Hybrid concrete and pultruded-plank slabs for highway and pedestrian bridges

Studies on two novel uses of hybrid structural members consisting of commercially produced glass reinforced pultruded ribbed fiber reinforced polymer (FRP) planks and concrete are discussed in this paper. Pultruded planks are produced by all the major pultruders in the world and are utilized primarily as decking for platforms. These highly optimized panels have the potential to be used in many other infrastructure applications, but their flexural stiffnesses have generally been too low to be used in highway and pedestrian bridges due to current span requirements. However, when used “compositely” with concrete or cementitious materials in a hybrid form they have the potential to be much more widely used. Two research studies conducted on two possible hybrid systems of different structural depths are discussed in this paper. The first study describes the use of pultruded planks as permanent formwork in highway bridge decks where the plank is used with concrete to produce a solid slab of 200 mm depth that is typical of slabs seen in highway bridge decks. The second study describes the use of pultruded planks in pedestrian bridge decks where the pultruded plank is used with a cement-board or a cast-in-place concrete panel to produce a hollow slab of 75 mm depth that is typical of timber decking used in FRP pedestrian bridges. Tests were conducted on beam-type specimens of the hybrid slabs to investigate the load transfer mechanisms between the pultruded plank and the cementitious “overlays” for both the 75 mm and 200 mm depths. From analysis of the load-carrying capacity and failure mechanisms of the hybrid slabs it was concluded that such hybrid slabs are viable systems for both highway and pedestrian bridge decks. A bridge deck using the 200 mm deep hybrid slab system was recently constructed on a highway in Wisconsin, USA.