The focus of this dissertation is the design and development of a functional three-dimensional steel-free multi-girder bridge deck system composed of longitudinal Glass Fibre Reinforced Polymer (GFRP) hollow box beam girders reinforced with Carbon FRP (CFRP) sheets on the bottom tensile face. An integrated cast-in-place Ultra-High Performance Concrete (UHPC) slab was placed overtop of the assembled girder system, with a two-part bond system used between the top flange of the GFRP hollow box beams and the UHPC slab. Transversely, a system of GFRP threaded rods was used as horizontal straps, horizontal post-tensioned GFRP rods as well as diagonal cross-bracing rods to provide transverse composite action between the adjacent girders. Small-scale experimental testing results led to the use of unbonded non-prestressed vertical GFRP threaded rod at the GFRP-UHPC interface in conjunction with an epoxy bonded coarse silica sand aggregate layer. Similarly, GFRP threaded rods post-tensioned to 2.5% of the ultimate strain capacity were used. Large-scale experimental testing of a quarter-scale bridge deck system specimen under service load conditions exhibited negligible signs of creep and stress relaxation when subjected to repeated loading. The performance of the bridge deck specimen under various concentric and eccentric wheel load configurations led to live load distribution factors of 25-30% for interior girders and up to 50% for outer girders. Experimental testing of the bridge deck specimen under ultimate load condition confirmed global pseudo-ductile behaviour in the system with good load transfer provided by the composite action systems. The governing areas of potential failure included cracking in the UHCP slab, tensile failure in the CFRP sheet and GFRP bottom flange, compressive buckling in the GFRP cross-bracing bars and anchorage failure in the post-tensioned GFRP rods. The developed three-dimensional finite element model was validated for global load-deflection behaviour as well as local performance in the main structural elements; however, it is not recommended for predictions of local strain in the horizontal and vertical GFRP threaded rods without additional model refinements.
The work performed in this research program led to the development of a functional transverse composite action system containing solely GFRP material. The previously designed hybrid FRP-UHPC girders were successfully incorporated in a feasible multi-girder bridge deck system capable of effective three-dimensional load distribution between adjacent structural elements. The developed hybrid steel-free multi-girder bridge deck system exhibited the desired pseudo-ductile global behaviour and performed in accordance with ultimate and serviceability load requirements in the current Canadian code.