GNGTS 2021 - Atti del 39° Convegno Nazionale

GNGTS 2021 S essione 2.2 356 1. Definition of the target spectrum: this first step allows the user to define a 5%-damping elastic spectrum, which is the target spectrum to match (on average). This can be automatically built according to user-definition or design provisions; i.e. Eurocode 8, Italian Building code or uniform hazard spectra (UHS). A new feature entails the selection of the site of interest directly from an interactive map. This also allows to retrieve automatically the corresponding peak ground acceleration (PGA) necessary to anchor the target spectrum, from the hazard maps made available both for Italy (MPS04 map; esse1.mi.ingv.it ) and Europe (ESHM13 map; SHARE, EU-FP7 project Seismic Hazard Harmonization in Europe; http://www.efehr.org/en/home/) . Once all input options have been entered, one can go ahead and generate the horizontal and vertical design spectra for 30 vibration periods, ranging from 0.01s to 4.00s. 2. Preliminary search: the second step allows the user to specify the record-selection criteria, as well as the number and type of ground-motion components to consider (1-, 2- or 3-component analysis), providing access to response spectra included in ESM that comply with the specified parameters. The selected spectra are ranked on the basis of a score index, which is a measure (namely the root-mean-squared-error) of the distance between the target and the spectrum of an individual record. This list of ordered spectra allows the program to speed up the spectral matching routine, including up to one thousand candidate records per single request. The program generates a plot of the preliminarily selected spectra along with the mean spectrum compared with the target spectrum (Figure 2). These plots are always returned both in terms of unscaled spectra (i.e. as-originally-recorded) and scaled spectra (i.e. computed from records linearly scaled to their PGA). 3. Spectrum matching: this step allows to set the tolerances and period bounds within which the average spectrum of a combination found has to be compatible with the target spectrum. In this step, it is possible to allow scaling of the records, which means searching among waveforms linearly scaled to the target spectrum’s PGA and assign a maximum admissible scale factor of the mean spectrum. It also allows choosing the size of the record suite among 1, 7, or 30 and the desired number of required spectrum- compatible suites of records. At the end of the analysis, a Summary Tab reporting the set of user options and a table with the list of the compatible waveforms and corresponding metadata are returned. An important feature in this step is that the records in the table are directly linked to the ESM contents and can be clicked by the users to access information on the event, station and waveform details of the ESM web pages. Finally, Fig. 1 - Target Spectrum Tab (panel on the left) and Map (panel on the right)