Maximum credible damage of RC bridge pier under bi-directional seismic excitation for all incidence angles

Extending conventional Park-Ang damage index, a simple yet rational damage measure applicable for bi-directional seismic shaking has been evolved. Comparing predicted damage states of a bridge pier in terms of the evolved damage index to the component strains, efficacy of the proposed index has been verified. Quantitative assessment of damage of a bridge pier demonstrates substantial magnification in damage due to bi-directional shaking relative to uni-directional companion. This amplification in damage may further vary with incidence angles. Unfortunately, conducting true bi-directional analysis is challenging and implications of incidence angles are elusive yet. Collectively investigating these two crucial issues, present study identifies suitable orientations/ incidence angles in terms of pure ground motion parameters. Maximum credible damage of bridge pier under bi-directional shaking may be estimated by combining damage (30% rule) due to less-rigorous uni-directional analysis conducted in the most preferred orientation defined by the ratio of energetic length of components. The present investigation thus appears to evolve a rational damage index and a novel strategy to quantify the same for bridge pier under bi-directional seismic excitation.