Anchorages and laps in reinforced concrete members under monotonic loading

In structural concrete members with reinforcing bars subjected to high longitudinal forces, bond zones are highly utilised. The bond strength between reinforcement and surrounding concrete depends on material and geometric parameters. Reinforcement with large-diameter bars bearing high longitudinal forces as well as dense reinforcement positioning further increase the utilisation of bond zones. For the second generation of Eurocode 2, a new design equation for the calculation of necessary anchorage and lap lengths was proposed. This equation is based on a model for the calculation of mean strength that was derived for Model Code 2010 on the basis of a comprehensive bond database. A transfer of the given design model from mean to design level corresponding with the safety concept of Eurocode 0 is not conducted, yet. While Eurocode 2 and the German National Annex comprise numerous additional rules for the application of large diameter bars Ø > 32 mm, the proposal for the next generation of Eurocode 2 does not include any rules for large diameter bars. For this reason, the necessity of additional rules for large diameter bars is closely investigated in this thesis. For the determination of the bond behaviour of structural elements with large diameter bars, beam-end tests, four-point bending tests with laps as well as anchorage tests at direct supports were conducted. The fundamental bond behaviour of large-diameter bars was investigated in beam-end tests. Since the additional rules for large-diameter bars are most restrictive for laps, the necessity of these rules were analysed on the basis of four-point bending tests with laps. The actual structural behaviour of end anchorages was tested in anchorages in simply supported beams to account for transverse pressure and densely positioned bars. While Eurocode 2 defines several possibilities for transverse crack width reduction in continuously reinforced structural elements, specifications for transverse cracks at lap ends and longitudinal cracks are not given. Hence, the key objectives of this thesis are the investigation of developable bar stress in bond zones and the crack development. Calibration factors for the transfer of mean values to design values are derived from the bond database. Initially, characteristic values of bar stress in bond zones and corresponding model uncertainties are obtained by a statistical evaluation of the test results given in the database. Subsequently, the design value for anchorage and lap lengths is obtained by applying the method according to Eurocode 0. The resulting calibration factor is verified by a level II reliability analysis. Besides the necessary calibration factor, detailing rules for highly utilised anchorages and laps are proposed. The detailing recommendations for practical application are based on the results of experimental load and crack width investigations