Criteria for the definition of the Equipment Seismic Levels (ESL): Comparisons between USA and European codes

In spite of the names of “building attachments” and “secondary elements” usually given to nonstructural components and equipment, they are far from being secondary in importance. In the worst case of critical facilities, the failure of equipment strongly impacts on the post-earthquake functionality, causing the loss of essential services or businesses. Such considerations highlight the need for a seismic qualification of equipment as the essential means to demonstrate its adequacy to perform the required function during the expected earthquake event. In the present paper, the authors deal with a new approach to the problem of seismic qualification, in which the seismic demand posed to the component is defined in terms of Equipment Seismic Levels (ESL), while its inherent seismic capacity is classified in terms of Equipment Qualification Categories (EQC). The determination of the ESL, subject of this work, has to satisfy the requirements prescribed by the codes for the seismic design of equipment. A comparative study of the current seismic codes in USA and in Europe is hence carried out, in order to critically assess their provisions and to develop a methodology that can be implemented straightforwardly also by designers not having expertise in the field of earthquake engineering.