Damage identification in cable-stayed bridges based on the behavior of neutral axis under traffic loading

A beam's Neutral Axis (NA) is a parameter that has been utilized to detect damage. Its position depends on the geometry of the cross-section and also a member's axial loads. Shifts in its position can indicate changes in either load distribution or geometric characteristics. When considering structures such as cable-stayed bridges where the inclined cables induce significant axial forces, the effect of axial loads on NA position is significant. In this research, a simplified analytical model was developed consisting of the key elements of a cable-stayed bridge (beam, cable, and bearing). The model was loaded with a vertical point load representing a vehicle load. The NA position was calculated beneath the load as it moves over the length of the beam. By changing element properties, one can observe how the NA position behaves in different locations of the beam, due to simulated damage in the beam, cable, or bearing. It was found that changes in NA position can capture not only whether damage has occurred, but also in which component of the structure the damage is located (beam, cable, or bearing). This ability to use NA position for damage identification renders it an excellent parameter for monitoring cable-stayed bridges.