Shear capacity of reinforced concrete one-way slabs without shear reinforcement under single loads

• Applicant: Professor Dr.-Ing. Josef Hegger
• Subject Area: Structural Engineering, Building Informatics and Construction Operation ; African, American and Oceania Studies
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 253183198

The present models for the shear capacity of reinforced concrete slabs without shear reinforcement were mostly developed based on the knowledge of the shear-bearing behaviour of beams. The slab-loadbearing behaviour under single loads is considered by different approaches for an effective width, which capture the actual bearing behaviour insufficiently. According to recent research, the influence of the shear-span-to-depth ratio and the load transfer due to a direct compression strut differs for slabs and beams. In particular, the interaction between arching action and effective width for shear depending on the static system and the moment-shear ratio seems to be of significance. In case of simultaneously acting single and line loads, the influence of the greater compression force due to bending is not clarified, especially for haunched slabs with inclined compression struts.The overall objective of the research project is to analyse the shear-bearing behaviour of one-way concrete slabs without shear reinforcement under single loads and to develop a consistent model for the shear capacity. In particular, the influences of the support conditions, the degree of restraint and the static system (cantilever slab, single- and multi-span slab), the shear-span-to-depth ratio and the reinforcement ratio on the load spreading of a single load and the shear capacity should be investigated. By tests on slab stripes and wide slabs, the influence of the effective width is evaluated. In addition, the interaction of multiple single loads should be analysed. The open questions are adressed by experimental and theoretical investigations. Starting point for the theoretical investigations are the present models for shear design. Based on the shear tests on slabs under single loads from literature, a database is established in order to evaluate the existing approaches. The experimental investigations extend of the database for parameters, which have not been studied so far. By evaluation of the tests and parameter studies on nonlinear finite-element models, the different contributions to the shear capacity depending on the moment-shear interaction are quantified. In combination with the experimental test data a sufficient database is provided allowing to develop an extended model for the shear capacity of concrete slabs under single loads.

• DFG Programme: Research Grants