Eaton approached Motovated to provide seismic assessment of two electrical cabinets for use in Australia and New Zealand. The cabinets had been shaketable tested in accordance with Chinese standards which are not directly referenced by the New Zealand or Australian Building Codes. As a result, an alternative method for determining compliance was developed which involved comparing the test response spectra (TRS) used during the testing with the spectral shape factors referenced in the earthquake standards referenced by the codes. Along with Ultimate Limit State compliance, serviceability requirements were also assessed by testing the functionality of the cabinets before and after the testing was carried out.

To determine the earthquake regions the cabinets were suitable for, the TRS of the tests were overlayed onto the spectral shape factors stated in the relevant earthquake loading standards. This allowed us to directly compare how the testing compared with expected earthquakes in New Zealand and Australia.

Of critical importance was to ensure that the testing covered the range where the natural frequency of the cabinets lay to account for resonance effects under the design earthquake accelerations. As the cabinets are symmetrical about two axis’ the testing also needed to be done in two separate directions.

For these particular tests the TRS and spectral shape factor profiles stated in standards differed at low periods (high frequencies). As this also corresponds to the region of the curves where the natural frequencies of the cabinets occurred, the allowable seismic zones the cabinets could be installed in were adjusted so the tested curve covered the critical ranges.

Based on the testing carried out, the Eaton cabinets have been certified for nearly every earthquake zone and height factor throughout Australasia for both Ultimate Limit State and Serviceability Limit State Earthquake actions.

Figure 1- Example comparison between 1170.5, 1170.4 and YD 5083-2005