Site amplification factors in NTC18 and International Seismic Codes: a benchmarking study

Seismic design standards are pivotal for enhancing structural resilience to earthquakes. This study compares the performance of predicted site effects by the Italian NTC18 against international codes—ASCE 2022 (USA), EC8 2021 draft (ongoing Eurocode 8 revision), and MLITT 2019 (Japan)— with reference to a set of equivalent linear site response analyses. Results show that MLITT 2019 offers the best performance in terms of ability to predict the numerical spectral amplifications at two different period ranges, although its results must be analyzed cautiously. EC8 2021 stands out for its continuous formulation avoiding unrealistic jumps between site classes B, C and D. Finally, NTC18 and ASCE 2022 tend to overestimate considerably spectral amplifications, especially in site classes C, D and E.