Lab-Simulated Earthquakes Test the Mettle of ‘High-Performance’ Building Materials

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.”

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 environmentallyconscious future.”

Sustainable Design

Top left: Iman Syed ’22 ascends a staircase inside Hadrian’s Aqueduct beneath the city of Athens, while Ebony Payne ’22 looks on.

Bottom left: Ebony Payne ’22 prepares to climb out of the 2,000-year-old aqueduct.

Right: Georgeen Theodore stands near a wellhead in Athens. Theodore is creating a three-dimensional model of the city’s Roman-era aqueduct that could help citizens access its water and offset intense heat island effects.

the water flow, see how it intersects with the existing urban landscape and design public green spaces that can be irrigated. Creating these green pockets will help offset the heat island effects in a metropolis where the temperatures can reach 111 degrees.

Without a visual guide, municipalities have no way to manage or utilize the water, says Theodore, who started researching the underground system in 2017.

“We are using our skills as designers to make visible what is invisible and make it negotiable, and enable residents to help inform the design. We are using the skills of designers to help democratize a big infrastructure project. We want to make it understandable at a glance and create tools to help people see it.”

Mapping an Ancient Solution to a Modern Crisis

thens is dense, dry and prone to drought. Together, rising temperatures, a lack of trees and intense heat island effects are baking the modern metropolis of more than three million people. Researchers think a nearly 2,000-year-old answer to the city’s problems may lie beneath its streets.

In 125 CE, Roman emperor Hadrian ordered the creation of an aqueduct that eventually stretched more than 12 miles. Despite being abandoned decades ago, the aqueduct continues to function — silently collecting groundwater. The missed opportunity, however, is that the water is currently routed to a sewer and dumped into the Aegean Sea.

Georgeen Theodore, a professor at the Hillier College of Architecture and Design (HCAD) and the coordinator of the Master of Urban Design Program, wants the people of Athens to be able to access that water — and have a say in how it is used. She’s building a toolkit that will include a richly detailed, three-dimensional digital model of the aqueduct and its adjacent watershed that will help municipalities access

Theodore, a founder and principal of the architecture, urban design and planning practice Interboro Partners, says the toolkit will include diagrams and infographics that will help local stakeholders understand the Roman-era water system. She’s currently working with two students to “build a digital and a physical model of the aqueduct and prototypical sites where we can test public space interventions that lower temperatures.” The project is part of a collaboration among the city, the regional water authority, the city of Chalandri, the National Technical University of Athens and NJIT.

In 2022, Theodore and two of her students went to Athens for a week and had the “thrilling” experience of entering the aqueduct at multiple spots. Above ground, all one can see are the wellheads.

“It was interesting to study something for a long time from afar and to then finally get to experience it in person. Climbing down into a deep, dark well that was built nearly 2,000 years ago was an extraordinary experience for me and my team. The fact that water still runs through the

A Room with a View

There’s a reason the daylight-filled corner office is a coveted prize for corporate achievers.

tunnels demonstrates the ingenuity of Roman design and engineering.”

Despite its significance as both a cultural artifact and an impressive feat of engineering, the fact that the aqueduct (and how it operates) are virtually invisible also makes it vulnerable to the risks of damage, pollution and depletion from above-ground urban land use. These vulnerabilities have been exacerbated over the past several decades, as urban development has resulted in several blockages in the aqueduct wells. The abandonment of its reservoirs has also led to unsustainable practices. For example, many communities in metropolitan Athens rely on the potable water from the mountains for irrigation, when non-potable water would be a better choice.

The project won’t just close the gaps in understanding the system, but will develop an interactive digital archive to host new visualizations of the aqueduct and the integration of citizen science through community engagement and participation in the project’s development.

Two years ago, Theodore got seed grants from HACD and NJIT for the project. The Athens water and sewer company paid for her students’ travel to Athens. Those two students, Ebony Payne ’22 and Iman Syed ’22, worked with her last semester to build a digital and physical model of the aqueduct and prototypical sites where they can test ideas about cooling.

Theodore, who is also working on a project around cooling stations in the South Bronx with the New York City Health Department, says the research in Athens has applicability to the larger world. “Think about U.N. sustainability goal 11 — to make cities more sustainable. The heat island in Athens is extreme, but the issues we are grappling with are global,” she says.

“A view from a window has a positive impact on emotions, cognitive performance and thermal comfort,” asserts WON HEE KO an assistant professor of architecture. Through experimentation, she seeks to quantify the benefits windows provide and to optimize the amount and quality of natural light that people receive throughout the day.

In her lab, Ko places sensors on the window and at eye and desk levels to measure how the conditions outdoors are filtered through it. She uses a fisheye camera lens to capture incoming visual information, including the level, distribution and color of light, as the human eye would.

“Specific bandwidths in the spectrum are directly related to mental and physical health. In keeping with circadian rhythms, we need more blueish light in the morning and less of it in the afternoon, for example.”

In a randomized study with 86 participants, she and collaborators at the Center for the Built Environment at the University of California-Berkeley found that in rooms with windows, people were happier, had increased workingmemory and concentration, and felt cooler and more comfortable, even in slightly overheated spaces. The latter finding has implications for sustainable design.

“If having a view to the outdoors helps occupants increase their satisfaction with a wider indoor temperature range, then we could relax the temperature set points and reduce building energy consumption,” she notes.

In the absence of an established framework for guiding window design, she is developing evidence-based standards for what constitutes window view quality, including the content and clarity of what room occupants can see of the outdoors.

Her goal is to develop models that can simulate design and view to optimize features such as building form, floor plan, orientation and glass selection, at the building and urban planning levels.

“We lack consensus on a unified definition for window view quality that is applicable across occupancies and building types,” she notes, adding, “But I believe windows in everyday spaces should be a minimum design element.”