Modeling Technique for Honeycomb FRP Deck Bridges Via Finite Elements

Fiber Reinforced Polymer (FRP) decks have been successfully used to rehabilitate highway bridges in the U.S. One important characteristic of these decks is their inherent high strength to weight ratio. These decks also have low stiffness. Their design is thus governed by serviceability rather than strength. Meanwhile, preliminary analyses have suggested that existing serviceability criteria, intended to limit vibrations, are not applicable to FRP deck bridges. There are two primary reasons for this conclusion: first, the inherently low mass and stiffness of the FRP deck, and second, the deck-to-girder connections adopted in FRP deck bridge design are discrete and do not provide full composite action between deck and girder. Both properties will certainly produce a vibration response very different than that from a traditional reinforced concrete slab. In attempts to satisfy the existing serviceability criteria with FRP decks, more material and possibly a large number of deck-to-girder connectors are required. This results in expensive, impractical designs. Therefore, a joint analytical-experimental investigation is being conducted to establish appropriate serviceability criteria for FRP bridge deck applications. In this work, honeycomb, sandwich FRP decks are investigated. These honeycomb FRP decks have a very complex geometry, and computational limits prevent modeling of these bridge decks in detail. A simplified finite element modeling technique for this type of FRP deck was developed, as a first step, using the commercial finite element program ANSYS 8.1. In this paper, the modeling technique of each FRP bridge component is described in detail. This includes the use of the eccentric beam model for the steel girders and the steel guardrails. For validation of the proposed modeling technique, a detailed model of the honeycomb FRP deck was also created for comparison to the simplified model. Deflections, frequencies, and mode shapes for each model are compared with the experimental data. For validation of the overall bridge model concept, an existing bridge with concrete deck was modeled in a similar manner. The resulting frequencies and mode shapes are compared to those obtained in the field.