Seismic performance of RC bridge column bents strengthened by infill walls

This dissertation describes the findings from a comprehensive experimental testing program and a complementary analytical study of the seismic performance of RC bridge column bents retrofitted by reinforced concrete infill walls.; The first part of this study includes a comprehensive experimental program to quantify the behavior of scaled bare and retrofitted column bents. Tests were performed on: (1) as-built bare column bent, (2) a column bent retrofitted with infill wall that was fully anchored to the columns and the bent cap, (3) a strengthened column bent with an infill wall where a gap was allowed between the bent cap and the infill wall for construction purposes, (4) a retrofitted column bent with an infill wall where the gap was filled with concrete paste, (5) an infilled column bent with a gap but with shorter dowels than in the other samples, and lastly, (6) a column bent retrofitted with infill wall with a gap but the columns were also confined in the lap splice zone by reinforced concrete jackets.; It was demonstrated that, under lateral cyclic loading, an infill wall can substantially increase the lateral strength of a deficient column bent, but reduces its displacement ductility. The gap between the infill wall and the bent cap may subject the latter to potentially unfavorable damage modes. When the gap was filled with regular strength concrete, the behavior of the system became similar to that of a system with dowels embedded in the bent cap. There was no significant decrease in the strength of the sample with shorter dowels. Providing a concrete jacket for the columns postponed the lap splice failure and increased the strength of the bent. In general, the infill wall retrofit system met its seismic design requirements for all samples as far as the demand and capacity are concerned.; The second part of this study includes a complementary analytical verification of the bare column bent and the retrofitted column bents. The analytical models were calibrated using the experimental results obtained from the first part of this study as well as results obtained form the literature. The Capacity Spectrum Method was used to evaluate the seismic performance of the infilled column bents under earthquake excitations, for which comparisons between capacities and demands were carried out. It was noted that good correlation may be achieved between the experimental and analytical results.; A parametric study was performed utilizing the analytical models developed for the modeling of the column bents. Sample parameters studied were the aspect ratio of the bent, the thickness of the infill wall, and the vertical dowels between the infill wall and the footings.