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CEE and NEES researchers: Retrofitting buildings to survive earthquakes

 

The lot behind CEE's Structural Engineering and Materials Research Lab needed to be dug up and prepped for the NEESR building project. Normally, this area is used to stage other large materials used by the lab. It will return to that use after the tests conclude.

A collaborative research project funded by the National Science Foundation’s Network for Earthquake Engineering Simulation Research (NEESR) Program is enabling CEE faculty and students to investigate new retrofits that could eventually help many older buildings survive earthquakes.

Inaugurated in 2010, the four-year, $1.2 million project will begin active testing on Georgia Tech's campus this January. During this time the two-story, 3000-square-foot structure will be subjected to earthquake-magnitude shaking. Special sensors embedded in the structure will record every detail of the seismic simulations – and the building’s response – providing researchers with terabytes of information that they will use to validate and refine their retrofit models.

 

“This project will provide a wealth of information that can be used to retrofit buildings and other structures in this country that were built before seismic design was routinely incorporated into the codes for reinforced concrete structures,” said Dr. Reginald DesRoches, the project’s principal investigator.

“The dynamic tests will determine which retrofit will be most practical to use to retrofit these non-ductile concrete buildings– here and around the world. We will be able to identify techniques that are easily installable, easily adaptable, scalable, and cost-effective. “

Excitement over the impending tests has been building on campus since early October, when construction of the test building was completed by a team of more than 20 subcontractors and vendors. Two local firms, Winter Construction, and Turner Construction took leadership roles in that phase, contributing in excess of $250,000 in services and materials.

 

“Typically when we construct a building, there are many steps we take to insure it is structurally sound and that the people who inhabit it will be safe,” said Winters Construction President and CEO Brent Reid, CE ‘82. “But it's rare, if ever, that we have an opportunity to help build one building that has the potential to make tens of thousands of other buildings and millions of people safe from collapse.”

Reid’s comments were echoed by Brian Burleigh, the project executive at Turner Construction:

“It was very interesting to be included in a team that built a structural framed system, designed to 1960’s standards, for the purpose of destructive testing and rehabilitating," he said. “I had never thought about exposure to earthquakes here in our own country where many buildings were constructed 50-plus years ago. The results of this project will impact the lives of people around the world and provide them with feasible solutions and options. This would not have been possible without the shared interest of our subcontractors, vendors and suppliers who contributed their time and resources to make this a success.”

Since walls do not play a significant role in maintaining the strength of the building during a seismic event, no walls were added to the NEESR structure, which is seen, here, during the final week of construction.

A series of different retrofits will be added to the building by CEE researchers in the coming weeks – each of them designed to improve the performance of this common, but very vulnerable type of building during a seismic event. Those retrofits will be systematically tested, using a hydraulically- powered shaker table which will simulate moderate to heavy earthquake loading. The shaking is the first of its kind anywhere in the world.

Structural damage from earthquakes is a problem in the developing world, where non-ductile concrete structures – susceptible to earthquake damage -- are a common building type. Severe damage is also a risk in certain parts of the United States, where building codes to protect against earthquakes were not developed and implemented until relatively recently.

NEESR was created by the National Science Foundation to prevent or minimize structural damage from earthquakes by aggressively improving infrastructure design and construction practices. The project funded the fabrication of the mobile shaker table to be used by research teams from different locales. The series of tests at Georgia Tech will be the first to actually use the unique shaker.

The reinforced concrete building to be used during the experiment will display many of the same structural vulnerabilities of older, less fortified concrete buildings. Eventually, the data produced by these tests will enable researchers to design retrofits that will address weaknesses currently found in structures throughout the world.

CEE Ph.D. student Tim Wright was on site for construction and will be overseeing the shaker tests.

More immediately, it will give scientists evaluable insight in a number of analytical and experimental systems, including:

• Identification of common configurations and building vulnerabilities
• Cost-benefit and life-cycle analyses for retrofit comparisons
• Fragility modeling of buildings with innovative retrofits
• Analytical models of components and retrofitted systems
• Advanced instrumentation and damage detection
• Component testing of recentering and damping systems
• Multi-scale shake-table testing of innovative retrofits (international collaboration)
• Full-scale field test of retrofitted buildings with mobile shakers

Also participating in the NEESR testing are research teams from Howard University and Rice University. The specially built mobile shaker table will be on loan from UCLA.