'Defense against earthquakes:' Phivolcs director encourages construction of strong buildings

ILOILO CITY, Philippines  -- Unlike other natural disasters, earthquakes occur without any warning and the devastation could be catastrophic, but the effects can be mitigated.

Renato Solidum Jr., director of the Philippine Institute of Volcanology and Seismology (Phivolcs), issued this statement during the recent regular meeting of the Regional Disaster Risk Reduction and Management Council in the city.

Solidum said Filipino homes are generally safer from earthquakes as long as they follow the prescribed guidelines in the building code such as the use of construction materials that pass quality standards.

"Dapat maganda ang desinyo. Ang building dapat umuga ng sabay. Hindi kikilos ang poste ng separate. Madaling bumagksak yun," he said, adding that for a building to withstand an earthquake, it must have a good design and good workmanship.

"Quality and standard construction materials must be used. The minimum should be six inches na hollow blocks and 10-meter corrugated steel bar and are spaced properly. In good workmanship, there must be no short cut," Solidum told the council officials.

A day before the March 11 earthquake in Japan, Phivolcs had a press release on the simulation tests it conducted in that country. In those tests, the DOST- Phivolcs and Japan's National Research Institute for Earth Science and Disaster Prevention determined that Philippine masonry houses that follow the building code could improve its performance during strong earthquakes.

Masonry houses are structures with no structural beams and columns. Low-income families preferred these because of the simple design.

There were two full-scale model masonry houses used during the simulation exercise. One followed the standard local building code. It used a standard 6-inch thick concrete hollow blocks (CHB) with 10 millimeter corrugated steel bars as reinforcement spaced at 0.4 meter vertically and 0.6 meter horizontally (or every three layers of CHB).

The other model used 4-inch thick concrete hollow blocks with substandard 6-mm smooth steel bars and whose construction fell below building code requirements.

"When they were simulated to a 6.9 na lindol, hindi tumumba ang model sumunod sa building code at yung isa, nagkaroon ng partial collapse. When a simulated aftershocks of similar scale were made, bumagsak na ang sub-standard. We put a 4-ton weight depicting a second floor, to the model that follow the building code, although it was not designed to do that, there were minor damage but it did not totally collapsed," he revealed.

This means, "kayang labanan ang malakas na lindol kahit na magnitude 7 or greater kung sumusunod sa building code," he said. "But the bottom line is, are we following the building code?"

For now, Solidum said the Phivolcs is working with the Iloilo city government, the Office of Civil Defense, the DOST, the Assessor's Office and the Engineering Office, on how to build a data base of buildings in the area.

"When you have a data base, it could give you an estimate how many buildings could be affected in case an earthquake happens," he said.

Earlier, the Office of the Building Official (OBO) listed 82 more dangerous buildings and structures in the city following its intensified review and inspection on safety and structural stability.

This brought to 154 the total number of buildings that were given notices regarding their stability to withstand the effect of a big magnitude earthquake.

The latest inspection, from March 31 to April 4, was done on structures along Valeria, Iznart, and Ledesma Streets in the City Proper district. —  (FREEMAN)