home :: features :: article page 1 :: article page 2 :: article page 3

The Expanding State of the Infrastructure

Researchers apply a layer of sophistication to a “system of systems”

Few words have taken on as much baggage in recent history as infrastructure.

For more than two decades, infrastructure has kept questionable company, appearing with adjectives like crumbling and aging, substandard and neglected.

It has been linked to tragedies like Hurricane Katrina (2005), the Los Angeles-Northridge Earthquake (1994) and the recent crisis at Japan’s earthquake- and tsunami-battered Fukushima nuclear power plant.

Politicians of all stripes have catalogued the decline of America’s public works and facilities and have pegged the cost of meaningful overhaul at $1 trillion or more.

Lehigh researchers who study the infrastructure are hardly oblivious to its shortcomings – many have sounded the warnings that helped bring the topic to the forefront of the public imagination.

But today, these researchers are focusing on the potential of infrastructure. They are working on advances in smart systems, software and sensors that will make it possible to allocate resources more efficiently and build more durable structures. They envision a day when infrastructure will be sustainable, engineered for a longer lifecycle and able to withstand extreme events without major damage.

When that day arrives, infrastructure will keep company with words like intelligent, personal autonomy and environmentally friendly. Technology will enable people to assume more responsibility for the resources they consume while affording greater protection against hackers, failures and down time.

Infrastructure is a broad term, encompassing the range of physical structures and services – levees and wastewater treatment plants, highways and airports, power grids and wireless networks, even schools and hospitals – that enable a society to function.

In the past two years, Lehigh’s engineering researchers have carved out strategic areas of focus in new areas such as the smart grid while enhancing their traditional expertise in the civil infrastructure and power generation. Their approach is governed by a philosophy that regards the infrastructure as a system of systems that are integrated and interdependent.

The following pages explore a few infrastructure research projects at Lehigh.

Saving lives, preserving community
Lehigh’s structural engineers took a step toward the goal of sustainable infrastructure recently with a successful experiment on the world’s largest earthquake shake table.

The test verified the superior performance of a reinforced concrete building system containing earthquake-resisting technology developed at Lehigh’s ATLSS (Advanced Technology for Large Structural Systems) Center.

Sustainable infrastructure, says ATLSS director Richard Sause, protects lives while enabling building and transportation facilities to remain operational after an earthquake. In the process, it preserves the social and economic value of the community.

“Think of San Francisco,” says Sause. “What will happen when the next big earthquake hits? Twenty years ago, the question was, ‘can we build structures that protect the lives of people?’

Lehigh’s structural engineers took a step toward the goal of sustainable infrastructure recently with a successful experiment on the world’s largest earthquake shake table.

“Today, the question is, ‘Where are people going to live if there’s extensive damage to the infrastructure?’ What will happen if one-third or more of the people and businesses have to leave?”

The ATLSS technology is a self-centering system with reinforced concrete wall panels designed to “rock” during an earthquake. after shaking concludes, post-tensioned steel strands act like a rubber band to pull the building back to its original position.

The shake table test was conducted at the Hyogo Earthquake Engineering Research Center, or E-Defense Center, in Japan. Lehigh researchers joined peers from the Network for Earthquake Engineering Simulation in the U.S. and the National Research Institute for Earth Science and Disaster Prevention in Japan. The project was led by E-Defense researchers and funded by the Japanese government.

Researchers built two full-scale models of a reinforced-concrete four-story building – one with the ATLSS system and one with conventional reinforced concrete. The shake table simulated the 1995 Kobe earthquake.

“The self-centering post-tensioned concrete wall system [sustained] very little damage under very strong earthquake ground motions,” Sause and Wesley Keller, a Ph.D. candidate, reported.

“We think that type of performance should be expected. By contrast, the conventional reinforced concrete in the adjacent building was badly damaged.”

Self-centering post-tensioned concrete walls are made by casting panels of reinforced concrete and then feeding steel cables through pre-existing hollow ducts in the panels. When the panels are in place, the cables are stretched and then anchored at the top and bottom of the wall, which clamps the panels together.

Lehigh researchers have found that by using “unbonded” post-tensioned steel, concrete walls can be designed to perform well under strong ground shaking. By not bonding the steel to the surrounding concrete, says Sause, deformations in the steel are distributed over a relatively long length rather than concentrated in a small critical region. Strain levels in the steel are thus significantly decreased during earthquake loading.

“An unbonded post-tensioned structure remains nearly elastic during earthquake shaking. As a result, it returns to its original shape after the earthquake without the need for costly repairs,” says Sause.

1 | 2 | 3 | Next >>
The E-Defense shake table (above) confirmed the superior performance of earthquake-resisting technology developed at Lehigh’s ATLSS Center (left).