Effect of lateral loading protocols on seismic performance of RC columns

Structural elements in buildings and bridges may experience varying levels of damage during seismic events. The extent of damage in RC columns during earthquakes is related to their material and cross sectional properties, as well as to the characteristics of the loading history. Unlike bridge piers, very few research studies have investigated the effect of loading histories on the behavior of RC building columns. Moreover, previous experiments lack sufficient information to understand the softening behavior of RC columns up to collapse level as they were terminated after the columns typically exhibited only a 20% reduction in their lateral load capacity. The effects of several monotonic and cyclic, lateral loading protocols on the behavior of RC columns were investigated during seven full-scale tests at the Multi-Axial Subassemblage Testing (MAST) Laboratory of the University of Minnesota. To study the post-peak behavior of RC columns, the loading protocols included large deformations, similar to those that columns may experience during extreme seismic events, and continued until the specimens lost approximately 80% of their lateral load capacity. The extent and evolution of damage in the column specimens is quantified by several cumulative and noncumulative damage indices. Quantified damage values are compared against visually observed damage in the column specimens to assess the accuracy of the indicators in tracking damage for the various loading protocols. The damage indicators are considered along with force-deformation cyclic envelopes to investigate the effect of the loading protocols on the RC column specimens.