How much are buildings in Russia protected against earthquakes?
The state when the ground crumbles under your feet is very dangerous for both people and buildings located in seismically active zones. For centuries people tried to build housing in such regions after taking into account natural peculiarities of the terrain.
What to irrigate the ground with? Milk!
In ancient times people had rather few opportunities for detailed calculation and construction of safe housing. Nevertheless, construction craftsmen in different countries bequeathed their descendants many objects, the architectural perfection and strength of which set modern historians, scientists and architects wondering.
According to historians, the first constructors who paid special attention to earthquake-proof capital structures were the Incas and other inhabitants of ancient Peru. The peculiarities of their architecture are in the careful laying of compact stone blocks without any use of a matrix. Due to this method there were no vibrancy and high stress concentration points in the ancient Peruvians’ buildings which gave floor structures additional strength.
When earthquake shocks were weak such structures remained almost still, and with strong shocks the stones moved a little and then returned to their primary position. According to researchers, the dry walling the Incas used may be considered the first arrangement of vibrancy control of buildings.
On the territory of Russia, examples of such architecture may be found in the Caucasus mountains, amongst outlook and pele towers.
— Our ancestors actually poured milk on the ground until it stopped absorbing it. This tradition was passed on from generation to generation and was in fact the simplest scientific experiment and technical method for checking the seismic safety of a land plot for a tower or a funerary temple construction, — Khamid Mamaev, Deputy Director of the Chechen Republic Academy of Sciences’ Humanities Institute, explains.
According to him, this peculiar observance, of “testing a place”, was widespread among many North-Caucasian peoples. A closed jug with milk or water used to be dug into the ground for future construction. In several days it was dug out and people checked how much liquid stayed inside it. If there was little or no liquid at all, the place was considered unsuitable for construction.
The construction was carried out on rocky bottoms of mountains, where the firm surface provided for the relative stability of a structure. According to the scientist, the seismic stability was taken into account in Dagestan in the early Middle Ages.
The double wall of the city fortress of Derbent, from the Sasanids period, is an example. According to Mamaev, the ancient craftsmen deserve credit for the fact that the ancient monuments they constructed survived until the present day as they knew the laws of earthquake-proof construction.
Where are the strongest earthquakes?
Earthquake endangered zones exist in many countries on different continents. The most active is the so-called Pacific Ring of Fire. It closes the Pacific with its coastal areas of North and South America, Japan, China and Russia.
Most earthquakes take part there. And most often we hear about Japan, where strong earthquake shocks are registered regularly.
Special requirements for construction exist in Japan. The Japanese have used the technology of suspended facades in framed housing construction since ancient times. By the end of the last century, the largest scientific research base in the sphere of construction technologies had been created in Japan. The country became the world leader in the production of extra high strength steel, and unique protection and security systems of a building’s management in case of emergency situations were created there.
According to experts, a traditional Japanese house is considered a unique earthquake-proof invention in the world. A light structure of a building folds during an earthquake, thus making it possible for people to survive during an emergency. Additionally, such a house is sustainable, where operable walls instead of windows allow rooms to be aired in summer, and for saving on heating in winter due to the small local zones inside.
How’s it in Russia? Not very efficient
There are seismically active zones on the territory of Russia: Northern Caucasus, the Altai, the Sayans, the Koriak highlands, the Kuril Islands, Sakhalin, the Amur region, and the Baikal zone.
According to seismologists, 60—90% of buildings in Russia cannot be acknowledged earthquake proof due to poor coordination between specialists participating in construction.
For example, in the Chechen Republic (North Caucasus) thousands of people live and work in buildings with little in the way of seismic resistance. Actually, every building does not correspond with the norms of seismic reliability.
However, many construction organisations do not research and check the terrain completely regarding its seismic safety. According to Richard Ismailov, Chief Engineer of the Centre for seismic safety of the Chechen Republic, the necessity for earthquake-proof construction should be a priority. Its results make it possible to determine how high a building constructed on the territory should be and the level of strong earthquake shocks it ought to be able to withstand. The requirement for all the objects constructed in the Republic today is to withstand 9-score shocks.
What should be done? Design quality to be raised
The main task of earthquake-proof construction is to forecast the consequences of a possible seismic impact. One of the most efficient tools, according to specialists, is the vibration monitoring of the seismic load, allowing for the construction of relatively light and cheap premises.
According to geo-scientists, to decrease the risks for the inhabitants of seismic zones, it is necessary to develop new and efficient methods for enhancing the seismic resistance of buildings and structures, plus to improve the quality of objects’ project designing in such areas after taking into account the current regulations.
One of the technical solutions for earthquake-proof construction is the increase of strength and stability of basic bearing structures. Thus, the technology of seismic insulators is widely used in the construction of buildings. Its main task is to level dynamic loads at the foundation. The use of such systems in Russia began recently. To render objects safe constructors also use special earthquake-proof foundations and other elements.
— During a seismic impact its destroying power is neutralised due to the strength of a building’s bearing structures, — Khasan Majiyev, Doctor of Science, Construction Structures Department Chairman of Grozny oil technical university named after D.M. Millionschikov, says.
According to him, the key role in providing the seismic safety of objects belongs to the choice of the construction ground. Current standards allow construction on plots with an 8—9-score maximum likelihood of an earthquake.
Seismic resistant construction materials are being developed. For example, special components are added to concrete, enhancing its strength. Infiltrated fine-grained concrete is popular with builders.
Municipal and governmental services are to pay special attention to increasing the earthquake resistance of buildings, especially those that are social, strategically important, industrial or educational.
Larisa KERIMOVA, Grozny