Seismic evaluation and retrofit of reinforced concrete buildings and bridges

Several design and detailing deficiencies have contributed to the poor performance of both older and modern reinforced concrete buildings in past earthquakes. As a step toward risk mitigation, seismic assessment and retrofit procedures continue to evolve to evaluate and improve the response of existing structures at both the component and global levels. These procedures aim to identify seismically vulnerable buildings that require prioritization for intervention and to develop retrofit solutions that enhance their safety and performance. However, in certain cases, existing codified procedures can be overly conservative, leading to unwarranted retrofits or building closures. Such conservatism imposes a significant financial burden on the global economy and may inadvertently hinder community resilience.

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Over the past few years, we have developed improved seismic assessment and retrofit methodologies to replace a number of conservative procedures in the New Zealand and American Seismic Assessment Standards. A distinguishing feature of our proposed approaches is their mechanics-based foundation. Unlike purely empirical models, mechanics-based models avoid problems of extrapolation and data overfitting, enabling more accurate and transparent predictions of structural performance under seismic demands.

 

A number of our seismic assessment procedures have been incorporated into the New Zealand Seismic Assessment Guidelines for Concrete Structures (C5). Furthermore, we have our models under consideration for adoption in ACI 369 (concrete chapter of ASCE/SEI 41) and other seismic assessment standards globally.

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Amongst relevant papers, the following published papers are worth highlighting:

• Matamoros, H. G., & Opabola, E. A. (2025). “Nonlinear Modeling Parameters for Reinforced Concrete Columns Retrofitted with Fiber-Reinforced Polymer Jackets.” Journal of Composites for Construction, 29(2), 04025012.

• Opabola, E.A and Elwood, K. J. (2023) “Modelling the Flexure-axial-shear interaction of ductile beams with single-crack plastic hinge behaviour.”  Earthquake Engineering and Structural Dynamics https://doi.org/10.1002/eqe.3873

• Opabola, E.A (2022) “Development and splice length model for straight plain bars in tension” ACI Structural Journal. https://doi.org/10.14359/51736111

• Opabola, E.A and Mangalathu, S. (2022) “Seismic fragility assessment of pre-1970s box girder and seat abutment bridges” Bulletin of Earthquake Engineering https://doi.org/10.1007/s10518-022-01521-w 

• Opabola, E.A and Elwood, K. J. (2021) “Seismic assessment of RC columns with short splices”  Earthquake Spectra  https://doi.org/10.1177/8755293021994834 

• Opabola, E.A., Elwood, K.J., and Pujol, S (2020). “Influence of biaxial loading on seismic response of reinforced concrete columns.” ACI Structural Journal https://doi.org/10.14359/51728069

• Opabola, E. A., Elwood, K. J., and Oliver, S. (2018). “Deformation capacity of reinforced concrete columns with smooth reinforcement.” Bulletin of Earthquake Engineering, https://doi.org/10.1007/s10518-018-00540-w

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Other relevant papers are currently under review in reputable journals.