IN 2-A SIMPLE ALTERNATIVE FOR IDA

Simplified inelastic procedures used in seismic design and assessment combine the nonlinear static (pushover) analysis and the response spectrum approach. One of such procedures is the N2 method, which has been implemented into the Eurocode 8 standard. The N2 method can be employed also as a simple tool for the determination of the approximate summarized IDA (incremental dynamic analysis) curve. Such analysis is called the incremental N2 method (IN2). The IN2 curve can substitute the IDA curve in the probabilistic framework for seismic design and assessment of structures. In the paper, the IN2 method is summarized and applied to two test examples of infilled reinforced concrete (RC) frames, which are characterized by a substantial degradation of the strength after the infill fails. The approximate summarized IDA curves, determined by the IN2 method, and the data on dispersion due to randomness in displacement demand, determined in a previous study by the authors, were employed in the probabilistic risk analysis of test structures. The results were compared with the results obtained using the “exact” IDA curves. A fair correlation of results suggests that the IN2 method is a viable approach.