Comparative study on seismic vulnerability of highway bridge with conventional and HyFRC piers

The vulnerability of bridges depends primarily on the seismic performance of its piers. This paper studies the seismic vulnerability of a bridge with conventional concrete and hybrid fibre reinforced concrete (HyFRC) pier. Combination of 1.0% steel fibres and 0.15% polypropylene fibres by volume fraction is adopted in the construction of HyFRC piers from the viewpoint of improved toughness. Hybrid testing of six bridge piers (three made of conventional concrete and three made of HyFRC) are carried out to obtain the limit-state capacities and numerical model of the bridge structure is calibrated using the experimentally obtained responses. Analytical fragility curves are developed using the calibrated numerical model for different damage states as a function of an engineering demand parameter that represents the ground motion. The damage states are decided based on the actual damages observed from the experimental investigation. The fragility curves show very clearly that at any damage state, the HyFRC piers are less vulnerable to earthquakes when compared to the bridge piers made of conventional concrete. The difference in probability of exceedance increases with an increase in the intensity of earthquake. Use of HyFRC in bridge piers can provide significant enhancement in seismic performance of bridges in earthquake-prone regions.