EARTHQUAKE-SAFE BUILDINGS

ABSTRACT

This article discusses options for assimilation of earthquake-proof building technologies and methods from widely used in Japan in the context of Uzbekistan. This is an attempt to analyze if base isolation or earthquake safety structure is expedient for use in our country.

АННОТАЦИЯ

В статье рассматриваются варианты освоения сейсмостойких строительных технологий и методов из широко используемых в Японии в контексте Узбекистана. Это попытка проанализировать, целесообразно ли использовать изоляцию основания или сейсмостойкую конструкцию в нашей стране.

Keywords: earthquake, earthquake-proof, earthquake-resistant, seismic, magnitude, Uzbekistan, Japan, safety, technology, structure, base isolation, building, isolator, law.

Ключевые слова: землетрясение, сейсмостойкость, сейсмическая защита, сейсмичность, магнитуда, Узбекистан, Япония, безопасность, технология, конструкция, изоляция основания, здание, изолятор, закон.

The issue of constructing earthquake-proof buildings has always been a major hazard all around the world, because earthquakes are one of the most destructive natural disasters. This obviously applies to Uzbekistan coupled with its location, where part of the country including the capital rests on one of geographic faults, which may possibly generate earthquakes with a magnitude of up to 7.5. Uzbekistan has a seismic hazard map where seismic intensity is shown according to the region (see Pic. 1.).  Earthquake-resistant buildings must stand up the uttermost earthquakes or at least give enough time to people to evacuate from the building to a safe place. To address this problem, there are two methods called earthquake-resistant and base isolated structure commonly used in Japan that can guarantee safety of the people and buildings. In Uzbekistan, these methods are used rarely and only in extremely expensive buildings, because these methods are costly.

Picture 1. Seismic intensity is shown according to the region [1]

According to Economist Intelligence Unit’s Safe Cities Index, Japan is considered as one of the safest countries around the world due to its excellence in earthquake-proofing technologies. Thus far, Japan has mainly been using earthquake-resistant structure and base isolation structure, which have proven to be effective in global practice. Moreover, Tokyo University has researched that 87% of the Tokyo’s structures were built in accordance with modern anti-seismic requirements [1].  Every year, around 500,000 measurable earthquakes occur across the world, approximately 20 of which are major [2].

Uzbekistan is located in one of the earthquake-prone regions in Central Asia. Earthquakes with a magnitude of up to 7.5 are possible in this area. In 1966, Tashkent was hit by a catastrophic earthquake with magnitude of 5.2 leading to a total devastation of Tashkent, the capital city. This accident pushed Uzbekistan to seriously consider earthquake safety and since then we have been gaining more experience, knowledge and preparedness in this area. The President signed a Law on 13 September 2021 “On Ensuring Seismic Safety of the Population and Territory of the Republic of Uzbekistan”, which will come into effect in six months [3]. This is especially relevant now when our country is experiencing a boom in housing and other type of construction at the moment. To help enforce the recent law, it is advisable to consider the two methods discussed in this article.

Seismic-resistant structures are the most typical for detached buildings in Japan. A seismic-resistant structure permits the primary building structures such as posts, walls, and floors, to absorb seismic shocks. Buildings are classified into two types: stiff structures (built rigorously to prevent collapse) and flexible structures (the main structural parts of which bow flexibly in order to spread the force of seismic motions). In an earthquake, conventional structures tremble together with the ground. They may withstand structural damage but are designed to remain standing. Thus, the magnitude of an earthquake is directly proportional to the movement of the building, the higher the intensity of the earthquake, the more the building moves in return. Consequently, if the building shakes too much, structural parts such as beams, columns, walls, and braces might be destroyed, leaving the structure nonfunctional [4].

Dr. Bill Robinson, invented base isolator bearings, which consist of layers of rubber and steel with a lead core in mid-1970s [5]. Seismic base isolation, which is commonly utilized as part of the foundation of high-rise structures, places quake-absorbing devices (isolators) such as laminated rubber that prevents seismic vibrations from reaching the building. Base isolation method enables a building to float on a system of bearings such as metallic or lead-core rubber bearing, heavy-duty springs, padded cylinders, sliders or even air cushions, while remaining upright during a quake. The goal of seismic base isolation is to passively absorb or deflect earthquake kinetic energy by placing an elastic or sliding buffer between the foundation and the building superstructure. Seismic isolated structures can lower seismic intensity by up to 80% in comparison to earthquake-resistant structures. Buildings that implement base isolation are more likely to survive and function after a big earthquake. For instance, Apple’s futuristic new headquarter near San Francisco (USA) sits on 700 base isolators [1]. Another example is of an architect for a large Japanese construction company in Kobe, Mr. Yasuhisa Itakura. During the Great Hanshin earthquake of January 17, 1995, that killed more than 6,000 people in and around the industrial port city, Mr. Itakura had been cushioned from the violence of the earthquake because his three-story office building was sitting on an experimental foundation made from rubber — an early version of an engineering technique called base isolation [4].

The current context in Uzbekistan including plentiful new construction and developments in the relevant legal and regulatory framework is ideal for piloting well-proven anti-seismic technologies: earthquake-resistant structures or seismic base isolation. Although construction of seismic-resistant structure is less expensive than seismic base isolation structure as it does not require extra equipment and monitoring, which possibly allow for savings on purchases and maintenance, in my opinion, seismic base isolation is more reliable and safer, because the whole structure swims not affecting the building and people as can be seen from Yasuhisa Itakura’s example. In addition, you may end up spending more money on equipment and maintenance, but you will gain in overall building safety, which will save you more money, but more importantly, people’s lives.

References:

1. Yakubova, N. R., et al. Ecological Atlas of Uzbekistan. National University of Uzbekistan named after Mirzo Ulugbek, A.E. Ergashev, 2007.
2. “Earthquake Proof Builing in Japan: Tokyo Advanced Technologies.” We Build Value - Webuild’s Digital Magazine, 27 June 2018, www.webuildvalue.com/en/reportage/tokyo-the-earthquake-proof-city.html.
3.  “Building Earthquake-Resistant Buildings.” URBAN HUB, www.urban-hub.com/cities/built-in-earthquake-safety-cities-and-designs-on-the-frontlines. Accessed 25 Oct. 2021.
4. “Закон республики Узбекистан об обеспечении сейсмической безопасности населения и территории республики узбекистан.” Lex.Uz - Законодательство Узбекистана, 13 Sept. 2021, lex.uz/docs/5630183.
5. Fuller, Thomas, et al. “Buildings Can Be Designed to Withstand Earthquakes. Why Doesn’t the U.S. Build More of Them?” The New York Times, 7 June 2019, www.nytimes.com/interactive/2019/06/03/us/earthquake-preparedness-usa-japan.html.
6. “Seismic Base Isolation.” Wikipedia, en.wikipedia.org/wiki/Seismic_base_isolation. Accessed 29 Oct. 2021.