Shear behavior of RC members without shear reinforcement – development of a consistent experimental, analytical and numerical characterization methodology

• Applicants: Professor Dr. Rostislav Chudoba; Professor Dr.-Ing. Martin Claßen
• Subject Area: Structural Engineering, Building Informatics and Construction Operation ; Applied Mechanics, Statics and Dynamics
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 420545423

Large efforts have been devoted in the past to analyze the shear behavior of RC slabs and beams without shear reinforcement. Albeit a considerable progress has been achieved, a consistent description of the shear zone behavior is still missing. This fact can be documented by an ongoing dispute in the scientific community on the exact role of phenomena governing the shear behavior, on their adequate quantification and their appropriate representation in modeling approaches.The major objective of the proposed research is to fill this gap by developing a new, theoretical and experimental framework that can thoroughly describe the shear failure process. The theoretical framework will consistently capture the elementary mechanisms involved in the shear failure, including (1) crack localization, (2) crack propagation, (3) pressure-sensitive friction of the crack faces due to aggregate interlocking, (4) bond behavior, (5) dowel action, and (6) nonlinear material behavior in the compression zone. The proposed modeling strategy will combine analytical models of the cross section along the critical shear crack (Level I) and enriched finite element model of the shear zone with discrete crack representation (Level II). By representing the elementary mechanisms involved in the shear zone behavior with a different degree of detail and different amount of computational effort, it will be possible to balance trade-off between accuracy and efficiency of the simulation. Successful implementation of the modeling strategy will lead to a very efficient simulation of the shear zone behavior including the accurate prediction of the crack propagation and the quantification of the interacting shear transfer contributions (residual tensile stress, aggregate interlock, dowel action and shear in compression zone) during the entire loading history.Calibration of the developed analytical and numerical models will be performed using a test program with a consistent set of component tests. Besides existing and standardized test setups used to identify the constitutive laws for compression, strain softening, debonding and dowel action, a new test setup for the characterization the aggregate interlock along the crack faces will be developed. The validation of the models at both levels will be provided by a set of reinforced concrete beam tests monitored using high-resolution measuring techniques (DIC).By bringing together the best practices of two disciplines, i.e. structural concrete and numerical mechanics, this research will significantly enhance our insight into the behavior of shear zone behavior. In the long run, it will provide a sound basis for structural design methods with reduced material consumption, extended service life, and increased reliability of engineering structures.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Josef Hegger