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The Importance of Seismic Restraints for Lighting

As the Earth evolves and tectonic plates shift, the displaced energy usually manifests in an earthquake.

Earthquakes normally strike suddenly and without warning, can be violent enough to heave people around, destroy cities and turn infrastructure into rubble.

Most deaths are related to building collapses and damages. Beyond the human toll, earthquakes come with substantial socio-economic costs. On the 16th of April 2016, a 7.3 Mw earthquake hit Kumamoto, Japan, after a series of pre-shocks. This large quake led to 64 deaths and infrastructure damage of approximately $5.6 billion USD. On the 24th of August 2016, Italy’s Umbria region suffered a much smaller 6.2 Mw quake that caused 293 deaths and left more than 4000 people homeless with a damage bill estimated at $3.96 billion USD.

The inestimable losses are in culture, heritage, human emotion, and quality of life also place a tremendous strain on society. Rebuilding can become a very politically charged discussion. The ancient stones that often turn into rubble are not as resilient as wood or other materials. Governments face the question of rebuilding what is safer or maintaining the region’s style and heritage.

Vastly Different Outcomes from Relatively Same Magnitude 

According to the World Bank, one of the most crucial factors limiting fatalities and fiscal damages during and after an earthquake is well-designed and well-constructed builds. Fragile construction is generally cited as the main factor for high death rates in developing countries, where strict adherence to zoning, building codes, and disaster prevention efforts is often perceived as a luxury.

For example, in 2003, two 6.6 Mw quakes occurred only four days apart but in two different locations. They recorded significantly different impacts. The Paso Robles quake in California resulted in two lost lives. The death toll from the Bam quake in Iran was over 45,000. Authorities attribute this colossal loss of life was due to the lack of enforcing building codes in Iran. Where in contrast, in California, the damage recorded was property-related as seismic-focused construction practices and other proactive measures are well-established.

The inevitability of an earthquake in APAC 

Not every country in APAC has the same propensity to seismic activity. The world’s top 5 earthquake-prone countries are China, Indonesia, Iran, Turkey and Japan.

Positioned directly on the 40,000 km Ring of Fire, Indonesia has recorded 113 earthquakes of significant magnitude (≥6.0 Mw) since 1900. New Zealand is also frequently rocked by tremors due to its location on the boundary of two of the world’s major tectonic plates – the Pacific and the Australian Plate.

Seismic events rarely occur within Australia but cause catastrophic consequences for communities when they do. Many Australians may be surprised to learn that, on average, 100 earthquakes of 3.0 Mw and above are recorded in Australia each year. Earthquakes above 5.0 Mw occur on average every one-to-two years.

Fortunately, earthquake activities in and around other regions within APAC, such as Vietnam, Singapore and Korea, are relatively low in number and intensity compared with others in the region. However, this does not mean there is no threat of seismic impact. Should a significant earthquake occur on their surrounding plate boundaries, there is a great likelihood that buildings located over sediments or reclaimed lands could be affected by the quake.

The importance of a well-designed structure 

Since most earthquake-related deaths are associated with building collapses and damages, the built environment must be engineered and reinforced to account for seismic loading. Compliance with seismic requirements is now commonly mandated within building services.

This is not to say that seismic requirement compliance means the effects of earthquakes are entirely preventable. It is expected that under seismic loading, every aspect of a build is subjected to a certain level of fragility and highly dependent on the direction and strength of impact. Therefore, seismic-resistant structural planning should occur at holistic and atomical levels, considering the primary, secondary and non-structural elements.

The primary structure is the fundamental element that ensures a building does not collapse. Secondary structure is defined as any structural elements that are not considered part of the primary structure, including precast panels, heavy internal partitions, stairs, etc. Lastly, non-structural components refer to aspects such as mechanical and electrical plant, ducting, cable pipeworks, suspended ceiling, and of course, light fittings.

A study conducted by the US Federal Emergency Management Agency (FEMA) identified that 15-25% of the commercial building’s cost is the primary and secondary structure. The remaining 75-85% is spent on non-structural elements. The most widely reported earthquake damage is the failure of non-structural components, specifically the ceiling and in-ceiling services. Not only are there significant capital costs to repair, but the lack of seismic planning in non-structural elements can lead to life-threatening injuries and loss of life.

A well-designed building with proper seismic-resistant planning and execution can mitigate and minimise catastrophic damages.

Seismic restraints for non-structural components 

The quality of a seismic-resistant structure is highly dependent on its energy dissipation capacity and the absorption of earthquake energy. With non-structural elements, the objective is to secure the items onto the primary or secondary structure with a restraint or bracing mechanism. Therefore, when under seismic forces, the earthquake energy experienced will be transferred onto the primary structure.

The majority of architectural lighting is secured to the secondary structure, either recessed, surface mounted or suspended with a secure canopy. Two types of luminaires are at high risk of dislodging and potentially becoming a dangerous projectile during a seismic event – pendants and panel lights in suspended (drop) ceilings.

Heavy ornate pendants and chandeliers pose severe risks in earthquakes unless properly secured. The energy from the earthquake transfers into the suspended object, making it a dangerous swaying pendulum. With no friction, mechanical energy is conserved. As the pendulum swings back and forth, there is a constant exchange between kinetic energy and gravitational potential energy. Depending upon the magnitude, duration and wave direction, the pendant can pull out of the ceiling and become a flying hazard.

Likewise, panel lights used within suspended ceilings can present a significant hazard if not correctly tethered. The suspended ceiling system floats on wires affixed to the ceiling or service infrastructure above. Generally, the suspended ceiling is connected to the walls (primary and secondary structures). However, the acoustic panels, ceiling tiles and lighting are often laid in the suspended ceiling without a mechanism that secures them onto the main structure. During the seismic event, the suspended ceiling will move in line with the structure to which it is attached. The ripple effect with significant upthrusts generally moves everything that is not adequately secured, sending ceiling tiles and panel lights in various directions.

When securing services to meet seismic guidelines, lighting needs to be considered and executed. Wire joiners, such as those from Gripple, terminate and suspend wire ropes to support the panel lights installed in suspended ceilings. This restraint system allows the light fittings to dissipate earthquake energy as a module of the overall complex structure instead of reacting as a single individual component, preventing light fittings from dismounting from the ceiling. Similarly, in existing builds, FEMA recommends retrofitting pendants with safety chains or cables to reduce the risk of the pendant becoming airborne.

Current seismic requirements 

The seismic code provisions are not focused on preventing damage but on protecting the safety and reducing risks for the occupants within the space. In a minor 3.0 Mw through moderate 5.9 Mw earthquake, the objective is no structural damage and some to no, non-structural damage. In major earthquakes 7.0 – 7.9 Mw, the objective is no collapse of buildings, some structural damage and some non-structural damage.

The requirements for seismic protection depend on the building risk category or risk classification and the building location. The higher the seismicity of the location and greater the building occupancy, the more stringent the requirements. Building use also plays a crucial part; for example, in seismically moderate areas, military or healthcare facilities always require bracing due to the buildings’ importance to disaster recovery.

Current challenges with seismic restraints and non-structural elements  

While researching the impact of seismic events on non-structural elements with a key focus on lighting, some procedures and practices can be implemented to ensure better conformity and execution of the current seismic standards.

During the design and planning phase 

The responsibility of seismic regulation conformity for non-structural elements is unclear. Many individual suppliers can advise the best practice for securing their products for seismic events. But, who has the overarching responsibility to ensure that all elements are secured adequately? After a seismic event, who will claim responsibility for ensuring non-structural elements remain structurally stable? Unless the responsibility of specific tasks has been assigned and agreed upon, it may not be accounted for and potentially overlooked.

According to FEMA, electrical engineers and architects play significant roles in ensuring that lighting used in a structure is seismically prepared. In the design and planning phase, the architects and electrical engineers must ensure that the client and key stakeholders are well informed about seismic-related industry standards and regulations. At the same time, they need to raise the conversation and become public advocates for the importance of seismic-resistant structures to ensure public and occupant safety.

During the construction phase 

A common practice in the building industry is the use of subcontractors to install non-structural elements after the primary structure is complete. The subcontractors are experts in various disciplines, including electrical, plumbing, HVAC system (heating, ventilation and air conditioning), etc. Some installations may be based on experience in the absence of an approved engineered design. Another outcome is a lack of understanding of the correct installation of the seismic restraints on non-structural elements. The improper installation of seismic constraints can render them completely ineffective. While on the surface, the non-structural elements may appear to comply with the seismic codes, the lack of review and verification by a certified engineer may not deliver the outcomes anticipated during an earthquake.

Currently, lighting manufacturers provide lighting solutions that ensure the safety of occupants and comply with seismic requirements when installed correctly. The industry consults with stakeholders on best practices. However, the critical decision making and implementation of the recommendations rests on the responsible entities within the complex structures and responsibilities within the construction industry.

All in all, it would take our best efforts, as an industry, to raise awareness and continue building on our knowledge of the issues and solutions associated with lighting and seismic events. The drive is to continue learning, striving and growing with strong commitments towards building safe structures that will withstand a seismic event within our current pool of knowledge and regulations.

References

U.S. Geological Survey, “The Modified Mercalli Intensity Scale,” [Online]. Available: https://www.usgs.gov/natural-hazards/earthquake-hazards/science/modified-mercalli-intensity-scale?qt-science_center_objects=0#qt-science_center_objects.

J. Sexton, T. Allen, M. Edwards and Geoscience Australia, “Earthquakes happen in Australia, but are we prepared?,” Australian Journal of Emergency Management, vol. 34, no. 2, p. 18, 2019. 

C. Kenny, “Why Do People Die in Earthquakes?: The Costs, Benefits and Institutions of Disaster Risk Reduction in Developing Countries,” Policy Research Working Paper, no. WPS 4823, 2009. 

C. Wilkerson, “How much economic damage do large earthquakes cause?,” Federal Reserve Bank of Kansa City, 04 March 2016. [Online]. Available: https://www.kansascityfed.org/publications/research/oke/articles/2016/economic-damage-large-earthquakes. [Accessed 30 July 2020].

Federal Emergency Management Agency, “Reducing the Risks of Nonstructural Earthquake Damage – A Practical Guide,” Federal Emergency Management Agency, 2012.

Federal Emergency Management Agency, Risk Management Series: Designing For Earthquakes – A Manual For Architects, CreateSpace Independent Publishing Platform, 2006. 

Government of South Australia: Department of Planning, Transport and Infrastructure (DPTI), “Seismic Restraint of Engineering Services,” AIRAH, 2014.

Standards Australia and Standards New Zealand, “AS/NZS 60598.1:2013: Luminaires – Part 1: General requirements and tests,” Australian/New Zealand Standard, 2013.

Wang J, Zhao H. High performance damage-resistant seismic resistant structural systems for sustainable and resilient city: A review. Shock and Vibration. 2018 Jan 1;2018.

MacLeod F. The latest developments in seismic mitigation of suspended ceiling systems. InProceedings of the 13th World Conference on Earthquake Engineering, Vancouver, Paper 2004 Aug 1 (No. 3364, p. 13).

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