Cumulative damage study for the 2010 “blind prediction contest” of a reinforced concrete bridge column O. Lara & C.E. Ventura The University of British Columbia, Vancouver V.A. Suarez Universidad Técnica Particular de Loja, Ecuador SUMMARY: In 2010 PEER, and NEES promoted a “blind prediction contest” of a reinforced concrete bridge column subjected to a set of six earthquake ground motions, tested at the shake table facility of the University of California, San Diego. The test results indicate no flexural failure mechanism for the set of records except Damage Accumulation, DA, in the materials. This was confirmed in the prediction made by Lara, Ventura, and Suarez in 2010 using a fiber finite element model. In this paper the results of additional studies of this problem are presented and discussed. Results of such studies show that three bars fracture due to DA reducing the strength and stiffness of the column. The cyclic damage index, a measure of damage proposed by the first author in 2011 varies from 0.68 to 0.96 and to 1.2 respectively for three consecutive simulations, An index equal to 1.0 indicates that the column is forced to reach one flexural failure mechanism in one run of the scaled set. 1. INTRODUCTION AASHTO (20011) requires for seismic design of reinforced concrete bridge columns to identify which of the following three flexural failure mechanism controls the design: crushing of the confined concrete, fracture of the longitudinal bars due to tension, or column instability due to P-Δ effect. Lara (2011) demonstrated that during severe earthquakes and aftershocks even columns designed under AASHTO (2007) specifications suffer damage accumulation, DA, inducing considerable reductions of strength and stiffness in the column. The “blind prediction contest” of a reinforced concrete bridge column, promoted by Peer and Nees in 2010, tested a bridge column under a set of six ground motion records which amplitudes and frequency content were filtered by the shake table. A white noise was applied after each record to keep the response of the column to the previous record. The test was conducted at the University of California, San Diego using the large shake table facility. The prediction by Lara, et al. (2010) deserved from Peer and Nees, (2010) a prize of excellence. The results of the test indicate that the column under the filtered records did not suffer any of the three flexural failure mechanisms but DA due to strains that resulted in spalling of the unconfined concrete and cracking of the confined concrete, and irrecoverable damage in the steel bars. Research results presented here show that there was an additional DA in the bars induced by cycles of plastic strains reducing the fatigue life in six bars as it was captured by the Finite Fiber Element Model, FFEM, Lara (2011). If two additional consecutive applications of the set shake the column, three bars fracture due to total reduction of their fatigue life, i.e. fracture due to low-cyclic fatigue, reducing the strength and the stiffness of the column by 33% and 50% respectively. A fourth run is applied and more deterioration is observed. To measure DA induced by earthquakes in columns, Lara (2011) introduced the cyclic damage index based on energy dissipation that is calculated here. 1.1 Objective The main objective of this study is to estimate DA on the tested column and the influence of such accumulation in its strength and stiffness when the column is subjected to the set of the filtered ground motions applied to the column during the test and to repetitions of the set.