No abstract

The present paper focuses on the nonlinear static pushover analysis of a 3-span existing RC bridge located in Indian seismic Zone IV as per IS1893-2016 using the Finite Element Method (FEM). The 3D model of the RC bridge is simulated using the FEM technique and pushover analysis is performed to analyze the structure for modal mass participating ratio, performance level, spectral demand, and capacity of the structure. The bridge pier and longitudinal girder are modeled using the two noded beam element and bent cap and abutment of the bridge structure is modeled using the 8 noded brick element. The base of the column is assumed fixed condition. The pushover analysis is performed using Displacement Modification (FEMA 440) and Capacity Spectrum Method (ATC 40). The outcomes of results appear that the considered bridge has inadequate capacity to cope up with any of the desired performance levels because spectral demand is greater than the spectral capacity. The modal analysis of the 3D bridge exposes that it has many closely-spaced modes. The mass participating ratio for the higher modes is not very high. After performing pushover analysis of the exiting RC bridge structure it has been concluded that the existing bridge structure does not meet seismic criteria of spectral demand as per the ATC 40 and FEMA 440, therefore retrofitting is required for bridge component i.e. piers, abutment, and bent cap.

The assessment of liquefaction potential in the present study is based on deterministic and probabilistic approach. The deterministic approach was used to analyze the liquefaction assessment of loose saturated river bed deposit with emphasis to two benchmark location. A wide range earthquake data in form of PGA’s value of 0.18g, 0.37g, 0.6g, 0.75g is used as input motion. The dynamic properties of soil were evaluated by using SPT data obtained from the bore log locations. The shear stress induced within soil deposit due to the seismic excitation in the form of cyclic stress ratio (CSR) and cyclic resistance ratio (CRR) was calculated in order to calculate the factor of safety (FOS) against liquefaction. In addition to that, liquefaction potential index (LPI) and probability of liquefaction was also calculated using input motion. It was observed that the shallow layer soil profile is safe against liquefaction whereas deep layer soil profile is unsafe based on probability of liquefaction index.