Experimental and analytical investigation on the combined effect of repeated loading and chloride exposure on the flexural performance of HPC beams

In this study, the flexural behavior of high performance concrete (HPC) beams under the combined effect of repeated loading and chloride dry-wet exposure is investigated. From the material perspective, a series of cubic specimens were subjected to axial cyclic loading with a stress level of 0.4 and subsequently exposed to chloride dry-wet cycles. The results revealed that the repeated loading would cause significant internal damage, as indicated by the measured relative dynamic modulus. Additionally, the compressive strength of cubic specimens showed a first rising and then falling process during the chloride dry-wet cycles. By comparison, a relation model between compressive strength and relative dynamic modulus is proposed for damaged HPC. Furthermore, ten HPC beam specimens were fabricated and subjected to a similar combined exposure to repeated-loading and chloride dry-wet cycles. These beams were then loaded to failure using a four-point loading mode and the findings indicate that the repeated loading history led to initial cracking damage and reduced the flexural performance of tested HPC beams. Meanwhile, the chloride dry-wet cycles could improve the concrete strength and consequently enhance the specimen's capacity. Their combined effect on the beam's ultimate loads was established considering the strength damage of HPC. Finally, an analytical derivation was proposed to capture the deflection of tested beams under the combined effect, which took the damage in the section's short-term stiffness into account, resulting in a more accurate prediction of deflection.