Wind loads, complexity of projects among the ‘significant risk challenges’ of tall buildings: Allianz

Fire, wind loads and the challenge of pumping concrete to extreme heights are among the risks of modern high-rise construction, Allianz Global Corporate and Specialty (AGCS) SE suggested in a recent report.

Munich-based AGCS, which has provided insurance for the world’s tallest buildings, released its Supertall Buildings Risk Bulletin this week.

“Increasingly complex high-rise building projects present significant risk challenges meaning insurance claims and risk consulting services are particularly important on a construction site,” AGCS stated.

AGCS is the lead reinsurer on the Kingdom Tower in Saudi Arabia, which is currently under construction in Jeddah and will be more than a kilometre in height when finished in five years.

Risks of tall buildings include seismic activity and other natural catastrophes, wind loads and the “unique complexity of managing projects that can involve as many as 10,000 workers and over 100 subcontractors,” AGCS noted. “Some significant technical issues including pumping and placing concrete at extreme heights; cranage and lifting items to such heights; and significant variation in wind speeds between ground level and higher levels.”

Fire risk also presents “a considerable challenge for designers and engineers,” especially in tall buildings that house hotels, residences, restaurants and retail, AGCS warned.

“Thus an enormous focus lies on the design of sprinkler systems, escape rooms and fire resistant structures at an early stage of design,” AGCS said in the bulletin.

“The foundations of a supertall or megatall building need to be strong enough to even withstand an earthquake or other natural catastrophe activity,” stated Clive Trencher, Senior Risk Consultant at AGCS, in the report. “In the initial building phase particularly, consideration also has to be given to potential exposures such as flash flooding, as there will be large excavations that could get filled with water.”

In a separate release, Schrobenhausen, Germany based Bauer Spezialtiefbau GmbH announced earlier that one of its subsidiaries, Saudi Bauer Foundation Contractors Ltd., has installed the foundation of the Kingdom Tower.

“The works involved installing 72 piles of 110 metres in length and 1.5 metres in diameter; a further 154 piles of 1.5 metres in diameter and between 49 and 89 metres in length; and 44 piles with a diameter of 1.8 metres, all down to a depth of 50 metres.”

When the Kingdom Tower is complete, AGSC stated, the elevators will travel at 10 metres per second.

“It is challenging for elevators to go faster because of the rapid change in air pressure over such a distance,” AGCS said, suggesting that at an elevation of 914 metres, the air pressure is about 10% lower than at ground level.

AGCS says the world’s tallest building is the 828-metre Burj Khalifa in Dubai, United Arab Emirates. AGCS has “been involved in insuring” both the Burj Khalifa and the 452-metre Petronas Towers in Kuala Lumpur, Malaysia.

The tallest building in Canada, Toronto’s 553-metre CN Tower, is also the tallest building in North America, according to the Council on Tall Buildings and Urban Habitat. CTUH notes the second through fifth-tallest buildings in Canada, also in downtown Toronto, are: the 298-metre First Canadian Place (which houses the Bank of Montreal head office); the 277-metre Trump International Hotel; the 275-metre Scotia Tower (which houses the Bank of Nova Scotia head office); and the 261-metre Brookfield Place (formerly known as BCE Place and the Canada Trust tower).

CTUH lists two Chicago buildings — the 442-metre Willis Tower (formerly known as the Sears building) and the 423-metre Trump Tower — as the second and third-tallest in North America. The fourth and fifth tallest buildings in North America are the 381-metre Empire State Building and the 366-metre Bank of America building, both of which are in New York City.

“In 1930 99% of the tallest 100 buildings were located in North America with 51% in New York,” AGCS stated in its report. “Today, this has declined to just 16%.”

Also today, the “vast majority of construction projects” are in China, South East Asia and the Middle East, AGCS reported.

“Dubai alone is already home to 20% of the world’s tallest 50 buildings, while China boasts 30 of the tallest 100 buildings across 15 cities,” AGCS said in its bulletin. “Indeed, this month China announced initial plans for its own 1-kilometre tall building, the Phoenix Towers.”