Earthquake Proofing Older Buildings in the Philippines

The Philippines experiences a lot of earthquakes and volcanic activities because it is in the Pacific Ring of Fire. This makes it essential for buildings, especially older ones, to be strong enough to handle these earthquakes. Many buildings from before stricter safety rules exist weren’t designed to withstand earthquakes. In this article, we will explore how to protect these buildings and ensure the safety of those living or working in them.

Understanding the Problem

In the Philippines, many older buildings, particularly those built before the 1970s, do not follow today’s earthquake standards. They were often built with older techniques and materials that lack the strength needed for modern seismic safety. For example, plenty of these buildings used reinforced concrete that does not meet today’s standards, and many designs did not account for the strong forces created by earthquakes. The ‘Batas Pambansa Blg. 220’ (the National Building Code of the Philippines) now has stricter rules regarding building safety, but buildings built before these rules are still at risk. A heartbreaking example of this vulnerability is the 1968 Manila earthquake, which caused considerable damage to many buildings. One of the worst incidents was the collapse of the Ruby Tower, leading to a loss of many lives.

Assessing Building Vulnerability

To begin the process of making buildings safer, the first step is to determine how vulnerable a building is. This requires a thorough structural assessment by a qualified engineer. The engineer will examine various factors, such as the building’s age, the materials used, its design, and any previous damage it may have. Different techniques can be employed during the assessment, such as visual inspections, non-destructive testing like ultrasonic testing, and core sampling—this involves taking small samples of the concrete to check its strength. The results of this assessment help pinpoint weaknesses in the structure, highlighting areas that may need strengthening. A common issue found in many of these buildings is the corrosion of reinforcing steel within concrete columns and beams, which decreases their capacity to face seismic forces effectively.

Retrofitting Techniques for Earthquake Resistance

Retrofitting refers to making adjustments to an existing building to improve its resistance to earthquakes. Several techniques can be used for retrofitting, depending on the unique needs of each building.

Strengthening Columns and Beams

The columns and beams are critical components of a building structure. They support the weight of the building and help resist lateral (side-to-side) forces during an earthquake. Strengthening these key elements is often the major aspect of retrofitting. One frequent method used is jacketing, which involves wrapping the columns and beams in steel or fiber-reinforced polymer (FRP) composites to bolster their strength and ductility (the ability to bend without breaking). In addition, another method includes adding steel plates to the sides of columns and beams, which can then be bolted or welded in position. For instance, incorporating carbon fiber reinforced polymers (CFRP) around columns is a popular method to significantly enhance a column’s resistance to shear forces.

Shear Walls

Shear walls are vertical walls specifically designed to resist lateral forces during earthquakes. Incorporating shear walls into a building can greatly boost its earthquake resilience. These walls may be composed of reinforced concrete or steel and are strategically placed within a building to help distribute earthquake forces, reducing lateral movement. For example, a common practice is to add concrete shear walls to older residential structures, such as bahay na bato (traditional stone houses), in a way that maintains the historic appearance while enhancing the structural integrity.

Base Isolation

Base isolation is an advanced retrofitting technique that involves separating the building from the ground using flexible bearings or isolators. This design allows the structure to remain stable during seismic events while the ground moves beneath it. Though it is usually a pricier option, it has proven to be incredibly effective. An example of base isolation in the Philippines can be found at the Asian Hospital and Medical Center, which employs base isolation techniques to protect its essential services during an earthquake.

Adding Steel Bracing

Another technique involves steel bracing, which consists of installing steel beams in an X-formation or other configurations within the framework of the building. These braces are helpful in distributing lateral forces across the structure, preventing excessive swaying during an earthquake. This comparatively low-cost method can be implemented in existing buildings without causing much disruption. Steel bracing is often particularly useful in reinforcing exterior walls of older buildings where it’s not feasible to add shear walls.

Importance of Proper Design and Construction

Retrofitting a building is not a trivial task. It requires careful planning and execution by skilled professionals. A retrofitting plan must be customized to fit the distinct traits of each building and the seismic hazards in that area. Additionally, it’s crucial that high-quality materials are used and that proper construction practices are followed. If retrofits are poorly designed or constructed, they may inadvertently make a structure even more vulnerable to earthquakes. For instance, just adding more weight to an already weak structure without addressing existing issues could increase the seismic load, potentially leading to collapse.

Cost Considerations

While making buildings earthquake proof can involve significant expenses, it is an investment in the safety of the property and those who occupy it. The costs associated with retrofitting can vary immensely, influenced by factors such as building size, type, the scope of work required, and material choice. Fortunately, many local governments offer subsidies or incentives to assist building owners with these expenses. Options can include tax breaks or low-interest loans specifically for earthquake retrofitting projects. Before proceeding, it is wise to obtain multiple quotes from qualified contractors and consider the long-term advantages of retrofitting.

Living Safely in a Seismically Active Region

In addition to enhancing building structures, there are several other crucial steps individuals can take to safeguard themselves and their possessions in areas prone to earthquakes.

Secure your belongings: Make sure to anchor heavy furniture to the walls to prevent tipping during an earthquake. Additionally, store breakable items in safe cabinets to minimize the risk of breakage.

Create an emergency plan: It’s beneficial to have a clear emergency plan prepared for an earthquake scenario. This plan should outline safe spots within your home or building, communication strategies with family members, and an emergency kit filled with essential items like water, food, and first-aid supplies.

Participate in earthquake drills: Regularly join earthquake drills to rehearse your emergency plan. This practice will help you and your loved ones respond swiftly and safely when an actual earthquake occurs.

Educate yourself about earthquake safety: Gain knowledge on what causes earthquakes, the effects they can have, and effective ways to protect yourself and your property.

FAQ

Call to Action

Investing in earthquake retrofitting is crucial to protect lives and preserve heritage in the Philippines. By taking actionable steps, assessing building vulnerabilities, and implementing effective retrofitting techniques, we can significantly reduce potential damage and save lives when disasters strike. Collaborate with professionals, engage with community initiatives, and actively participate in safety practices to foster a more resilient environment. Don’t wait for the next earthquake; act now to ensure the safety of your buildings and those who inhabit them.

References

National Structural Code of the Philippines (NSCP)

Association of Structural Engineers of the Philippines (ASEP)

Philippine Institute of Civil Engineers (PICE)

Department of Public Works and Highways (DPWH) Guidelines on Retrofitting

Earthquake Engineering Research Institute (EERI) Publications