Report - PEER - University of California, Berkeley

The variability of the response increases with the seismic intensity and stabilises ataround 30% for the higher values. This relatively low variability indicates that thechosen intensity measure, S a( T = 0. 8s), is effective in reducing the ground-motioninducedvariability and, hence, the number of records (non-linear analyses) requiredfor a target confidence in the estimates.The statistics of the demands for all elements, including their mean, standarddeviations and correlation coefficients, as well as their derivatives with respect to fandf , are evaluated from the results of the non-linear analyses, carried out foryparametrically increasing values of the seismic intensity.Figure 5 shows sample results for the flexural and shear demands at the first flooron column C6, which is among those critical in determining the total fragility.cFigure 5. Column C6: maximum concrete strain (above) and shear force(below) versus seismic intensity: demand and sensitivities with respect to f andf .yThe dependence of the flexural demand εccis almost linear on the seismic intensity,which confirms, even for this rather complex system, the approximate validity of theequal-displacement rule: for the higher intensity values, in fact, the column is wellwithin the inelastic range. The adjacent plots show the sensitivities of ε ccwithrespect tofcandfy(multiplied by the corresponding standard deviations, in orderc229