"A Clear and Present Danger 2-the use of QT/TMT Bars in Seismic Zone 4".

Hunyo 28, 2018

"A Clear and Present Danger 2-the use of QT/TMT Bars in Seismic Zone 4".

"The outer skin is STRONG but the inner core is NOT STRONG than the outer skin." Coseteng said.

The public should have been informed that in addition to MA rebars, the steel manufacturers were tgen introducing a new line called Quenced Tempered/Thermomechanically Treated (QT/TMT) bars where vanaduim need not be part of the formulations as this would bribg down the price of bars where vanaduim need not to be part of the formulation as this would bribg down the price of bars that would not be used for low rise buildings and non-sensitive structures.

The production of micro alloy steel bars should have been continued therby offering the consumers an informed and intelligent choice.

The National Structural Code of the Philippines 2015 Volume 1 Buildings, Towers, and others Vertical Structures. #SECTION 420.7.6.2 (NZS 3101 5.3.2.2) Restrictions on In-line Quenced and Tempered Reinforcement : Reinforcement bars manufactured by the in line quenced and tempered process shall NOT be used when welding, galvanizing, hot bending, or threading of bars occurs. 420.7.6.3 ( NZS 3161 C5.3.2) It is important to note that any process involving heat e.g. welding, galvanizing, hot bending can adversely affect the mechanical properties of quenced and tempered reinforcing bars by the motification of the micro-structures.

Threading of quenced and tempered bar removes some to all hardened outer layer resulting in a disproportionate loss of strength. In 2010, Engineer #EmilioMorales wrote a study entitled "A Clear and Present Danger 2-the use of #QT or #TMT Bars in Seismic Zone 4". The paper stated that micro alloy (MA) steel has been replaced with quenced tempered (QT/TMT) steel in the market without the knowledge of contractors, architects, end users and the general public. Quenced tempered steel, when bent, welded, threaded, or galvanized, poses a high intensity earthquake which is imminent since the Philippines is a seismic zone 4 country. QT/TMT rebars have brittle, outer skin, when tested, will pass for Grade 60 steel, but the inner core will only Grade 40 after welding, bending, threading, galvanizing. Despite the warning, the major steel manufacturers have taken it upon themselves, without informing the contructors, engineers, architect, end users and the general public, to replace the MA steel bars with QT/TMT and have been selling these for use not only in low rise structures , but also in high rise buildings. In the case of a fire or an earthquake, the steel will faik, thereby leaving insufficient time for people to vacate the buildings. Pertinent questions Former #SenatorNikkiCoseteng raised in the #DepartnmentofTradeandIndustry (DTI) forum.