If there is no terrorist attack, the pure steel structure of the skyscraper will "stand up". When Americans began to reflect on the sturdiness of skyscrapers, the Chinese were thinking too – because in the event of a natural disaster, cheaper reinforced concrete structures could not match the pure steel structure.
Chinese current tallest timber-framed building, the county wooden tower, was built in 1056 and has been in existence for more than 900 years. The Zhaozhou Bridge built by Li Chun in 610 still straddles the Weihe River in Zhao County. The Limeila Bridge, which was earlier than Zhaozhou Bridge, was built in the 3rd century AD. This ancient Roman bridge is still in the ancient city of Turkey. (Limyra)
The Great Pyramid of Giza was completed in 2560 BC, but the world's first skyscraper, the New York Home Insurance Building, was demolished in 1931. It was built only 46 years ago, the famous pure steel structure of the Empire State Building. It has only stood for 81 years.
In July 2012, the Emporis Real Estate Database released a list of the top ten skyscrapers in the world, five of which are in China. When the era of Chinese skyscrapers arrives, will their quality make them collapse before the term of property rights comes?
The collapse of the Twin Towers allowed the industry to reflect, and the era of pure steel structures in the skyscrapers was over.
Most of the famous buildings in history can't escape the two fates,which are fire and earthquake. The Greek poet Antipater of Sidon listed four of the seven wonders of the ancient world, four of which were destroyed by the earthquake. The other two, the Temple of Artemis, were burned by the Greek young man Johors Darts. The arsonist just wanted to be written into history with the architecture of one of the seven wonders. The Zeus image of Olympia was also destroyed by the fire. The only thing left is the Giza Grand Pyramid, a limestone building in a dry desert that has stood the test of time and stands still.
The Chicago fire destroyed a city of 9 square kilometers in 1871. The significance of this fire is the birth of the Chicago School of Architecture, which has propelled the era of skyscrapers. Most of the early skyscrapers were pure steel structures. The Home Insurance Building was built in Chicago. The 42-meter-high 10-story building is considered to be the world's first skyscraper. The lower 6-layer pig iron column is a wrought iron beam frame. The top 4 floors are Steel frame, according to a 2000 data, there are 59 pure steel structures in 101 super high-rise buildings around the world. These include the Empire State Building built in 1931, the former World Trade Center in New York, and the Sears Tower in Chicago.
Peng Wu, head of the Shanghai branch of the Shanghai branch of Gensler's Shanghai office, said that at the same height, the construction of pure steel structures is lighter and more flexible, but relatively expensive. The construction of pure steel structure is relatively fast. The Empire State Building was built in only one year and two months. It is more suitable in countries with expensive labor. In China, the labor is relatively cheap, and the concrete structure is obviously more adaptable to the national conditions, which can reduce the material cost without a large burden of labor costs. Whether or not to use pure steel structures is also geographically relevant. Hong Kong's skyscrapers rarely have pure steel structures, and are basically reinforced concrete structures. The activity of earthquakes in Hong Kong is relatively low, and skyscrapers mainly need to resist wind.
After "9.11", the industry has a reflection on the super-high-rise building with pure steel structure, because it has natural defects in fire resistance. When the temperature reaches 1000 degrees or more, the steel structure will immediately fail, resulting in continuous collapse effect. From the top to the bottom, the Twin Towers in New York collapsed like this. Peng Wu said that the new super high-rise buildings are no longer using pure steel structures. The core tube section must use a reinforced concrete structure, that is, the steel structure is wrapped with concrete. For example, the Shanghai Center is like this. The core of the giant pillar is covered with concrete and the inside is shaped steel. Peng Wu said that if you want to talk about construction risks, for now, there is no greater risk than terrorist attacks. Of course, he refers to the scale of "9·11".
In the event of a major earthquake, you should flee to the tallest building in the city. Because in history, it seems that there is no skyscraper because of the earthquake.
The most dangerous aspect of a super high-rise building in a fire is the chimney effect. In a vertical space, the fire will spread rapidly. Today's skyscrapers are generally built using partitions, with more than a dozen layers as a partition to isolate the continuity of the space, and each partition has a refuge. The center of Shanghai is 632 meters, with a total of 9 divisions.
The only continuous space in a super high-rise building is the elevator shaft. Therefore, there are many obstacles from the use of flammable materials to the elevator shaft, such as fire doors, so as to ensure the isolation between the elevator shaft and the flammable materials, there will be no fire to the elevator shaft.
There have been no skyscrapers in history due to the collapse of the earthquake. Therefore, skyscrapers are a good shelter if there is a major earthquake. From a professional point of view, Peng Wu said that the design requirement of the skyscraper is that there is no problem with small earthquakes. After a medium-sized earthquake, it can be repaired and reused. It will not collapse in a major earthquake. In addition to the earthquake, the most important thing about the skyscraper is to keep out the wind. The 828-meter-high Burj Khalifa has a top wind speed of 198 km/h.
The design of the skyscraper also follows the concept of aerodynamics. Just like an airplane wing, if the shape is wrong, it will not fly. Peng Wu said that when designing super high-rise buildings, it is necessary to verify with the wind-driven engineers that the shape of the building should be round, the top is small, the bottom is large, there are some rounded corners, and the asymmetrical shape minimizes the effect of wind on the building. force. The current parametric design allows the building to have more rounded corners, which is of great help to structural engineers.
In Peng Wu's view, the life of a building cannot be simply compared. The complexity of contemporary architecture is certainly higher than that of Egypt and the Tang Dynasty. The Egyptian Pyramid is a stone-built tomb that has a single function and does not even have to build an elevator shaft. As a temporary building in the industrial revolution era, the Eiffel Tower can stand for so many years and will continue to survive for hundreds of years, mainly because it is a single-function steel structure. The fire protection facilities are not as complicated as the houses, just need to be preserved, not Let the metal corrode and let it stand in place.
"Building life is a combination of many requirements. For example, today's buildings use a lot of adhesives. The life of the adhesive is at most 20 years. The regulation is only a bottom line. If it is continuously tested, the aging materials will be used. Timely replacement, then the building life will definitely be more than 70 years." Peng Wu said.
"Extended life is actually a problem of late detection and maintenance. The 425 Park Avenue Tower in New York has been 65 years old, but this year it has been rebuilt by rebuilding the rest of the design by retaining 25% of the base. New 75 The weight of the building does not exceed the original index, because the application of a large number of glass and aluminum frame systems makes the outer skin lighter.