The Evolution of Skyscrapers:
From Chicago’s Steel Tubes to Dubai’s Height Records Automatic translate

A skyscraper is an engineering equation in which the variables are wind, gravity, materials, and money. In the century and a half since the first steel-frame building was erected in Chicago, architects and engineers have solved this equation again and again — each time under new conditions and at new heights.

The Chicago School and the First Steel Skeleton

Until the 1880s, high-rise construction was limited by the physics of masonry. The taller the building, the thicker its load-bearing walls at the base had to be. As a result, a multi-story office building would become a pyramid, with the lower floors wasted — the walls simply ate up the space.

A breakthrough came in 1884–1885, when William LeBaron Jenney completed the Home Insurance Building in Chicago. The ten-story, 42.1-meter-tall structure was the first in which the loads from the floors and roof were supported not by the walls, but by an internal metal frame made of steel and iron. The walls became curtain walls — they no longer supported the building, but simply sealed it off from the outside. City officials were so concerned about this concept that they halted construction and demanded inspections.

The building’s weight was approximately one-third that of a comparable stone structure. This had direct economic consequences: a lighter building required shallower foundations and less excavation. Iron and steel — expensive but compact materials — allowed for higher construction with the same footprint.

At the same time, a second problem facing high-rise buildings was being addressed: vertical movement of people. Elisha Otis demonstrated his hydraulic elevator as early as the 1850s, and by the 1880s, elevators had become standard equipment. Without an elevator, floors above the fourth or fifth floor lost commercial value — tenants were unwilling to climb. The combination of a steel frame and a reliable elevator paved the way for true high-rise construction.

New York Heights Race

Chicago originated the idea, but New York turned it into a competition. From the late 19th century until the 1970s, New York City held the title of the world’s tallest building for 66 consecutive years. The Flatiron Building (87 meters) was built in 1902, the Singer Building (187 meters) in 1909, then the Metropolitan Life Tower, and finally, the symbols of interwar optimism — the Chrysler Building and the Empire State Building.

The Chrysler Building, completed in 1930 to designs by William Van Allen, reached a height of 319 meters — the first building to surpass the Eiffel Tower. Its distinctive 27-ton stainless steel spire was raised into place in 90 minutes. The Chrysler held the title of tallest building for only 11 months: on May 1, 1931, the Empire State Building opened at 381 meters (443 meters with its antenna), and the new record stood for nearly 40 years.

Architecturally, both buildings belong to the Art Deco style, with its stepped silhouettes. The stepped design wasn’t just an aesthetic whim: New York City’s 1916 zoning law mandated that upper floors be set back from the red line to ensure street-level buildings weren’t deprived of daylight. This rule changed the appearance of an entire generation of New York skyscrapers.

The Twin Towers and the Structural Revolution

After World War II, the construction industry gained new tools: high-strength steel, welded joints instead of rivets, and the first computers for structural analysis. In the 1960s, ideas about how a high-rise building should perform under wind loads were almost completely rethought.

Fazlur Khan and trumpet concept

Bangladeshi engineer Fazlur Rahman Khan, who worked for Skidmore, Owings & Merrill in Chicago, developed several structural systems that defined high-rise construction for decades to come. His central idea — the "tubular" design — was as follows: instead of distributing columns across the entire floor area, he placed them densely around the building’s perimeter, connecting them with rigid beams at each level. Thus, the building itself functioned as a hollow, cantilevered box, supported by a foundation.

The system proved cost-effective: columns in the building’s core were no longer needed, and steel elements were used more efficiently. Khan developed several variations of the tubular concept — the framed tube, the truss tube, and the bundled tube — and all found practical application in real buildings. Modern structural systems still rely on his principles.

In 1972–1973, the World Trade Center towers (110 stories, 415 and 417 meters, respectively) were built in New York City. They utilized a framed tube with densely spaced perimeter columns. For its time, this was an extremely material-intensive solution, but it was space-efficient — there were no columns inside, only a central shaft housing the elevators.

Willis Tower: A Bundle Tube in Action

In 1970, construction began on the Sears Tower (now known as the Willis Tower) in Chicago — the tallest building in the world at the time. The design was developed by architects Bruce Graham and Fazlur Khan, who employed their most mature concept, the bundled tube.

Design and parameters

Nine steel tubular cells, each measuring 23 x 23 meters, are assembled into a 3 x 3 matrix and operate as a single unit without any internal columns between the core and perimeter. Two cells rise to 50 floors, two to 66, three to 90, and two to 108 floors. This stepped configuration not only creates a recognizable silhouette but is also structurally sound: by terminating the tubes at different heights, the engineers disrupted the regularity of wind vortices around the building, reducing aerodynamic loads.

All the main welding of the structural elements was performed not on-site, but at the factory, and the completed sections were simply bolted together on-site. The idea for the bundled tube, according to Khan himself, was inspired by a pack of cigarettes, from which several were extended to different lengths — the image of unevenly protruding sections naturally created a stepped appearance.

The building utilized approximately 67,000 tons of steel, 1.8 kilotons of aluminum, and 410,000 square meters of concrete flooring. The antenna reached 527 meters in height, and the roof reached 442 meters, making it the tallest building in the world from 1973 to 1998.

Construction was completed in 1973. Foundation work began in August 1970: a 15-meter-deep pit was dug, approximately 5,100 cubic meters of soil was removed, and a reinforced concrete slurry wall was built around the site. The foundation consisted of 201 casing piles, reaching down to the bedrock.

A place in the history of high-rise construction

Willis Tower wasn’t just the tallest building of its time — it demonstrated that the tubular beam system allowed for high-rise construction at a lower cost per unit of area than any previous solution. Afterward, engineers had no doubt: Fazlur Khan’s principle worked at scale. The building held the world record for roof height for 25 years.

Kuala Lumpur and the Concrete Supercolumns

By the mid-1990s, Southeast Asia’s economy was growing so rapidly that construction ambitions were almost measured by GDP. In 1998, the Petronas Twin Towers opened in Kuala Lumpur — at the time, the tallest buildings in the world, each 451.9 meters high.

Concrete vs. steel

The designers of the Petronas Towers took an unconventional approach: instead of steel, they chose high-strength reinforced concrete as the primary structural material. The reasons were pragmatic: importing structural steel in such quantities to Malaysia was expensive, and local contractors were skilled in working with concrete. Concrete is twice as effective as steel at reducing wind sway, although it makes the structure twice as heavy.

Each tower rests on a central concrete core measuring 23 x 23 meters and a ring of 16 cylindrical supercolumns made of the same high-strength concrete. Ring beams connect the supercolumns, forming a moment-frame outer tube — a classic "tube-in-tube" design, where both tubes are made of concrete rather than steel.

The 13,200-cubic-meter concrete foundation slab was poured continuously over 54 hours for each tower. Weighing 32,500 tons, this foundation raft held the world record for the largest single concrete pour until 2007.

It’s worth noting that the towers were originally designed to be 427 meters tall. To surpass the Willis Tower, the architects and engineers redesigned the structure and added a dome with an integrated spire. As a result, the Petronas Towers surpassed the Sears (Willis) Tower by approximately 10 meters.

Taipei 101: A 660-ton pendulum

In 2004, the title of the world’s tallest building passed to the Taipei 101 tower in Taiwan — 508 meters and 101 floors. The building was constructed in one of the most seismically active and typhoon-prone areas in the world, requiring special structural solutions.

Structural system

Taipei 101’s load-bearing system combines a reinforced concrete core with eight 2.4 x 3-meter steel supercolumns located around the perimeter. The columns are steel box sections filled with 69 MPa concrete. Outriggers — horizontal rigid trusses — connect the core to the perimeter columns at multiple levels, allowing the system to collectively support horizontal loads.

The building’s exterior features an octagonal motif, repeated eight times — a number traditionally considered lucky in Chinese culture. Each eight-story module is slightly wider than its base, creating a distinctive stepped profile.

Tuned vibration damper

The key technical feature of Taipei 101 is its tuned mass damper (TMD), a steel sphere approximately 5.5 meters in diameter and weighing approximately 660 tons, suspended by cables between the 87th and 91st floors. When the building sways, the sphere moves in antiphase, damping the vibrations. This solution reduced horizontal displacement of the upper floors during a typhoon by approximately 40%.

The building’s foundation rests on 380 bored piles, each 1.5 meters in diameter, spaced at 4-meter intervals. A concrete foundation slab, 3 to 4.7 meters thick, distributes the load across the entire pile field.

Burj Khalifa: The Limit of What Has Been Achieved

Construction of the Burj Khalifa in Dubai began in January 2004 and was officially opened in January 2010. The building’s spire is 828 meters tall, with 163 floors (or 160 above ground, depending on the calculation methodology). The architectural design was developed by Adrian Smith, and the principal engineer was Bill Baker — both from Skidmore, Owings & Merrill, the same firm that previously designed the Willis Tower.

Form dictated by the wind

The tower’s plan section is Y-shaped. This shape was chosen for aerodynamic reasons: it breaks up the formation of Karman vortex streets, which cause resonant vibrations in the building. Furthermore, as the tower gains height, its sections taper in stages, constantly changing the location and size of their "aerodynamically active" edges. This means that wind vortices do not have time to synchronize along the building’s height.

Five primary structural elements form the system: a central hexagonal core of reinforced concrete, three "petals" of residential and office floors supported by perimeter columns, and wing-shaped outriggers extending from the core. Baker and his team dubbed this concept a "buttressed core": the three "petals" mutually support the central core, preventing it from buckling under wind loads.

Construction site in numbers

Construction required 330,000 cubic meters of concrete and 55,000 tons of steel reinforcement. The total labor intensity amounted to 22 million man-hours. At the peak of the work, approximately 12,000 people were working on the site simultaneously.

Concrete was pumped using a specially designed Putzmeister BSA 14000 SHP-D pump with a higher-than-standard operating pressure. In May 2008, the concrete was pumped to a height of 606 meters — a world record for concrete pumping at the time. Above 606 meters, the structure transitions from reinforced concrete to a steel frame — lighter and more practical at such heights.

Three tower cranes on the upper levels could lift loads of up to 25 tons each. On average, it took three to four days to complete one floor. In 2006, the tower reached the 50th floor, in January 2007 – the 100th, and in April 2008 – the 160th.

Foundation in soft soil

Dubai’s soils are not Chicago rock. Beneath the Burj Khalifa site lie layers of limestone, dolomite, and loose sediments saturated with groundwater containing high levels of sulfates. This required a special concrete composition with increased resistance to chemical attack.

The building’s foundation is a monolithic slab approximately 3.7 meters thick, supported by 192 piles, each 1.5 meters in diameter and 43 meters long. Despite the challenging soil conditions, the foundation work was completed within the timeframe required for similar projects on high-rise buildings with more stable foundations.

Comparison of structural systems

The four key structures, each of which was the tallest in the world in its time, demonstrate a progressive increase in the complexity of engineering solutions.

Materials: steel, concrete and their combinations

Early skyscrapers were built primarily from steel — lightweight, strong in tension and compression, and easy to manufacture in factories. But steel is expensive, and at heights above 400 meters, its high flexibility becomes a drawback: the building sways more than residents would like.

Concrete solves the pumping problem twice as effectively per unit cross-sectional area. This is why Petronas Towers, Burj Khalifa, and many other 21st-century buildings use high-strength concrete as their primary structural material. For Burj Khalifa, a concrete with a cubic strength exceeding 21 MPa under operational conditions was specially developed, with the addition of microsilica and special plasticizers to ensure pumpability.

Modern practice involves combined systems, where concrete acts in compression and provides rigidity, while steel handles tension and simplifies installation. Steel box columns filled with high-strength concrete are used in Taipei 101; in Burj Khalifa, the steel frame takes over from the concrete core at higher altitudes.

High-strength concrete

A concrete three times stronger than conventional structural concrete was developed for the Petronas Towers. This became the starting point for a whole generation of "super-strong" concrete mixes. The Merdeka 118 Tower in Kuala Lumpur (679.9 meters, completed in 2023) uses grade C105 concrete, with a compressive strength of 105 MPa. This is approximately ten times higher than conventional structural concrete.

Wind as the main enemy

At an altitude of 400 meters, wind loads are fundamentally different than at ground level. Average wind speed increases with altitude, but the most serious threat comes not from constant horizontal loads but from vortex shedding — the periodic shedding of vortices from the building’s sides, creating alternating lateral forces.

If the vortex shedding frequency coincides with the building’s natural frequency, resonance occurs. This is precisely the phenomenon the designers of all four buildings under consideration addressed. Willis Tower addressed the problem by staggering the tube breaks. Taipei 101 uses a mass damper. Burj Khalifa has a Y-shaped cross-section with a gradual taper as it rises.

Wind tunnel testing of models has become standard since the 1970s. For the Burj Khalifa, over 40 series of tests were conducted in several leading aerodynamic laboratories worldwide. The models were tested in various configurations of the surrounding buildings, as adjacent buildings significantly influence the airflow patterns at the base.

Outrigger systems

The idea of outriggers — horizontal rigid trusses connecting the central core to the perimeter columns — emerged as a logical development of tubular concepts. While a tube resists horizontal loads through the combined action of its entire perimeter, an outrigger adds a vertical lever: the perimeter columns are brought into play to relieve the core from bending.

In Taipei 101, outrigger trusses are arranged on multiple levels, each occupying an entire technical floor. In Burj Khalifa, the three "petals" of the structure themselves act as outriggers for the central core, preventing it from bending under wind loads while simultaneously supporting its own gravity loads.

Timeline of world records

The title of the tallest building on the planet has passed from city to city: New York for 66 years, then Chicago with the Willis Tower (25 years), then Kuala Lumpur with the Petronas Towers (1998–2004), then Taipei with the Taipei 101 tower (2004–2010), and from 2010 to the present day, Dubai with the Burj Khalifa.

Logistics of construction at extreme heights

The taller the building, the more complex its construction. Three challenges recur on any record-breaking construction project: vertical transport of materials, working in extreme weather conditions, and ensuring precision installation while allowing for thermal expansion.

At Burj Khalifa, concrete was poured at night to avoid exposure to Dubai’s daytime heat. At high temperatures, the water-cement ratio in the mix changes, affecting strength gain. The tower cranes on the upper levels had to be able to handle wind speeds significantly higher than those at ground level.

At Petronas Towers, construction progressed at a rate of approximately one floor every four days, and even faster during peak periods. The tower cranes were repositioned using special self-climbing mechanisms: each crane that reached a new level would automatically raise itself to the next position.

Installation accuracy at such a height has direct structural consequences. Column deviations from vertical are cumulative over the entire height of the building. At Willis Tower, tolerances were specified in millimeters for each section; prefabricated steel elements were delivered to the installation site from the factory already welded into sections.

Engineers as the true creators of skyscrapers

In architectural criticism, the authorship of a skyscraper is almost always attributed to the architect. Meanwhile, the shape of a high-rise building is largely determined by the structural engineer, working with specific loads, periods of oscillation, and safety factors.

Fazlur Khan formulated this bluntly: he distinguished between the building’s architectural function and its structural logic, insisting there was no contradiction between the two. His tube-shaped structure in the Willis Tower dictates not only its form but also its commercial layout: each tubular cell is an independent block of space, which can be rented separately or combined with its neighbors.

Bill Baker applied the same logic to the design of the Burj Khalifa: the Y-shaped cross-section and the "supported core" system are not decorative solutions, but a response to specific loads. Architect Adrian Smith worked with Baker, and the building’s final form is the result of an iterative dialogue, with each subsequent design tested in a wind tunnel.

From steel frames to ultra-high-rise systems

The journey from the 42-meter Home Insurance Building to the 828-meter Burj Khalifa took 125 years. During this time, the record-breaking building’s height increased 20-fold, but the fundamental goal remained the same: build higher and more affordably than before, without sacrificing strength and comfort.

Every time engineering reached a new practical limit, it found a way around it. Masonry walls became too thick — steel framing was introduced. Steel framing proved too flexible — tubular systems were introduced. A single tube didn’t provide the necessary rigidity — bundled tubes were introduced. An unsupported core buckled in the wind — outriggers and "supported cores" were introduced.

Exchange of technologies between continents

A characteristic feature of this story is the geography of innovation. The Chicago School of Engineering was based in Illinois, but its ideas were embodied decades later in the concrete towers of Kuala Lumpur. Bangladeshi engineer Fazlur Khan, working in the American office, developed a system used by Malaysian contractors during the construction of Petronas. German concrete pump manufacturer Putzmeister developed a special pump for pouring concrete at altitudes of over 600 meters in Dubai.

The construction of the Burj Khalifa brought together an American design firm (SOM), a Korean general contractor (Samsung C&T), a Belgian construction company (BESIX), a local contractor (Arabtec), and workers primarily from South Asia. By the 21st century, high-rise construction has become a global industry, with technological chains crossing several continents.

Seismicity and wind: regional specifics

Willis Tower and Petronas Towers were built in zones of moderate seismic activity. Taipei 101 is located in a zone of high seismic hazard and frequent typhoons, which directly dictated the use of a tuned mass damper. Burj Khalifa was built in an area where strong earthquakes are rare, but prevailing coastal winds create specific loads.

Each of these buildings is a response to the local physical environment. Engineers don’t simply copy successful solutions, but adapt them to the specific site conditions, climate, and geology. This is why each design is something new, even if the basic principles remain the same.