Probe use of poor steel in high rise buildings

• Source: http://punto.com.ph/News/Article/29461/Volume-11-No-63/Headlines/span-style-color-rgb-255-0-0-span-style-text-decoration-underline--CONGRESS-ASKED-span--span-br-Probe-use-of-poor-steel-in-high-rise-buildings
• Friday, May 18, 2018

By Ding Cervantes

CLARK FREEPORT -- Former senator Nikki Coseteng has asked both Houses of Congress to look into reports that contractors, without being aware of it, have used inferior reinforced steel bars (rebars) supplied to them by local manufacturers to build highrise buildings in Metro Manila which is under threat from a major earthquake.

“I am building another school and my daughter lives on the 26th floor of a high-rise building. I also want to know if people are safe in such buildings,” Coseteng said at the News@Hues press forum at the Park Inn by Radisson Clark here Tuesday.

Coseteng is now the president and chief executive officer of the Diliman Educational Corp. Coseteng was with structural engineer Emilio Morales who, in 2010, first raised the issue of local steel manufacturers replacing micro- alloyed (MA) steel rebars with cheaper quench-tempered (QT) rebars which, he insisted, was not advisable for use in high-rise buildings, especially in earthquake- threatened Metro Manila.

She noted reports that MA rebars disappeared from local market and replaced with inferior QT rebars since about 10 years ago.

It is possible that the highrise buildings which mushroomed in Metro Manila over this period could have used inferior steel, she noted.

Morales debunked claims of steel manufacturers that QT rebars were safe for high-rise buildings, saying “herein is where the danger lies, because QT rebars behave quite differently under cyclic loading and also are very much affected by heating, welding, bending, galvanizing and threading procedures employed in their use, particularly in high-rise buildings under Seismic Zone 4.”

His study on the issue, first submitted to his professional peers in 2010, was titled “A Clear and Present Danger- The Use of QT rebars in Seismic Zone 4.”

Earlier, the Philippine Institute of Volcanology and Seismology (Phivolcs) announced that Metro Manila is ripe for a major earthquake that could reach 7.2 intensity.

A study it conducted by Phivolcs a few years ago estimated that only two percent of high-rise buildings with 30 to 60 stories could be heavily damaged by a significant earthquake in Metro Manila, as against the estimate of eight to 10 percent of older public- purpose buildings, but Coseteng noted that the study did not consider the use of QT rebars in the high-rise structures.

Morales could not immediately say whether here is any technology to “retrofit” high rise buildings which used QT rebars, but he stressed that apparently, contractors for high-rise projects were not aware the QT rebars were delivered to them by suppliers as they merely identifi ed their needs for Grade 60 rebars.

Because the issue could involve the lives of thousands, especially in case of a major earthquake, Coseteng said she has formally asked the Senate, through Senate President Aquilino Pimentel Jr., as well as the House, through Davao Oriental Rep. Corazon Malanyaon, to look into the issue.