Earthquakes are among the most destructive forces of nature. Usually, structures and infrastructures suffer the most when earthquakes strike a seismically active area in the world. Therefore, seismic loadings must be taken into account when designing structures, specifically these that are considered as skyscrapers.
Let us roam around the world and discover the top five earthquake-proof structures and see how buildings can be designed to resist extremely strong earthquakes.
We all know about the existence of tectonic plates and how they affect the movement of the Earth’s crust. Earthquakes occur when the tectonic plates collide with one another and produce big magnitudes of energy which are measured by using the Richter scale. The movement of those tectonic plates can be attributed to one simple physical phenomenon – convection.
Sabiha Gökçen is one of the two international airports in Istanbul, Turkey, located next to the North Anatolian fault. It was designed by the Ove Arup to have 300 base isolator systems that can withstand up to 8.0 Mw earthquake. The base isolators can lower lateral seismic loadings by 80%which makes it one of the most massive seismically isolated structure in the world.
The Transamerica Pyramid is an iconic structure of 1970 hosted by the Californian city of San Francisco that sits closely beside the San Andreas and Hayward faults. The Loma Prieta earthquake struck the structure at a magnitude of 6.9 Mw in 1989, that caused the top story to sway, by approximately one foot from side to side, for over a minute. However, the building stood tall and undamaged. That earthquake resistance feat might be attributed to the 52-foot-deep steel and concrete foundation which is designed to move with seismic loadings freely. These vertical and horizontal loadings are supported by a truss system above the first level with interior frames that extend up to the 45th level. The complex combination of the structural systems makes the building resistant to torsional movements and this way, large horizontal base shear forces can be absorbed.
Burj Khalifa is among the most iconic supertall structures in the world. Additionally, it’s earthquake resistant! It’s composed of mechanical floors where outrigger walls connect the perimeter columnsto the interior walling. By doing that, the perimeter columns can contribute support for the lateral resistance of the structure and the verticality of the columns help with carrying the gravity loads. Therefore, Burj Khalifa is exceptionally stiff in both lateral and torsional directions. A complex system of base and foundation design was derived by conducting extensive seismic and geotechnical studies which gave the skyscraper stringent structural measures against earthquakes.
Apart from the architecture, the mind-blowing fact about Taipei 101 is that it houses the largest tuned mass damper (TMD) in the world! It’s a gigantic metal ball that counteracts huge transient loadings such as wind and earthquake to lower the sway of the supertall tower. The TMD is supported by hydraulic viscous damper arms as well as a bumper system that function in the same way as a car’s shock absorber. When large forces act upon the tower the TMD sway in the opposite direction bringing the entire building in equilibrium by damping out the transient forces using the ball’s mass.
Taipei 101’s tuned mass damper [Image Source:Taipei 101]
The arena was designed by Populous, an Australian architecture firm, and Buro Happold, an elite engineering firm. The Philippine plate sits along the Pacific ring of fire, the most notorious and active chain of earthquake fault lines in the world. Previous earthquakes in the country have surmounted up to 8.2 Mw and have claimed thousands of lives where the epicenters originate, and the seismic activities were also responsible for igniting volcanic eruptions and tsunamis.
Inside the Philippine Arena with large roof truss [Image Source:Buro Happold]
Philippine Arena’s vast stadium roof, spanning 165m in the shortest direction, was engineered to withstand major transient loadings such as earthquakes, winds, and typhoons. During an earthquake tremor, the lateral loads which generate throughout the structure can be up to 40 percent of its mass. Buro Happold smartly responded with an independent base design for the whole structure which means that the main structural body of the arena is isolated from its base and foundation.
The gap between the main structure and base foundation system is composed of lead-rubber bearings (LRB) which are a flexible arrangement of materials with high energy dissipation properties. That allows the base and foundation system to freely move with the earthquake force while the top structure remains stationary during dynamic actions.