Analysis of T Beam bridge for seismic characterization

Abstract

Roads are the lifelines of modern transport and bridges are the most critical parts of transportation systems. They are susceptible to failure if their structural deficiencies are unidentified. A large number of bridges constructed around the world were designed during the period when bridge codes had no seismic design provisions, or when these provisions were insufficient according to the current standards. Also, due to aging and the growth of vehicular loads in magnitude and volume, many existing bridges in India are experiencing deterioration. As the construction of new bridges involves huge time and money, the repair and rehabilitation of old and damaged bridges are necessary, to preserve their load carrying capacity and service performance. In the present study, an existing reinforced cement concrete T-beam cum slab road bridge (Koyambedu bridge) was assessed for its seismic characterisation. A live load test on the study bridge was conducted, to measure the flexural responses of the longitudinal and the cross girders. The strain histories obtained from the experimental investigation indicated the nonlinear response of the longitudinal girder and linear response of the cross girder. The effective flexural stiffness (EIeff) of the longitudinal girder was found to be 0.8 times the gross flexural stiffness (EIg).A three-dimensional nonlinear finite-element model of the reinforced cement concrete bridge, was developed and analysed, using SAP2000. On modal analysis, two modes (mode#1 and mode#8) were participating in the vibration of the structure in the transverse direction and a single mode (mode#2) was participating in vibrating the structure in the longitudinal direction. Modal pushover analyses were performed in both the transverse and longitudinal directions independently. In the mode#1 and mode#8 pushover analyses in the transverse direction, the performance level of the plastic hinges at the bottom of the columns in the mid-bent exceeded the collapse prevention performance level.