Hybrid Energy Dissipation System Shields Bridges Built Across Active Faults

When a bridge spans an active fault, the ground beneath it does not simply shake during an earthquake. It tears. The two sides of the fault move permanently in different directions, and the structure straddling that rupture must absorb a displacement that never reverses. Conventional seismic design, which assumes that the ground eventually returns to something close to its original position, struggles to cope with this reality. A new study published in the Bulletin of Earthquake Engineering by Xilun Ma of Ningxia University and colleagues proposes an answer: a hybrid energy dissipation system that combines rocking self-centering piers with shape memory alloy-enhanced friction pendulum bearings, creating a multi-level defense along the very path where fault-crossing bridges tend to fail.

The problem these researchers set out to solve is fundamentally different from ordinary bridge seismic engineering. Bridges crossing active faults experience permanent ground displacements, sometimes called fling-step effects, in which the earth on either side of the rupture is left offset by meters. For a continuous girder bridge, this imposes two simultaneous demands that conventional structures cannot easily meet. The bridge must tolerate large deformations without collapsing during the event, and it must return to a usable configuration afterward, because residual displacements that leave a bridge crooked or its bearings displaced render it unusable until costly repairs are completed. In regions such as northwestern China, where the study’s authors are based, highways routinely cross fault zones, making this an urgent practical concern rather than a theoretical one.

The first component of the hybrid system is the rocking self-centering pier, abbreviated RSC. Unlike a conventional reinforced concrete pier, which is fixed to its foundation and resists lateral forces by bending, a rocking pier is designed to lift off its foundation and rock during strong shaking. This deliberate uplift converts the damage mechanism from plastic deformation of concrete and steel into rigid-body rotation, dramatically reducing the permanent damage the pier accumulates. Post-tensioning elements, and in advanced designs shape memory alloy components, pull the pier back upright once the shaking stops. The result is a column that bends far less, yields at a higher threshold, and springs back to vertical after the earthquake passes.

The study’s numerical modeling quantified exactly how much benefit the rocking configuration delivers. Compared with conventional reinforced concrete piers, the yield curvature of the RSC piers increased by approximately 31.6 percent, while the yield bending moment increased by roughly 23 percent. In practical terms, this means the pier’s cross-section can deform substantially further before it begins to yield, and it can carry more moment when it does. Just as importantly, the rocking mechanism improves the post-earthquake self-centering capacity of the pier sections, so the column returns toward its original alignment rather than remaining permanently tilted. For a bridge that must remain serviceable after a fault rupture, this recovery ability is arguably as valuable as the increased strength itself.

The second component addresses a different vulnerability: the bearings that connect the bridge deck to its piers. Friction pendulum bearings are a well-established seismic isolation technology. They allow the superstructure to slide on a curved spherical surface, so the deck moves relative to the substructure during an earthquake, lengthening the structure’s period and dissipating energy through friction. The problem in fault-crossing scenarios is that permanent ground displacement drives enormous sliding demands, and a conventional friction pendulum bearing can slide so far that it loses its ability to recenter or, in the worst case, falls off its support. The researchers’ solution, the SMA-FPB system, embeds shape memory alloy elements into the friction pendulum bearing.

Shape memory alloys are remarkable materials that can undergo large deformations and recover their original shape, either through heating or, in the superelastic regime used here, simply upon unloading. When superelastic nickel-titanium or similar alloys are stretched, they absorb energy through a stress-induced phase transformation and then pull back elastically, providing both damping and a restoring force. In the SMA-FPB bearing, these alloy elements act as recentering restrainers that resist uncontrolled sliding and pull the bearing back toward its centered position after large displacements. The nonlinear time-history analyses showed that this addition reduces the maximum sliding displacement of conventional friction pendulum bearings by approximately 35 to 40 percent under fault-crossing seismic excitation, a substantial improvement in the margin of safety against unseating and loss of isolation function.

Neither device alone, however, addresses the full chain of vulnerabilities in a fault-crossing continuous girder bridge. The critical damage path runs from the ground, through the bearings, into the piers, and back down to the foundations. If the bearings are protected but the piers yield permanently, the bridge still ends up damaged. If the piers rock back to center but the bearings slide off, the deck is still at risk. This is the rationale for the hybrid RSC-SMA-FPB system, which the authors describe as forming a multi-level energy dissipation and self-centering mechanism along that critical damage path. Energy is dissipated at multiple points, and self-centering capacity is provided at multiple levels, so no single component is asked to absorb the entire fault displacement alone.

The performance gains from combining the two systems were significant. The hybrid configuration reduced the residual relative displacement of key piers by approximately 30 percent compared with the baseline, and it improved the sliding control capacity of the key bearings, keeping them within their functional range even under the severe displacement demands of fault rupture. Residual displacement is the single most important indicator of whether a bridge can be reopened quickly after an earthquake, because it reflects permanent structural distortion that must be corrected before traffic can resume. A 30 percent reduction in this quantity translates directly into shorter closures, lower repair costs, and greater resilience of the transportation network that depends on the crossing.

The research methodology relied on nonlinear time-history analysis, in which detailed numerical models of the bridge are subjected to recorded or simulated ground motion records and the full nonlinear response of every component is tracked through time. The team built models of the rocking self-centering piers, the SMA-enhanced friction pendulum bearings, and the combined hybrid system, then compared the seismic responses of a typical continuous girder bridge under different damping scenarios. This scenario-based comparison allowed them to isolate the contribution of each device and to formulate engineering applicability recommendations, identifying which configurations suit which bridge layouts and fault conditions. The work was supported by the National Natural Science Foundation of China and the Natural Science Foundation of Ningxia.

The broader significance of this study lies in its contribution to a shift in earthquake engineering philosophy, from structures that merely survive earthquakes to structures that recover from them. For bridges crossing active faults, where the ground displacement is permanent and unavoidable, the only viable strategy is to distribute the damage intelligently and ensure that whatever deformation occurs is recoverable. By pairing a pier that rocks and recenters with a bearing that slides under control and pulls itself home, the hybrid system offers what the authors describe as an efficient and post-earthquake recoverable seismic design strategy. As seismic hazard maps continue to place highways and railways across known fault traces, designs of this kind may determine how quickly communities reconnect after the next major rupture.

Subject of Research: Seismic response mitigation of fault-crossing continuous girder bridges using a hybrid rocking self-centering pier and SMA-friction pendulum bearing energy dissipation system

Article Title: Seismic response reduction for fault-crossing continuous beam bridges using a hybrid energy dissipation system

Article References: Ma, X., Zhou, T., Song, Y., Hui, Y., Lv, J., Jia, H., & Li, J. (2026). Seismic response reduction for fault-crossing continuous beam bridges using a hybrid energy dissipation system. Bulletin of Earthquake Engineering. https://doi.org/10.1007/s10518-026-02703-6

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02703-6

Keywords: fault-crossing bridges, seismic response reduction, rocking self-centering piers, shape memory alloy, friction pendulum bearings, hybrid energy dissipation, permanent ground displacement, nonlinear time-history analysis, residual displacement, self-centering capacity, earthquake engineering, continuous girder bridge