The recent Italian regulation, Norme Tecniche per le Costruzioni “D.M. 17 gennaio 2018” (NTC 2018), and the European proposal, CEN/TC 250/SC 8 (NP-EC8), provide simplified methods to define the design seismic actions, which take account the site effects through amplification factors to be applied to elastic design response spectra described on a reference site. The aim of the thesis is to verify these amplification factors with an experimental approach, by performing a residual analysis based on the experimental data contained in ESM (Engineering Strong Motion) and KiK-net (Kiban-Kyoshin network) databases. The analysis consists in the extraction of the systematic site term (δS2S_A) from the total residuals, obtained by logarithm difference between observations and predictions of 4 Ground Motion Models (GMMs) of several intensity measures. δS2S_A can be considered as representative of the site amplification if computed with respect to the site reference level of the GMM, e.g. V_(S,30)= 800 m/s. The verification was performed by comparing the δS2S_A median values, computed in period range 0.07-0.2 s and 0.7-2.0 s, with respect to NTC 2018 and NP-EC8 amplification functions. A good agreement between NTC 2018 and δS2S_A median values for 138 Italian accelerometric stations was observed; for class E sites at intermediate periods, there is an overestimation of NTC 2018 amplification factor with respect to that obtained by δS2S_A. A good agreement was observed between NP-EC8 and δS2S_A both for ESM and KiK-net. In particular, the large number of recording sites in KiK-net with a V_S profile along the depth compared to ESM (599 vs 114) allowed to validate the proposed amplification functions also for class E sites, whose ESM data were not enough. The amplification functions for the new class introduced in NP-EC8, i.e. class F which takes into account the soft soil sites with bedrock deeper than 100 m, were also consistent with the empirical data. Finally, an analysis was conducted to verify the evidences of non-linearity effects for KiK-net dataset; however, the few data available for this purpose did not allow to provide satisfactory results at the moment.
La recente normativa italiana, Norme Tecniche per le Costruzioni “D.M. 17 gennaio 2018” (NTC 2018), e la proposta europea, CEN/TC 250/SC 8 (NP-EC8), forniscono al progettista metodi semplificati che tengono conto degli effetti di sito, tramite fattori di amplificazione da applicare agli spettri di risposta elastici di progetto definiti su un sito di riferimento, al fine di definire le azioni sismiche di progetto. Lo scopo della tesi è verificare tali fattori di amplificazione con un approccio sperimentale, eseguendo un’analisi dei residui basata su dati sperimentali contenuti in due dataset accelerometrici, ESM (Engineering Strong Motion) e KiK-net (Kiban-Kyoshin network). L’analisi consiste nell’estrarre il termine ripetibile di sito (δS2S_A) dai residui totali, ottenuti per differenza logaritmica tra valori osservati e predetti da 4 modelli di attenuazione dei parametri di intensità sismica. δS2S_A può rappresentare l’amplificazione al sito se calcolato rispetto al sito di riferimento del modello. La verifica è stata eseguita confrontando i valori mediani di δS2S_A, calcolati negli intervalli di periodo 0.07-0.2 s e 0.7-2.0 s, con le funzioni di amplificazione proposte dalle due norme. Si è osservato un buon accordo tra NTC 2018 e δS2S_A per 138 stazioni italiane; fanno eccezione i siti di classe E ai periodi intermedi in cui si osserva una sovrastima del fattore di amplificazione di NTC 2018. Anche tra NP-EC8 e δS2S_A, sia per ESM che KiK-net, si è osservato un buon accordo. In particolare, il maggior numero di siti in KiK-net con un profilo di V_S lungo la profondità rispetto a ESM (599 vs 114) ha consentito di validare la proposta anche per i siti di classe E, i quali in ESM non erano sufficienti. Le funzioni di amplificazione per la nuova classe introdotta in NP-EC8, la classe F che tiene conto di siti di terreno soffice con profondità del substrato roccioso maggiore di 100 m, sono in buon accordo con i dati sperimentali. Infine, è stata condotta un’analisi per verificare l’evidenza di effetti non-lineari per il dataset di KiK-net; tuttavia, i pochi dati a disposizione per tale scopo non hanno consentito all’analisi di fornire al momento risultati esaustivi.
Norme tecniche ed effetti di sito : verifica dei fattori di amplificazione tramite l'analisi di dati accelerometrici
DOTTI, MARCO
2018/2019
Abstract
The recent Italian regulation, Norme Tecniche per le Costruzioni “D.M. 17 gennaio 2018” (NTC 2018), and the European proposal, CEN/TC 250/SC 8 (NP-EC8), provide simplified methods to define the design seismic actions, which take account the site effects through amplification factors to be applied to elastic design response spectra described on a reference site. The aim of the thesis is to verify these amplification factors with an experimental approach, by performing a residual analysis based on the experimental data contained in ESM (Engineering Strong Motion) and KiK-net (Kiban-Kyoshin network) databases. The analysis consists in the extraction of the systematic site term (δS2S_A) from the total residuals, obtained by logarithm difference between observations and predictions of 4 Ground Motion Models (GMMs) of several intensity measures. δS2S_A can be considered as representative of the site amplification if computed with respect to the site reference level of the GMM, e.g. V_(S,30)= 800 m/s. The verification was performed by comparing the δS2S_A median values, computed in period range 0.07-0.2 s and 0.7-2.0 s, with respect to NTC 2018 and NP-EC8 amplification functions. A good agreement between NTC 2018 and δS2S_A median values for 138 Italian accelerometric stations was observed; for class E sites at intermediate periods, there is an overestimation of NTC 2018 amplification factor with respect to that obtained by δS2S_A. A good agreement was observed between NP-EC8 and δS2S_A both for ESM and KiK-net. In particular, the large number of recording sites in KiK-net with a V_S profile along the depth compared to ESM (599 vs 114) allowed to validate the proposed amplification functions also for class E sites, whose ESM data were not enough. The amplification functions for the new class introduced in NP-EC8, i.e. class F which takes into account the soft soil sites with bedrock deeper than 100 m, were also consistent with the empirical data. Finally, an analysis was conducted to verify the evidences of non-linearity effects for KiK-net dataset; however, the few data available for this purpose did not allow to provide satisfactory results at the moment.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/150074