Rocking damage‐free steel column base with friction devices: design procedure and numerical evaluation

Abstract

Summary Earthquake‐resilient steel frames, such as self‐centering frames or frames with passive energy dissipation devices, have been extensively studied during the past decade, but little attention has been paid to their column bases. The paper presents a rocking damage‐free steel column base, which uses post‐tensioned high‐strength steel bars to control rocking behavior and friction devices to dissipate seismic energy. Contrary to conventional steel column bases, the rocking column base exhibits monotonic and cyclic moment–rotation behaviors that are easily described using simple analytical equations. Analytical equations are provided for different cases including structural limit states that involve yielding or loss of post‐tensioning in the post‐tensioned bars. A step‐by‐step design procedure is presented, which ensures damage‐free behavior, self‐centering capability, and adequate energy dissipation capacity for a predefined target rotation. A 3D nonlinear finite element (FE) model of the column base is developed in abaqus. The results of the FE simulations validate the accuracy of the moment–rotation analytical equations and demonstrate the efficiency of the design procedure. Moreover, a simplified model for the column base is developed in OpenSees. Comparisons among the OpenSees and abaqus models demonstrate the efficiency of the former and its adequacy to be used in nonlinear dynamic analysis. A prototype steel building is designed as a self‐centering moment‐resisting frame with conventional or rocking column bases. Nonlinear dynamic analyses show that the rocking column base fully protects the first story columns from yielding and eliminates the first story residual drift without any detrimental effect on peak interstory drifts. The study focuses on the 2D rocking motion and, thus, ignores 3D rocking effects such as biaxial bending deformations in the friction devices. The FE models, the analytical equations, and the design procedure will be updated and validated to cover 3D rocking motion effects after forthcoming experimental tests on the column base. Copyright © 2017 John Wiley & Sons, Ltd.

Proposed methodology for building‐specific earthquake loss assessment including column residual axial shortening

“…The inherent flexibility of exposed or embedded column base connections may significantly influence the column residual axial‐shortening Field observations from past earthquakes (eg,) along with numerical studies suggest that the inelastic behavior of columns in structures as well as bridge piers could be considerably affected by soil‐structure‐interaction, which was neglected in the present study. The paper findings suggest that recently proposed structural solutions may be further exploited to potentially minimize steel MRF column structural damage due to local buckling. These have a high potential to reduce the likelihood of building demolition due to column residual axial‐shortening. Exploiting the benefits of controlled soil plastification in prospective seismic designs may be an alternative to minimize column residual axial‐shortening in steel MRFs.…”

“…• Field observations from past earthquakes (eg, 63,64 ) along with numerical studies 65 suggest that the inelastic behavior of columns in structures as well as bridge piers could be considerably affected by soil-structure-interaction, which was neglected in the present study. • The paper findings suggest that recently proposed structural solutions 66,67 may be further exploited to potentially minimize steel MRF column structural damage due to local buckling. These have a high potential to reduce the likelihood of building demolition due to column residual axial-shortening.…”

11.11: Rocking damage‐free steel column base with friction devices: Development of advanced 3D finite element models in Abaqus

“…Moreover, Table 1 provides the assumed material properties (E: Young's modulus; f y : yield stress; f u : ultimate stress; and β: strain hardening ratio), which have been selected on the basis of experimental results [21,22]. Applying the design methodology presented in [17], PT bars with length and diameter equal to 2242 and 15mm respectively are chosen and a T PT force equal to 30kN. The rotations θ PT,u ,y and θ PT,d,f are equal to 0.0252rads and 0.0255rads, respectively.…”

“…A detailed FE model is built in ABAQUS in order to validate the theoretical monotonic and cyclic behaviour of the column base as well as a simplified numerical OpenSees model, which is used in [17] for the seismic assessment of a SC-MRF. For the FE discretization, the eight-node linear brick element (C3D8R) based on 'reduced integration' and 'hourglass control' is used for all components.…”

“…More details on the design and the influence of the rocking column base on the seismic response of selfcentering moment resisting steel frames (SC-MRFs) under earthquake ground motions are presented in Freddi et. al [17]. Fig.…”