Structural integrity
AS A MATTER OF FACT - Sara Soliven De Guzman (The Philippine Star) - April 29, 2019 - 12:00am

Last April 22, 2019, we feared for our lives and the safety of our families when a 6.1 earthquake rocked Luzon and Metro Manila at 5:11 p.m. People came down from swaying high-rise residential and commercial buildings, ready to evacuate should the situation calls for it. MRT and LRT stopped operations immediately after. Traffic was at its peak as buses ply the main thoroughfares for commuters trying to get a ride home. It was a horrific sight! Evening classes and work were suspended allowing everyone to go home to their families.

The Chuzon Supermarket in Porac, Pampanga collapsed with around 100 people believed to have been buried in the supermarket. A concrete boundary arc across MacArthur highway between Pampanga and Bataan also collapsed causing the highway to be impassable to vehicles for an hour. The Clark Airport control tower sustained a broken glass. Although no damage to the runway was reported, assessment conducted by Clark International Airport Corporation led to the decision of closing the airport operations for 24 hours. As a result, a number of domestic and international flights were cancelled. The Emilio Aguinaldo College building in Taft Avenue leaned to an adjacent building.

A report from the Pampanga Provincial Disaster Risk Reduction and Management said that the Consuelo Bridge in Floridablanca town was temporarily closed due to the damage sustained from the tremor. The road at the Porac portion of the Subic-Clark-Tarlac Expressway cracked. Portions of the St. Augustine Parish Church in Lubao town and the St. Catherine Church in Porac town sustained damages. Surprisingly no casualties were reported in the municipality of Castillejos, Zambales, the epicenter of the quake. Reports say that a total of 635 aftershocks have been recorded from the earthquake that left 16 dead in the hardest-hit province of Pampanga.

A day after, a magnitude 6.5 earthquake hit parts of Visayas, with the epicenter at 9 kilometers northwest of San Julian, Eastern Samar, and with a depth of 63 kilometers below the ground.  Is this related to the first one? Apparently not. The first one is said to have originated from the local fault in the Zambales and Pampanga area while the second one is trends-related meaning it came from a subduction zone. The Philippine Sea Plate moved against our archipelago.

The earthquake generated 70 aftershocks. The tremor described by some residents as a “sudden jolt”, left cracks on some roads and bridges and also in private and public buildings including a church. A report from the Eastern Visayas police said that 10 persons were injured in the entire region.

In light of these recent earthquakes that hit multiple parts of the country in the past week, it is essential to remember some reminders to keep ourselves and our families safe.

One of the most important is to be aware of the threat that earthquakes pose. The nearer you are to a fault line, the higher the risk you face when one occurs. You should check PHIVOLCS’ Fault Finder website (http://faultfinder.phivolcs.dost.gov.ph) and find out how far your house is from the nearest fault. If you live in Metro Manila, the Valley Fault System (VFS) should be the one you choose on the website. Double click a point in the map to find out that point’s distance from the fault.

Another thing to remember is to be aware of the nearest evacuation center in your barangay and know how to go to that area by heart. In case you are away from your family members when an earthquake hits (at work, school), it is also ideal to have a designated place to meet afterward to know that everyone is safe. You should make sure to discuss this as a family even for other emergencies to be prepared for any eventuality.

In 2014, PHIVOLCS and the Japan International Cooperation Agency (JICA) developed a 12-item checklist based on engineering experiments and the National Building Code and Structural Code of the Philippines. The higher your score in the list, the more resistant your house would be against earthquake-related damages. You can access it through the PHIVOLCS website (http://202.90.128.67/html/update_SOEPD/jica_phivolcs_how_safe_is_your_house_feb2014.pdf) or a 2014 Rappler article by Pia Ranada entitled “12-point checklist for an earthquake-resistant house”(https://www.rappler.com/move-ph/issues/disasters/preparedness/50984-checklist-earthquake-ready-house).

Basically, the checklist contains the following questions: 1) Who built or designed my house? 2) How old is my house? 3) Has my house been damaged by past earthquakes or other disasters? 4) What is the shape of my house? 5) Has my house been extended or expanded? 6) Are the external walls of my house 6-inc (150 mm) thick CHB? 7) Are steel bars of standard size and spacing used in walls? 8) Are there unsupported walls more than 3 meters wide 9) What is the gable wall of my house made of? 10) What is the foundation of my house? 11) What is the soil condition under my house? and 12) What is the overall condition of my house?         

The Rappler article also mentioned that a house designed by a civil engineer or architect instead of a mason or carpenter has a higher chance of not collapsing because the expert is expected to follow the Building Code and Structural Code. Another information shared is that a house built in 1992 or after is also more earthquake-ready because it was the year after more earthquake resistance standards were introduced to the codes. The article also pointed out that a regular-shaped house – symmetrical, rectangular, box-type is more stable than an irregularly-shaped house.

Since 1972, the Structural Code has been updated 6 times. Records show that the code was last enhanced in 2010. The present NSCP was written in an “ultimate strength basis.” This means structures following the code should be able to withstand earthquakes with magnitudes 8 to 9 on the Richter scale, according to engineer Cesar Pabalan, National Director of Philippine Institute of Civil Engineers and former ASEP president.

We need our government officials to be strict. Structural integrity checks must be done regularly. But if corruption continues in the issuance of building permits we will lose more lives.

EARTHQUAKE STRUCTURAL INTEGRITY
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