Optimal seismic analysis of degrading planar frames using a weighted energy method to associate inelastic mode shapes: Part I optimal parameters

Abstract The objective of this paper is to compute three optimal parameters that are subsequently used to formulate the pre-yielded and post-yielded portions of an equivalent single degree of freedom system (E-SDOF) that is used to predict the seismic target demands in planar frames. The procedure uses an optimal number of inelastic mode shapes from a structure’s capacity (pushover) curve to account for any significant higher-mode effects (HME) and predict the inelastic demands. Using a variant inertial load pattern, weighted energy gradients under the capacity curve are used to define an optimal ductility parameter, which is in turn used to combine the inelastic (and elastic) mode shapes into a single mode shape. This is used to determine the pre-yielded portion of the E-SDOF system, where the post-yielded portion is determined using an inelastic modes parameter. The procedure also utilizes a reduction factor parameter to adjust the one-second spectral acceleration demand. The three optimal parameters are established using several buildings, whose responses are generally influenced by specific material strain hardening and plastic flow rules, and by the dissipated energy due to the yielding of the individual members. Using this methodology, the predicted target displacement demands are very reasonably predicted when compared to a nonlinear time-history analysis, which enables the parameters to later be used in the formulation of other buildings’ E-SDOF systems.

[1]  Rui Pinho,et al.  DEVELOPMENT AND VERIFICATION OF A DISPLACEMENT-BASED ADAPTIVE PUSHOVER PROCEDURE , 2004 .

[2]  John M. Biggs,et al.  Introduction to Structural Dynamics , 1964 .

[3]  Amr S. Elnashai,et al.  Static pushover versus dynamic collapse analysis of RC buildings , 2001 .

[4]  Qiang Xue.  Need of performance‐based earthquake engineering in Taiwan: a lesson from the Chichi earthquake , 2000 .

[5]  Sashi K. Kunnath,et al.  Seismic Performance and Retrofit Evaluation of Reinforced Concrete Structures , 1997 .

[6]  Subhash C. Goel,et al.  Seismic design by plastic method , 1998 .

[7]  Peter Fajfar,et al.  THE N2 METHOD FOR THE SEISMIC DAMAGE ANALYSIS OF RC BUILDINGS , 1996 .

[8]  Helmut Krawinkler,et al.  PROS AND CONS OF A PUSHOVER ANALYSIS OF SEISMIC PERFORMANCE EVALUATION , 1998 .

[9]  Munich Re,et al.  Topics 2000: Natural Catastrophes-The Current Position , 1999 .

[10]  Arthur C. Heidebrecht,et al.  Evaluation of the seismic level of protection afforded to steel moment resisting frame structures designed for different design philosophies , 1999 .

[11]  H. Krawinkler,et al.  Estimation of seismic drift demands for frame structures , 2000 .

[12]  Anil K. Chopra,et al.  A modal pushover analysis procedure for estimating seismic demands for buildings , 2002 .

[13]  Kuo-Chun Chang,et al.  An improved capacity spectrum method for ATC‐40 , 2003 .

[14]  Hanbin Ge,et al.  Applicability of pushover analysis-based seismic performance evaluation procedure for steel arch bridges , 2004 .

[15]  Apostolos Fafitis,et al.  Plastic hinge development of frame members using a nonlinear hardening rule , 2005 .

[16]  Hassan Sedarat,et al.  SR5 Lake Washington Ship Canal Bridge pushover analysis , 1999 .

[17]  J. Neter,et al.  Applied Linear Regression Models , 1983 .

[18]  Chin-Hsiung Loh,et al.  Earthquake responses of RC moment frames subjected to near‐fault ground motions , 2001 .

[19]  Rui Pinho,et al.  ADVANTAGES AND LIMITATIONS OF ADAPTIVE AND NON-ADAPTIVE FORCE-BASED PUSHOVER PROCEDURES , 2004 .

[20]  Yi Zheng,et al.  SEISMIC DESIGN METHOD FOR THIN-WALLED STEEL FRAME STRUCTURES , 2001 .

[21]  C. Allin Cornell,et al.  Three Proposals for Characterizing MDOF Nonlinear Seismic Response , 1998 .

[22]  Sashi K. Kunnath,et al.  Adaptive Spectra-Based Pushover Procedure for Seismic Evaluation of Structures , 2000 .