English | Dzongkha Thursday, April 2, 2020

Japanese experts conduct successful pull-down test of rammed earth structures

Sonam Phuntsho, Thimphu
Sep 21, 2017

A Japanese team of experts successfully conducted a pull-down test of rammed earth structures as a part of ongoing scientific research in Bhutan to constructing a seismic or earthquake resilient traditional buildings yesterday.

The test is one of the activities by the joint project between the government and Japan International Cooperation Agency (JICA).

One of the prerequisites under the “Evaluation and Mitigation of Seismic Risk for Composite Masonry Buildings in Bhutan” project is a test that involves pulling down of the rammed structures. According to experts, this will help them assess the characteristics of rammed earth structures and effectiveness of strengthening them.

“We are doing two separate tests today. One is with reinforced and another is without the reinforcement with maximum load,” said Dr. Takayoshi Aoki, the Professor of Structural Engineering, Nagoya City University in Japan.

He added, “Reinforced structured floor is rigid to carry a load but structures which are not reinforced does not have enough strength to carry a load. We plan to do real scale test which is fundamental to know how to lay reinforced structures.”

With technical support from Science and Technology Research Partnership for Sustainable Development, the test result is also likely to benefit agencies like Department of Disaster Management in risk reduction.

“Till now we don’t have any guidelines for the rammed work structures in the country. So that is why the buildings that were constructed long time ago or the buildings that are going to be constructed in future, we don’t have any guidelines to be followed,” said Yeshey Loday, the Executive Engineer with the Department of Disaster Management. “Through this pull-down test, we can come up with guidelines which can be imparted to communities to follow for the preparation for any events in future.”

As per the recent statistics, 66 per cent of households in the country are traditionally built using indigenous materials and techniques which do not have specific code of standards. One of the implementing organisations, Department of Culture, said it would also help them guide citizens to improve the seismic resilience of traditional houses without compromising the aesthetic values.

“If you look into housing typological construction, it is either rammed or stone masonry. And till now, there is no scientific data on construction of rammed or be it stone masonry,” said Pema, Deputy Executive Engineer with the Department of Culture. “So we are doing scientific test so that we could preserve the traditional knowledge system of Bhutanese construction typology.”

A remarkable number of buildings constructed of indigenous materials and techniques were destroyed due to earthquakes in 2009 and 2011. Since then, it became a critical task for the government to come up with earthquake resilient traditional houses guidelines. For seismologists, the test has a definitive link which can help them to create a zonation seismic hazard map.

“Looking at the ground behavior can be quite different from one place to another depending on type of site. So basically there is a strong link between what we are doing in terms of assessing the seismic hazard and what they are doing to strengthen the structures,” said Dowchu Drukpa, the Chief Seismologist of the Department of Geology and Mines.

Once the project is completed in 2022, the government is expected to be well-equipped in terms of seismic or earthquake disaster and mitigation of the composite masonry buildings across the country.

According to the Geophysical Research Letters, a journal of the American Geophysical Union, Bhutan experienced the mega earthquake in the year 1714, measuring 8 on Richter Scale.



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