Damage Mode and Structural Response of SCS Sandwich Beams with Lacing Bars Subjected to Near-Field Explosions

In this paper, a novel lacing system was used for steel–concrete–steel (SCS) sandwich walls to resist near-field explosions. To study the performance of laced SCS sandwich walls under near-field explosions, five wall strips were extracted from a wall as beam specimens for conducting field blast tests. Test results indicated that SCS sandwich beams showed combined global and local damage under near-field explosions. The beam specimen without lacing bars kept global integrity under a scaled distance of Z=0.4 m/kg1/3, although the concrete core was prone to spalling, and thin shear cracks formed. However, severe spalling and shear failure of concrete occurred as Z was decreased from 0.4 to 0.2 m/kg1/3. Adding lacing bars as shear connectors could effectively improve the blast resistance of the beam specimens. The lacing bars increased the out-of-plane shear strength of the specimens and provided interlock action to the faceplates, thereby enhancing the integrity of the specimens. Increasing web reinforcement ratio slightly decreased the deflection of the specimen. Decreasing longitudinal reinforcement ratio ρ significantly increased the deflection of the specimen. Numerical study was performed with LS-DYNA to further investigate the effects of Z and ρ on blast responses of laced SCS sandwich beams. Finally, a single degree of freedom model that is capable of considering combined global and local damage was proposed to predict the displacement response of laced SCS sandwich beams under near-field blast loading.