Verification of the shear resistance of UHPFRC beams - Design method for the German DAfStb Guideline and database evaluation

This contribution focuses on the verification of the shear resistance of Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) beams. A verification method following Eurocode 2 and the German DAfStb Guideline Steel Fibre Reinforced Concrete" is presented, which superimposes the shear resistance of a member without shear reinforcement, the shear resistance provided by stirrups, and the contribution of the fibers activated in the shear crack. With regard to the contribution of the fibers, the verification method differentiates between members with I-shaped and approximately rectangular solid cross section. This provides a more favorable design of members with I-shaped cross section. Reliability of the design approach is statistically evaluated by means of a total of 208 shear tests on UHPC and UHPFRC beams with different configuration. For 133 tests on beams with I-shaped cross section the ratio between ultimate shear force from experiment Vexp and theoretical shear resistance V-cal shows a mean value of X- = 1.48 and a 5 % quantile of Q(0,05) = 0.94. For 75 tests on beams with approximately rectangular solid cross section the results are X- = 1.59 and Q(0,05) = 0.94. For all 208 tests included in the database X- = 1.52 and Q(0,05) = 0.94 are obtained. Based on the statistical parameters it is concluded that the prediction model is sufficiently reliable for being considered with the forthcoming German DAfStb Guideline on Ultra-High Performance Concrete.