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A Framework for Sustainable Seismic Design of Earthquake-Resisting Structures: Foundational Principles of Plasticity, Sequential Yielding, and Post-Earthquake Realignment and Repair

This paper proposes a foundational framework for Sustainable Seismic Design that establishes three core principles—plasticity, sequential yielding, and post-earthquake realignment and repair—to guide the development of low-damage, resilient structural systems capable of recentering and repair, thereby moving beyond conventional damage-accepting approaches.

Original authors: Siavash Sedighi, Armin Aziminejad, Abdolreza S. Moghadam

Published 2026-10-01

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CC BY 4.0

Original authors: Siavash Sedighi, Armin Aziminejad, Abdolreza S. Moghadam

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

When engineers design buildings to withstand earthquakes, their primary goal has long been simple: keep the structure standing so people can escape. This approach, known as life-safety design, has saved countless lives by preventing total collapse during major tremors. However, a building that survives a quake often comes away with severe internal damage. Walls may be cracked, beams bent, and the entire structure shifted out of place. While the people inside are safe, the building itself is frequently too damaged to be used, requiring expensive repairs or even total demolition. This creates a cycle of destruction and reconstruction that is costly, wasteful, and disruptive to communities. The emerging field of sustainable seismic design seeks to change this outcome. Instead of just preventing collapse, the goal is to create structures that can absorb the shaking, stay upright, and return to their original shape with minimal damage, allowing them to be repaired quickly and put back into service.

A team of researchers has now proposed a new framework to guide this shift, moving beyond the idea of simply surviving an earthquake to one of truly recovering from it. Their work introduces a structured approach called Sustainable Seismic Design, which relies on three core principles to ensure a building can be repaired and realigned after a seismic event. The first principle involves controlling how the building bends and deforms. Rather than letting damage happen randomly throughout the structure, the design intentionally directs the stress to specific, replaceable parts. Think of these parts as safety fuses in an electrical system; they are designed to take the hit and can be easily swapped out, leaving the main structure intact. The second principle is about the order in which these parts give way. The researchers suggest that different components should be arranged so they yield, or bend, in a specific sequence. This predictable behavior ensures that the building's gravity system remains stable and that the damage is concentrated in areas where it can be managed. The third and perhaps most critical principle is the ability to realign the building. After the shaking stops, the structure must be able to return to its original vertical position, or be easily nudged back into place, so that it does not remain leaning or distorted.

To test these ideas, the researchers built simplified computer models of a single structural unit, representing the basic behavior of a building frame. They simulated how this unit would react to lateral forces, mimicking the side-to-side motion of an earthquake. In their models, they incorporated a system of pre-tensioned cables and replaceable metal plates. As the simulated earthquake pushed the structure, the metal plates were designed to bend and absorb the energy, acting as the sacrificial elements. Once the shaking stopped, the tension in the cables, which had been stretched during the event, pulled the structure back toward its center. The models showed that if the building was designed with these specific features, it could return to its original position without needing to be pushed back by heavy machinery. However, the researchers also explored what happens if the internal pulling force isn't strong enough to overcome the damage on its own. In those cases, they proposed a method called global stiffness reduction. This involves removing the damaged, bent plates that are now stuck in place. By taking these damaged pieces out, the overall stiffness of the structure drops, making it much easier for the remaining tension to pull the building back into alignment. Once realigned, new plates can be installed, and the building is ready for use again.

The study emphasizes that this approach requires a fundamental change in how engineers think about damage. In traditional design, some damage is accepted as inevitable, but the new framework treats damage as a controlled process that must be planned for from the start. The researchers found that by combining these three pillars—controlled plasticity, sequential yielding, and post-earthquake realignment—it is possible to create systems that are not only safe but also resilient. They demonstrated that even if the initial restoring force is insufficient, the combination of removing damaged parts and adjusting the restoring forces can still achieve a state where the building is straight and stable. This suggests that with the right design, a building does not have to be a total loss after a major earthquake.

The paper also addresses the practical side of bringing these concepts to life. It outlines the necessary conditions for such a system to work, including the need for specific details in how parts are connected and the importance of designing non-structural elements, like walls and facades, so they do not interfere with the building's ability to move and return to center. The authors acknowledge that while their current work relies on simplified models, the principles are intended to be applied to more complex, real-world structures like post-tensioned frames and rocking wall systems. They argue that the initial cost of these specialized designs is offset by the long-term savings in repair, downtime, and reconstruction. By establishing a clear set of rules and objectives, this framework provides a roadmap for engineers to move away from the old standard of "collapse prevention" toward a future where buildings are designed to heal themselves, ensuring that communities can recover quickly and sustainably after a disaster.

Technical Summary: A Framework for Sustainable Seismic Design of Earthquake-Resisting Structures

Problem Statement
Conventional seismic design has successfully prioritized life safety and collapse prevention. However, structures designed under current provisions frequently sustain significant structural and non-structural damage during major earthquakes, leading to costly repairs, prolonged downtime, or demolition. While recent advances have introduced resilient systems (e.g., self-centering frames, rocking walls), the field lacks a unified conceptual framework defining the principles necessary to achieve truly sustainable seismic performance. Specifically, there is a gap in integrating repairability, recenterability, and post-earthquake realignment as fundamental design objectives rather than secondary considerations.

Methodology
The paper proposes a foundational framework for Sustainable Seismic Design (SSD) rather than a specific design code or methodology. The study employs simplified analytical models, primarily Single-Degree-of-Freedom (SDOF) systems, to establish the theoretical basis for the framework. The authors utilize:

Idealized Hysteresis and Pushover Diagrams: To visualize controlled plastic behavior, unloading paths, and recentering capabilities.
Sequential Yielding Analysis: Examining Mixed Multiple Systems (MMS) where different Earthquake-Resisting Systems (ERSs) are arranged in parallel with varying Yield Drift Ratios (YDRs).
Component-Level Modeling: Analyzing tension bars with replaceable splice plates and pre-loaded restoring mechanisms (e.g., high-strength cables, post-tensioned tendons) to demonstrate controlled damage and recovery.
Conceptual Derivations: Formulating relationships between stiffness, strength, residual drift, and the capacity for Post-Earthquake Realignment and Repair (PERR).

Key Contributions: The Three Pillars of SSD
The framework is built upon three foundational pillars:

Pillar I: Principles of Plasticity for Repairability
- The framework redefines plasticity not merely as energy dissipation but as a controlled mechanism for damage localization and recovery.
- It introduces the concept of Global Stiffness Reduction (GSR) and Restoring Force Adjustment (RFA). GSR involves the removal of damaged, sacrificial components (e.g., Replaceable Energy Dissipating Devices or REDDs) to lower global stiffness, while RFA utilizes stored elastic energy (e.g., from post-tensioning) or manual intervention to return the structure to its original position.
- The authors argue for the inclusion of the unloading path and residual distortion in design diagrams, moving beyond the traditional "pushover" endpoint to ensure the structure can be realigned.
Pillar II: Implementation of Sequential Yielding
- This pillar advocates for a hierarchical arrangement of system components to dictate a predetermined order of yielding.
- By utilizing Mixed Multiple Systems (MMS) with different Yield Drift Ratios (YDRs), the framework ensures that damage occurs in a predictable sequence, concentrating it in replaceable elements while protecting the gravity load-carrying system.
- The paper derives equations linking the ultimate load distribution to the maximum post-elastic drift ratio ( $\phi_u$ ), allowing designers to calibrate the strength and stiffness of constituent ERSs to achieve specific performance targets.
Pillar III: Enabling Post-Earthquake Realignment and Repair (PERR)
- PERR is established as a fundamental prerequisite for sustainable performance. The framework distinguishes between two technical approaches:
  - Predefined Recentering Solutions: Systems with inherent self-centering capabilities (e.g., rocking systems with post-tensioning).
  - Global Stiffness Reduction (GSR): A strategy applicable to conventional systems where damaged components are disengaged to facilitate manual or assisted realignment.
- The framework emphasizes that realignment alone is insufficient; it must be paired with practical repair strategies, including residue-free connections and accessible damage zones.

Results and Technical Findings

Residual Drift Management: The study demonstrates that residual deformations can be minimized or eliminated by ensuring the restoring force exceeds the combined resistance of P-delta effects and plastic resistance. If automatic recentering is not possible, GSR techniques can reduce the restoring force demand to a manageable level.
MMS Behavior: In parallel MMS configurations, the sequence of failure is directly proportional to the ascending order of the YDRs of the constituent systems. This allows for the design of "fail-safe" mechanisms where the gravity system remains stable even after the yielding of energy-dissipating components.
Equivalent Stiffness: The paper introduces the concept of equivalent global stiffness ( $K_{Eq}$ ) at the maximum ductile deformation ( $\phi_u$ ). This parameter allows the nonlinear response of complex systems to be approximated as a quasi-linear elastic system for the purposes of ultimate load distribution and PERR analysis.
Feasibility of Repair: Analytical models confirm that by designing for specific failure modes (e.g., yielding of splice plates rather than main bars) and incorporating restoring mechanisms, structures can return to a plumb state with minimal residual stress, enabling functional recovery.

Significance and Claims
The authors position this work as a conceptual foundation rather than a complete design code. The significance of the paper lies in:

Bridging a Conceptual Gap: It provides a unified set of guiding principles that link plasticity, sequential yielding, and PERR, addressing the lack of a cohesive framework for repairable structures.
Shifting Design Philosophy: It advocates moving beyond the "Near Collapse" objective of traditional Performance-Based Seismic Design (PBSD) toward a paradigm where functional recovery and repairability are primary goals.
Roadmap for Future Research: The framework is intended to guide the development and evaluation of advanced resilient systems, such as post-tensioned self-centering frames and rocking wall systems. The authors explicitly state that while the principles are derived from simplified SDOF models, they serve as a basis for extending these concepts to complex Multi-Degree-of-Freedom (MDOF) systems through future numerical and experimental validation.
Practical Implementation: The paper outlines specific engineering preconditions (concept, detailing, theoretical, maintainability, and economic) required to implement SSD, offering a checklist for transitioning from theoretical resilience to practical, sustainable engineering practice.

The paper concludes that by incorporating these principles, the engineering community can develop earthquake-resisting structures that not only prevent collapse but also ensure rapid recovery and long-term sustainability, thereby reducing socio-economic and environmental impacts following seismic events.

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