The new building design reduces earthquake shocks by more than half

Researchers have found that adding force-limiting connections between floors and a building’s main supports, the structural system of beams and supports that resist lateral earthquake forces, can sharply reduce the most damaging bursts of vibration.

This change redirects how earthquake energy moves through the building, cutting off the forces that normally damage both the structure and internal systems.

What the model showed

Inside a nine-story steel office building designed for the Los Angeles earthquakes, added connections changed how motion was transmitted from the floor to the frame.

By testing the system against multiple earthquake records, Georgios Tsampras of the University of California, San Diego (UCSD) and Richard Seuss of Lehigh University showed that peak ground accelerations and strut forces were significantly reduced compared to a rigid design.

The decline persisted across most floors and vibration scenarios, with only limited exceptions associated with specific vibration patterns within the structure.

These patterns indicate a residual source of uneven stress that requires careful examination of how different vibration modes affect masonry response.

Where danger builds

Much of that compression came from the higher-mode action, and the faster building vibrations riding on top of the main effect.

These faster movements can increase ground acceleration and support power even when the overall lateral drift seems ordinary.

Here, the seventh floor changes less because it is located near a quiet point in the second vibration pattern.

This uneven response explains why engineers overlook damage risks when they focus only on erosion or base shear.

How do joints work?

Each force-limiting link, a link that covers the load by sliding, is coupled to a friction device with low-damping rubber bearings.

Once the vibration exceeds a certain force, the friction device slips and prevents the floor from transferring the full load to the frame.

At the same time, the bearings maintained the alignment of the floor and increased rigidity after the start of sliding, so the movement remained under control.

Changing the path of force at ground level weakened the vibrations that caused the sharpest surges.

Drift behavior explained

In the solid design, the floors used to vibrate more forcefully, but the new joints reduced that movement by more than half.

Forces within the building’s support system also decreased sharply, relieving pressure on key structural members.

Even in cases where the links moved during vibration, the movement remained small and within safe limits.

These numbers show more than the best average: they show smaller extremes, requirements that break parts and bloat designs.

Why did the drift remain the same?

The overall effect has changed little because the main lateral movement still comes from the controlled rocker base, an essential detail that lifts and re-centers.

This oscillation dealt with the slow movement of the entire building, while the ground connections mainly worked for faster vibrations.

“Force-limiting connections primarily reduce the contribution of higher-mode responses,” Tsampras and Soss wrote.

For designers, this dichotomy is important because it reduces harmful acceleration without giving up the self-centering behavior that limits permanent lean.

When impulses take over

Not every seismic record has rewarded the system equally. Two movements showed that long pulses of velocity can drive the oscillation so strongly that drift becomes the biggest concern again.

Under one log, peak story drift reached about six percent and residual drift about two percent as the main period of the building extended during shaking.

This limit does not erase the gain, but it cautions against treating these connectors as a complete solution for pulse-dependent events.

Choose a power cap

The connection can be adjusted, and this adjustment is important. Across design cases, the authors found the best balance when the communication design factor was between 1.5 and 2.5.

Within this range, force and acceleration decreased sharply without a meaningful deflection penalty, and contact motion remained modest.

Beyond this range, softer settings provided less benefit, making calibration more important than increasing power.

What builders can earn

Bottom strut forces indicate a practical benefit beyond improved performance. Due to lower peak loads, future versions of this frame may be able to use lighter steel sections.

The team has not redesigned the building to demonstrate weight or cost savings, so this step still belongs in future work.

However, more predictable forces can help engineers size beams, columns, and braces with less guesswork.

Why is predictability important?

Earthquakes don’t strike buildings in one neat, repetitive way. By reducing the spread across the 18 records taken from the database, the system improved predictability, not just averages.

The smaller dispersion gives engineers a more consistent prediction of ground acceleration, contact force, and demand support under different conditions.

This consistent behavior can make repair planning and rapid return to use easier to target in real designs.

What comes next?

This study demonstrates that a well-placed ground connection can reduce the rapid vibrations that penalize upper floors and attached equipment.

Next comes broader testing and a complete redesign of the building, especially for locations where pulse-like movements may still overwhelm the oscillatory response.

The study is published in Resilient Cities and Structures.

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