A two‐step direct method for estimating the seismic response of nonlinear structures equipped with nonlinear viscous dampers

Abstract

SUMMARYThe insertion of fluid viscous dampers in building structures is an innovative technology that can improve significantly the seismic response. These devices could be very useful also in the retrofit of existing buildings. The effect of this typology of damping system is usually identified with an equivalent supplemental damping ratio, which depends on the maximum displacement of the structure, so that iterative procedures are required. In this paper, a simplified direct assessment method for nonlinear structures equipped with nonlinear fluid viscous dampers is proposed. The method proposed in this study is composed by two steps. The first one yields the direct estimate of the supplemental damping ratio provided by nonlinear viscous dampers in presence of a linear elastic structural response. The second step extends the procedure to structures with nonlinear behavior. Both graphical and analytical approaches have been developed. The proposed method has then been verified through several applications and comparisons with nonlinear dynamic analyses. Moreover, an investigation has been performed with regard to the influence of the relations that define the damping reduction factor and the hysteretic damping.

Direct estimation of seismic response in reduced‐degree‐of‐freedom isolation and energy dissipation systems

“…Some useful, albeit crude, guidance in this direction (along with some criteria for selecting the type of devices) is occasionally provided, using high‐damping elastic spectra in the pseudo‐acceleration vs displacement response spectra format, disregarding the contribution of viscous dampers to peak inertia forces transmitted to the substructure. More refined direct approaches, based on nonlinear static and response history analysis (NLRHA), may be capable of facilitating preliminary selection of the hardware considering design requirements from different performance levels. However, these approaches are currently restricted to specific types of devices/structures (eg, structures isolated through bilinear hysteretic isolators, non‐isolated yielding frames with dampers); hence, they do not readily meet the needs of design of isolated bridges.…”

“…More refined direct approaches, based on nonlinear static and response history analysis (NLRHA), may be capable of facilitating preliminary selection of the hardware considering design requirements from different performance levels. However, these approaches are currently restricted to specific types of devices/structures (eg, structures isolated through bilinear hysteretic isolators, non‐isolated yielding frames with dampers); hence, they do not readily meet the needs of design of isolated bridges. On the other hand, codes do not provide specific recommendations regarding the above issues.…”

Effectiveness evaluation and optimal design of nonlinear viscous dampers for inelastic structures under pulse‐type ground motions

“…Detailed descriptions of calculating these parameters can be found in Diotallevi et al, 23 and all other parameters are the same as those defined before. In this study, the associated damping index Π ξ,n * of Equation (8) with c d substituted with c d * and m replaced by m * is compared with ξ 1 * that is given in Equation (24). Table 4 shows the comparison results among Π ξ,n * , ε 1 and ξ 1 * for the eight-story structure with different damper fractional values when subject to the aforementioned Type-B pulse motion.…”

Application of a Direct Procedure for the Seismic Retrofit of a R/C School Building Equipped with Viscous Dampers

“…Several approaches have been proposed in literature (Peckan et al, 1999;Diotallevi et al, 2012;Landi et al, 2014b;Tubaldi et al, 2014). Here, the following formula, based on the energy equivalence over a full cycle of harmonic motion, is used:…”