A practical guide for engineers on friction dampers as applied in (seismic) structural engineering, how friction dampers work, where they’re used, and why they matter.
Introduction
In modern structural and mechanical engineering, the ability to control motion and absorb energy is critical. Whether it’s an earthquake, wind load, or machine vibration, excessive movement can cause damage, fatigue, or failure.
A friction damper is one of the simplest yet most effective ways to reduce that motion. It uses the natural resistance between two sliding surfaces (‘friction’) to dissipate energy as heat, protecting structures and equipment from damage.
Friction dampers have become a key technology in seismic design and retrofitting, especially in buildings and bridges, where they’ve been proven to reduce design forces, limit damage and shorten downtime after major earthquakes.
The concept of using friction for damping motion has a long history. Early mechanical systems relied on friction in clutches, brake-type assemblies and machinery. But its deliberate use in building and structural engineering, especially for seismic protection, began in the late 20th century and evolved over recent decades.
What began as a clever adaptation of mechanical friction has matured into a reliable element of seismic-resilient design. Understanding its evolution helps engineers appreciate the assumptions, successes and limitations embedded in current practice.
A friction damper consists of steel plates clamped together by bolts or springs. When forces acting on the structure exceed a preset limit, known as the slip load, the plates begin to slide against each other.
That sliding converts kinetic energy from the structure into heat through friction, similar to the way a car’s brake pads dissipate energy. When shaking stops, the damper stops sliding.
In seismic applications, this controlled slip keeps the main frame from yielding or cracking, making the structure more resilient and easier to repair.
There are three main categories:
Each type serves the same purpose — to dissipate energy — but their differences lend themselves to different performance objectives or to different parts of a structural system.
Engineers are likely to choose friction dampers because they are:
For many projects, friction dampers provide a very competitive cost-to-performance ratio when compared to other passive energy dissipation devices.
Friction dampers can be installed wherever relative movement occurs during loading. Common locations include:
Placement is typically chosen to maximize the amount of energy dissipated while keeping structural deformation within safe limits.
Friction dampers installed as both diagonal braces and shear wall hold downs on a university building project in New Zealand.
The design starts with selecting the target slip load i.e. the force level at which the damper begins to slide. Engineers choose this value so the damper activates during earthquakes but remains rigid during normal service (in countries where the seismic code has a Serviceability Limit State, such as in New Zealand or Canada, this can be a useful feature to optimise performance).
In computer models (ETABS, SAP2000, OpenSees), friction dampers are represented as nonlinear elements with a rectangular hysteresis loop — meaning constant resistance during sliding. For more advanced systems like the RSFJ, engineers use a flag-shaped hysteresis model that includes both friction and re-centring springs.
Modern friction dampers are designed for long-term stability. The sliding surfaces use materials like friction pads, brass, or specialized coatings that resist wear.
To keep the slip load consistent, bolts may be preloaded using disc springs that are intended to maintain clamping force even under temperature changes and repeated cycles.
Engineers specifying friction dampers should request longitudinal testing from the supplier to observe any degradation of performance over time.
In the United States, friction dampers are referred to as 'energy dissipation devices' in codes such as:
While the codes don’t prescribe exact damper designs, they require that each system be dynamically tested, modelled, and verified to perform as intended under seismic loads. Dynamic testing is critical, since some friction dampers have demonstrated different performance at different velocities.
Friction dampers have shown reliable performance in real-world events and laboratory tests:
Buildings in New Zealand, Canada, Japan, and the U.S. using friction dampers have performed exceptionally well during major seismic events.
While reliable, friction dampers have been associated with some limitations:
Proper design, testing, and maintenance address most of these concerns.
Yes. While they’re best known for seismic protection, friction dampers are also used in:
Their simple design and predictable response make them versatile for any situation involving dynamic motion control.
There is a wealth of information available on Tectonus' website. In recent years, Tectonus has become synonymous with state-of-the-art performance when it comes to friction dampers. Our team of experts is more than happy to provide 'lunch and learn' sessions and technical presentations for those want to know more. To arrange a time, please get in touch.