Shear transfer across a single crack in reinforced concrete under sustained loading. Part I: Experiments

The experimental investigation relates to the behaviour of concrete specimens with a single crack under sustained shear loading. The crack plane is crossed perpendicularly by embedded reinforcing bars, each of 8mm diameter. The variables of the tests were the concrete grade, the initial crack width, the shear stress level and the reinforcement ratio. The constant shear stress level was 45%-90% of the static shear strength. The experimental program comprised 34 specimens. The duration of load application was at least 90 days. Periodically the crack width and the shear slip of the opposing crack faces were measured. Experiments started at a concrete age of 28 days at 20°C and 50% RH. On the one hand, the test results refer to measured material characteristics such as development of concrete compressive strength, shrinkage and loss of weight by the drying process. On the other, the measured instantaneous and the time-dependent displacements under sustained shear loading are given for each specimen. Moreover the crack-opening path and the displacements after release of the shear force are presented. The measured displacement-paths are described by non-linear regression analysis. Detailed information is also presented in report 5-85-6 [39]. In an additional test series similar specimens were used. Now the normal restraint stiffness of the crack was governed by four steel bars having no bond with the concrete. As an advantage the axial steel stresses could be measured by strain gauges. Moreover, pull-out tests were performed to study the bond behaviour of 8 mm diameter reinforcing bars. See reporc 5-85-11 [40].