Engineers simulate restoration strategies for reinforced concrete columns – ScienceDaily

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The steel-reinforced concrete columns that support many bridges around the world are designed to withstand earthquakes, but still need to be inspected and often repaired once the shaking is over.

These repairs typically involve replacing loose concrete and fractured steel bars and adding additional material around the damaged area to further strengthen it against future loads.

Engineers from Rice University’s George R. Brown School of Engineering and Texas A&M University have developed an innovative computer modeling strategy to make planning these repairs more efficient.

The study by Rice postdoctoral research associate Mohammad Salehi and civil and environmental engineers Reginald DesRoches of Rice and Petros Sideris of Texas A&M appears in the journal Engineering Structures. DesRoches is also Rice’s current provost and new president.

“When we design bridges and other structures for earthquakes, the goal is collapse prevention,” DesRoches said. “But especially during larger earthquakes, we expect them to be damaged. In this study, we show analytically that this damage can be repaired in such a way that the original performance, or close to the original, can be achieved.

Their models simulate how columns are likely to react globally (in terms of base shear and lateral displacement) and locally (with stresses and strains) during future earthquakes when using various methods. of repair.

The models also predict the effects of rebar slippage and buckling on the strength and ductility of columns before and after repair.

The models will be made freely available through open-source structural analysis software OpenSees to help engineers understand what types of repairs are best, Salehi said.

“What we are primarily concerned about is life safety, of course, and we know that after a strong earthquake we are going to see some level of structural damage,” he said. “If a column is badly damaged, it may need to be replaced, but that can be very expensive. Our computer models can help engineers determine if the column can be repaired cost effectively and efficiently.

The concrete and the steel of the reinforced columns are represented in the models by “fiber” elements. The models predict how they will react to an arbitrary load taking into account the nonlinear stress-strain behaviors of columns and repair materials.

After initial loading to simulate some level of damage, Salehi said the models allow engineers to manipulate the fibers of the model and analyze the performance of repaired columns under seismic loads.

He said the bar slip and buckling modeling tools, unique to the software, have been validated against existing experimental data. Salehi also validated the overall modeling strategy using data from tests on real reinforced concrete bridge columns before and after various repair methods, including concrete and carbon fiber reinforced polymer coating. .

DesRoches is also chairman of the National Institute of Standards and Technology (NIST) National Construction Safety Team (NCST) Advisory Committee, formed in 2002 to investigate building failures. Although the new study focuses on earthquake-damaged bridge columns, he said the tools could also be used to assess the repair of any structural element.

“We are seeing more and more of existing infrastructure deteriorating due to corrosion and other causes,” DesRoches said. “Thus, this general methodology can be applied to understand how repairs can also restore and improve the performance of deteriorating structures.”

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Materials provided by rice university. Original written by Mike Williams. Note: Content may be edited for style and length.

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