

Future

Both glass and ETFE allow for the integration of LEDs or digital media projections that are increasingly superimposed over the facades of large sporting or entertainment venues such as London’s proposed MSG Sphere and Morris’ own Beijing Water Cube. 

But there are other developments in glass technology that O’Callaghan claims will increase the suitability of glass as a spherical building material, even if he admits that at present these attract a “specialist premium” in cost terms. 

“While the methods for creating double curved spherical sections are still relatively artisanal, there are very recent developments in toughening double curved glass emerging in China which will see an increase in glazing strength and greater variation in moulds. This potentially offers the opportunity to reduce price via the use of a more mechanised production-line process.”

And Chipchase maintains there are other BIM-related processes that spherical buildings of the future will be able to take advantage of. “Computational tools now mean that literally millions of different spherical patterning options – such as triangular, hexagonal, geodesic, icosahedric – can be easily explored at the touch of a button until the most efficient one is found; 20 or 30 years ago this was unthinkable,” he says. 

“Also, developments like CNC fabrication mean that the accuracy, precision and quality control required to deliver a perfect form can be achieved without the excess material waste that may have once been the case.” 

Regardless of the futuristic innovations used to deliver it, like all spheres London’s MSG Sphere is likely to capture the public imagination due to the geometric purity and simplicity of its form. Or as Chipchase puts it: “Spheres resonate with people because they have the wow factor.”