New models assess bridge support repairs after earthquakes
Engineers simulate restoration strategies for reinforced concrete columns


Date:
January 18, 2022
Source:
Rice University
Summary:
Civil engineers develop a computational modeling strategy to help
plan effective repairs to damaged reinforced concrete columns.



FULL STORY ========================================================================== Steel-reinforced concrete columns that support many of the world's bridges
are designed to withstand earthquakes, but always require inspection
and often repair once the shaking is over.


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

Engineers at Rice University's George R. Brown School of Engineering and
Texas A&M University have developed an innovative computational modeling strategy to make planning these repairs more effective.

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 the current provost and the incoming
president of Rice.

"When we design bridges and other structures for earthquakes, the
goal is collapse prevention," DesRoches said. "But particularly in
larger earthquakes, we fully expect them to be damaged. In this study,
we show analytically that those damages can be repaired in a way that
the original, or close to the original, performance can be achieved."
Their models simulate how columns are likely to respond globally (in
terms of base shear and lateral displacement) and locally (with stress
and strain) in future earthquakes when using various repair methods.



==========================================================================
The models also predict the effects of slipping and buckling of
reinforcement bars on the columns' strength and ductility before and
after repair.

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

"What we mainly care about is life safety, of course, and we know that
after a strong earthquake, we are going to see some level of damage to
the structure," he said. "If a column is severely damaged, it might need
to be replaced, but that can be prohibitively expensive. Our computer
models can help engineers determine whether the column can be repaired
in a cost- and performance- effective way." The concrete and steel in reinforced columns are represented in the models by "fiber" elements. The models predict how they will respond to arbitrary loading considering
the nonlinear stress-strain behaviors of columns and repair materials.

After 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 bar slip and buckling modeling tools, unique to the software,
were 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 jacketing.

DesRoches is also chair 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 seismically damaged bridge columns, he said the tools could also be used to evaluate the repair of any structural elements.

"We're seeing more and more that existing infrastructure is deteriorating
due to corrosion 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, too." ========================================================================== Story Source: Materials provided by Rice_University. Original written
by Mike Williams. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Mohammad Salehi, Petros Sideris, Reginald DesRoches. Numerical
modeling
of repaired reinforced concrete bridge columns. Engineering
Structures, 2022; 253: 113801 DOI: 10.1016/j.engstruct.2021.113801 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220118145952.htm

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