Engineers simulate reinforced concrete column restoration strategies – ScienceDaily

The reinforced concrete columns that support many bridges in the world are designed to withstand earthquakes, but they always require inspection and repair often once the shaking is over.

These repairs usually involve replacing loose concrete and broken steel bars and adding additional materials around the damaged area to further strengthen it against future loads.

Engineers at George R. Brown Engineering at Rice University and Texas A&M University have an innovative computational modeling strategy to make planning for these reforms more effective.

The study, led by Rice postdoctoral researcher Mohamed Salehi and civil and environmental engineers Reginald Desroches of Rice and Petros Sideris of Texas A&M, was published in the Journal of Structural Engineering. De Roches is also the current dean and incoming chairperson of Rice.

“When we design bridges and other structures for earthquakes, the goal is to prevent collapse,” Desroches said. “But particularly in large earthquakes, we fully expect damage to it. In this study, we analytically show that such damage can be repaired in a way in which the original performance can be achieved, or close to the original performance.”

Their models simulate how plumes are likely to respond globally (in terms of core shear and lateral displacement) and locally (with stress and strain) in future earthquakes when different repair methods are used.

The models also predict the effects of slipping and torsion of reinforcing bars on the strength and wearability of bars before and after repair.

Salehi said the models will be freely available through the open-source structural analysis software OpenSees to help engineers understand preferred types of repairs.

“What we mainly care about is the safety of life, of course, and we know that after a strong earthquake we’re going to see some damage to the building,” he said. “If a shaft is severely damaged, it may need to be replaced, but it can be very costly. Our computer models can help engineers determine if the shaft can be repaired in a cost- and performance-effective manner.”

Concrete and steel in the reinforced columns in the models are represented by “fibrous” elements. Models predict how they will respond to arbitrary loading considering nonlinear stress-strain behaviors of columns and repair materials.

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

He said the slip and torsion modeling tools, unique to the software, have been validated against existing 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 casing and carbon fibre-reinforced polymer.

Desroches is also chair of the National Institute of Standards and Technology’s (NCST) Advisory Committee, which was formed in 2002 to investigate building failures. Although the new study focuses on bridge pillars that have sustained seismic damage, he said the tools can also be used to assess repair of any structural elements.

“We are seeing more and more deterioration of the existing infrastructure due to erosion and other causes,” Desroches said. “So this general methodology can be applied in terms of understanding how repairs can restore and improve the performance of deteriorating structures as well.”

Story source:

Materials provided by Rice University. Original by Mike Williams. Note: Content can be modified according to style and length.

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