Load Rating of Deteriorated and FRP-Retrofitted Bridge Abutment Timber Piles

Conventional load-rating methods for bridge timber piles consider only concentric axial loads. However, in the case of abutment piles, earth pressure and surcharge loads exert a significant lateral force on the piles. There is need for a load-rating procedure that can account for combined axial loads and bending from lateral loads. This paper proposes a load-rating method specifically for deteriorated and fiber-reinforced polymer (FRP) retrofitted abutment timber piles. The new load-rating method accounts for various factors, including dead load, pile length, earth pressure, and timber pile deterioration. The proposed load-rating method is demonstrated on a prototype timber pile bridge model using finite-element methods. Results show that timber pile deterioration affecting as low as 10% of the pile cross section can significantly reduce the load-carrying capacity of abutment timber piles. In addition to the load-rating technique, this paper introduces a simplified elastic design method for retrofitting the tensile face of abutment timber piles using FRP composites. Both the load-rating and FRP design methods are presented as a series of charts that engineers can easily use to aid their decision-making process.