Last Wednesday, Feb. 21, 2018, the Consumers' Union of the Philippines, headed by its president, Atty. Rodel A. Taton, organized an excellent forum at the Quezon City Sports Club on a most important and urgent topic: "Earthquake Preparedness., Are We Ready for the Big One?"
The guest speaker was Civil Engr. Emilio M. Morales, MSCE, F.ASCE, F.PICE, F.ASEP, Chair of the National Structural Code Committee of the Association of Structural Engineers of the Philippines (ASEP). Engr Danilo Domingo, incumbent ASEP President, was also present.
Engr. Morales obtained his bachelor's degree in Civil Engineering from Mapua Institute of Technology and his Master’s degree in Civil Engineering from the renowned Carnegie Institute of Technology, Carnegie-Mellon University, in Pittsburgh, USA. Morales is the principal partner of EMZA Partners & Co.. the first Filipino Consulting Company accredited under ISO 9001, He is also connected with the Philippine GEOANALYTICS, Inc., the first Philippine laboratory accredited under ISO 17025 and the First laboratory outside Continental US accredited under US NVLAP.
|Engr Emilio M. Morales|
My purpose in raising this subject here is to call attention to the dangers posed by the use of the reinforcing bars in high rise buildings and also to seek remedial measures---so as to prevent a bigger disaster in our country from happening, in case a magnitude 7.2 earthquake will hit Metro Manila or other parts of the country ,similar to what hit Taiwan over three weeks ago.
Morales anchored his talk on the crucial element in the construction of high rises---the steel bars that form the skeletal backbone of the skyscrapers' structural members, such as beams, columns and shear walls.
Morales contended that in the past 10 to 12 years, the technology called the "Quench Tempered (QT)," steel bars---also known as the Thermo-mechanically Treated (TMT) rebars---has crept into the construction market. These QT-TMT rebars have almost totally replaced the more expensive but more reliable "Microalloyed (MA) steel bars which was being used at that time---without the attendant concerns connected with use of those QT or TMT rebars.
From what we laymen gathered from Engr. Morales' lecture-- which I pursued further with him in last Sunday's 6 pm. dzRH program that I regularly co-host with RM Awardee Cecile Guidote Alvarez---the introduction into the construction market of the QT rebars is a most WORRISOME development, almost passing unnoticed until ASEP made representations and qualified such use in the NSCP 2015. ASEP stressed that the Philippines, with the exception of Palawan, lies in the Seismic Zone 4---which means we are in a region beset by severe earthquakes
In the Consumers' Union forum, Engr. Morales stressed that the summary paper he issued there is aimed "at alerting the Engineering Community and the public to the uninformed use of QT/TMT rebars, and to reduce the dangers posed by such usage."
Unfortunately, this is a matter very few people seem to be aware of, not to mention that it is rather technical and therefore above the heads of lay minds. This is why I assert that THERE SHOULD BE A SENATE HEARING ON THIS ISSUE BY THE COMMITTEE ON PUBLIC WORKS AS SOON AS POSSIBLE. Let the truth be ferreted out---before an unthinkable catastrophe is upon us.
The prospect of a new Ruby Tower tragedy is heightened in our era by the fact that so many skyscrapers have mushroomed all over Greater Manila as well as in various other big cities in the country---not to mention the important projects in the "Build, Build, Build" battle-cry of the Duterte administration.
As Engr. Morales explained, the outer part of these QT rebars---also known in engineering parlance as the "SKIN" of those steel bars---should hold a significant share of the strength of those bars, while the CORE of the bars itself holds the remainder strength. This outer skin, however, could be damaged and rendered brittle when subjected to the inevitable welding and even the threading of steel rebars (when joining one rebar to another by splicing). Similarly, these rebars, when bent by using heat, can be affected, thus removing the effect of the Tempering process.
If this outer core is damaged, THE STEEL BAR'S STRENGTH WOULD BE REDUCED SIGNIFICANTLY. In residential structures such strength could hold even in a moderate earthquake. In high-rises, however, where it is hoped that the various structural elements could hold together LONG ENOUGH TO FACILITATE THE FAST EVACUATIONS OF PEOPLE, this could indeed pose quite a problem---especially if the quake is as big as what hit Taipei weeks back.
According to Morales, the QT rebars crept into the market in the last 10 to 12 years and appeared to have replaced in many sites the "Micro-alloyed Steel" (MA) which has proved superior in performance, without the attendant weaknesses of the QT/TMT rebars. MA rebars, as he explained, derive their strength from the addition of rare alloying materials, specifically "vanadium" which is mined in Russia, and "Carbon" which are added during the steel-making process.
The end result, as structural engineers stress, "is a bar which, unlike the QT bar, has the same consistent hardness, strength and flexibility right across the whole cross-section of the bar."
The MA rebar derives its strength from these rare alloys, but unfortunately, says Morales, this fact has also made the MA rebars more expensive than the QT rebars. This may be the reason why various steel producers in our country quickly resorted to using the QT rebars despite safety issues involved in the latter.
It is significant to note, however, as Morales points out, that Japan, which is very earthquake prone, does not use the QT rebars and that Taiwan has reportedly banned it after the recent big quake Also notable is that, as the Structural Engineering Association's paper points out, "...even international codes such as the New Zealand Code and the Australian Standards prohibit the use of QT/TMT rebars (which involve) Welding, Heating, Bending, Threading and even Tack welding of QT/TMT rebars." Similar studies in other countries highlight the vulnerability of these rebars to normal construction activities during rebar erection.
In addition, full-scale tests of reinforced concrete under simulated earthquake-loading conducted in the University of Padova, in Italy have shown that premature failure can occur, compared to ordinary MA rebars. Thus, the ample evacuation time that structural engineers are building into their design could be lost with the use of QT /TMT rebars and a SUDDEN catastrophic collapse could occur.
I think it is imperative that the construction industry take a more serious look at what has been going on, and certainly the Senate should open a probe into the use of the QT/TMT rebars before it's too late.
The structural engineers' advocacy is "to encourage the Philippine Steel Industry, through the Philippine Iron & Steel Institute (PISI) to again bring the MA rebars into the market---to provide a choice for designers by categorically specifying this in their design and categorically stating that QT/TMT rebars are not to be supplied as an alternative in Seismic Zone 4 Building Designs."