Despite advances in construction design and materials, a powerful 7.8 magnitude earthquake on the San Andreas fault could kill a projected 1,800 people, injure an additional 50,000 and demolish 200 million square feet of commercial, public and residential buildings, according to a recent study. Even the newest, most up-to-date structures would be toppled at a rate of up to 1 in 10.
“Ten percent is not a random figure — it’s the accepted failure rate in today’s building code when weighing the economics of improving construction with the risk of such large events,” says Matthew Bandelt, associate professor of civil engineering and co-director of NJIT’s Materials and Structures Laboratory. “The risk is rising, however, as more people move into urban areas. As a result, we now have very concentrated losses when a natural disaster, in any form, hits a major metropolitan area.”
Engineers increasingly use a new class of high-performance concrete to bolster new and existing bridges against harsh conditions, but there has been little push to incorporate
them in the construction of buildings.
“We don’t know how buildings would behave with these new materials, including during earthquakes, so it’s difficult to quantify the benefits,” notes Bandelt, who secured a CAREER award from the National Science Foundation to assess the seismic response of materials known as high-performance fiber-reinforced cementitious composites (HPFRCC) in structures of various configurations and to develop design criteria for using them.
The HPFRCC materials that Bandelt and his team study have small fibers made of steel or polymers that are one-half to 1 inch in length and range in thickness from that of a human hair to the tip of a pen. When building components made with HPFRCC materials are subjected to seismic shaking, the fibers help keep the concrete together, potentially making it stronger and more able to deform or bend.
Buildings designed with high-performance fiber-reinforced concrete are also potentially more sustainable, meaning they would require less steel, for example, because the concrete itself bears more of the load. “The beams and columns could be smaller,” Bandelt says, “because less material carries the same amount of weight.” He hopes that his research will contribute to the establishment of LEED-like standards for building resilience.
Earthquake forces push and pull the beams and columns that make up a building. Bandelt uses hydraulic machines that apply up to 220,000 pounds of force to simulate these impacts on individual building components, and to better understand their behavior under the combined effects of axial load and bending. Their studies have shown that HPFRCC dramatically improved the seismic response: increases in strength of 30% to 40%, or even more, are common in comparison to traditional reinforced concrete. But the deformation capacity — the amount a structural component can bend before breaking — requires further consideration.
The team is now building mathematical representations of buildings with different frame configurations, story heights, building layouts, structural element geometries and HPFRCC mechanical properties to test the materials’ performance at the system level. They apply nonlinear dynamic structural analysis, a technique to computationally simulate structural response under loading, to see how much shaking would make the buildings collapse.
“We have component-level information, but not for an entire building, and without it, we’ll never get buy-in,” Bandelt says, adding that part of their research is to perform risk assessments to understand how rates of damage change with these new materials and to analyze cost-benefit scenarios for HPFRCC systems.
They’re investigating methods to engineer and place HPFRCC in key regions of buildings, while quantifying their impact on performance, safety and life-cycle costs. Specifically, Bandelt and his team will study how HPFRCC can be placed in “plastic hinge regions” where damage is expected to occur during an earthquake, with the expectation of reducing damage while also increasing strength and elasticity. Their goal is to help people understand the relative benefit of using the new composites under different risk scenarios.
“If a building owner asked for their structure to be immediately occupiable after a specific earthquake magnitude, for example, we would tell them how to meet that standard,” he says. “We do this by using our computational models to simulate performance under various earthquake magnitudes and integrating those results with the risk of different earthquake hazards based on how likely they are to occur and how much shaking they cause.”
According to the Federal Emergency Management Agency (FEMA), about half of the U.S. population, not including residents of Hawaii and Alaska, are at risk of damage from earthquakes. Regions that are most vulnerable to earthquakes are largely uninsured or underinsured against them, Bandelt notes. As of now, the federal government through agencies such as FEMA covers the lion’s share of damage repairs.
“There is a lot of loss in natural disasters, not just in terms of lives and revenues, but also in community,” he says. “Buildings are places people gather.”
Novel Forms for Broken Glass
On the roof of NJIT’s Campus Center, speckled slabs composed of recycled glass and plastic bottles have successfully weathered the first leg of a year-long stress test.
“We’re seeing how this composite withstands ultraviolet light, fluctuations in temperature, freezing and thawing cycles, rain and snow,” explains Richard Marsh, a master’s student in environmental engineering. “So far, there’s no crumbling or cracking.”
Marsh is part of a team of engineers and architects who hope to develop innovative construction products from mixed-color container glass that “go beyond the tried and tested paving materials or cementitious composites.” Think architectural facade elements or landscaping products such as planters, pavers and retaining wall blocks.
“We’re trying to find a use for mixed-color glass without going through all of the processing that now occurs when it’s ground into fine powder and used as a replacement for sand in concrete,” he says. “We use it as an aggregate.”
Marsh’s group argues that manufacturing new glass products utilizing recycled glass requires 20% less energy and creates 20% less air pollution than glass produced from virgin materials.
Yet only a quarter of the glass Americans use is currently recycled. The reasons range from the logistical, to the aesthetic, to the psychological. To begin with, Americans don’t separate glass. To do so at a recycling facility would require expensive equipment, such as optical sensors and robots.
“The system is in place and it’s hard to change that,” Marsh says. “If you’re recycling, you think you’re doing a good thing. If we tell you that it’s mostly going to a landfill, you might be demoralized and possibly recycle less.” Manufacturers don’t use recycled mixed-color glass to
make new containers, because when it’s melted together it becomes the color of mud.
While there is a long way to go before commercialization, he is optimistic. The group chose plastic bottles (25% of the mix) as a binder for their new product, because they’re also recycled materials, easily recognizable everyday objects, “and so help raise awareness for recycling,” he adds.
“The material’s surprisingly high compressive strength and durability, coupled with its unique speckled look,“ Marsh says, ”may make it a popular commodity in an environmentally-conscious future.”
From the Interim Provost
Atam P. Dhawan
Interim Provost and Senior Executive Vice President
Senior Vice Provost for Research
Distinguished Professor of Electrical and Computer Engineering
Building Resilience
Scientific Innovation for a Sustainable, Equitable Future
Learn MoreConstruction Engineering
Lab-Simulated Earthquakes - Test the Mettle of ‘High-Performance’ Building Materials
Learn MoreSustainable Design
Mapping an Ancient Solution to a Modern Crisis
Learn MoreEnvironmental Chemistry
The Rise of a Climate-Triggered Neurotoxin in the Arctic Tundra
Learn MoreNJIT in the World
Alumni Q&A
Learn MoreWater Remediation
Harvesting the Toxic Blooms of Summer
Learn MoreDiversity in Science
Shark Science
Learn MoreUndergraduate Research
From City Streets to Waterways, Undergraduates Use Data for Change
Learn MoreDefusing Disaster
Defusing Disaster
Learn MoreESSAY - Novel Building Materials
Converting Yesterday’s Rubble into Tomorrow’s Cities
Learn MorePower Electronics
Working the Wind
Learn MoreLanguage Development
Singing Lessons
Learn MoreApplied Optics
Tracking a Deadly Rise, Historic Fall of Insect Populations
Learn MoreEconomics of Recycling
New Futures for Old Plastics
Learn MoreCommunity-Engaged Architecture
Tiny Home Designs Offer Big Community
Learn MoreNew Faculty
New Faculty
Learn MoreFaculty Accomplishments
Faculty Accomplishments
Learn MoreResearch at NJIT: By the Numbers
Research at NJIT: By the Numbers
Learn MoreView and Download PDF
View or download the complete PDF.