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The Role of Vibration Analysis In Stair Design

Complex stair designs can face challenges with vibrations caused by movement. Vibration analysis often leads to innovative solutions that help these structures balance design integrity with user comfort.

BALANCING ART, ENGINEERING, AND COMFORT

Monumental stairs are both challenging and breathtaking. As designers push the boundaries of materials and geometry, creating slender and complex forms, vibrations caused by human movement are becoming a growing concern. These subtle movements, triggered by people walking up and down, can ripple through the stairs and even into other parts of the building, leading to discomfort for occupants.

At Synergi, we know that managing these vibrations isn’t an exact science. While advanced vibration models can predict performance for most stairs, complex designs often demand additional solutions after the stairs are erected. This is where our expertise in vibration risk management comes into play, ensuring that the final structure aligns with the client’s design vision and performance expectations.

MEETING VIBRATION SERVICEABILITY REQUIREMENTS

Understanding the level of vibration a stair is designed to accommodate is crucial. We guide clients through this decision-making process, offering opportunities to visit completed projects to experience vibration levels firsthand. This helps set realistic expectations and informs the design. Clients should understand that stiffer stairs, which minimize vibration, typically require more steel and higher costs or simpler design elements. Striking this balance is an essential part of the design-assist process.

UNDERSTANDING FREQUENCY AND FORCE

Every structure, including stairs, has a natural rhythm—or frequency—shaped by its materials, design, and support system. When people walk, run, or climb stairs, their movements create forces at their own natural pace. Problems arise when these human rhythms align with the stair’s frequency, causing vibrations that can be felt underfoot. While subtle at first, these vibrations can become uncomfortable and, in extreme cases, unsettling.

Monumental stairs—sleek, long-spanning, and with minimal finishes—are especially vulnerable. Their lightweight stringers and heavy treads create lower natural frequencies, making them more likely to react to movement. This can result in swaying or vibration transfer to other building parts, often leading to safety concerns.

Anticipating how a stair will perform under real-world conditions during the design phase allows us to address potential vibration issues early, helping to preserve both architectural integrity and user comfort.

MITIGATING VIBRATIONS

Great design starts with precision, and vibration analysis is key to understanding how stairs will respond to movement. By addressing these factors early in the design-assist phase, we can manage potential vibration issues while preserving both the stair’s aesthetic appeal and functionality.

When design constraints limit structural adjustments, innovative, non-structural solutions like tuned mass dampers (TMDs) come into play. These devices use a spring, mass, and damping element to reduce vibrations and enhance stability. Using the data from vibration pattern analysis, TMDs can be tailored to fit the unique needs of a stair.

VIBRATION ANALYSIS IN ACTION: A CASE STUDY

Synergi is currently working on a large, curved atrium stair for a higher education research facility. Shaped like a cancer ribbon, the monumental stair connects four stories. The stair size and complex curved design presented a unique engineering challenge, particularly in terms of vibration and safety.

As part of our design-assist process, we conducted detailed vibration analysis, identifying areas where the stair was most likely to flex and resonate, as illustrated in the animation below.

This data led us to recommend the installation of a damper system to control vibrations and improve stability. The dampers, placed at three key points of the stairs, were designed to absorb the energy of the vibrations.

The dampers effectively reduced the stairs’ resonance, ensuring a smooth and stable user experience. This not only addressed potential discomfort but also ensured that the stairs could withstand the demands of high foot traffic without compromising its architectural elegance.

This approach demonstrates how vibration analysis can optimize both the design and functionality of monumental stairs, ensuring that architectural vision and user comfort align seamlessly.

Location of the dampers.

Split section of the damper.

Project rendering.

ENHANCING CLIENT COLLABORATION

Our collaborative approach helps clients balance cost, complexity, and performance. By involving clients early and offering insights into the trade-offs between design stiffness and budget, we ensure their expectations align with the final outcome. Field trips to complete projects and vibration testing on-site are just two of the ways we demystify this process and provide practical guidance.

OPTIMIZING STAIR ACOUSTICS

A quiet stair is a sign of thoughtful design. Beyond enhancing stability, reducing vibrations creates a more refined, serene environment—essential in workplaces, libraries, and healthcare settings where noise can disrupt productivity and well-being.

Carefully selected materials and finishes, like softer treads or isolating structural connections, help absorb sound and reduce impact vibrations. This approach minimizes noise and promotes calm and concentration in the workplace, improving the overall user experience. Quiet stairs contribute to a space that feels intentional, supporting both collaboration and focused work.

ENSURING SAFETY

Safety is paramount, especially in regions prone to storms or earthquakes. Dynamic forces like seismic activity or high winds can challenge structural integrity if not addressed early.

Vibration analysis helps:

anticipate how stairs will respond under stress, ensuring they remain stable and secure in extreme conditions
meet building codes and regulations for specific performance criteria in disaster-prone areas
incorporate energy-dissipating features that provide stability and peace of mind

SUPPORTING EVOLVING TRENDS IN STAIR ENGINEERING

Vibration analysis also supports broader industry trends in sustainability and compliance. Optimizing materials early in the design phase minimizes waste and ensures adherence to performance codes, reducing costly revisions. By embracing these trends, we help clients create stairs that are not only functional and visually stunning but also aligned with long-term building performance goals.