The Effect of Combined Loads on Core Sample Strength

Abstract

This experimental investigation focuses on the influence of structural damage on the concrete compressive strength of reinforced concrete vertical members subjected to complex combined actions consisting of axial load, bending moment, and torsion. Concrete core samples were obtained from structural members tested under various loading configurations, as well as from undamaged specimens serving as reference cases, and their compressive strengths were evaluated comparatively. The experimental results consistently reveal that core samples extracted from damaged members exhibit lower compressive strength values than those obtained from undamaged reference samples. The magnitude of strength degradation was found to vary between 9% and 29%, depending on the specific loading combination applied. The most pronounced reduction in compressive strength, reaching 29%, occurred in specimens exposed to loading conditions dominated by torsional effects. These outcomes provide quantitative evidence that, in the evaluation of seismically damaged reinforced concrete structures, the determination of in-situ concrete strength should account not only for test measurements but also for the loading history and the extent of damage experienced by the structural member.