Philvocs Guide: Quick Test on Earthquake Proofing your Building

Philvocs Guide: Quick Test on Earthquake Proofing your Building

Being situated in the Pacific Ring of Fire, the Philippines is no stranger to earthquakes. Through centuries, Filipinos have adapted with equal courage and bravery to face fire. Throughout history, building construction relied on the flexibility of Bamboo and wood. But with modernity, building with concrete has become a necessity.

Earthquake Ring of Fire with Dragon

Enter the New Millenium.

The Philippine Government, in responding to the certain challenge of building in an earthquake prone region formed  Philippine Institute of Volcanology and Seismology (PHIVOLCS) under the Department of Science and Technology (DOST) The mission of Phivocs is to mitigate disasters that may arise from volcanic eruptions, earthquakes, tsunami and other related geotectonic phenomena.

To illustrate the concern with concrete structures and earth movement let us see, Phivocs research and testing on actual movment and effects on concrete hollow blocks construction.

After the findings, the Philippine Institute of Volcanology and Seismology (Phivolcs) and the Japan International Cooperation Agency (JICA), launched a campaign to spread understanding on building safety. The “How Safe is My House? Self-check for Earthquake Safety” is a 12-point questionnaire building owners can use to assess the earthquake readiness of their building.

The checklist was tailored for concrete hollow block (CHB) houses, one of the most common types of Philippine homes because of its low construction cost.

Quick Test on Earthquake Proofing your Building

Phivocs1-3 – designed by Arch, built before 1992, no prev damage

Phivocs7-9 – standard steel bars, 3m col spacing, no gable

Phivocs10-12 – reinf concrete foundation, hard soil condition, good condition

Phivocs4-6 – reg shape, expanded by engr, outer walls 150cm

The features recommended by the checklist are based on the National Building Code and Structural Code of the Philippines. They were tested by a full-scale shaking table experiment conducted by Filipino and Japanese experts.

The higher the total score, the more earthquake-resistant the house:

• 11-12 : Though this seems safe for now, please consult experts for information.
• 8 – 10 : This requires strengthening, please consult experts.
• 0 – 7 : This is disturbing! Please consult experts soon.

Characteristics of Earthquake proof Buildings

An “earthquake-resistant” house is a house that will not collapse even in the face of an intensity 9 earthquake, said Phivolcs Director Renato Solidum.

So what makes a house earthquake-resistant?

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.

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.

A regular-shaped house – symmetrical, rectangular, box-type – is also more stable than an irregularly-shaped house.

“The shape influences the behavior of the building during ground shaking. If it’s irregular, the house will be twisted and various parts will move in various ways, so it’s not good,” explained Solidum.

Features	Properly-built	Improperly-built
Concrete hollow block wall	6 inches thick (400 x 200 150mm)	4 inches thick (400 x 200 x 100mm)
Vertical steel bars	10mm diameter spaced 40cm from each other	6mm diameter spaced 90cm from each other
Horizontal steel bars	10mm diameter spaced 60cm from each other or laid every 3 layers	6mm diameter spaced 60cm from each other or laid every 3 layers
Mortar mix (Cement : sand)	1:4 Compacted	1:4 Not compacted
Roof frame/roofing	Wood/Galvanized iron sheets	Wood/Galvanized iron sheets

The building materials used also determine the strength of the house. Walls made of 6-inch (150 mm) thick concrete hollow blocks are much stronger than the cheaper but more commonly used 4-inch blocks.

The reinforcement of vertical and steel bars embedded in the walls are just as important. Vertical bars have to have a diameter of 10 mm and must be only 40 centimeters away from each other. Many substandard homes have thinner bars (6 mm) spaced farther away from each other (90 cm).

For horizontal bars, they must be 10 mm thick and spaced 60 cm from each other (or between 3 layers of concrete hollow blocks).

Walls that are more than 3 meters wide must be supported to prevent it from falling down during a quake.

COMMON HOUSE. Concrete hollow block (CHB) houses are common in the Philippines.

A foundation of reinforced concrete would resist the shaking of an earthquake making it the ideal foundation for a house. This much more stable than a foundation of stones or unreinforced concrete.

The kind of soil on which the house is built is another factor. Rock or stiff soil is more stable while muddy or reclaimed soil literally puts your house on shaky ground.

Make your loved ones safe. Work with Licensed Professionals.

Archian Designs Architect Studios , Philippines

Archian Designs Architect Studios is a Collaboration of Architects, Urban Planners, Interior Designers, Landscape Designers and Engineers in the Philippines. To see the contact information, email to archiandesigns@yahoo.com, call 0907 7240452 or contact us.

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