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Thursday, 10 March 2011 11:02

In tests conducted at a shaking table laboratory in Tsukuba, the DOST-Philippine Institute of Volcanology and Seismology (PHIVOLCS) and Japan’s National Research Institute for Earth Science and Disaster Prevention (NIED) were able to determine that Philippine masonry houses that follow the required size of concrete hollow blocks and reinforcing bars and meticulous application of mortar can improve its performance during a strong earthquake similar to the magnitude 6.9 earthquake that struck Kobe in 1995. Masonry houses are structures with no structural beams and columns and are often the preferred houses by low-income families because these have simple design and can be easily constructed.


Two full-scale model masonry houses, only one of which followed the standard local building code, were constructed on top of NIED’s 1-directional large-scale shaking table laboratory. Model A used the standard 6-inch thick concrete hollow blocks (CHB) 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 building code requirements.
The shaking table tests, witnessed by DOST Assistant Secretary Robert Dizon and DOST-PHIVOLCS Director Renato Solidum, Jr., 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.
“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 Solidum.
Once fully documented, the results of this test, which was conducted February 24, 2011 in the presence of scientists and engineers from Japan and the Philippines, shall be used by PHIVOLCS-DOST and its partner organizations toward improving and ensuring adherence to proper construction practices of houses especially for lower-income families.
For his part, DOST Secretary Mario G. Montejo expressed his wish to put up a shaking table for the country. “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.”
The need for strong homes and buildings came again to the fore in the wake of the magnitude 6.3 earthquake that recently rocked Christchurch, New Zealand as well as those in recent memory like the May 2008 Sichuan China earthquake and the Haiti catastrophe which killed more than 200,000 in January 2010.
The shaking table test of Philippine concrete hollow block houses is one of the activities under the collaborative project “Enhancement of Earthquake and Volcano Monitoring and Effective Utilization of Disaster Mitigation Information in the Philippines” between DOST-PHIVOLCS and Japanese institutions led by NIED, which is supported by Japan International Cooperation Agency (JICA) and Japan Science and Technology (JST).


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