Load transfer of small-diameter GFRP and stainless steel doweled-joints in slabs-on-ground

Abstract

Large diameter steel and glass fiber-reinforced polymer (GFRP) dowel bars are commonly used in rigid concrete pavements in highways for load transfer across joints to combat the concrete deterioration due to corrosion of steel dowels. Small-diameter GFRP dowel bars can be used at the expansion joints in slabs-on-ground, walkways, industrial floors and concrete-lined channels, which are not subjected to heavy traffic loads. This study investigated the performance and behavior of small-diameter GFRP dowels. GFRP dowels with three diameters (14 mm, 16 mm, and 38 mm) and stainless steel dowels (12 mm dia.) were embedded across a 25 mm-wide joint in a test slab with overall dimensions of 1500 × 750 × 200 mm3. The variables of the study were the type of dowel material (GFRP and stainless steel), the diameter of GFRP dowels, the spacing of the dowels (200 mm and 250 mm c/c), and the type of loading (monotonic and cyclic). The slabs were loaded up to the failure of the joints under a concentrated load applied at the edge of the joint. The performance of the dowel-jointed slab specimens was investigated based on the cracking and ultimate loads, modes of failure, and load-displacement response. The ability of the small-diameter dowel bars to transfer displacements across the joint was quantified using the quantitative measures of joint effectiveness (E), load transfer efficiency (LTE), and relative deflections (Δ). Failure of the specimens with 14 mm and 16 mm diameter dowels occurred predominantly due to shear failure of the dowels before the cracking of concrete. However, for the specimens with large-diameter GFRP dowels and the stainless steel dowels, failure was associated with cracking of the concrete. A smaller spacing of the GFRP dowels and a longer embedment length gave a stiffer load-displacement response. Reducing the spacing from 250 mm to 200 mm resulted in a 4.1-fold reduction in relative deflection under the AASHTO H10 design wheel load (∼35.6 kN). Increasing the dowel length had no significant effect on the load-carrying capacity of the dowel-jointed slabs. Cyclic load tests on the specimens revealed that the joint effectiveness (E) and the load transfer efficiency (LTE) of GFRP dowels were within the AASHTO and ACPA limits up to a concentrated load higher than the AASHTO HL93 dual tandem-axle wheel load (∼55.6 kN).