Performance-Based Seismic Fragility and Residual Seismic Resistance Study of a Long-Span Suspension Bridge

Table 1

Characteristics of the curvature ductility index.

Damage status	Damage characteristics	Specific parameter index
Nondamaged	The outermost longitudinal reinforcement is not yielded
Slightly damaged	The yield strain of the outermost longitudinal bars is less than the initial strain, and the compressive strain of unconstrained concrete is less than 0.004	,
Mid damaged	The longitudinal reinforcement strain is less than 0.55 times of the ultimate tensile strain, and the constrained concrete is less than 0.75 times of the ultimate compressive strain	,
Severely damaged	The longitudinal reinforcement strain is less than the ultimate tensile strain, and the constrained concrete is not larger than the ultimate compressive strain	,
Completely damaged	The longitudinal reinforcement strain is greater than the ultimate tensile strain and the restrained concrete cracks	,

where represents the tensile strain of the outermost longitudinal reinforcement of the section; represents the compressive strain of unconstrained concrete on the outermost side of the cross section; represents the theoretical yield strain of longitudinal reinforcement; represents the compression strain of the outermost constrained concrete of the section; represents the strain corresponding to the peak compressive stress of unconstrained concrete; represents the tensile strain when the longitudinal reinforcement is initially hardened; represents the tensile strain of the outermost constrained concrete of the section.