The development of Saudi Arabia’s Kingdom Tower is set to reach unprecedented heights – becoming the tallest building in the world and the first structure to reach the 1km-high mark. Construction of such unique projects can pose unique risks.
Saudi Arabia’s Kingdom Tower will be the centerpiece and first phase of a development known as “Kingdom City” that will be located on a 50-hectare plot of waterfront land along the Red Sea on the north side of Jeddah.
When completed, the tower, which is expected to weigh nearly one million tons and comprises a mixture of residential and commercial property, will reach unprecedented heights, becoming the tallest building in the world and the first habitable structure to reach the 1km-high mark.
With a projected finishing date of 2019, construction began last year, with the piling and foundation work already being completed. Both posed challenges: the foundation and piling – which involves the use of large diameter bored piles to ensure structural stability within the foundations – has had to be uniquely designed to overcome subsurface issues such as soft bedrock and porous coral rock without the pile loads overstressing the ground conditions. Added to that, the concrete also has to have low permeability in order to resist the saltladen ground water which is characteristic of the region.
According to foundation contractors, Saudi Bauer the work involved installing 72 piles of 110 meters in length and 1.5 meters in diameter; a further 154 piles of 1.5 meters in diameter and between 49 and 89 meters in length; and 44 piles with a diameter of 1.8 meters, all down to a depth of 50 meters.
The construction work also needs to ensure that the finished tower suffers only minimal building sway, which is more prevalent in high structures because of stronger winds and the sheer scale of the building.
To achieve this, the Kingdom Tower has been designed to prevent the excessive movement that would otherwise make the occupants of upper floors experience sickness or discomfort on windy days, including using very high strength concrete that will be up to several feet thick in certain parts of the core. This, along with the highly integrated steel frame and shear walls, is also intended to prevent catastrophic structural failure. Additionally, the tower will incorporate a large core not only to support the structure, but also to contain many of the high-speed elevators and extensive building services needed. The stability design of the building is crucial. At Kingdom Tower’s projected height, it is considered unfeasible to use a traditional square design. Instead, like the Burj Khalifa in Dubai – presently the world’s tallest building – it will have a three-petal triangular footprint for stability and a tapering form with a sloped exterior, which will reduce wind loads.
The smooth, sloped façade of the building will create a phenomenon known as “wind vortex shedding”. Normally, when wind moves around a building it can create tornado-like vortices which initiate sway in the building due to variations in pressure, direction, and velocity. However, the smooth taper of the Kingdom Tower’s design is more aerodynamic, which reduces the risk of the vortices forming, just one of many innovative features that will ensure the futuristic
skyscraper will lead the way when it comes to cutting-edge building design, as well as height, when it is completed in five years’ time.
Assessing the Key Risks with the World's Tallest Buildings
Claims and risk consulting services are especially important on a construction site, even more so when dealing with increasingly complex high-rise building projects which can present a number of significant challenges, according to AGCS experts.
AGCS has been involved in insuring a number of internationally-renowned high-rise building projects, including the Petronas Towers in Kuala Lumpur, Malaysia – formerly the world’s tallest building – and the current holder of this title until the Kingdom Tower project is completed – the Burj Khalifa in Dubai. It is acting as a reinsurer on the Kingdom Tower project, via its subsidiary Allianz Risk Transfer, the group’s specialist risk transfer arm.
For an insurer or reinsurer acting on projects of this nature one of the key issues is to assess what level of risk – and impact – any seismic activity might have on the structure in question.
“If an event such as an earthquake or another natural catastrophe was to occur, it could obviously have a potential impact,” says Clive Trencher, Senior Risk Consultant at AGCS.
“Therefore the foundations need to be very strong to withstand such an event.
“Consideration also has to be given to potential exposures such as flash flooding, which may pose a risk when initial building work starts on such projects because there will be large excavations in the ground that could get filled with water,“ he adds.
"The choice of building materials also poses challenges. Glass panels need to be thicker and more durable for the higher storeys, while concrete mixes design also have to vary so that they can withstand the differing buildings loads which vary with height. And this is no easy feat. Ahmet Batmaz, Global Head of Engineering Risk Consultants at AGCS, says that “it is very difficult to pump concrete at this height – the high-strength concrete requires a specialized mix design to enable it to be pumped and it requires special equipment and pump lines as pressure can reach over 400 bar. It also creates some technical challenges during the stage where the concrete is mixed and placed as such concrete tends to set after two hours only,” he adds.
Although many of the technical issues that the latest high-rise building projects face may appear to be similar to previous super-tall skyscraper developments, AGCS experts advise against making assumptions that the same technical solutions can be used.
“Such constructions are unique projects that will face unique risks. Every construction project faces challenges and the more ambitious and large-scale the project might be, the more challenges it will create,” says Trencher.
“Each project has to be planned and assessed on its own merits and specific risks. While we may learn some techniques from the construction of other tall buildings, it would be wrong to assume that they can be fully risk assessed or planned just because they have been used on similar tall structures.”
Construction projects of this size need to be fluid, according to Stefan Atug, engineering underwriter at AGCS/ART Dubai: “Timelines may extend, design plans may need to change, engineering challenges may arise, and technical risks may need to be managed or mitigated in different ways. As a reinsurer, we need to be able to take a flexible approach and adapt our services to suit the client’s needs, which means forging as close a relation ship as possible to be able to react to changing circumstances.”