Strong quakes put spotlight on structural integrity of buildings

ABS-CBN News

Posted at Apr 25 2019 12:43 PM

MANILA - The two strong earthquakes that recently shook Luzon and Visayas have placed the structural integrity of buildings under the spotlight, putting urgency on the need for regular inspections.

"We should be inspecting buildings from time to time to maintain its structural integrity. It is required of us to do these inspections more regularly to determine if the building is OK," said Ronaldo Ison, Vice President of the Association of Structural Engineers of the Philippines.

A magnitude 6.1 quake struck Luzon Monday afternoon with its epicenter in Castillejos, Zambales, killing around 16 people. Many of those who died were from a collapsed 4-storey supermarket in the town of Porac in Pampanga.

President Rodrigo Duterte has ordered an investigation to determine the structural integrity of the 4-year old building.

Ison said newer buildings abide by the National Building Code or the National Structural Code, which lays down requirements on how to build earthquake-resistant structures.

"I would say that most buildings in Metro Manila are complying with the National Building Code and would be able to resist the Big One," he said.

The Big One refers to an earthquake with a range of magnitude 7 or above. 

Ison explained that there is no earthquake-proof building, only earthquake-resistant ones which could withstand strong temblors.

"There will be some damages, cracks on the walls, the beams but the whole building would not collapse, enough for the people to go out of the building," he said.

However, older buildings constructed with older materials should be checked, analyzed, and upgraded to comply with the present building code.

Ison said building officials normally have structural integrity checks. 

"Every year, they would require structural certification for commercial buildings for the issuance of business permits. However, for most private residential structures, I would say we have not had any distinct ordinance to have these inspected. It's voluntary to private owners to have their buildings inspected," he said.

 LEANING EAC BUILDING

The building of the Emilio Aguinaldo College (EAC) in Manila also suffered damage from Monday's quake.

The Department of Public Works and Highways (DPWH) has asked EAC occupants to vacate the facility after it was found to be tilting.

Photos that circulated online showed that the school was left leaning on an adjacent structure in the wake of the 6.1-magnitude earthquake that was also felt in Metro Manila. 

"In my personal opinion, I would not use it anymore. A building should be vertical. Definitely, if it leans there would be some structural damages," said Ison. 

He said after an earthquake, the building sways and then goes back to its original vertical position.

"Most likely there will be some structural concerns on the building or probably there would be some settlement that would have triggered the leaning of that building," he said.

Soil liquefaction has been eyed as the possible cause of the tilting.

Ison, meanwhile, clarified that buildings could still be built on liquefiable soil.

"You can still build on liquefiable soil but you have to put extra measures or different foundation system to carry the building," he said.