Modal criticality index of an existing reinforced cement concrete T-beam bridge

An existing reinforced cement concrete T-beam bridge is evaluated using inelastic analysis procedures namely capacity spectrum method (CSM) and modal pushover procedure (MPA). In this paper, MPA is performed in both the transverse and the longitudinal directions of the bridge structure independently. The capacity curves that represent the response of the bridge in transverse direction for the particular modes of the vibration are generated using MPA. Modal Criticality Index (MCI), a value which is the ratio of the Spectral acceleration (Sa) for demand and the Spectral acceleration (Sa) for capacity is determined. Modal criticality index value was calculated, considering the initial stiffness and the secant stiffness of the bridge structure, for identifying the critical mode. From the calculated modal criticality index value, the critical mode of the structure was inferred to be the higher mode irrespective of the stiffness (initial/secant) adopted.