On the role of dowel action in shear transfer of CFRP textile-reinforced concrete slabs

Carbon-fiber-reinforced polymer (CFRP) grids or textiles for concrete have high application potential in thin planar members such as bridge deck slabs or facade plates. With the high tensile strength of CFRP, shear failure governs design in wider regions, which calls for optimized shear models incorporating all relevant load-transfer mechanisms. The contribution of dowel action to shear resistance is often neglected in shear models derived specifically for FRP reinforcement. As reasons, the low transverse modulus of the anisotropic material and the small cross-sectional areas per reinforcement element and thus small cross-sectional stiffness are mentioned. Yet fundamental research on this mechanism for CFRP grids is amiss. This paper presents a new test setup for characterizing the dowel action of CFRP grids that are pre-strained, similar as in real applications where the reinforcement in the shear crack is stressed in flexural tension. The influence of (pre-) crack width, pre-strain and concrete cover is discussed. By comparison to results from flexural shear-tests it can be shown that, depending on the effective depth, the contribution to shear resistance can be significant. Furthermore, the important role of dowel cracking in the shear-compression failure mechanism could be analyzed using the results of the new dowel test.