Although the critical damping ratio is one of the most important structural properties that determine the response of buildings under dynamic effects, it still contains many uncertainties . For the same structure, different sources suggest critical damping ratios of three, five, two percent, or even completely negligible. It is known that the structure inherently has a damping capability, but since it cannot be mathematically calculated, values based on past experiences and experiments are used.

Another significant factor causing uncertainty is the different damping capacity of the structure when exposed to service conditions or near its carrying capacity. For the five percent critical damping ratio generally recommended by regulations for reinforced concrete structures to be achieved, there must be pre-determined damage in the structure. Damping is already dependent on a damage state that contains many uncertainties.

Engineers who want to evaluate the performance of buildings more accurately and raise it to a higher level have decided to create their damping mechanisms instead of relying on the three to five percent inherent damping ratio of buildings. With the damping ratio that can be added to the structure up to 30-35 percent, the inherent damping ratio of the structure can become genuinely negligible. The structure can reach a performance level that will not be damaged even in the most severe earthquakes.

Viscous dampers, which have been used in many buildings in recent years and provide performance enhancement in structures, are one of these mechanisms and are based on suspension technology that dates back to 3000 years ago in the war chariots of Ancient Egypt. A bump or hole in the road causes the wheel to deform positively or negatively in the direction perpendicular to the road axis. This movement generates kinetic energy in the tires. A small portion of the energy is absorbed by rubber tires. The remaining energy is transferred to the suspension spring. The spring deforms and stores the kinetic energy as potential energy. This stored energy is sent to the shock absorber, where it is converted back into kinetic energy by the movement of the viscous fluid. As the viscous fluid moves, the kinetic energy is converted to thermal energy due to the pressure and friction within the shock absorber, dispersing into the air without reaching the vehicle’s chassis and its occupants.

This mechanism, which works vertically in vehicle tires, is generally used horizontally against earthquake and wind forces in buildings. When the ground beneath the building moves, the foundation moves with it. While part of the movement is converted into potential energy by the elastic floor displacements and stiffness of the building, a portion is converted into kinetic energy due to the floor movement. Viscous dampers convert kinetic energy into thermal energy, making it harmless for the structure.

Since viscous damper systems do not have rigidity in the longitudinal direction, they do not stiffen the building. The less rigid the building, the less it is exposed to earthquake acceleration, which is actually beneficial.

Since horizontal displacement in the structure is reduced due to damping, there is no need to use large-section columns and beams.

The material savings achieved through the reduction in element sizes help offset the additional cost of viscous dampers. The structure can achieve a performance level that allows uninterrupted use even during the largest possible earthquake without sustaining damage. Currently, for a standard building designed to meet the minimum requirements of the codes, the target is to ensure life safety during an earthquake with a 10% probability of exceedance in 50 years, with damage to the structural system being non-severe and mostly repairable. In the case of the largest possible earthquake, it is expected that the structural elements of the building will experience advanced levels of severe damage, reaching a near-collapse state. However, partial or complete collapse of the building is prevented. Considering that viscous damping systems also reduce floor deformations and accelerations, thereby decreasing the seismic effects on non-structural elements such as walls and ceilings, as one viscous damper manufacturer’s slogan goes: “Would you buy a car without suspension? Then don’t buy a building without suspension either!”