Coupling influence of low strain rate and structural size on splitting-failure of concrete: Tests and Mechanism analysis

The Static and Dynamic unified Size Effect Law (SD-SEL) captures the combined effects of strain-rate and structural size on the nominal strength of concrete, and it can quantitatively predict the nominal strength of concretes with different sizes under both static and dynamic loads. To verify it, splitting failure tests of cubic concrete samples with five structural sizes (maximum structural size up to 300 x 300 x 300 mm) subjected to four strain-rates (i.e., 10(-5) /s, 10(-4) /s, 10(-3) /s, and 10(-2) /s, covering seismic load) were conducted. The results indicate that with an increasing strain-rate, the crack tortuosity is reduced, more coarse-aggregates are split by the cracks and the splitting-tensile fracture surface is smoother. As the strain-rate changes from 10(-5) /s to 10(-2) /s, the failure strengths of concrete samples D75, D100, D150, D200, and D300 increase by 16.2 %, 22.9 %, 25.9 %, 63.3 %, and 93.2 %, respectively, indicating that a large structural size could enhance the effect of strain-rate on the splitting-tensile strength. Due to the combined effects of multiple cracking mechanism, viscosity mechanism and inertia mechanism, the size effect on splitting-tensile strength is reduced as the strain-rate increases from 10(-5) /s to 10(-2) /s. The Static and Dynamic unified Size Effect Law (SD-SEL) is shown to fit the experimental results well at low strain-rates and the maximal error is around 20.0%.

Automated summary

The study demonstrates that the Static and Dynamic unified Size Effect Law accurately describes the variation of nominal strength of concrete under different sizes and strain-rates. As the strain-rate increases, the failure strength of concrete also increases, with a more significant effect seen in larger structural sizes. The size effect on splitting-tensile strength of concrete decreases as the strain-rate increases, attributed to the combined effects of multiple cracking, viscosity, and inertia mechanisms.