GNGTS 2022 - Atti del 40° Convegno Nazionale

338 GNGTS 2022 Sessione 2.2 Fragility curves development. Fragility curves allow engineers to estimate the probability of attainment of a definite damage state (e.g., Collapse Limit State) given a specified magnitude of an Engineering Demand Parameter, EDP (e.g., inter-storey drift ratio). As mentioned in the § 3, in this work fragility functions are developed via Cloud Analysis Procedure, using the regression line intercept “b” and slope “a” within the bi-logarithmic plane. The curves are presented in the form of cumulative distribution function by eq.(9) with respect to the IM. (9) Where: - aIM b is the equation of the regression line of the reference correlation; - σ is the standard deviation of the reference correlation; λ = ln( EDP 0 ) – ln( a ) - λ = –––––––––––– ; λ =     b - ζ = σ / b . In order to generate fragility curves for MIDR and MCRC two performance level are considered, (NTC2018): Life Safety (LS) and Collapse Prevention (CP). For MIDR the assumed capacity thresholds are identified by means of pushover analysis carried out for each structure. The thresholds are as follows: • CP: evaluated as the MIDR at which the collapse chord rotation defined as per the Italian Building Code: ( C.S.LL.PP 2018) is attained: - EDP CP RF = 5% • h - EDP CP NRF1 = 5% • h - EDP CP NRF2 = 5% • h With “ h” the inter-storey height. • LS: defined as 3– edp CP : LS: defined as 4 - EDP LS RF = 3.75% • h - EDP LS NRF 1 = 3.75% • h - EDP LS NRF 2 = 3.75% • h For MCRC the assumed capacity thresholds edp pl are identified as follows: • CP: defined as the chord-rotation demand and chord-rotation capacity ratio is equal to 1: - EDP CP RF = 1 - EDP CP NRF 1 = 1 - EDP CP NRF 2 = 1 • LS: defined as 3– edp CP : LS: defined as 4 - EDP LS RF = 0.75 - EDP LS NRF 1 = 0.75 - EDP LS NRF 2 = 0.75