The recent spate of earthquakes that jolted northwestern Japan, southern China, the Flores region in Indonesia and several Mindanao provinces, has authorities in the local steel industry worried.
The lingering fear is that thousands of high-rise buildings in the country—built over the last 10 years using substandard, locally made steel bars—may be in peril should a high intensity quake hit the country.
A 6.8-magnitude earthquake jolted northwestern Japan last Tuesday prompting the Japan Meteorological Agency to issue a tsunami alert. Last Monday, a 6.0-magnitude quake hit Sichuan province in southern China, resulting in the collapse of a hotel in Changning country of Yibin City, southwest of the province, causing the death of 11 people and injury to another 122.
Also last Monday, a 5.5-magnitude earthquake happened in Flores region in Indonesia, while six quakes struck in Mindanao, including the provinces of Agusan del Sur, Davao Occidental and Surigao del Sur.
Two months ago, a 6.1-magnitude quake hit Luzon, swaying and destroying buildings in Metro Manila and leveling the four-story Chuzon supermarket, in Porac, Pampanga, killing 18 people and injuring 282. In the same month, several 6.1-magnitude quakes rocked Eastern Samar and Zambales.
The ‘Big One’ is real
“The series of tremors that hit the country and our neighboring nations are quite alarming,” said Philippine Institute of Volcanology and Seismology (Phivolcs) Director Renato U. Solidum Jr. last week. “But being situated near the Pacific Ring seismic faults, together with countries like Taiwan, New Zealand and Japan, it is expected for the country to experience frequent seismic and volcanic activity.
“Many earthquakes of smaller magnitude occur very regularly due to the meeting of major tectonic plates in the region,” he said.
Solidum added that the 100-kilometer (km) West Valley fault line that stretches from Bulacan up to Laguna is in grave danger once a 7.1-magnitude earthquake occurs.
According to studies, the West Valley Fault appears to move every 400 to 500 years. “For this reason, we feel that what they call the ‘Big One’ could happen in our lifetime, which would kill more than 30,000 people and injure 100,000 others,” he warned.
‘Ampaw’ steel
But former chairman of the Association of Structural Engineers of the Philippines (ASEP) Engr. Emilio Morales, raised a bigger worry in the face of recent quakes in the region: the stability of locally manufactured steel bars for high-rise buildings.
Morales revealed that substandard construction materials, particularly reinforced steel bars (rebars), are still being used to build high-rise commercial buildings and residential condominiums in key business districts.
“Being near the Pacific Ring is the main reason certain types of steel materials are not recommended for use in high-rise buildings in the country,” he explained.
“Substandard construction materials, particularly rebars, would not withstand a 7.2-magnitude earthquake,” Morales stressed.
Morales added that big local steel manufacturers changed the steel bar manufacturing process some 12 years ago, without notifying the government or the public.
These manufacturers reportedly replaced micro-alloyed (MA) steel bars with quenched-tempered (QT) bars without the knowledge of the contractors, developers and end-users.
China, Taiwan banned QT steel, but PHL lags behind
QT steel is made by spraying cold water on a red-hot steel bar. “This process alters the steel’s metallurgy: the outer core becomes very strong and brittle, but it is relatively very thin—about 1 or 2 millimeter in thickness,” Morales said. “This kind of multilayered steel can kill, as the thin outer layer, which is brittle, can be easily damaged during an earthquake.”
Morales said China has started banning QT steels bars, with Taiwan banning these outright two years ago, despite inconclusive metallurgy test results undertaken on QT rebars. As a precaution, Taiwan government testers decided that QT steel are only strong on the outer layer due to quenching process.
Morales claimed that the standards of testing steel in the Philippines are not as thorough—“a product that is made with grade 40 steel could pass as grade 60 because of QT coating.”
According to the former ASEP chairman, in the event of a high-magnitude earthquake, QT steel bars could cause the foundation of the buildings to crumble. “They cannot weather the pressure because they are not specifically made for the type of building construction. Grade 40 steel bars, experts say, are only for mid-rise buildings, not high-rise condominium units,” he said.
Last week, the Department of the Interior and Local Government spearheaded a nationwide earthquake drill. But Morales said this may not be enough to save lives unless the structural integrity of buildings are ensured of withstanding the impact of the Big One.
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