Damping reduction factors and code‐based design equation for structures using semi‐active viscous dampers

Abstract

Summary This study uses a semi‐active viscous damper with three different control laws to reshape the structural hysteresis loop and mitigate structural response, referred to as 1–4, 1–3 and 2–4 devices, respectively. The 1–4 control law provides damping in all four quadrants of the force‐displacement graph (it behaves like a standard viscous damper), the 1–3 control law provides resisting forces only in the first and third quadrants, and the 2–4 control law provides damping in the second and fourth quadrants. This paper first outlines the linear single degree of freedom structural performance when the three types of semi‐active viscous dampers are applied. The results show that simultaneous reduction in both displacement and base‐shear demand is only available with the semi‐active 2–4 device. To enable guidelines for adding a 2–4 device into the design procedure, damping reduction factors (RFξs) are developed, as they play an important role and provide a means of linking devices to design procedures. Three methods are presented to obtain RFξ and equivalent viscous damping of a structure with a 2–4 semi‐active viscous damper. In the first method, the relationship between RFξ and the damping of a semi‐active structure can be obtained by calculating the area under the force‐deformation diagram. The second and third method modified the Eurocode8 formula of RFξ and smoothed results from analysis, respectively. Finally, a simple method is proposed to incorporate the design or retrofit of structures with simple, robust and reliable 2–4 semi‐active viscous dampers using standard design approaches. Copyright © 2016 John Wiley & Sons, Ltd.

Seismic Behavior of a Self-Centering System with 2–4 Viscous Damper

“…Similarly, a 2-4 viscous damper provides damping in the second and fourth quadrants. Spectral analysis shows typical viscous dampers increase the base shear of long period linear structures, typically greater than 2.7 sec [Hazaveh et al, 2016b]. However, adding a 2-4 viscous damper decreases base shear and displacement for all periods [Hazaveh et al, 2015, Hazaveh et al, 2016b, Mulligan et al, 2009, Rodgers et al, 2007.…”

“…Among supplemental dissipation devices, viscous dampers have been widely used in rocking wall and post-tensioned rocking bridge piers to improve the seismic behavior of these selfcentering system, as shown in Figure 1 [Marriott et al, 2008, Kam et al, 2010, Marriott et al, 2009]. Viscous dampers dissipate significant energy, but their reaction loads can increase foundation and overall base shear demands, reducing the ability to use them broadly in retrofit without significant added cost [Lin and Chopra, 2002, Hazaveh et al, 2016b, Filiatrault et al, 2001, Miyamoto and Singh, 2002, Vargas and Bruneau, 2007, Kam et al, 2010, Kam et al, 2008. Thus, on the basis of a traditional performance-based seismic design and retrofit philosophy, designers are challenged by the difficult tradeoff between costs and acceptable damage (or targeted performance).…”

“…Thus, on the basis of a traditional performance-based seismic design and retrofit philosophy, designers are challenged by the difficult tradeoff between costs and acceptable damage (or targeted performance). To address these issues, Hazaveh et al [Hazaveh et al, 2016a, Hazaveh et al, 2016b, Hazaveh et al, 2015 introduced and examined two types of viscous dampers. Based on semi-active resettable stiffness devices [Mulligan et al, 2009, Rodgers et al, 2007 a 1-3 viscous damper provides resisting forces only in the first and third quadrants of the force-displacement plot.…”

“…Spectral analysis shows typical viscous dampers increase the base shear of long period linear structures, typically greater than 2.7 sec [Hazaveh et al, 2016b]. However, adding a 2-4 viscous damper decreases base shear and displacement for all periods [Hazaveh et al, 2015, Hazaveh et al, 2016b, Mulligan et al, 2009, Rodgers et al, 2007. The 2-4 device also has the potential benefit that it does not provide added forces during uplift, which can help to limit the total compression force applied to the toe of the wall during uplift, potentially reducing toe crushing during uplift of reinforced concrete rocking walls, while damping the return motion and re-seating of the wall.…”

“…However, the effect of the 2-4 viscous damper has only investigated on linear elastic structures [Hazaveh et al, 2015, Hazaveh et al, 2016b. Therefore, there is a need to investigate the seismic behavior of self-centering system with these devices to validate this potential and growing area before application, including the need for design method to enable uptake.…”