Experimental Characterization, Modeling, and Numerical Evaluation of a Novel Friction Damper for the Seismic Upgrade of Existing Buildings

Abstract

The paper presents the experimental characterization, the formulation of a numerical model, and the evaluation, by means of non-linear analyses, of a new friction damper conceived for the seismic upgrade of existing building frames. The damper dissipates seismic energy through the friction force triggered between a steel shaft and a lead core prestressed within a rigid steel chamber. The friction force is adjusted by controlling the prestress of the core, allowing the achievement of high forces with small dimensions, and reducing the architectural invasiveness of the device. The damper has no mechanical parts subjected to cyclic strain above their yield limit, thereby avoiding any risk of low-cycle fatigue. The constitutive behavior of the damper was assessed experimentally, demonstrating a rectangular hysteresis loop with an equivalent damping ratio of more than 55%, a stable behavior over repeated cycles, and a low dependency of the axial force on the rate of displacement. A numerical model of the damper was formulated in the OpenSees software by means of a rheological model comprising an in-parallel system of a non-linear spring element and a Maxwell element, and the model was calibrated on the experimental data. To assess the viability of the damper for the seismic rehabilitation of buildings, a numerical investigation was conducted by performing non-linear dynamic analyses on two case-study structures. The results highlight the benefits of the PS-LED in dissipating the largest part of seismic energy, limiting the lateral deformation of the frames, and controlling the increase in structural accelerations and internal forces at the same time.

Assessment of Non-Linear Analyses of RC Buildings Retrofitted with Hysteretic Dampers According to the Italian Building Code

“…Figure 6 shows the capacity curves of the case study buildings and the relative d p s which correspond to the ending point of the elastic branch, or at most at the beginning of the second branch relevant to the cracked concrete [43]. In this study, the two structures are retrofitted by using hysteretic steel dampers installed into diagonal steel braces (Figure 7), which is a common configuration for frame buildings [1,5,6,[43][44][45]]. An elastic-perfectly plastic constitutive behavior is assumed for the dampers, similarly to other studies [1,6,41,43,44].…”

“…The case study structures are modelled as 3D buildings in the OpenSees software program version 3.6.0 [47,48], adopting the modelling procedure presented in [49] and validated in [1,5,6,41,43]. Beams and columns are implemented through the forceBeamColumn element object [50], assigning a non-linear behavior to the external sections and a linear elastic behavior to the internal section of the element, as shown in Figure 9.…”

“…Hysteretic dampers are widely used for seismic passive protection of both new and existing structures [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. According to the European standard EN 15129 [16], hysteretic dampers, which are further classified in steel hysteretic dampers, friction dampers and metal extrusion dampers, belong to the category of Displacement-Dependent Devices (DDDs).…”

“…In a structure equipped with damped braces, ξ eq , and consequently η, depends upon the damping capacity of the dampers. In this regard, it must be emphasized that steel hysteretic dampers available nowadays, such as Buckling Restrained Braces (BRBs), friction and extrusion dampers, are characterized by high damping capacity, with ξ eq > 28% [3][4][5][6][32][33][34][35][36]. Therefore, the contribution of such dampers to increase the overall damping ξ eq of the combined structural system may be not completely considered in the analyses due to the limitation on η [30].…”

Experimental and Numerical Study on Hysteretic Behavior of Frictional Energy Dissipation Steel Truss

“…According to research by Kim et al [ 14 ] on a 3D-office building frame, a limited number of BRBs (Buckling-Restrained Braces) could enhance the seismic capacity of the structure by minimizing story drift. Using two numerical models, Bruschi et al [ 15 ] tested a novel friction damper used in existing building retrofitting. According to the study’s findings, the friction damper is advantageous for dispersing seismic energy, preventing the frame’s lateral deformation, and simultaneously managing a rise in internal forces and structural acceleration.…”