How Can Skyscrapers Be So Tall?

Before skyscrapers could be built, seven engineering breakthroughs had to occur.

As I was admiring some futuristic skyscrapers in San Diego during the last ACVS meeting this October 2014, I was reminded of a fascinating documentary* on that very topic. Without the seven following engineering breakthroughs, we would not be able to build extravagantly tall towers.

1. Elevator

The most obvious advancement is the elevator, which appeared in the 19th century. Architects knew that in order to make taller buildings, people needed a way to climb higher. To resolve this issue, the elevator was invented.

The problem with the elevator’s prototype was that, if the rope suddenly broke, there was nothing to stop if from falling down. In 1854, a mechanic named Elisha Otis (yes, same as the company) created a safety device that would stop the elevator from falling. Should the hoisting cable snap, the wagon would securely lock into metal prongs along the sides of the lift.

2. Steel

The next problem to solve was that preventing taller (i.e. heavier) buildings made of stone from sinking into the ground.

When the triangular Flatiron building (87 m tall) was created in New York City, architects used steel columns and beams to develop a steel skeleton—which was thin and light enough to support the weight of the building, letting its stone-like exterior hang like curtains.

3. Heat

Skyscrapers coated in glass windows allow a lot of light to come in. But solar radiation could easily make a building act like an oven.

To control the heat in the United Nations HQ in New York City (168 m tall), the first air conditioner was invented by an engineer named Willis Carrier (yes, same as the company).

4. Speed

In construction, time is money. To speed up construction of the World Trade Center (417 m tall), workers preassembled parts offsite and would assemble them onsite as if they were parts of a gigantic puzzle.

A second improvement to speed things up was the kangaroo crane (a.k.a. self-erecting crane or self-assembling crane). It is capable of raising itself up as construction grows upwards.

5. Wind

Buildings over 100 floors are more susceptible to wind forces. Chicago, a.k.a. “the windy city,” presented a challenge to builders, given the winds blowing up to 90 km/h around the Sears Tower (442 m tall).

Instead of building an internal steel skeleton similar to the Flatiron Building, an outer frame, forming a steel “exoskeleton” was imagined.

6. Earthquakes

Taipei 101 (509 m tall) was built in an earthquake-prone city (Taipei, Taiwan). While designing this building, architects realized that elasticity was the solution. In order to maintain its shape, the building would have to be rigid with concrete columns for strength, yet possess elasticity to keep top floors intact in case of an earthquake.

7. Terrorism

When the 9/11 attack occurred in 2001, many questioned whether more skyscrapers would ever be built again. Evacuating people, injured or not, through flights of stairs, is a phenomenal challenge.

The Burj Dubai (830 meters tall, or twice as much as the Twin Towers in NYC) is the tallest building in the world. It features 9 refuge rooms, with fireproof doors, that can withstand fire for two hours. Since each room is placed every 30 floors, reaching these rooms is more practical.

The evolution of the skyscraper is fascinating. The Burj Dubai uses every lesson learned from previous towers. I wonder what else it will take to build a skyscraper taller than the Burj Dubai.

* Source: “Big Bigger Biggest – Skyscrapers,” a National Geographic documentary.

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