Development of a kinematic punching shear model for eccentrically loaded footings with and without punching shear reinforcement

• Applicants: Professor Dr.-Ing. Martin Claßen; Professor Dr.-Ing. Josef Hegger
• Subject Area: Structural Engineering, Building Informatics and Construction Operation
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555778696

Despite its significant relevance in construction practice, the load-bearing and deformation behavior of eccentrically loaded footings remains largely unexplored. Systematic investigations on eccentrically loaded footings without punching shear reinforcement (PSR) are limited to the previous project, while studies on footings with PSR are completely absent. In addition, the influence of load eccentricities in the area of the gaping joint is unknown. The few existing investigations clearly show load redistributions throughout the loading process, but suitable models that consider the physical background and allow for accurate predictions of punching shear capacity and deformation are lacking. Thus, the aim of the research project is the fundamental investigation of the punching shear behavior of eccentrically loaded footings with and without PSR as well as the development of a consistent model allowing for the representation of the kinematic behavior and the punching shear capacity of centrically and eccentrically loaded footings over the entire loading process. A key requirement for analyzing the physical relationships lies in capturing the complex non-rotationally symmetrical fracture kinematics as precisely as possible. For this purpose, a novel measurement methodology is being developed combining various continuous measurement methods (e.g., fiber optic strain measurement, digital image correlation) with a 3D laser scan of the deformed surfaces, which is carried out after each load increment. This allows for the measurement of the rotational and translational deformation as well as column penetration before, during, and after shear cracking to analyze load redistributions and the resulting shear transfer mechanisms. Based on the measured kinematics, the shear transfer mechanisms are determined in individual sectors of the footing using constitutive laws. To recalculate and predict the punching shear resistance of eccentrically loaded footings, a new model based on the Punching Shear Response Theory (PSRT) developed by the applicants will be proposed. Currently, the PSRT is already able to depict not only the punching shear resistance of rotationally symmetrically loaded slabs and footings, but also the complete load-deformation behavior over the loading process. Thus, the PSRT can depict different load levels in the individual sectors of the footing and the redistribution of stresses from the higher to the less loaded side of the footing throughout the loading process. The required compatibility conditions between the sectors are derived using the previously analyzed punching shear kinematics. In addition, the PSRT is extended for the consideration of PSR.

• DFG Programme: Research Grants