A novel seismic strengthening method for ageing steel bridge piers

The seismic resilience of steel bridge piers can be weakened due to the ageing effect that occurs throughout their entire life-cycle stage. Seismic strengthening is a practical approach to enhance the seismic performance of ageing piers. Nevertheless, the conventional strengthening methods often result in a higher stiffness of bridge piers. This can potentially intensify the local seismic responses of the strengthened bridge pier and change the failure mode during seismic events. Hence, this study extends a strengthening technique, the Contact Stiffener Strengthening Method (CSSM), which aims to enhance the ductility of ageing steel bridge piers without causing an excessive increase in stiffness. This method uses the contact effect to increase the seismic performance of aging piers by ingeniously designed stiffeners. The static and dynamic approaches are employed to compare the effects of CSSM and traditional strengthening methods on seismic performance enhancement. Finally, this study proposes the prediction methods for the ultimate strength and displacement of the strengthened piers. The analysis results reveal that the occurrence of the contact phenomenon and buckling at the free-end plate indicate the initiation and ultimate states of the contact stiffeners. The strengthening efficiency in retrofitted piers is greatly influenced by the parameters of the free-end plate. The strengthening efficiency of bridge piers can be significantly affected by varying parameters of corrosion when using the same contact stiffener. The errors in the proposed prediction methods for the ultimate displacement and ultimate strength of the strengthened piers can be controlled within 15% and 10%, respectively.