Conference Agenda

High strength strain hardening cementitious composite (HS-SHCC) is a new type of high-performance cement-based material with excellent tensile ductility and crack control ability. Investigating the fatigue performance of HS-SHCC is of great significance for the design of engineering structures. This paper studied the influence of stress levels (0.9, 0.85, 0.8, 0.75, 0.7) on the fatigue life of HS-SHCC under uniaxial compressive fatigue loading. The failure modes were observed, and the effect of stress level on the fatigue creep curve was analyzed. The results indicate that the failure mode of the specimen under compressive fatigue was shear failure which shows little relationship with the stress level. The maximum strain of HS-SHCC display obvious three stages of rapid development, stable development and instability. The fatigue life decreases with the stress level increasing. Similar to ordinary strength SHCC, the S-N curve of HS-SHCC specimens shows a bilinear trend. Based on the obtained S-N curve and three-parameter Weibull distribution theory, a compressive fatigue life prediction model of HS-SHCC under different failure probabilities is proposed. On this basis, the maximum stress level corresponding to the fatigue strength limit (corresponding to 2 million fatigue cycles) of HS-SHCC is predicted to be 0.638.

Currently, the verification of concrete structures exposed to fatigue is very conservative and does not utilise the possibilities of modern concrete mixtures. For this reason, current research projects are focussing on the fatigue properties of high-strength concrete (HPC) and ultra-high-strength concrete (UHPC). Significant influencing factors such as load frequency, load level, composition, and concrete moisture were identified. Several studies have consistently shown that concrete moisture adversely impacts fatigue behaviour across both low and high test frequencies. This detrimental effect becomes significantly more pronounced when specimens heat up during loading. So far, this phenomenon has been most clearly observed under uniaxial loading conditions.
The present experimental study aims to investigate the influence of moisture on different types of loading. For this purpose, fatigue tests were carried out under uniaxial, triaxial and combined shear-compression fatigue loading. The latter was introduced using a special test setup, referred to as refined punch-through shear test (PTST). To reduce the influence of temperature, the fatigue tests were conducted at a test frequency of 2 Hz. The confinement level in both the PTST and triaxial tests was set at 20 MPa, while the corresponding lower load level was 5% of the static shear/compressive strength. The upper load level varied between 75% and 95%. Wet and dried concrete were analysed for all three types of loading. The results emphasize the significant impact of moisture on the number of cycles to failure, which varies substantially with the type of loading.

Corrosion fatigue can be more damaging than corrosion or pure fatigue alone in reinforced concrete (RC) structures. RC bridges in corrosive environments are exposed to coupled corrosion fatigue, potentially leading to an overestimation of the fatigue life of bridge structures. Understanding and modelling fatigue crack propagation in the context of corrosion is crucial for improving the durability and safety of RC bridges under cyclic loading in corrosive environments. In this study, a model is developed to predict the fatigue life of reinforcement bars in aging RC beams exposed to corrosive environments. The model is based on Paris’ law, integrating fracture mechanics principles and corrosion growth kinetics. It evaluates the critical crack size by accounting for the combined effects of mechanical loading and corrosive exposure. A correlation has been developed to relate equivalent initial flaw size to the degree of corrosion. The model’s fatigue life predictions are validated against experimental results for corroded RC beams reported in the literature.

For the reliable and economical design of concrete structures under fatigue loading, a comprehensive understanding and accurate prediction of concrete fatigue life, especially under complex loading scenarios with variable amplitudes, is critical. Recent experimental studies on concrete compressive fatigue behavior demonstrate that fatigue life is closely linked to the strain rate in the second phase of strain development. Based on extensive testing of cylindrical specimens, a linear relationship between the strain rate in this phase and the number of cycles to failure has been observed in double-logarithmic space. This correlation provides a more consistent evaluation of fatigue life with significantly less scatter compared to traditional S-N curves. Moreover, the predictive capability of the strain-rate criterion can be used to estimate the fatigue life of runouts, which also enables the possibiliy of highly accelerated fatigue tests.
This contribution extends the analysis of the linear correlation across a broader range of fatigue stress configurations and varied parameters. In addition to compressive fatigue behavior observed through cylindrical tests, experimental data on tensile fatigue, using notched three-point bending tests (3PBT), and shear fatigue, using punch-through shear tests (PTST), are evaluated. Furthermore, this study re-evaluates the effect of loading sequence—a key factor in fatigue design—by applying the strain rate criterion across different stress states