CICE 2010 - The 5th International Conference on FRP Composites in Civil Engineering September 27-29, 2010 Beijing, China Composite behavior of a pultruded hybrid CFRP-GFRP beam with UFC deck Hiroshi Mutsuyoshi, Kensuke Shiroki, Nguyen Duc Hai & Tatsuya Ishihama Department of Civil and Environmental Engineering, Saitama University, Saitama, Japan ABSTRACT: Hybrid Fiber Reinforced Polymer (HFRP), which is composed of Carbon FRP (CFRP) and Glass FRP (GFRP), has many advantages over conventional materials such as light weight, high specific strength, and corrosion resistance. HFRP is expected to find its application in severe corrosive environments or where light-weight rapid construction is required. This paper presents the development of a composite beam using an HFRP I-beam and precast Ultra-high strength Fiber reinforced Concrete (UFC) slab. UFC has high strength and high ductility, so it allows for reduction of the cross-section area and self weight. Full-scale flexural beam tests were conducted with different geometry of UFC slab and shear connection methods be- tween the UFC slab and HFRP beam. For the composite beams with bolted-only connection, slip occurred be- tween the HFRP beam and the UFC slab. On the other hand, slip was not observed in the composite beams with bonded-and-bolted connections. The flexural stiffness of beam specimens with bonded-and-bolted con- nection increased significantly compared with that of bolted-only connection specimens. Delamination failure was not observed in the compressive flange of the composite beams and the high tensile strength of the CFRP in the bottom flange could be utilized effectively by addition of the UFC slab on the top flange. 1 INTRODUCTION Fiber Reinforced Polymer (FRP) has many advan- tages over conventional materials such as high spe- cific strength, light weight and corrosion resistance. In recent years, FRP materials have been applied to structural members in many pedestrian and road bridges. Presently, a hybrid FRP (HFRP) composite beam for bridge applications is being developed. This beam optimizes the combined use of Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) in HFRP beam cross section. While CFRP has high tensile strength and higher stiffness, it is relatively expensive, whereas GFRP is comparatively less expensive but its me- chanical properties are lower than those of CFRP. In a beam subjected to bending about the strong axis, the top and bottom flanges are subjected to high ax- ial stress. In the HFRP beam, these flanges are fabri- cated using a combination of CFRP and GFRP lay- ers. On the other hand, the web is composed entirely of GFRP because it is not subjected to the same high stresses. The hybrid FRP beam therefore utilizes the advantages of both CFRP and GFRP for strength, stiffness and economy. Hybrid FRP is expected to find application in severe corrosive environments or where lightweight and rapid construction is required. The application of hybrid FRP composites could al- so contribute to a reduction of life cycle costs (LCC) and environmental load. In previous laboratory studies of HFRP beams, it was reported that the design was governed by de- formation rather than strength limitations due to the low elastic modulus of FRP materials compared with equivalent steel or reinforced concrete beams. In ad- dition, the HFRP I-beams subjected to flexural load- ing failed in the compressive flange due to delami- nation at the CFRP and the GFRP interface (N.D. Hai et al. 2009). These prior studies suggest that in- dividual HFRP beams could not utilize the high ten- sile strength of the CFRP in the tension flange. To fully utilize this strength, the delamination failures in the compression flange must be avoided. One ap- proach to accomplish this is to reduce the stresses in the HFRP compression flange by adding a concrete topping slab to resist the compression. This is analo- gous to composite steel construction where com- pression buckling failure of the steel top flange can be avoided by using the concrete topping slab to car- ry compression. This research aims to develop a composite beam using HFRP I-beams and a UFC topping slab. It is expected that the composite beam system will in- crease beam stiffness, prevent buckling and delami- nation in the HFRP compressive flange and more ef- fectively utilize the high tensile strength of the