16 th World Conference on Earthquake, 16WCEE 2017 Santiago Chile, January 9th to 13th 2017 Paper N° 3904 Registration Code: S-P1464297289 Detailed Nonlinear FE Pushover Analysis of Alto Rio Building J.I. Restrepo (1) , J.P. Conte (1) , R.S. Dunham (2) , D. Parker (2) , J. Wiesner (2) and P.A.C. Dechent (3) (1) University of California, San Diego, Department of Structural Engineering, La Jolla, California, USA. (2) Anatech Corp. San Diego, California, USA. (3) Universidad de Concepción, Concepción, Chile. e-mail: jrestrepo@ucsd.edu, jpconte@ucsd.edu, Bob.Dunham@anatech.com, Dan.Parker@anatech.com, Jeremy.Wiesner@anatech.com, pdechen@udec.cl Abstract The fifteen story Alto Rio building built between 2007 and 2009 in the city of Concepción, Chile, was the only modern building to experience catastrophic collapse during the 27 February 2010, Mw 8.8 Maule earthquake. This building was representative of those medium-rise buildings designed and built in Chile during the period 1996-2009 in which seismic resistance is provided by a dense array of thin wall bearing walls oriented in two orthogonal directions. A detailed nonlinear model of this building was developed in the computer program ABAQUS/Standard FE. This program was used in conjunction with the ANACAP-U concrete and reinforcing bar constitutive models developed by ANATECH Corporation. A parametric pushover analysis of the building was conducted considering several possible scenarios: with and without lap splice failure, and with and without the removal of some small gravity columns. This paper describes the development of the finite element model and discusses the results obtained from a parametric nonlinear static pushover analysis of the Alto Rio Building. Keywords: Collapse, Lap splices, Maule earthquake, Nonlinear finite element model, Pushover analysis 1. Introduction The fifteen story Alto Rio building built between 2007 and 2009 in the city of Concepción, Chile, was the only modern building to experience catastrophic collapse during the 27 February 2010, Mw 8.8 Maule earthquake, see Figure 1. Eight lives were lost as a result of the collapse of this building. This building was representative of many medium-rise buildings designed and built in Chile during the period 1996-2009. The lateral force resisting system of the Alto Rio building consisted of a dense array of predominantly 0.2 m thick transverse and longitudinal reinforced concrete bearing walls and a few thin and oblong columns. In a quest to understand the causes of collapse from the system behavior point of view, the entire Alto Rio building was modeled directly from its CAD files by using the Rhinoceros 3D computer graphics software followed by the FE mesh generation software FEMAP. The FE model consisted primarily of conventional 4-node shell elements of approximately 0.2 m x 0.2 m in size for the concrete walls and slabs and smeared rebar sub-elements for the steel reinforcement. The structure was modeled almost entirely using 4-node shell elements with embedded smeared reinforcing bars. The 4-node, 24 degree-of-freedom shell element used involved 2x2 Gaussian integration over the surface of the element and Simpson’s quadrature with three integration points (mid-surface and inner/top and outer/bottom surfaces of the shell) through the uniform thickness of the shell. The reinforcing bar sub-elements were modeled directly from the reinforcement detailing of the various structural components of Alto Rio defined in the CAD drawings. The analysis software of choice for performing a detailed nonlinear pushover analysis of the Alto Rio building was the ABAQUS/Standard FE computer program used in conjunction with the ANACAP-U concrete and reinforcing bar constitutive models developed by ANATECH and described below in this paper. A parametric pushover analysis of the building was conducted considering several possible scenarios: with and without lap splice failure, and with and without the removal of some small gravity columns. This paper discusses the development of the model and the results obtained from the parametric pushover analysis of the Alto Rio Building.