A number of bridges designed by the AASHTO Specifications and the Ontario Highway Bridge Design Code (OHBDC) were constructed during the early nineteen eighties. The AASHTO designs for the deck slabs were based on flexural considerations and required larger amounts of reinforcement than the minimum isotropic reinforcement required by the empirical method of the Ontario Code. Fourteen bridges were load tested to compare the performance of deck slabs designed by the two different techniques and built during this period. The applied test loads were generally less than 40 percent of the calculated punching shear capacity of deck slabs, but far exceeded the factored wheel load specified by both the AASHTO Specifications and the OHBDC. Under the test loads, the slab pannels displayed no visible signs of distress. The test data and the analysis of punching shear capacities show that the amount of reinforcement has a comparatively small effect on the strength and stiffness of the slab panels and that the slabs designed by the OHBDC have adequate strength to carry heavy wheel loads from modern trucks. The major parameters affecting the strength and stiffness are slab thickness, girder type and girder spacing. The measured deflections at the centre of slab panels were found to be significantly smaller than those calculated by the conventional plate-in-flexure analysis assuming a cracked section and concrete in tension being ineffective. The effect of 'tension stiffening' in concrete is investigated in order to explain a part of this difference. For the covering abstract of the Conference see IRRD Abstract No. 807839.

An experimental investigation was undertaken to determine the effects of transverse confinement using glass fibre reinforced polymer and steel bars in deck slabs. Researchers in Nova Scotia and Ontario have expressed the opinion that only the bottom transverse layer of reinforcement is required for strength and safety of conventionally reinforced deck slabs. Further, they have hypothesized that the bottom transverse reinforcement acts as a lateral tensile tie, in a manner similar to that of steel straps in steel-free deck slabs. Studying the transverse confinement provided by the lateral restraints, which enables the arching action in conventionally reinforced and steel-free bridge deck slabs, will facilitate innovative and increasingly durable designs using advanced composite materials such as GFRP. The first component of the study was to assess the function and effectiveness of each layer of steel reinforcement in conventionally reinforced deck slabs. The second component was to determine if GFRP bars could also be used to perform the same function as the steel straps and lower transverse steel bars, based on equivalent axial stiffness.