Zum Querkrafttragverhalten von einachsig gespannten Stahlbetonplatten ohne Querkraftbewehrung unter Einzellasten

The present design rules for the shear capacity of members without shear reinforcement in Eurocode 2 were calibrated based on a database containing the experimental results of shear tests on simply supported beams. In practical dimensioning, these rules are also applied on the shear design of members with various other support conditions and on one-way slabs under concentrated loads, for instance wheel loads on bridge deck slabs. For this purpose, the slab-bearing behaviour is taken into account by an effective width for shear or assuming a load spreading. While the existing approaches for the effective width for shear are for most cases highly conservative, the assumption of a load spreading may lead to an unsafe design especially for large load distances from the support. Alternatively, the distribution of shear forces may be determined by linear-elastic finite-element simulations. However, the numerical results may significantly vary depending on the chosen support conditions and modelling settings.In order to develop more appropriate design approaches for the shear design of one-way slabs under concentrated loads, systematic experimental and theoretical investigations on the effective width for shear have been conducted. The experimental programme consisted of shear tests on 0.28 m thick reinforced concrete slabs with a width varying between 0.5 m and 3.5 m. While the 0.5 m wide slab strips were activated over their full width to carry the load, the effective widths of the 3.5 m wide slabs were unattached of the load distance from the support with a small number of exceptions with 2 to 3 m smaller than the existing width. To investigate further influences on the effective width, numerous parametric studies have been conducted by non-linear and linear-elastic finite-element simulations and a database comprising 560 shear tests on one-way slabs and slab strips has been evaluated. The findings were used to develop a practicable approach for the effective width for shear.Furthermore, different loading and support conditions have been investigated. In order to account for the larger shear capacity of continuous members with small load distances from the support, the load reduction factor was modified considering the point of zero moment. Moreover, the influence of an inclined compression strut on the shear capacity in haunched members without shear reinforcement was quantified. The results of the own approaches in combination with existing design concepts for the shear capacity adequately coincide with the experimental data of the own tests and further tests from literature collected and prepared in shear databases. The new approaches ensure both an appropriate assessment of existing bridge deck slabs as well as a safe and economic shear design of new structures