Effective Stiffness and Seismic Response Modification Models Recommended for Cantilever Circular Columns of RC Bridges, Second Part: Collapse Prevention Limit State

Abstract

This paper aims to assess the structural overstrength (R), seismic behaviour factor (Q), and effective inertia factor (keff), of which the effective elastic stiffness (Keff) is a function, i.e., Keff (keff), of reinforced concrete (RC) cantilever columns with solid circular sections in urban bridges. The R and Q factors proposed in the design codes have been based mainly on an empirical basis. However, some studies suggest that, in the case of RC bridge columns, both factors are determined by a range of geometric and structural parameters. These results indicate that equations incorporating the main geometric and structural parameters of the columns, rather than the use of fixed values, are the appropriate method for estimating the values of R, Q and keff for the columns. Therefore, the results confirm the relation between R, Q and keff with the mechanical properties of the concrete, the aspect ratio length–depth, the axial load–strength ratio of a column, as well as its longitudinal reinforcement steel ratio. Finally, the research proposes models for estimating R, Q and keff that are recommended for the collapse prevention limit state of cantilevered circular columns of RC bridges.

Keywords

• response modification factors
• collapse prevention limit state
• reinforced concrete bridges
• seismic response