A day before Japan disaster, DOST calls for quake-resistant house materials

For a change, the Philippine government was proactive in disaster preparedness when the Philippine Institute of Volcanology and Seismology (Phivolcs) and its mother agency, the Department of Science and Technology (DOST), held a press briefing on Thursday – exactly a day before a killer 8.9-magnitude earthquake devastated Japan – to call for the use of quality construction materials for safer homes in times of earthquakes.

Phivolcs director Renato Solidum and DOST secretary Mario Montejo during the presscon on Thursday at the Phivolcs office in Quezon City

The call came after a shaking table test conducted on two full scale (or true dimension) Philippine model masonry houses in Tsukuba, Japan last February 24, 2011. Masonry houses are concrete hollow block (CHB) structures with no structural beams and columns.

In the test conducted by DOST-Phivolcs and Japan’s National Research Institute for Earth Science and Disaster Prevention (NIED) on the two model houses, they were able to determine that the Building Code-compliant or engineered house (Model A) performed better than the substandard or non-engineered house (Model B) and can withstand a 6.9-magnitude earthquake similar to the one that struck Kobe, Japan in 1995.

Model A used the standard 6-inch thick CHBs with 10 millimeter deformed steel bars as reinforcement spaced at 0.4 meter vertically and 0.6 meter horizontally (or every three layers of CHB).

On the other hand, Model B only used 4-inch thick CHB with substandard 6-millimeter smooth steel bars and whose construction fell below the building code requirements. Both model houses used 864 pieces of CHB from Marikina and exported to Japan for the experiment.

The shaking table tests showed that Model B was easily damaged and eventually collapsed. Model A was able to hold its ground with minor damages after it was subjected to a magnitude 6.9 shock.

Officials look at the presentation showing the test done in Japan

“The lesson in all these is that Filipino homes are generally safer from earthquakes just as long as they follow prescribed guidelines in our Building Code, including the use of construction materials that pass quality standards. There are no shortcuts to safety,” said Phivolcs director Renato Solidum.

Solidum stressed that even if the test is just one dimensional simulation of an earthquake, it validates properly designed and constructed structures can withstand and survived tremors better than poorly constructed ones. An earthquake has three directions, one vertical and two horizontal movements.

The need for strong homes and buildings came again to the fore in the wake of the recent earthquakes like the magnitude 6.3 earthquakes that rocked Christchurch, New Zealand and China.

According to Phivolcs, the experiment is important for awareness and disaster mitigation campaign for most of the masonry type houses in the country are located in seismic prone areas.

Phivolcs said that it is necessary to investigate the seismic performance of the masonry houses for most loss of lives in past earthquakes occurred due to collapse of these non-engineered buildings.

The agency further stated that the Model B type are widely used here in the country for these are favored by low-income families because of the simple design and can be easily erected, which most often are done by homeowners themselves or neighbors.

A closer view of the shaking table test

DOST secretary Mario Montejo said the DOST will try to put up a shaking table in the country for similar tests. “With this kind of facility, we will be able to raise the level of seismic research by providing the means to replicate conditions that are identical to true earthquake ground motions,” said Montejo.

Once fully documented, the result of the test shall be used by Phivolcs-DOST and its partner organizations to improve and ensure adherence to proper construction practices of houses especially for lower-income families.

The agency said it will also come up with a checklist or awareness tool for homeowners to check if their houses are building compliant. The tool will also include viable, economic and safe retrofitting methods for existing substandard CHB houses and construction of new houses.

Video footage of the shaking experiment is being distributed for public consumption for implementation and monitoring of construction standards especially for local government building officials for monitoring new construction substandard houses.

The experiment is a project of DOST- Phivolcs with Japan Science and Technology and Japan International Cooperation Agency (JICA) for Science Research Partnership for Sustainable Development under the program “Enhancement of Earthquake and Volcano Monitoring and Effective Utilization of Disaster Mitigation Information in the Philippines.”

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