Innovative bridge deck with reduced reinforcement and strain -hardening fiber -reinforced cementitious composites.

Abstract

Since corrosion of steel reinforcements in concrete is a major factor in the deterioration of bridge decks, this research proposes a new bridge deck system in which the top reinforcement is totally eliminated and instead, a strain-hardening fiber reinforced cement composite (or HPFRCC) is used. With the HPFRC matrix, the restraining resistance provided by the fibers, acts isotropically, thus temperature and shrinkage reinforcements are not needed. Also, the fibers help reduce crack widths, therefore minimizing ingress of corrosive agents. The bottom reinforcement is kept continuous and placed far away from the surface of the deck to prevent contact with penetrating corrosive agents, if any. This research deals with verifying the possibility of implementing this new system in real bridges. It comprises both experimental and analytical investigations. The first phase of the experimental work consists of testing the mechanical properties of HPFRC composites in order to better understand their behavior. The results obtained are used for modeling the proposed bridge deck system. The second phase of the experimental program includes the testing of thirteen two-span continuous beams simulating slab slices of bridge decks to evaluate their behavior. Parameters investigated included three types of fibers (Spectra, Torex, PVA), three types of reinforcements (steel bars, prestressing strands, CFRP), and two design concepts (reinforced concrete, prestressed concrete). The analytical work focused mainly on predicting the overall response of the proposed deck system with the combined use of nonlinear section analysis and nonlinear member analysis. Based on the findings, the proposed deck system works as anticipated. Indeed, with strain-hardening matrices, a plastic hinge mechanism formed under increasing load, leading to a response better than that of conventional reinforced concrete decks, even though the top reinforcement was eliminated, also, the proposed deck system showed higher inelastic stiffness, higher energy absorption, and higher ductility. Fibers in the HPFRC matrices help improve deck serviceability; under maximum service load, smaller permanent deflection and rotation as well as smaller crack width were observed in comparison to conventional reinforced concrete deck. Design recommendations are provided and conclusions are finally drawn.