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Manmade Quake to Test Building Safety

Thursday, August 15, 2013

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Structural engineers from Johns Hopkins University plan to shake a two-story building with seismic forces comparable to those at the epicenter of the 1994 Northridge earthquake in Los Angeles.

The magnitude 6.7-quake claimed dozens of lives and caused billions of dollars in damage.

Now, using two massive moving platforms and more than 100 sensors and cameras, the team is trying to determine how well a building, constructed of cold-formed steel, can stand up to a lab-generated Southern California quake, the researchers reported in an announcement.

Johns Hopkins University / YouTube

Lead researcher Benjamin Schafer says the seismic simulation project is intended to close knowledge gaps with respect to lightweight cold-formed steel.

The team says the project could result in safer buildings and improved building codes and have implications for future design and construction methods.

3 Years, $1M

The testing, taking place at the University of Buffalo’s earthquake engineering research center in New York during the month of August, marks the culmination of a three-year, $1 million research project involving scientists from five universities and design consultants from the steel industry.

The University of Buffalo facility is the only structure in the United States that is capable of replicating an earthquake in three directions beneath a building measuring 50 feet long, 20 feet wide and 20 feet tall.

Building Code Improvements

The results are expected to fuel improved nationwide building codes that will make future cold-formed steel buildings less expensive to construct than current ones, the Baltimore, MD-based team says.

“In earthquake-prone regions, code updates should help structural designers and builders reduce the likelihood of a costly and life-threatening building collapse,” the engineers note.

Cold-Formed Steel Study

Funded primarily by the National Science Foundation, with additional support from players in the steel industry, the research could lead to broader use of building components made of cold-formed steel, made of 100 percent recycled steel, the team says.

Johns Hopkins researchers
Will Kirk / Homewoodphoto.jhu.edu

Professor Benjamin Schafer (left) and his students tested cold-formed steel in the lab at Johns Hopkins in Baltimore before heading to Buffalo, NY, for the earthquake trials. Doctoral student Kara Peterman (right) is overseeing testing in Buffalo; Luiz Vieira worked on the project while earning his doctorate.

Cold-formed steel pieces, often used to frame low- and mid-rise buildings, are made by bending sheet metal, roughly one-millimeter-thick, into structural shapes without using heat.

The steel has been used in structures such as college dorms, assisted living centers, small hotels, barracks, apartments and office buildings.

“Although the material is popular, some large knowledge gaps exist regarding how well cold-formed steel structures will stand up to extreme conditions—including earthquakes,” according to the team.

Closing Knowledge Gaps

Lead researcher Benjamin Schafer, from the Whiting School of Engineering at Johns Hopkins, says the current tests conducted atop two “shake tables” should help close those information gaps and lead to better constructed buildings.

“This is the first time a full building of cold-formed steel framing has ever been tested in this way, so even the small things we’re learning could have a huge impact,” said Schafer, the Swirnow Family Scholar, professor and chair of the Department of Civil Engineering.

“We’ll see code changes and building design changes. We think this will ultimately lead to more economic, more efficient and more sustainable buildings,” he said.

Test Building Construction

In May, Schafer’s team began supervising a construction crew in assembling a first version of the test building.

The structure—about the size of a small real estate or medical office building—was mainly composed of the cold-formed steel skeleton and oriented strand board (OSB) sheathing.

When the initial tests were complete, that structure was torn down and replaced by an identical building that also included non-structural components, such as stairs and interior walls, the researchers report.

The researchers say they are discerning whether those additions, which do not support the frame of the building, can still help reduce damage during a quake. The second version of the test building will face the strongest seismic forces in the lab.

Data and Tracking

Kara Peterman of Fairfax, VA, a Johns Hopkins civil engineering doctoral student, has overseen the test site, construction of the buildings, shake trials and collection of data.

Johns Hopkins project
Screenshot via Johns Hopkins / YouTube

The tests at the University of Buffalo's earthquake engineering research center will replicate a tremor comparable to the 1994 Northridge earthquake in Los Angeles.

She has gathered data from more than 150 sensors and eight video cameras installed in and around the test buildings.

During a simulated Southern California quake, these instruments are designed to track the three-dimensional movement of the structure and to record any piece in the building that has “failed,” such as beams that have bent or screws that have come loose, the researchers report.

Tremor Trial and Predictions

Peterman said tests on the first version of the building yielded surprisingly good results.

“It moved a lot less than we were predicting,” she said.

“We did find one small portion of the steel that failed, but that was because of a conflict in the design plans, not because of the way it was constructed.

“And that small failure was purely local—it didn’t affect the structure as a whole.”

Peterman predicts that the final high-intensity seismic test is likely to damage the test building, but not enough to cause a catastrophic collapse.

When the testing is completed and the results are analyzed, Schafer’s team plans to incorporate the findings into computer models that will be shared freely with engineers who want to see how their designs are likely to respond in an earthquake.

“The modeling,” Schafer said, “will create cost efficiencies and potentially save lives.”

Project Participants

In addition to the Johns Hopkins participants, academic researchers from the following schools have taken part in the project: Bucknell University, McGill University, University of North Texas and Virginia Tech.

Steel industry partners provided technical expertise, materials and additional funding. Those partners were: Bentley Systems Inc.; ClarkDietrich Building Systems; Devco Engineering Inc.; DSi Engineering; Mader Construction Company Inc.; Simpson Strong-Tie Company Inc.; the Steel Framing Industry Association; the Steel Stud Manufacturers Association; and the American Iron and Steel Institute.

The research has been funded by National Science Foundation, under the George E. Brown, Jr. Network for Earthquake Engineering Simulation Research program. The research was also supported by a George E. Brown, Jr.  Network for Earthquake Engineering Simulation Operations award.

   

Tagged categories: Architects; Building codes; Building design; Building materials; Construction; Laboratory testing; Recycled building materials; Research; Steel

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