Seismic effects on enclosures

Seismic effects on enclosures

 

In areas where seismic activity is possible, enclosures have to withstand

more influences and material-stress than in zones with no or a minimum

seismic risk. During an earthquake, sensitive electric/electronic equipment

can be subjected to motions that can over-stress equipment framework,

whereas the amount of motions and resulting stress depends on several

factors, like:

• Structural characteristics of the building

• Framework in which the equipment is contained

• Severity of the earthquake

Therefore, it is important to use enclosures that have been tested for

specific seismic zones.

Seismic certification

If compliance with the UBC-Zone certification is required, the requirements

for conformity are stated in GR-63-CORE ‘NEBS Requirements: Physical

Protection (NEBS or Network Equipment-Building System). This standard

identifies the minimum generic compatibility criteria for telecommunications

equipment, especially for:

• Earthquake and Office Vibration (Zone requirements)

• Fire resistance

• Thermal robustness

• Transportation and Handling

• Acoustic Noise

• Airborne Contaminates

The testing criteria of the GR-63-CORE are as follows:

• Door does not open during test.

• Equipment still operable immediately before and after test.

• Enclosure must be base mountable.

• Enclosure is bolted down to concentrate slab.

To test for physical performance, the GR-63-CORE contains some different

physical performance criteria and certification levels, such as:

• R4-44: All equipment shall be constructed to sustain the waveform

testing without permanent structural or mechanical damage.

• R4-45: Maximum single amplitude deflection at top of enclosure

relative to the base does not exceed 75mm (3”).

• R4-46: System should have a natural mechanical frequency greater

than 2.0Hz as determined by swept sine survey.

 

RITTAL