Numerical and experimental investigations on the Park-Ang damage index for high-speed railway bridge piers with flexure failures

The traditional Park-Ang damage index (DI) has been devised for damage assessment of highway bridge piers and building columns, but is inappropriate for high-speed railway (HSR) bridge piers, which have much larger cross sections, much less longitudinal bar ratios and much less axial compression ratios under earthquakes. In order to obtain the appropriate DI for HSR bridge piers, numerical analysis of 144 HSR bridge piers and quasi-static test of 7 HSR bridge piers was done to study the combined parameter beta in DI. The new DI was subsequently validated by pseudo-dynamic testing of 2 HSR bridge piers. The results show that the new combined parameter beta in the reformulated DI for HSR bridge piers is mainly affected by the longitudinal bar ratio and the axial compression ratio; however, the traditional beta and DI are significantly affected by the stirrup reinforcement ratio. It is suggested that 0.06, 0.19, 0.49 and 1.0 should be taken as the critical values for the new DI among the basically intact, slightly damaged, moderately damaged, severely damaged and collapsed states of HSR bridge piers with axial compression ratio being less than 0.09, while values 0.11, 0.33, 0.49 and 1.0 are recommended for HSR piers with an axial compression ratio from 0.09 to 0.15. As for the collapse state of HSR bridge piers, the cumulative damage contribution of energy to the full DI (of value 1.0) is 0.64. It is a large value and indicates that HSR bridge piers are vulnerable to cumulative damage from earthquakes.