Optimal DCFP bearing properties and seismic performance assessment in nondimensional form for isolated bridges

Abstract

The study analyzes the influence of double concave friction pendulum (DCFP) isolator properties on the seismic performance of isolated multispan continuous deck bridges. The behavior of these systems is analyzed by employing an eight‐degree‐of‐freedom model accounting for the pier flexibility in addition to the rigid presence of both abutment and deck, whereas the DCFP isolator behavior is described combining two single FP devices in series. The uncertainty in the seismic input is taken into account by considering a set of nonfrequent natural records with different characteristics. The variation of the statistics of the response parameters relevant to the seismic performance of the isolated bridges is investigated through the proposal of a nondimensionalization of the motion equations, with respect to the seismic intensity, within an extensive parametric study carried out for different isolator and bridge properties. Moreover, two cases related to different ratios between the sliding friction coefficients of the two surfaces of the DCFP devices are analyzed with the aim also to evaluate the corresponding optimal values able to minimize the seismic demand to the pier. In this way, all the presented nondimensional results are useful for the preliminary design or retrofit of multispan continuous deck bridges, isolated with DCFP devices, located in any site and in relation, especially, to the seismic ultimate limit states.

Optimal sliding friction coefficients for isolated viaducts and bridges: A comparison study

“…49,50 In this study, the abovementioned term is set equal to the spectral pseudo-acceleration, S A (T d , ξ d ), corresponding to the isolated period of the bridge T d = 2π/ω d with the damping ratio Π ξ d ¼ ξ d . As also observed in Castaldo et al and Tubaldi et al, [25][26][27][28][29] since the spectral acceleration is related to the spectral displacement…”

“…describe the peak dynamic response of the deck and of pier, respectively. Moreover, from Equation 6, it is possible to observe that the five nondimensional Π terms 25,26,28,42,43 that control the system nondimensional response are as follows:…”

“…In this analysis, the record-to-record variability is considered using 30 nonfrequent 28,44,45 seismic records selected from 19 seismic different events. [46][47][48] Table 1 reports the details of the earthquakes used for the study.…”

“…Equations 6 and 12 are repeatedly and numerically solved in Matlab-Simulink 52 computing a set of samples for each response parameter for the two structural models. As also described in Castaldo et al, Ryan et al and Karavasilis and Seo, 25,26,28,51,53 the response parameters are modeled in probabilistic terms: the generic response parameter D (i.e., the extreme values ψ u d , ψ u p of Equation 15a and 15b) can be fitted by a lognormal distribution estimating the sample geometric mean, GM(D), and dispersion, β(D), defined, respectively:…”

“…[14][15][16] Several experimental and numerical researches have explored the behavior of the FPS isolators. [17][18][19][20][21][22][23][24] In Castaldo et al and Tubaldi et al, [25][26][27][28][29] with reference to equivalent multidegree-of-freedom (mdof) models, respectively, for base-isolated building frames and isolated bridges with single or double FPS devices, a nondimensionalization of the motion equations for different isolator and system properties has been proposed. The seismic response of isolated multispan continuous deck bridges is investigated in Kunde et al 30 confirming the effectiveness of simplified models in relation to the flexibility of the deck and of the piers.…”