Evaluation of displacement coefficient method for seismically retrofitted buildings with various ductility capacities Murat Dicleli* ,† and Cengizhan Durucan Department of Engineering Sciences, METU, Ankara, Turkey SUMMARY This research study is aimed at evaluating the accuracy of the displacement coefficient method (DCM) of FEMA 440 and associated nonlinear static procedure (NLSP) for actual buildings with soft story mechanism and various ductility capacities. The DCM and associated NLSP are evaluated using two existing seismically vulnerable buildings with soft story mechanism. The buildings are first retrofitted using a ductile steel-brace-link system to represent those with good ductility capacity and then retrofitted with RC squat infill shear panels (SISPs) to represent those with relatively poor ductility capacity. The evaluation of the DCM of FEMA 440 and associated NLSP is then performed by comparing the roof displacements (target displacements), maximum interstory drifts, and maximum plastic hinge rotations of the original and retrofitted buildings obtained from NLSP (at the target displacement level of DCM) with those obtained from nonlinear response history (NRH) analyses for three different seismic performance levels. It is observed that the DCM, and hence, the NLSP fail to accurately predict the NRH analyses results mainly due to uncertainties in the coefficient C 1 of the DCM in the short period range, the inability of the DCM to capture the failure of structural members beyond a certain lateral displacement or plastic rotation limit and associated soft story mechanism. Copyright © 2013 John Wiley & Sons, Ltd. Received 28 March 2013; Revised 5 November 2013; Accepted 10 November 2013 KEY WORDS: displacement coefficient method; target displacement; seismic retrofitting; reinforced concrete building 1. INTRODUCTION In many municipal areas around the world, several destructive earthquakes in the last two decades resulted in extensive damage to RC buildings. Practically most of the structural and nonstructural damage sustained in such buildings is produced by lateral displacements. Accordingly, a common consensus has been reached by the earthquake engineering community at large to adopt the performance-based seismic design procedure that requires an accurate estimation of the inelastic lateral displacement demands in the buildings. Currently, there are several well-known performance- based seismic evaluation and rehabilitation methods such as the displacement coefficient method (DCM) of FEMA 440 [1], capacity spectrum method of ATC-40 [2], N2 method [3], and its extension to asymmetric buildings [4]. FEMA 440 is an improvement of nonlinear static seismic analysis procedures of FEMA 356 [5] and ATC-40 for seismic rehabilitation of buildings. There are four seismic rehabilitation design procedures proposed by FEMA 440 to estimate whether structures meet a predefined performance level (PL). These are the linear static procedure, the linear dynamic procedure, DCM, and the nonlinear dynamic procedure. In this paper, the DCM and associated nonlinear static procedure (NLSP) are discussed and evaluated. In the DCM of FEMA *Correspondence to: Murat Dicleli, Department of Engineering Sciences, METU, Ankara, Turkey. † E-mail: mdicleli@metu.edu.tr Copyright © 2013 John Wiley & Sons, Ltd. EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS Earthquake Engng Struct. Dyn. (2013) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/eqe.2397