Design and Field Testing of a First Continuous Slab-on-Girder Bridge with a Hybrid GFRP–Steel-Reinforced Bridge Deck in Canada

Abstract

This paper introduces field tests of the first continuous multispan slab-on-girder bridge with hybrid glass fiber-reinforced-polymer (GFRP)–steel reinforcement in Canada. The bridge was constructed in 2012 on Chemin Dunant overpassing the extension of Highway 410 in Sherbrooke (Quebec). The bridge consists of three spans with a maximum span of 44.6 m and is a typical slab-on-girder bridge with three traffic lanes. The bridge cross section consists of five steel girders, 1.9-m depth, covered with a 200-mm-thick concrete slab. The deck slab was reinforced with hybrid GFRP–steel reinforcement with a top mat of GFRP bars and a bottom mat of galvanized-steel bars. The Ministry of Transportation of Quebec recommends using galvanized-steel bars instead of black-steel bars because the former has higher corrosion resistance. The amount of reinforcement was determined using the empirical design method based on a steel reinforcement ratio of 1.0% according to existing design codes . The bridge was examined under live-load field testing involving seven load cases of truck locations. The steel-girder deflection was measured, and the strains in the GFRP and steel bars over an intermediate bridge pier were recorded. The field test showed very low strains in the GFRP and steel bars. The visual field inspection over approximately 6.5 years revealed that the bridge performed well under normal traffic conditions, confirming the applicability of using hybrid reinforcement in continuous bridges. An analytical parametric study was conducted examining the effects of changing the top reinforcement bar diameter, top and bottom reinforcement spacing, the hybrid- or GFRP-reinforced deck slab, and the dimensions of the steel-girder cross section (noncompact). The study revealed that the empirical method is conservative and calls for an unreasonable amount of reinforcement. Accordingly, the flexural design method (sectional analysis) should be used for the negative moment section.