GERB Spring Systems for Building Vibration Control

GERB is the leading, worldwide manufacturer of elastic bearing systems for buildings. For more than 30 years GERB systems have been supporting approximately 500 buildings, entirely or partly, on spring elements - solutions demanded by different reasons, including earthquake and subsidence. About 100 of these are supported on a 3 to 5 Hz anti-vibration bearing system comprising steel springs. Those buildings are mostly situated in the close vicinity of railway lines requiring a highly effective isolation system for the attenuation of vibration and noise. The large number of elastically supported buildings includes residential and office buildings as well as hotels, cinemas, theatres, churches, and a hospital. The building design load ranges from just 500 up to 550,000 kN.

Helical steel springs have little damping effect. If system damping is required, damping devices are available. When required, GERB spring systems are complemented by VISCODAMPER®s. They

  • limit the motion of a spring-supported system in all directions when passing resonances,
  • reduce the effects of shock or random excitation, and
  • dissipate energy by transforming energy into heat.

GERB VISCODAMPER®s are available as separate units, or as an integrated part of a spring element. They are an essential part of a GERB base control system designed for deployment in seismic zones. They are usually not applied to ordinary building vibration control systems.

Spring Elements for Buildings

GERB offers three types of spring elements for building isolation:

1. Prestressable spring elements Type SU and GSU

These elements possess solid steel housings and prestression bolts designed for partial pre-compression prior to the placement on site. As a result, the pre-loaded elements are used like rigid bearings during construction of the building. Only minimal building settlement occurs at the completion stage when the building achieves it`s final load. The housings are designed to take small hydraulic presses to enable readjustments of the spring heights after completion of the building. For height adjustment, steel shims are used. This action requires access to the elements.

2. Fully-prestressable spring elements Type GP

Due to their extremely stiff housings, these elements can be pre-compressed even to solid spring height prior to placement. This important feature excludes any building settlement during construction and makes any readjustment of spring heights as well as shifting, swapping or replacement of elements possible thus ensuring the full success of the system. Again, this action requires access to the elements and their prestression bolts.

Fig. Spring element, Type GP

Fig. Spring element, Type GP

The choice of this element type is highly recommended for large and complex buildings, where the precise prediction of the actual loads is difficult or when the later function is not clear at design stage or when the building is to be prepared for future changes or extensions. These elements are especially required in cases where highest demands regarding vibration attenuation are essential to ensure the intended use of a building.

3. Non-prestressable spring elements Type K

This type of building elements comprises steel springs sandwitched between two steel plates, simply held together for transport and installation by a system that comes off automatically on loading.

The elements can be arranged close together with optimal use of the available space. The spring deflections adapt to the actual loads reaching the design value when the corresponding load becomes effective. On load deviations no readjustments are possible. Therefore no access to the elements is required.

Fig. Spring element, Type K

Fig. Spring element, Type K

The use of type K-elements is recommended for buildings of a simple structure making the realistic prediction of the actual loads possible. During the construction of the building all elements should , as far as possible, be loaded uniformly in relation to their load capacities at any time to avoid unequal settlements. The arrangement of a comparatively stiff concrete slab or an equivalent beam system above the springs is advantageous.

Answers to Frequently Asked Questions (FAQS):

  1. GERB vibration control systems are designed to a system natural frequency of 2.5 - 5Hz

  2. GERB spring elements are provided with a highly efficient long-term corrosion protection.

  3. GERB spring elements are fatigue proof.

  4. GERB spring elements are fixed just by adhesive resilient pads.

  5. All horizontal wind loads are taken by the supporting springs. No additional restraints are required.

  6. For the design of the spring system the dead and live loads must be given separately.

  7. Although steel springs possess only little material damping ,the system damping of a spring supported building can be assumed at 3 - 5% due to piping, joint sealing material, etc.

  8. All GERB spring elements for buildings can be equipped with CRDS (Coil Resonance Damping System) which improves attenuation of ground-borne noise and contributes to the system damping.

  9. GERB VISCODAMPER®s are used only in base control systems designed for seismic zones.