After a strong earthquake in Turkey and Syria, which destroyed hundreds of buildings and killed tens of thousands of people, the Committee for Architecture and Construction of Tajikistan decided to test the seismic resistance of new buildings in Dushanbe, Khujand and Bokhtar. Checks have already begun.
The commission that will deal with this will include specialists and the deputy chairman of the committee (chairman of the commission), employees of the Service for State Control of Architecture and Construction, the Institute of Geology and Seismology, the Research Institute of Construction and Architecture, State Unitary Enterprise Loihakash and the Department of State Expertise of Urban Planning Design Documentation.
Buildings and structures put into operation in 2018-2022, as well as construction in progress, will be tested. What punishment will await developers who do not pass these checks is not yet known, it is not clear what will happen to the buildings themselves.
The results of the inspections will be presented to the Chairman of the Committee for Architecture and Construction by March 10, 2023.
Will Dushanbe survive?
Meanwhile, on February 8, the head of the Committee for Architecture and Construction, Nizom Mirzozoda, told reporters that “buildings in Dushanbe will withstand an earthquake of magnitude 8.5 and magnitude 9.” Asia-Plus turned to seismologists and found out that this is real only if seismic safety standards are met during construction.
Director of the Institute of Geology, Seismic Construction and Seismology of the National Academy of Sciences, a specialist in the field of seismic construction Pulod Aminzoda told Asia-Plus about everything in detail.
“Tajikistan is located in one of the most seismically dangerous zones in Central Asia. According to the current standards, 50% of the territory of Tajikistan belongs to the 9-point zone, 38% to the 8-point zone and 12% to the 7-point zone, determined in accordance with the seismic scale MSK.
In this regard, we must always be prepared for a possible strong earthquake, – says the expert. – At present, it is impossible to predict the time and place of a strong earthquake for the next, say, a few days, as is done with a weather forecast. But at the same time, it is possible to prevent the consequences of a probable destructive earthquake.”
First of all, Aminzoda says, this can be done on the basis of a seismic zoning map or a seismic hazard map, which is, in fact, the result of a long-term earthquake forecast.
“The basis for their construction is historical data on strong and destructive earthquakes, the frequency of shocks, the presence of faults in the earth’s crust, the results of earthquake monitoring and other data,” he explains.
What caused the great destruction in Turkey?
In his opinion, one of the reasons for the devastating consequences of Turkish earthquakes, which are 9-10 points in manifestation, is the untimely response to the developed seismic hazard maps presented in the 2018 Turkish seismic resistance standards.
Dushanbe, archive photo
Photo cabar.asia
“According to estimates, these maps fully reflected the seismic hazard in terms of maximum ground accelerations that occurred during earthquakes according to instrumental observations. And these are accelerations up to 0.6-0.7g (g = 9.81 meters per second squared – acceleration of free fall ) and specifically for the zone where the February earthquakes occurred, – says the director of the institute. – According to the materials available on the Internet, most of the destroyed buildings were built during the early 2000s and, as follows from the same Internet, according to the standards of 1997, in which the maximum calculated ground accelerations were 0.4g.
That is, if timely attention was paid to the increase in the seismic hazard level in the norms and the necessary measures were taken to reduce the risk from it, in other words, if work was carried out in a timely manner to strengthen insufficiently earthquake-resistant buildings in accordance with the new norms, then, obviously, the losses from earthquakes in Turkey would have been much lower.”
The specialist notes one more nuance that should be noted: “all normative seismic hazard maps for the territory of Turkey are developed for an earthquake return period (a term accepted in seismology) of 475 years.”
“According to the recommendations of some foreign standards, the calculations of buildings and structures for this level of earthquakes should be carried out in an elastic setting, that is, not allowing any significant damage to the buildings, not to mention destruction,” Aminzoda said.
Photo: Asia Plus
There are principles, but what about norms?
As for Dushanbe, according to Pulod Aminzoda, the design and construction of all buildings without exception above 5 floors is carried out based on a magnitude 9 earthquake, although according to historical data, earthquakes of such intensity have not yet been observed in Dushanbe.
“If we talk about the devastating Karatag earthquake of 1907 with a force of 9-10 points in the epicentral zone, then in Dushanbe it manifested itself with a force of no more than 8 points. Despite this, taking into account the high-rise buildings of the city, its dense population, the estimated seismicity for Dushanbe is taken at 9 points , – explains the specialist.
Speaking about the seismic resistance of a building, the following should be noted: an earthquake-resistant building is a building in which, during a calculated earthquake, damage, cracks, partitions and other factors may appear in the supporting structures, but the building does not collapse.
That is, during a calculated earthquake, the safety of people and the safety of valuable equipment should be ensured. And this is precisely what is regulated by the current principles of seismic resistance,” Pulod Aminzoda concluded.
But these principles, as the head of the Architecture Committee said above, work if seismic safety standards are observed during construction.
But what should they be?
Unfortunately, we have not yet been able to get an answer to this question. The Architecture and Construction Committee promised to respond only after a written request. We sent it and will wait for a response. Among other things, we asked what would happen to those objects that would not pass the inspection of the established commission.
Source: Asia Plus TJ