Experimental and Numerical Study on Blast Resistance of RC Beams with Different Stirrup Ratios

Investigating the blast resistance performance of reinforced concrete (RC) beams under explosive loads holds significant importance for structural safety engineering. As critical components of RC beams, stirrup configurations substantially affect their mechanical behavior. This study systematically examines how varying stirrup ratios affect blast resistance performance, aiming to establish quantitative relationships between stirrup ratios and dynamic responses and to identify performance-improvement saturation thresholds through integrated experimental explosion tests and finite element simulations. Two reinforced concrete beams with distinct stirrup ratios (0.64% and 0.37%, corresponding to 80 mm and 140 mm stirrup spacing, respectively) were designed and constructed. The specimens underwent four intensified blast scenarios (20 g, 40 g, 80 g air explosions, and 80 g contact detonation) within a controlled explosion chamber. Comprehensive dynamic response data of the beams were captured using accelerometers, strain gauges, and displacement sensors, while failure modes were meticulously documented. Subsequently, experimentally validated numerical models were developed in ANSYS/LS-DYNA finite element software, employing advanced fluid-structure interaction techniques for multi-material simulations. This study comprehensively evaluated the blast resistance performance of RC beams with five stirrup ratios (0.26%, 0.30%, 0.37%, 0.47%, 0.64%) and systematically compared their acceleration responses, strain distributions, mid-span displacements, and failure patterns. Experimental data demonstrated that under identical blast loads, Beam B₁ with 0.64% stirrup ratio showed 18%~22% reductions in peak acceleration, 25%~30% lower strain responses, and 35%~40% decreased mid-span displacements compared to Beam B₂(0.37% stirrup ratio), while maintaining superior structural integrity with 50% fewer diagonal shear cracks. Across all four blast scenarios, Beam B₁ demonstrated 9.4%, 10.0%, 11.6%, and 12.1% reductions in maximum mid-span displacement compared to Beam B₂. The failure analysis revealed that Beam B₂ developed substantially more cracks with severe blast-side concrete crushing and larger spallation areas, confirming that higher stirrup ratios effectively suppress diagonal crack formation and propagation while improving concrete damage resistance. Numerical simulation further confirmed a consistent inverse relationship between stirrup ratio (0.26%~0.64%) and structural response metrics, with progressive decreases in both peak concrete strain and mid-span displacement. Experimental data revealed significant performance improvements with increasing stirrup ratios:compared to the 0.26% reference beam, specimens with 0.30%, 0.37%, 0.47%, and 0.64% ratios demonstrated progressive reductions in peak strain (9.7%, 20.8%, 28.5%, and 35.4% respectively) and peak displacement (3.8%, 10.0%, 14.9%, and 18.2%). The study identified diminishing returns in dynamic response reduction-displacement improvements decreased from 10.0%(0.26%~0.37% ratio range) to 4.9%(0.37%~0.47%) and ultimately 3.3%(0.47%~0.64%), indicating a performance enhancement plateau beyond certain stirrup ratios. These findings provide critical quantitative guidelines for optimizing blast-resistant RC structural design in practical engineering applications.