Special Issue on Design and Analysis of Structures with Seismic Damping Systems

Abstract

The papers in this special issue focus on the theme of design and analysis of structures with seismic damping systems, the intent being to provide a summary of current research activities within the general field of seismic energy dissipation systems. The special issue originated within the ASCE-SEI Task Committee on Supplemental Damping Systems for Seismic Applications, a committee serving under the ASCE-SEI Committee on Seismic Effects. Two members of the task committee, Finley A. Charney and Andrew S. Whittaker, were particularly helpful in developing the special issue, assisting with its early development, and the soliciting manuscript reviews. Their efforts are gratefully acknowledged. In addition, the general membership of the Seismic Effects Committee supported the efforts of the task committee by serving as reviewers for many of the manuscripts. Their collective efforts are sincerely appreciated. The special issue begins with a lead paper, “Energy Dissipation Systems for Seismic Applications: Current Practice and Recent Developments,” which is coauthored by a mix of academicians and practitioners Symans, Charney, Whittaker, Constantinou, Kircher, Johnson, and McNamara. The lead paper provides an overview of current practice and recent developments in the application of passive energy dissipation systems for seismic protection of structures, with particular attention given to the application of such systems within the framing of building structures. Furthermore, emphasis is given to descriptions of viscous, viscoelastic, metallic, and friction damping systems, including recent applications of such systems. In the paper “Design Formulations for Supplemental Viscous Dampers to Building Structures,” Hwang, Huang, Yi, and Ho examine the accuracy of existing design formulas for determining the damping coefficients corresponding to a specified added damping ratio. They conclude that the effect of flexural deformations of a building is as significant as the shear deformations and that neglecting flexural deformations leads to inaccurate damping ratios. New design formulas are presented that account for both flexural and shear deformations, providing more accurate predictions of the damping ratio contributed by linear viscous dampers and ensuring a more conservative design for buildings that employ nonlinear viscous dampers. In “Comparison of Methods for Computing Equivalent Viscous Damping Ratios of Structures with Added Viscous Damping,” Charney and McNamara demonstrate that the approach used to compute modal damping ratios can have a significant influence on the computed values and that the axial flexibility of toggle-brace linkages can result in reduced system damping as the damping constant of the damper increases, a phenomenon that is readily observed through examining complex-valued mode shapes. In their paper “Seismic Protection of Frame Structures by Fluid Viscous Damped Braces,” Sorace and Terenzi present results from experimental testing of two three-story building frames, one constructed of steel and the other of reinforced concrete, each containing a bracing system employing fluid viscous dampers. The method by which the damping coefficient of the dampers was selected is discussed and evaluated by comparing the target response with the experimentally measured response. An analytical study entitled “Fluid Dynamics and Behavior of Nonlinear Viscous Fluid Dampers” is presented in the paper by Hou. In this study, the dynamics of the fluid flow are evaluated through solving the Navier-Stokes equations, and the shear-thinning effect and viscoelasticity of the fluid are considered. Comparisons with experimental data show that both the nonlinear viscous and restoring force behavior can be captured. The seismic response of a three-story reinforced concrete frame with viscous wall dampers is investigated by Lu, Zhou, and Yan in their paper “Shaking Table Test and Numerical Analysis of RC Frames with Viscous Wall Dampers.” In addition, the effect of the wall dampers on the seismic performance of a partially damaged reinforced concrete frame is examined. The test results demonstrate that the viscous wall dampers add significant damping while also providing some increase in stiffness, reducing the test structure displacements, and in some cases, increasing accelerations.