P-Delta Limit State in the Design of Slender RC Bridge Columns Open Access
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The main objective of this research program is to evaluate the seismic response of slender reinforced concrete (RC) bridge columns to second order P-Delta effects. This research has led to the development of a new methodology for explicitly addressing P-Delta effects in the seismic design of slender RC bridge columns. This is achieved in terms of a displacement ductility that corresponds to the limit state when RC bridge columns become unstable under the combined actions of gravity and seismic loads. Different methods are currently specified in Seismic design codes for including second order P-Delta effects in the design of RC bridge columns. However, design codes do not address the limit state when RC bridge columns become unstable under the combined actions of gravity and seismic loads. Likewise, current seismic design guidelines do not include explicit target ductility demands that can address the instability of RC bridge columns resulting from the combined effects of lateral deformations and gravity loads.By implementing a combination of nonlinear pushover and time history analysis, design charts were developed and are proposed in this research, which can be used to obtain a displacement ductility that corresponds to the limit state when RC bridge columns become unstable under the combined actions of gravity and seismic loads. It is proposed to use this displacement ductility limit state in the design of RC columns to explicitly incorporate the inclusion of P-Delta effects in the design process.