Residual displacement ratios for assessment of existing structures

Abstract

SUMMARYResults of an analytical study aimed at evaluating residual displacement ratios, Cr, which allow the estimation of residual displacement demands from maximum elastic displacement demands is presented. Residual displacement ratios were computed using response time-history analyses of single-degree-offreedom systems having 6 levels of relative lateral strength when subjected to an ensemble of 240 earthquake ground motions recorded in stations placed on ÿrm sites. The results were statistically organized to evaluate the in uence of the following parameters: period of vibration, level of relative lateral strength, site conditions, earthquake magnitude, and distance to the source. In addition, the in uence of post-yield sti ness ratio in bilinear systems and of the unloading sti ness in sti ness-degrading systems was also investigated. A special emphasis is given to the uncertainty of these ratios. From this study, it is concluded that mean residual displacement ratios are more sensitive to changes in local site conditions, earthquake magnitude, distance to the source range and hysteretic behaviour than mean inelastic displacement ratios. In particular, residual displacement ratios exhibit large levels of record-torecord variability and, therefore, this dispersion should be taken into account when estimating residual displacements. A simpliÿed expression is presented to estimate mean residual displacements ratios for elastoplastic systems during the evaluation of existing structures built on ÿrm soil sites.

Proposed Methodology for Earthquake-Induced Loss Assessment of Instrumented Steel Frame Buildings: Building-Specific and City-Scale Approaches

“…This is consistent with prior studies associated with the estimation of residual drifts [8,12]; the effect of record-to-record variability on the residual drifts is much larger than that observed in other EDP counterparts. It should also be noted that residual SDRs are largely influenced by component modeling parameters [8,11,12,[49][50][51]. In that respect, it is confirmed that the large uncertainty of residual SDRs observed in analysis results is reflected in the smaller R 2 observed in the regression model.…”

“…This is not the case for higher seismic intensities associated with low probability of occurrence earthquakes (i.e., MCE). Previous research has identified that residual drifts are very sensitive to the earthquake magnitude, distance to the source range, the adopted component hysteretic behavior as well as the analytical model representations of a building [8,51,54,55]. For the aforementioned reasons, it is recommended that a lower/upper bound analysis should be employed based on the 16th/84th percentile of the predicted values of the proposed approach as shown in Figure 4(c).…”

The use of post-earthquake residual displacements as a performance indicator in seismic assessment

“…The residual displacements calculated for stiffness-degrading SDOF systems are reported to be on the average smaller than those for non-stiffness degrading systems (Riddell and Newmark, 1979;Mahin and Bertero, 1981;Pampanin et al, 2002b;Ruiz-Garcia and Miranda, 2006d). Moreover compared to maximum displacements, the prediction of residual displacements by means of numerical analysis is found to be more sensitive to the hysteretic rule parameters (Pampanin et al, 2002b;Dazio, 2004).…”

The Efficiency of Reduced Beam Section Connections for Reducing Residual Drifts in Moment Resisting Frames

“…Regarding system level studies, it has been deemed that several factors directly associated with the variability of ground motion parameters and the inherent characteristics of MDOF systems have profound implication for amplitude and allocation of RD demands [9]. Besides, it is noteworthy that the type of hysteretic models in systems exhibiting stiffnessdegrading behavior considerably influences the level of residual deformation demands [10,11]. In addition to effects of material nonlinearity which was referred above, some sorts of geometrical nonlinearities in terms of socalled P-Δ effects in framed structures drastically alter the amplitude and height-wise pattern of RDs.…”