Seismic Design of Bridges: Analytical Investigation of AASHTO LRFD Response Modification Factors and Seismic Performance Levels of Circular Bridge Columns

In AASHTO LRFD, three different importance categories are presented as “Critical”, “Essential” and “Other” bridges to be considered in seismic design. These classifications are mainly based on the serviceability requirement of bridges after a design earthquake. The bridge''s overall performance during a given seismic event cannot be clearly described. Serviceability requirements specified for a given importance category are assumed to be assured by using different response modification factors (R-factors). Although R-factor is directly related with strength provided to resisting column, it might be correlated with selected performance levels including different engineering response measures. Within the scope of this study, 27216 single circular bridge column bent models designed according to AASHTO LRFD and having varying column aspect ratio, column diameter, axial load ratio, R-factor and elastic design spectrum data are investigated through a series of analyses. Three performance levels such as “Fully Functional”, “Operational” and “Delayed Operational” are defined in which their criteria are selected in terms of column drift measure corresponding to several damage states.