Seismic Safety: 5 Innovations Shaking Up the Construction Industry
In February 2011, just one year after the Canterbury earthquake of 2010, New Zealand was struck again; this time by a devastating 6.3 magnitude earthquake. The Christchurch area took the brunt of the destruction as many of its buildings, which had been significantly weakened by the previous year’s quake, crumpled. When the ground finally stopped shaking, almost 200 people had lost their lives and thousands more had been injured by falling bricks and toppled masonry walls. It was one of the most tragic and deadly natural disasters in the country’s history.
In the years since, several comparable earthquakes have rocked New Zealand, none as catastrophic but each a sobering reminder that seismic-resistant construction is essential for the future of our cities. In fact, with some geoscientists and seismologists warning that a magnitude 9.0 earthquake — 11,000 times more powerful than Christchurch — may be on the horizon, earthquake-resistant technology is more important now than ever before. The good news is that researchers, designers and engineers have been hard at work developing ingenious new systems for protecting buildings against these detrimental natural disasters. The following are the five most promising innovations for the future of seismic safety:
CFRP wrap being installed on an existing beam; photo via Structure Magazine.
Carbon Fiber Wraps
Carbon Fiber is a remarkable material weaved from strands of carbon. It is highly flexible, durable, lightweight and resistant to extreme temperatures, making it a popular material for use in automobile parts, aircrafts and weaponry. Civil engineers have also discovered a new use for carbon fiber as a tool for strengthening older buildings against earthquakes. This retrofit technology, known as Carbon Fiber Reinforced Polymer (CFRP) wrap, is a composite of carbon fibers and epoxy which can easily wrap around existing beams and columns. The carbon fiber’s significant tensile strength helps the structural members withstand the force of earthquakes while the materials lightweight and flexible nature drastically reduces installation costs — making it up to 50% cheaper than traditional retrofit solutions.
Steel brace with smart metal alloy cables inside; photo via Georgia Tech University.
Smart Metal Bracing
Buildings are only as sturdy as their reinforcements. Unfortunately, most buildings in the world are constructed with inelastic reinforcing materials, such as concrete or masonry, which are relatively ineffective against bending forces. Instead, researchers at Georgia Tech’s School of Civil and Environmental Engineering are studying a new kind of bracing using shape memory alloys. This material, also known as smart metal, is made from a combination of different metals, such as nickel and titanium alloys, creating a dynamic new product. Smart metals are incredibly flexible and always return to their original shape, even after significant deformation.
As Reginald DesRoches, a professor at Georgia Tech, explains: “The idea behind seismic retrofit is that you want the structure to bend, but not break. So we have these braces and shape-memory alloy cables in this brace, and when it deforms, it puts the force right back on the structure to pull it back into position. What we’re trying to do in an earthquake is limit the deformation, particularly in an area where we know it is vulnerable… and we believe this material can do that for us.”
Resilient Slip-Friction Joint tested for the Nelson Airport Terminal in New Zealand; photo via Tectonus.
Resilient Slip-Friction Joints
The Resilient Slip-Friction Joint (RSFJ) is an innovative, award-winning technology created by Pouyan Zarnani, a PhD student at New Zealand’s prestigious University of Auckland. The device is used to connect vertical and horizontal structural elements, such as beams and columns. Interlocking grooved plates connected by bolts and disc springs allow the structure to expand and contract without becoming permanently distorted. The friction created by this movement also helps dissipate seismic energy acting on the joint by earthquakes and their aftershocks. RSFJs can be implemented in steel, concrete or timber constructions and are appropriate for both new construction and retrofit applications. As its inventor told the New Zealand Herald: “the Christchurch re-build is a golden opportunity to implement this. Later on, we will aim to expand to Japan and the US and further consider internationalization.”
The recently completed Nelson Airport Terminal in New Zealand is the first commercial building to utilize RSFJ technology. You can watch a video of the airport’s joints being tested by clicking here.
EDCC concrete being sprayed on to a concrete block wall; photo by UBC Public Affairs.
Eco-friendly Ductile Cementitious Composite, or EDCC, is concrete mixed with polymer fibers to create an astonishing new product with the strength of concrete and the malleability of steel. The mixture can be sprayed onto existing masonry walls to help them better withstand the shaking and bending of earthquakes. Studies have shown that a masonry block wall with a minimal, 10-millimetre coating of EDCC is capable of surviving 9.1 magnitude earthquakes. This year, EDCC will be put to the test outside of the lab for the first time, as it is used to retrofit the walls of the Dr. Annie B. Jamieson Elementary School in Vancouver.
In addition to being stronger than regular concrete, EDCC is also much more environmentally friendly. It is composed mainly of recycled flyash, an industrial byproduct, which generates a fraction of the carbon emissions during production.
New Zealand’s three seismic risk zones; image via Stuff.
The Earthquake-prone Buildings Act
Legislation may not be as interesting as high-tech building products or experimental materials, but it has the power to save countless lives. As of July 2017, New Zealand’s Earthquake-prone Building Amendment Act has officially taken effect. This sweeping overhaul organizes the country into three distinct seismic zones — high, medium and low risk — depending on their chances of being affected by earthquake activity. It also institutes a system for managing, repairing and strengthening existing, earthquake-prone buildings.
While it is important to continue developing advanced earthquake-resistant technologies for new construction applications, historic and existing buildings pose the greatest threat to public safety. Most earthquake injuries and fatalities are caused by older buildings, as substandard construction methods fail and neglected stonework breaks loose. In fact, the vast majority of victims in the deadly Christchurch earthquake were killed in the tragic collapse of the Canterbury Television (CTV) headquarters, which had been improperly constructed nearly 25 years earlier — a somber reminder that we cannot construct a better future without first repairing the past.
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