Deciphering the effect of load sequence in concrete fatigue: An interleaved numerical-experimental methodology

• Applicants: Dr.-Ing. Abedulgader Baktheer; Professor Dr.-Ing. Martin Claßen
• Subject Area: Structural Engineering, Building Informatics and Construction Operation ; Applied Mechanics, Statics and Dynamics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544805481

Optimizing material utilization and enhancing structural durability are crucial for sustainable infrastructure. Concrete structures, serving as the backbone for critical infrastructures like bridges and wind power plants, face a significant challenge - predicting their fatigue life. The central hurdle lies in understanding the intricate relationship between loading sequence and fatigue life, compounded by the wide variability and high cost of fatigue testing scenarios. Without studying the effects of load sequencing and variable amplitudes, safety factors can be set unreasonably high, leading to inefficient material utilization, or dangerously low, compromising the safety of critical infrastructure. The primary objective of the proposed project is to develop a comprehensive experimental-numerical methodology for understanding fatigue behavior in concrete structures, with a specific focus on the influence of loading sequence. The research centers on exploring fatigue-induced degradation in critical zones of structural elements across various loading scenarios, including systematic loading blocks and realistic random loading sequences. Moreover, the project is actively testing a new hypothesis that suggests the stabilization of cumulative fatigue life in highly nonuniform loading scenarios, showcasing a deviation from the predictions of the widely used Palmgren-Miner (P-M) damage accumulation rule. To achieve the project objective, the research involves further development of macro- and meso-scale numerical modeling approaches, emphasizing their physical rigor and thermodynamic consistency. This theoretical development is accompanied by the development of tailor-made experimental characterization methods that can isolate fatigue dissipative mechanisms at both material and structural scales, with a specific focus on the impact of loading sequence. The refined numerical and experimental framework is extensively employed to investigate the effects of loading sequence across a diverse range of loading scenarios. Additionally, it is utilized to explore the intricate interaction between loading sequence effects and structural stresses redistribution during fatigue life. The outcomes of this research project will establish the foundation for formulating a precise and improved damage accumulation rule, enhancing the prediction of concrete fatigue life by incorporating the influence of loading sequence and variable amplitudes. This comprehensive approach, unifying numerical modeling and experimental validation, offers a powerful tool that is expected to make a significant contribution to the domain of concrete fatigue life prediction. Anticipated impacts include advances in design methods that will increase the durability of critical infrastructure.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Rostislav Chudoba