Reach for the sky: why safety must rule as tall buildings aim higher

3 Oct 2017

Australia’s tallest building is currently the Gold Coast’s Q1, at 322.5 metres (including the spire).

But the 78-floor largely residential tower is set to be challenged by taller buildings planned in Melbourne and the Gold Coast.

And Australia’s tall buildings are still relatively small when compared to giants overseas, such as Dubai’s 828m, 163-floor Burj Khalifa, and the 1km tall Jeddah Tower planned for Saudi Arabia.

So if the right environmental conditions exist, is there an upper limit to building tall? Actually, our planning should include safety considerations, not just engineering capability.

A mile-high tower

The concept of a mile-high skyscraper was first touted by the American architect Frank Lloyd Wright in 1956.

Wright proposed a 548-storey tapering form more than four times the height of the Empire State Building in New York.

While Wright’s vision was an ideal, a historical review of tall buildings reveals a more steady, incremental approach to innovation. At various points in time, different technologies have been both the enabler and then limiter of building taller.

Technical challenges grow, technology evolves to meet the needs, reaches its limits, and the cycle begins again. The structural engineer Richard Tomasetti noted in 2013’s The Tall Buildings Reference Book that “limitations are best perceived as a function of time”. This suggests that, over time, structural engineering can match any desired height given the right innovations.

The first tall office buildings, made from load-bearing stone walls, appeared in Chicago and New York in the late 1800s. They were a response to the demands of a thriving economy and pressures on land and commercial floor space. The development of framed structural systems – first in cast iron such as New York’s famous Flatiron building (above), then steel, then hybrid concrete and steel systems – revolutionised tall buildings.

New innovations such as fire resistance, electric lighting, bathrooms and steam-powered radiators provided levels of comfort and safety that were unimaginable in older buildings.

Flatiron Building
The Flatiron building in New York. Flickr/Jo Christian Oterhals, CC BY-NC-ND

Gaining the lift

One particular invention that enabled building height was the elevator. Before its adoption, there was a diminishing rental return on the highest floors, which had to be reached by foot.

By making the upper stories more easily accessible, the elevator flipped the business model and the pursuit of height became an economic driver. Higher floors were marketed as healthier, quieter, more prestigious - and much more expensive.

Many structural innovations were beyond the scope of contemporary regulations and some more revolutionary engineering, such as metal cage construction, were applied in the field before the building codes caught up with the new technology.

The approach to firefighting has been the most obvious constraint. Buildings more than seven or eight storeys tall are beyond the reach of a typical firefighter’s ladder. The requirement for suppressing fires has to be designed within the building itself.

Some of the strategies developed for skyscrapers included compartmentalisation (containing and preventing the spread of fire), protected stairways for escape and for fire fighter access, a defend-in-place strategy, and the concept of phased rather than simultaneous evacuation of the building.

The money constraint

Building tall comes at a premium, and economies are an important motivator in developing cost-efficient designs. Greater financial return on higher floors can offset the cost, but the financial case can be complex...

Read the full article on The Conversation