Dynamic increase factor of concrete compressive strength in confined split hopkinson pressure bar tests

This study presented a methodology to evaluate the pure strain-rate effect on concrete compressive strength and developed a pure rate dynamic increase factor (DIF) model through numerical and experimental investigations into confined split Hopkinson pressure bar (SHPB) tests. The numerical investigation proposed the methodology to determine the pure rate DIF through confined SHPB tests. Subsequently, the confined SHPB tests were conducted on concrete specimens, and a pure rate DIF model was developed based on this methodology. Additionally, conventional SHPB tests were performed to obtain an apparent DIF, which was then compared to the developed pure rate DIF. The results indicated that the apparent DIF exceeded the pure rate DIF, thus confirming its tendency to overestimate the strain-rate effect on concrete. Therefore, the proposed methodology using confined SHPB tests provides an alternative approach to overcome the limitations of the apparent DIF determined from conventional SHPB tests. Lastly, the developed pure rate DIF model was validated through numerical analyses on conventional SHPB tests and drop-weight impact tests of reinforced concrete beams. This validation demonstrated that the proposed pure rate DIF model effectively considers the strain-rate effect on concrete structures, thereby enabling assessment of the performance of concrete structures under extreme loading conditions.