The Shard is the tallest building in Western Europe
Thankfully, such meteorological influence has not afflicted another of the new glass-clad towers helping to transform London’s skyline. Indeed, the iconic Shard building is, in the words of its creator, Renzo Piano, far from “a symbol of arrogance” and more “a sparkling spire, flirting with the weather”.
It is not easy to associate such understatement with a Qatari-funded building, which, at almost 310 metres high, stands as the tallest building in western Europe and accommodates a blend of retail units, business offices, hotel rooms, residential apartments, and observation decks providing impressive views of the city.
It is these factors of height and function, as well as historic and global influences, which presented a distinctive set of challenges to the design team involved in the fire safety engineering and management aspects of the building.
The strategy adopted by fire-safety consultancy Arup in designing The Shard is an example of what it calls total fire engineering. Developed by the firm’s founder, Sir Ove Arup, the concept states that the basis for a successful building has to consider all the needs of stakeholders in its design, construction, and operation.
This approach was explained in more detail at a seminar, hosted by London Fire Brigade, at which Dr Graeme Flint, a senior fire engineer at Arup, described the design challenge as the need to “engineer solutions that meet the goals within the constraints”.
The goals established at the outset were: the life safety of the occupants; meeting approvals of the planning authorities; and business continuity and property protection. The Shard, however, is not a building that could have been designed according to the Building Regulations Approved Document B, which covers fire safety. A back-to-basics approach was necessary, explained Dr Flint, in order to avoid getting bogged down in a debate about the relative merits of prescriptive or performance-based design, and concentrating instead on the key risks of the building: its mixed uses; the large population it holds; and, of course, its height.
The design team approached the building’s construction by addressing five problems: how to get people out; how to alert occupants as to the presence of a fire; how to keep a fire away from people and stop it spreading; how to extinguish a fire; and how to identify who needs to know what in regard to fire safety management.
Traditional fire evacuation strategies are generally designed with one group of occupants in mind, but the concept of the “vertical city in the sky” has led to a more flexible approach in which different evacuation tactics are followed depending on the circumstances and the people at risk. At The Shard, a hybrid phased/staged evacuation strategy is used. At basement level, simultaneous evacuation takes place, with phased evacuation via stairs two floors at a time for those in the lower-level retail units and offices, which reach up to level 28.
Above the offices is a three-floor restaurant and a further two levels of hotel public and conference facilities. Occupants in these parts of the building are evacuated simultaneously, with emergency evacuation lifts serving the restaurant. A phased evacuation procedure two floors at a time is followed between levels 36 and 52, which comprise the hotel bedrooms.
The next 14 levels are devoted to 10 residential apartments (not yet on the market). The option of providing simultaneous alarm to occupants on these levels is available and, while no emergency lifts serve these areas, they will be able to use the lifts on the restaurant levels once they have evacuated to this point.
Above the apartments is the viewing gallery — the building’s highest occupied levels — which is also served by evacuation lifts. At various points, unoccupied levels separate the different uses of The Shard and also act as a fire barrier, while refuge points at the restaurant level provide capacity for keeping people away from fire during an evacuation.
Given the large population within the building, limited automation gives the estates management team the necessary flexibility to cancel an evacuation if it deems it is safe to do so. This need to minimise disruption is also evident in the fire detection and alarm solutions. Bespoke, tailored messages are used as part of a voice alarm system, which allows estate management to control use of the evacuation lifts. The potential for malicious or false activation of fire alarms is reduced by use of a double-knock system, which allows the source of the alarm to be determined before the evacuation procedure kicks in.
Suppression of the fire and the need to keep the smoke and flames away from occupants is provided primarily via sprinklers as well as compartmentation, with fire resistance of two hours in many areas. Reliability of sprinklers is often estimated to be around 95 percent, but Arup was keen to explore what could be done to improve this statistic. Research conducted found that 34 percent of failures were due to people simply having turned the sprinklers off; 30 percent were a result of a fire being extinguished by occupants before the sprinklers were activated; 15 percent were due to lack of maintenance; and 16 percent were a consequence of incorrect specification.
Armed with this knowledge, the design team devised several measures to mitigate the potential for sprinkler failure. These include: the system’s water storage being twice that required by BS EN 12845; extra redundancy in the pump systems; and fully twinned sprinkler valve sets. Gas suppression is also provided in certain electrical plant rooms.
The Shard uses controversial emergency evacuation lifts
Having addressed the elements of evacuation, detection and alarm, and containment and suppression, the next objective is to extinguish the fire. The fire command centre is integrated with the security hub in the basement of The Shard in order to provide full control of all systems. Access for London Fire Brigade is provided via three firefighting shafts, each including stairs and a fire lift. Level 37 acts as a special interface point for the protected transfer of firefighters and equipment.
Pumps are capable of feeding each wet rising main simultaneously at 1500 litres/min at every level, while the water supply is sufficient for 45 minutes at 4500 l/min. Mains intake at 1500 l/min allows for indefinite supply to two fire-fighting jets.
The final element in Arup’s strategy involved the communication and procedural protocols to ensure that the fire safety management measures adopted work effectively in the event of an incident — all of which were important in gaining approval and buy-in from Southwark Council and other relevant stakeholders.
As stressed by Dr. Flint, a building such as The Shard has to go beyond the Building Regulations and associated codes, with every decision justified in regard to fire safety. The use of evacuation lifts, for example, is still a novel concept — and, to some, a controversial one — but it has gained credence, particularly since the Twin Tower attacks, and is much more common in Asia.
But the use of evacuation lifts apart, many of the technical solutions employed in The Shard are not particularly innovative, insists Dr. Flint. Where this project can truly offer lessons for future high-rise or complex structures is through its liaison with myriad stakeholders; the design focus around the risks it presents, its location and its multiple uses; and through its holistic approach to fire safety management, which is under continuous review.
Other than its height, perhaps the most striking architectural feature of The Shard is its splintered peak, which last year attracted some less-than-flattering descriptions from several commentators: it has been referred to as a messy cake-icing nozzle and a pencil minus its lead, while one architect suggested during a Twitter conversation that its crown implied the structure represented “a hollow vessel”.
Whether the image conjured is that of a subtle, flirtatious spire or a domineering, empty container, the connective consideration of all aspects of design, construction and operation — particularly in respect of fire safety management — gives The Shard an organic, symbiotic and constitutional feel, which is not always associated with skyscrapers and high-rise structures. And this participating, reciprocal and universal approach is not simply necessary from a legislative and cost-saving perspective; it is also very much compatible with the wider technological and social forces at play in the early 21st century.
