Multihazard Assessment and Retrofit of Deteriorated Timber Pile Bridges

Compared to research studies on the behavior and performance of reinforced concrete and steel structures, there is almost no information available in the literature relating to heavy timber structures such as timber pile bridges. With growing interest to expand the scope of structural designs to extreme loads from multiple hazards, the knowledge gap is expanding. In this study, the performance of a model bridge with timber pile substructures and a precast concrete superstructure was examined in a multihazard scenario involving three hazards: timber deterioration, earthquake, and tsunami loading. As a countermeasure to timber deterioration, a retrofitting strategy using fiber-reinforced polymer (FRP) composites was investigated. Material models for as-is timber piles and FRP-confined timber piles were derived based on experiments conducted on field-extracted specimens. The earthquake and tsunami events were simulated sequentially. The particle finite element method is used to conduct the tsunami simulation. Results show that even a modest level of timber deterioration can considerably affect the capacity of timber pile bridges under earthquake-tsunami loading. However, the FRP retrofitting technique considered in this study shows significant improvements can be achieved in terms of earthquake and tsunami capacity by strengthening a few selected timber piles.