Fiber-Reinforced Polymer Decks for Bridge Rehabilitation: A Case Study: Fid-Bau Portal

Fiber-Reinforced Polymer Decks for Bridge Rehabilitation: A Case Study

Lombardi, Nicolas / Rodriguez-Vera, Rita E. / Liu, Judy / Sotelino, Elisa

Fiber reinforced polymer (FRP) bridge decks are used in bridge rehabilitation projects, often because of their relatively low self weight and high durability. Related benefits of FRP include rapid construction and advantages in terms of life cycle costs (e.g., corrosion resistance). A case study bridge in Tippecanoe County is the first in Indiana to be rehabilitated with a FRP deck. Among the bridges evaluated, County Road 900E over Wildcat Creek is a three-span continuous steel stringer bridge with two concrete approach spans. The FRP deck replacement would only take place on the three main spans. This bridge rehabilitation project presents a unique challenge in that the deck would be widened with no changes to the superstructure. The resulting overhang would also be the longest seen for this application. Since the properties of FRP are such that serviceability issues govern deck design, requirements for the overhang dominate decisions related to deck type and geometry, and choice of barrier or guardrail. These and other project details will be discussed. The choice of deck is affected by deflection limits of the overhang at the exterior stringer. Based on American Association of State Highway and Transportation Officials (AASHTO) span-to-deflection ratio recommendations, a deck produced by hand lay-up rather than pultrusion is selected. The ability to tailor the deck cross section geometry to satisfy serviceability limits motivated this decision. The FRP deck consists of a honeycomb core sandwiched between two faces, or structural surfaces. This bridge design also involves a trade-off between a deeper section to satisfy deflection criteria and overall cost. Specifically, a deeper section will increase material cost for FRP and the cost of building up the concrete approaches to match the deck height on the main spans. The deck geometry also affects the decision regarding proposed stiffener brackets, which would supply discrete support points to the overhang at each diaphragm location. Finite element analyses show that the deck is significantly more flexible in its transverse direction, affecting distribution of load and resulting in absolutely no reduction in deflection or stress with the bracket supports. The brackets are therefore excluded from the design. Finally, the choice of vehicular rail/ barrier is also affected by the overhang. Both concrete barrier and steel guardrail options are evaluated. AASHTO allows for a reduction in overhang loading for concrete barriers due to the structural continuity provided to the deck. However, finite element analyses demonstrate that this provision is not applicable for this FRP deck application. This and dead load considerations result in the choice of a steel guardrail.