A MOST practical assurance that a high-rise residential condominium is reasonably safe when hit by a killer earthquake is to make sure that the developer’s family members themselves reside on its top floor. But that is not always doable.
The average condo buyer or tenant is unable to test the integrity of his unit since he does not have the chance, nor the expertise, to examine its structural design and construction before he pays for it. The most he can do is go by the reputation of the developer and builder.
This is one of the reasons why it is crucial that government regulators must do their jobs and not connive with, or be bribed by, suppliers and the builders of high-rise commercial buildings and residential condominiums. Who regulates the regulators?
It is interesting that a former Department of Trade and Industry top official is now the president of one large steel-making firm, and the chair of another steel company that funded the research by then chair of the Association of Structural Engineers of the Philippines on reinforcement steel bars (rebars) now heads the technical committee of the Bureau of Product Standards.
The DTI is the main government body responsible for testing and certifying steel products, while BPS is in charge of issuing standards certification for steel materials.
Steel manufacturers should not be laying down their regulations and deciding what standards and tests to apply. Appointing people with vested interests to regulatory positions could compromise safety standards as well as the lives of people and the quality of infrastructure.
Two Senate hearings have been held to investigate the effects of the use of quenched-tempered (QT) steel bars in the construction of high-rise buildings, but until now no decision has been made to address the issues raised.
The first hearing was held Aug. 28, 2018, with a big steel manufacturer saying they were making grade 40 steel, which after quenching was sold as grade 60. They also admitted selling the grade 40 steel for use in high-rise structures nationwide. The second hearing on Sept. 11, 2018, discussed mislabeling and the effects of the use of QT bars in tall buildings.
Rebars are just one of several items affecting the structural integrity of buildings. We hinted at this last time, saying “(Also subject to quality check are other elements, including the concrete, which is the mix of cement, aggregates [gravel and sand], and water in correct proportion.)” but without elaborating for lack of space.
Digressing, let us share with laymen who use “semento” and “konkreto” interchangeably. “Cement” is that powdery material we buy in bags. It becomes “concrete” only when properly mixed with sand, gravel and water. And we call the mix “reinforced concrete” when we put in the steel bars.
Contractors have told us about scrimping in some projects such as roads. With expert mixing, a stretch requiring, for instance, 1,000 bags of cement can still “look” acceptable with just 800 bags. To stretch it farther, instead of, say, a 12-inch-thick pavement, 10 inches can be laid out selectively. Motivating government inspectors helps.
Some contractors may try impressing laymen by talking grandly of “aggregates.” All they mean is sand (fine aggregate) and gravel (coarse aggregate). Btw, Capampangans are proud of their “Porac” sand which they swear is whiter and of more consistent good quality.
But then came volcanic “lahar” that flowed from Mt. Pinatubo after its eruption in 1991. Some businessmen misrepresent and sell lahar as sand. Lahar has a high content of pumice, a lighter material vomited by Pinatubo, making concrete using lahar less dense and durable.
• Conflicting views aired on rebar use
ENGINEER Emilio Morales, former chair of the Association of Structural Engineers of the Philippines whom we quoted last Sunday, said that with the frequency of earthquakes in the Pacific Ring of Fire – raising anxiety over the “Big One” – the use of substandard rebars in high-rises is worrisome. https://tinyurl.com/y5ebxd2c
The “Big One” is the temblor of at least magnitude-7.2 that experts warn may hit Metro Manila any day based on their monitoring of seismic pressures waiting to be released in the Marikina Valley fault system. In 2014, the Philippine Institute of Volcanology and Seismology projected in a risk analysis that more than 41,000 people may get killed in the heavily built-up area in the national capital.
Morales said that substandard construction materials, particularly QT rebars that are still being used in high-rise commercial buildings and residential condominiums, cannot withstand a magnitude-7.2 quake.
The big steel maker that commissioned Morales ignored his research on rebars and went on to produce steel bars using QT process presumably because of its lower cost and higher profit. Morales said he was told not to release his findings.
Our Postscript last Sunday took up the risks of using substandard rebars. The feedback we got indicates wide public concern/interest. For lack of space, we pick only one email, from Howard McKay, who identified himself as a retired Chartered Civil Engineer (UK) with about 50 years of experience. He said among other things:
“The Department of Trade and Industry finds no factual or technical basis to support the allegation that quenched and tempered (QT) steel is unsafe for high-rise construction, following a series of consultations conducted with the Philippine Constructors Association, Philippine Iron and Steel Institute, Association of Structural Engineers of the Philippines, and other relevant stakeholders.
“The DTI-BPS strongly upholds its stance that the use of QT steel bars in construction is safe, even stressing that the DOST-MIRDC study in itself confirms this provided that restrictions on welding, hot bending, treading, and galvanizing are strictly followed. The discussions during the consultations that were convened also coincide with Philippine National Standard (PNS) 49:2002 on steel bars for concrete reinforcement. The quenching and tempering methodology indicated in the PNS likewise adheres to the principles of the American Society of Testing Materials that is accepted worldwide.”